Data For Seismic Well Tie: 6 Condition

4300 -i

At 0 DT

4400

P □ DRHO

Y

a

GR Rp □ ILD

=

4600

RD □ RT

4700 -j

£+ □ SP

4800

p a RHOB

R«o □ SFLU

Fra □ VCL Rn □ SN

4900

Diatnond_14.cs AJICheckSh0t3.cs

t>

gAPI

- E, l~t

S5 Well section tern

I:' us/ft 303.8C

RHOB

207.751ÿ010

2ÁA\ 1 4380 »cm3 2 6620 |'l 4 90

m

f

[bblVUJ

1

1

c

t

4500

*ii □ NPHI <%, □ PHIT

P

)iamond-14

t

Rn □ ILM

0

286915 66

4131.8;

R„□ CILM

*

:-=ÿ

Hz-;

Log attrfoutes

SSTVD

J

> \

I

V

r ?

-

;

.

5. On the Well Section tab, in the Cross-section group, click if-t

a

Well correlation

File Well section tern

Stratigraphy *

Template settings

correlation!

New template Templates

ism

n

v*

____

Petroleum Systems

Seismic Interpretation

1 snow vertical tracks

Cross section

|

Show cell boundary

Visualization

Decision Support

Set production chart mode

Structural Modeling

Domain;

|H

Well correlation

-r’

SSTVD '

•

Window settings

5

. The Tool Palette opens.

Property Modeling

_4®. ¡¡¡¡¡ Scaling

|l|J

view all

Fracture Modeling

4*-

Equalize scales

ww Sync

View entire well Vertical scaling

6. Color fill logs by clicking Curve fill correlation Tool Palette.

360 •Condition input data for Seismic well tie

Production

rolling

Well Design

Relative 50000

Sync

j scaling

[a| Insert (2 Show ¡§ Mane

Horizontal scaling

in the Well

Petrel Geophysics

>

0 Diamond-14 SSTVD GR CALI 1:2869 5.66 gAPI 207,75 -0.10 in 2.44 Caliper ima rav

SSTVD] RHOB

'~ 43.S0 3.cm3 2.6620

DT 14.90 usffl 303.80

lensitv

4200

Sonic

l

4131.8: 4

4300

4400

4

4500

T

>1

4600

IT

0 4700

_¿j Q 3D grid 4800

_

Completions design Edit fault properties

Facies

4900 ■:

'Á 5000 -i

__

@

<M[•,;

T= 1 oo4

Fault model Geobody interpretation

•fjjj Z] Geomechanics tools 5100 c

¿

Geopolygon editing

__

Log conditioning Mesh editing

5200 c

Palette

Select Wel correlation

33 » X

ipffeas”!

¥

['

-s

Microseismic Pad editing

5300

Point editing

Polygon editing

5400 c

Prestack seismic 5500

Í [2 i

__ Z}

~

Seismic interpretation

Seismic well tie

5600 c 5700

QI tools

-IB{

Stratigraphic chart editing

n Surface editing_

!S 3 Well correlation 5800

Well design

-

IjS 5900

6000

6128.8a

Petrel Geophysics

X-section editing

F

I Condition input data for Seismic well tie •361

switched on, click on a curve 7. With Select/Pick mode [P] in Well section window and then click Adjust color table in the Quick Access toolbar to refresh the color fill of the curve.

<

□•[!]«

Siy D

>

1SI =

8. From the Well section Window toolbar, click Template

1=1

settings . From here, you can adjust the template and curves for suitable display. 0

|Q

fe

SSTVD

•

Well section ten

-

I,D Undef

•

fif®*

!

.

M- Retake

50000

■

B-B* Q

- HE'S H

t

9. Set the log curve values of GR and DT to 0-200 and 30-300, respectively, to display the logs better in the Well section window. [ÿ]

S3

Settings for 'Well section template 3'

0 Info”! [{§}

Well section template

Template objects

ns B m

B

r@Y Eü

i3HTro

toÿCALI

É

Hi

Template objects

n■@0

Index track

¿ÿÿVIA GR

0Y

Co

a

Normal

|_Both

@P RHOB

-

.

— TSatMl Borehole markers wjua

a

Objects settings

O

Into

[ÿ¡ Definition| fTf Umitsj

0 Min value:

GR

0¿CALI 0gjCAU RHOB

-

200

□ Wrap

¿

Vertical tracks (5)

E

Ü.

0

m Max value:

@flt DT

la-

1]

0 Min value

Borehole markers Background Deviated tracks (0)

E)

fa

Qg} Definition )[ÿ] Limits! V Style

Info

Direction:

RHOB

L-gjp RHOB 0j£. DT

a

Objects settings

0

@ (] Index track -

El

U-

_

| Vertical tracks (5)

Style

d

30

@j Max value: 300 Direction

E

Wrap:

Normal

| Both

D= Background Deviated tracks (0)

*/ /tpply

362 •Condition input data for Seismic well tie

]

■/ OK

A Cancel

|

Petrel Geophysics

10. In Select/Pick mode [P]

, click

on a curve in Well section

window and click Log conditioning IsS in the mini toolbar to open the Log conditioning Tool Palette. >

<

k SSTVD GR 1:2869 OOP gAPI

SSTVD

+>Diamond-14 [SSTVD] _ _ 200.00|-Vl0 CAU

iñ

ÍT]

_

RHOB

Z44 V4380*cm3 2.6620

I’ ( us/ft 300.00

*30.00

•ensitv

liper

4131.8

Well section tern

▼

Sonic

=

4200

1 ¡a

4300 4400 -i 4500 -

4600

m»r ni a

4700

m ti T I *I I—&*1 '

CALI (Continuous well log)

Show the selected item in tree

4800 M

4900 5000

5100

5200

5300

5400

I*

Send to Studio

rifll Retrieve from Studio

&

Edit global color table

. ..

{ |=]ft

Copy as derived log

1 ({=)

Copy continuous well log (data only)

\*

IJJ 1ÿ

Delete

Add to global template

Add to local template Log set

Guru

5500

5600

C7(W

11 . Identify the zones with spikes on the sonic log.

12. In the Log conditioning Tool Palette, click Selection

Petrel Geophysics

Condition input data for Seismic well tie •363

13. Click and drag the mouse to select an area around spiky sections in the DT track. If you double-click the track, the entire log is selected.

<

__ _

® Diamond-14

SSTVD ( GR C-LI 1:2437 0.00 gAPI 200.00-0.10 in

1:-=

: ::

::

3900 -j

RHOB

2.44

BÿBcaiioer

mma rav 3773.3:

SSTVD]

BÿB"Densrty |*HC= :

'30 00

>

DT us/ft 300 00 Sonic |DT 133.01

)

4000

0

4100

4200

■

4300

= — I»... 4500

l

-!

■

Tool Palette

W

Selptfíion * stag condit oning

x

R ?k Sx ll t r •? ST h «? *ui

4600 -j

4700

Domain

SSTVD (ft)

Start

End

3864.84

9126.80

Log DT

Well Diamond-1

Enable

0

Delete

0

Ü1

J

r 14. In the Log conditioning toolbox, click Eliminate

spike

364 •Condition input data for Seismic well tie

P* .

Petrel Geophysics

<

Note how the selected area of study can be affected by changing the parameters (Number of standard deviation, Spike analysis window, and Replacement method). 15. Continue until you are satisfied with the level of removed spikes.

I to remove the spikes.

£liminatc

16. Click Eliminate spikes

>

($> Diamond-14 SSTVD] SSTVD GR 1:1706 0.00 gAPI 3335

-

_ CAU

200.001 -0.10 (

imma rav

1

0

in Caliper

DT

RHOB

2.44"'.4380 3.'cm3 1.6623 |ÿH""DeñsitY

30.00

us.m

000.00

I Sonic

\

3900

4000

4100 Tool Palette

Eliminate spikes Log conditioning

tf R

Si

Ri|2|K

1

4400

i

Spike detection options:

'Number of standard deviation:

1.73

Spike ana ysis window:

1000

X

*<> n r •? ST H *‘U

F

-

Replacement method: Interpolate

samples

I Eliminate spikes

I

4500 -

K

17. After reviewing the complete sonic log section in line with key logs and despiking where necessary, click

Save modified logs Palette. Petrel Geophysics

E3 in the Log conditioning Tool Condition input data for Seismic well tie •365

1 22. Select the Min value and Max value check boxes and enter 30 and 300. [BJ

Settings for ’Well section template 3'

0 Info

Well section template -

Template objects

m £ s

Vertical tracks (6) 0|] Indextrack -

-

Q.

a ft

m

E

©

B

0AGR uY GR 0&CAU

0® CALI

a&RROB 0P RHOB

0ADT

I Lj|

a

Objects settings

Info

|y] Min value:

®

1

[~@ Definition 1~[ Limits | 4/ Style 30

a

Max value: 300

Direction:

Normal

□ Wrap:

Both

0At

- 0ÿ

DT Sonic Despked

l2)At Borehole markers Background Deviated tracks (0)

23. On the Style tab, choose Selected from the list next to the color section. 24. Choose a different color for Sonic Despiked and click Apply. 25. Highlight the Sonic Despiked log from the object list on the left side of the dialog box. Move it under the track that contains DT by using the blue arrow.

Petrel Geophysics

Condition input data for Seismic well tie •367

I 26. Remove the empty track, click Apply, and click OK. |S I»

1

'

- |tj* Well section tem

VI I'»

B3

Unde!

•

Llj

<

IE

B-B- Q

Settings for Wril section template 3'

Olnto R

>

-a

itm

0 Info

H L*'™15

[7,j Definition

♦' Style

a

h

m Show

Color

-

i-ii

Q.

m

E

3

ft

kiA Track

□ Show

Sold

a

*ÿ•1 Btest

'

H

Deviatedtracks (0)

•i

3

foa*

il

-a .

“»

03

“»i

¡¡ü™

03

|

031«.... -I nc*r mi*- -i

27. Save your project.

*

Review questions

• •

What are the main quality control steps for importing checkshot data? Name five major functionalities in the Log conditioning tool?

Summary In this module, you learned about: • loading and quality controlling checkshot data • defining time-depth relationships • using the Log conditioning Tool Palette

368 •Condition input data for Seismic well tie

Petrel Geophysics

I Module 7 — Sonic calibration <

In this module, you learn how to use sonic log and checkshot data to create a consistent time-depth relationship. In addition, you are

Q.

presented with some theoretical background about sonic calibration. jo

Learning objectives <

After completing this module, you will know how to: • calibrate a sonic log • select input data and parameters • define knee points and outputs

Petrel Geophysics

m

Sonic calibration •369

I

flf <

Lesson 1 — Sonic log calibration Calibrating the sonic log corrects the log velocities to time-depth data (typically checkshots) and accurately hangs the sonic log in time. A time-depth relationship can be generated from the calibrated sonic log. It is used as the preferred time-depth relationship for the well of study.

>

You perform calibration by increasing or decreasing the sonic slowness values slightly over sections of the log until the integrated sonic log travel times match the times derived from the checkshot survey. The mechanism used to control this process is termed Drift Curve (Figure 1).

Q. 3

Drift can be computed at every depth level and is defined as: Drift = checkshot time - integrated sonic time (Tcheckshot- Tlog)

<

usmt

93 33

_

Dolomite-BI [SSTVD]

L

133.0*1-29.40

fÜTMH

>

Checkshottime

ms Sometime

1796 5:

i

4000

©

6000

7000

8000

. 8729

m

o

© 21 \

£

Figure 1 Sonic times corrected to match checkshot times to obtain Drift curve

1 2 3

4 370 •Sonic calibration

DT Sonic TD curve Checkshots Drift: Sonic T - checkshots Petrel Geophysics

I If the drift curve is positive, the checkshot travel time is longer than the integrated sonic travel time, meaning that the sonic log is too fast. If the drift curve is negative, the sonic log is too slow. <

Q.

jo

Use calibration to define a drift curve that goes through the checkshot data that corrects the sonic log to the known travel time values that are derived from the checkshot data. The result is a calibrated sonic log (Figure 2).

>

There are two ways to apply the necessary corrections: • The differential correction method uses multiplication to shift the sonic log to higher velocities. The correction is applied as a velocity-dependent percentage, so that larger corrections are applied to the lowest velocity sections. This correction is based on the assumption that low velocity sections of the log are prevalent in poor borehole conditions and contribute heavily to transit time errors. • The linear correction method uses simple addition to shift the sonic log to lower velocities. This correction is based on the assumption that high velocity sections of the log are in better borehole conditions and make up only a small part of the transit time errors overall.

In Figure 2, the updated TD is converted to the calibrated sonic log DT_Calib.

Petrel Geophysics

Sonic calibration •371

Dolomite-B1 ÍSSTVDl 1 11450

>

< □

g

z □

0 r

2

Figure 2 Drift curve is added to the sonic TD curve; Sonic log + Drift curve = DT_Calib

Procedure — Calibrate a Sonic log using the SWT dialog box 1. File

On the Seismic interpretation tab, in the Seismic-well calibration group, click Seismic well tie. Home

Stratigraphy

'99 Managers

3

Seismic (default)

Houston_Restorat

D

As a minimum for the sonic calibration, a sonic curve must exist in the well. If one or more objects related to time-depth information (such as checkshots) are associated with the well under study, they are available from a list in the dialog box.

•

372 Sonic calibration

Setup

»

QQ

Seismic Interpretation

< > Seismic

well tie

Petroleum Systems

•yjy.

Wavelet toolbox

§§

Log conditioning

if E Insert

Well tie editing

Seismic-well calibration

Decisionÿ

»

Seismic interpretation

2D/3D interpretation

ft

The Seismic well tie dialog box opens.

Petrel Geophysics

B

O

2. In the Seismic well tie dialog box, select Sonic calibration as study type and select the well to use. 3. Select the default sonic calibration template. 4. Select the parameters on the various tabs in the dialog box. (These tabs are discussed in the next section.) 5. When you are satisfied with the parameters, click OK.

If no checkshots exist for the well, a checkshot object can be dropped in from another well. In this situation, you also can use a sonic or velocity log as TDR.

■pll Seismic well tie Q.

Seismic well tie 9

□I jo

El

Hints (Study 1) Diamond-14 Sonic calibration

Create study:

£ O Edit study: Type of study:

Well:

_| sfr |

TÜ Copy template: Input

Sonic calibration

Output

¿ Diamond-14

| Datuming | Time-depth | Options | Statistics

$

TDR:

c£>

At Sonic Despiked

-

©

Sonic calibration default template

Parameters:

At Sonic log:


|

a

©

c£>~] V) Diamond-14/AIICheckShots cs

»

T2

O Drop from other well

A Well section window opens where you can calibrate your sonic log (discussed later in this lesson).

Petrel Geophysics

Sonic calibration •373

I Input tab The Input tab (Figure 3) in the Sonic calibration study controls the input of sonic logs, checkshots, and the time-depth relationship (TDR). Checkshots are the most common TDR used; however, if this data is not available, integration of either the sonic and velocity logs is supported. The input options are available according to the selected well.

<

Input

[ Output | Datuming | Time-depth |

Options

| Statistics | Track manager

a

Parameters:

Q.

At Sonic log:

I I

TDR:

[ÿ]

At Sonic Despiked Diamon
▼

»

□ Drop from other well

Jo Figure 3 Input tab in the Seismic well tie process dialog box

Sonic log: Input sonic log that is calibrated. Velocity logs also are accepted. 2 TDR: Name of the TDR (usually a checkshot) that is used to calibrate the sonic log. If no checkshot is available for the well, you can drop in a different one from another well.

1

374 •Sonic calibration

Petrel Geophysics

>

1 Output tab

<

Q.

a

n

On the Output tab (Figure 4), you can control the output logs from the sonic calibration study. The Output tab has these options: • Calibrated sonic • Time-depth relationship (TDR) • Integrated sonic • Drift curve/TcmTI • Knee points • Knee curve • Residual drift Input | Output A

The Auto save option automatically saves any changes made to the output during the process.

| Datuming I Time-depth I Options I Statistics Track manager

) Calibrated sonic

Calibrated sonic:

A

Calibrated sonic

□

O Auto save

® Time depth relationship (TDR) TDR name:

Calibrated TDR Sample interval:

16 40

; ft

4IB

□ All samples

I’/; Autosave |

|Set as active TDR|

(v) Integrated sonic

® TcmTl (v) Knee points v

i

Knee curve

© Residual drift Figure 4 Output tab in the Seismic well tie dialog box

Petrel Geophysics

Sonic calibration •375

>

I The time-depth relationship (TDR) derived from the calibrated sonic can be used to convert the wells in time. In the Settings dialog box for the Wells folder, on the Time tab (Figure 5), there is a priority list for sources to establish TDRs. All possible velocity data sources that can be used to establish a TDR in the project are listed there.

<

For any given well, the TDR is established from the top of the list using only the selected objects (with a check mark). If the data object does not exist for the well, the process goes to the next object down. Q.

To rearrange the priority list, click the item that you want to move and use the up and down arrows to reposition it. Select the check box next to the objects to include them as a possible TDR source (blue check

3

mark). AA *

0

Settings for 'Wells'

® Info

Statistics

Itl

I Thickness

D

Lock calculated logs

Report

¡

Make logs

Simulation settings

Quality attributes

Lateral

Create new

O E<* existing

-

|ouT Oneway time

□ Apply to al wells

a

C From shared TDR:

®[ $ From velocity function

ffr]

(Study 1) Diamond-14 Sorec calibfation'Calibrated TDR

V

(5) h/tt □

tip

Some Despiked

-

(Study 1) Diamond-14 Sonic calibratior'/isual Calibrated sonic log (Study 1) Diamond-14 Sonic calibration Diamond_14.cs

AIICheckShots.cs

□ Manual adjustment ®

®[

Insert extra point at SRD If not covered

lag, ft»

| VAH» J I. V OK

|

K

_aJ I

Figure 5 Time tab in the Settings dialog box

The From shared checkshot option uses data from one well to establish time-depth relationships in other selected wells. Activate the option, choose a well from the Well filter of the available checkshot item, and insert “v* it into the dialog box.

The Manual adjustment option allows you to adjust the TDR manually based on Well tops. 376 •Sonic calibration

Petrel Geophysics

>

I When you click on Set as active TDR in the Seismic well tie dialog box, the output TDR derived from the calibrated sonic log is selected automatically on the Time tab only for the well of study. <

Q.

It is not applied to the other wells. It overrides the global settings for this well only.

>

Sample interval When saving or autosaving the time-depth relationship (that is, saving with continuous generation), there are options to set the sample interval of the time-depth relationship.

jo

Datumingtab Datuming is of key importance. By default, the Seismic well tie process picks up the project datum and kelly bushing of the currently used well. The kelly bushing (distance from Mean Sea Level) is returned as Elevation of sonic log depth datum. These options are used only if the project datum and Seismic Reference Datum do not coincide with Mean Sea Level.

Figure 6 shows the marine datum options on the Datuming tab. Figure 7 shows the land datum options on the Datuming tab.

Petrel Geophysics

Sonic calibration •377

Input

I

I

| Time-depth |

Output Datummg

Options

| Statistics ¡

Track manager

U

0 Land datum 9 Marine datum Checkshot

Log depth datum (KB)

depth cfetvm

<

v Vw Vb

Datum elevation

1 0

W

B *•:

%

ITIf

Checkshot time-zero (b):

0 00 ft

@| Use SRD

Output time (TWT) (c):

0.00 ft

□ Use SRD

Above mean sea level: Elevation of sonic log (a):

118 00 ft

Replacement velocity (Vr):

4862 20 ft/’s

Velocity (Vw):

Velocity (Vb):

Seabed

a a

0.00 ft 4862 20 ft's

a

Below seabed Depth of seabed (from MSL) (e):

_

a

Water layer

Elevation of water surface (d):

>

Tme datvm (SRD)

0 00 ft 4862 20 ft's

Figure 6 Options for Marine datums on the Datuming tab

378 •Sonic calibration

Petrel Geophysics

I Input

| Output)

Datuming

| Time-depth | Options | Statistics )

Track manager

a

| © Land datum | Marine datum Cheefcjhot

,log depth datvn (KB)

depth datum

<

>

,Trrw datum (SRDI

Vr

-jLllilfcjfcj

Q.

a

Datum elevation

3

ii

Checkshot time-zero (b):

OOP ft

g]UseSRD

Output time (TWT) (c):

0 00 ft

□ UseSRD

Above ground surface

<

Elevation of sonic log (a):

118.00 ft

Replacement velocity (Vr):

486220 ft/s

Weathering:

Velocity (Vw):

118 00 ft 7874.02 ft/s

a

Below weathering: Elevation of the base of the weathering (e): Velocity (Vb):

>

a

-

Elevation of ground surface (d):

a

118 00 ft 7874 02 ft/s

Figure 7 Options for Land datums on the Datuming tab

Datums and replacement velocities The process of bringing sonic log velocities into agreement with seismic velocities does not, by itself, guarantee a correct depth-time relationship. The logs also must be placed in the correct position relative to the seismic data before integration using datums and replacement velocities.

In the context of sonic log calibration and well-seismic tie, a datum is defined as the elevation at which a property is set (typically) to 0.0, in either the depth or time domain. The location of the datum is coaxial with, or directly above, the wellbore trajectory.

In most cases, a datum consists of a single scalar value. However, in some cases, a datum is derived from a surface with either a constant or variable elevation, which can be important when dealing with deviated wells (such as ground surface or water bottom elevation). Petrel Geophysics

Sonic calibration •379

I Replacement velocities, when used, cause static (vertical) shifts to seismic and other time domain data (checkshots, VSPs). These velocities bring a specific point in time (or some time domain surface) into alignment with some common elevation feature. This feature can be real (ground level) or arbitrary (3,000 m above MSL). These velocities can be constant (air-ground surface replacement velocity) or spacevariant (ground surface-based weathering layer replacement velocity).

<

Datum errors are a common cause of confusion when working with well and seismic data. A clear understanding of the datums is required to ensure that all necessary shifts are applied and that all data objects are properly aligned.

Q. 3

Alignment errors can result in mis-ties or erroneous phase estimations, which is true particularly when working with VSP data on land. The VSP acquisition and processing reports are crucial to understanding mis-ties and inconsistencies.

As described in more detail in the next section, many vertical shifts and artificial datums are used when processing seismic and VSP data. If the data is not put back in the right place, a residual (and often difficult to identify) shift is embedded in the data. Seismic reference datum Initial seismic acquisition and processing occur in the time domain, along with many post-processing analytical activities such as waveletbased inversion. A convention in the seismic industry is that processed seismic records begin at a time of 0.0 sec. This 0.0 time reference point must be associated with an elevation reference point, which is known as the Seismic Reference Datum (SRD).

In almost all marine and many land cases, SRD is set at a constant value - a flat surface. However, there are cases where SRD is a non-flat surface with different values at each seismic trace. For this case, you can define the depth at which the checkshot passes through time zero. This option is available when you clear the check box Use SRD.

380 •Sonic calibration

Petrel Geophysics

>

I Marine seismic In the marine seismic case, 0.0 time typically is adjusted to mean sea level (MSL) and SRD most often is set at 0.0 feet/meters above MSL. During processing, however, data often is realigned (static shifts are applied) to alternative datums, such as water bottom or gun depth.

Q. 3

If marine data appears to be 25 feet shallower than expected, ask the processors if they remembered to move back to MSL after processing at gun depth. If they did not, the data can be zero datumed at 25 feet below MSL. Similarly, data acquired in land-marine transition areas or very shallow water can be processed using datums related to tidal fluctuations during acquisition.

There are three common datum-related causes of alignment ambiguity between seismic and well data for marine cases: • Use of a constant (or linear trend) water column velocity. (This velocity is not valid in deepwater Gulf of Mexico, proximal offshore Brazil, and other areas where salinity changes affect water column velocity.) • Inconsistencies between log and seismic shallow velocity profiles. Often, no logs are available for a significant distance below the mudline. Linear trends frequently are substituted and often are incorrect and typically too fast. • Assumption that water velocity represents the lowest possible velocity. For example, the presence of biogenic gas in near¬ shore shallow deltaic or marsh sediments can result in velocities that are significantly lower than water velocity.

Petrel Geophysics

Sonic calibration •381

I On the Datuming tab (Figure 8), the graphic display changes according to the parameters. By default, the Seismic well tie process picks up the project datum, but you can change the parameters on this tab.

<

>

V,,.* 1480 m1% Mb * 2000 mJs

a Output fcm«(TWT)(c):

Q.

OOO ft

O UMSRD

000 ft

ElheSRO

11800 ft

3

7 -CtlKttHOt

a

a

ii

V, =2100 m/s

-a

1000m

V2= 2200 ml%

p

V-CMOM

-

V] 2400 m/s

7 -ClwtaM

Figure 8 Marine datum and its parameters selection in the Seismic well tie process dialog box

Land seismic (and VSPs) The land seismic case can be more complex because of surface topography and near-surface phenomena that are not present in the marine case. It also can be more severe in the land case.

In many areas, the irregular thickness and rapid lateral variation of near-surface layers, water table anomalies, and karsting cause velocity anomalies that cannot be characterized adequately in the seismic velocity model. As a result, time shifts (static shifts) often are present from one trace to the next, causing timing perturbations that affect deep reflectors. It is common practice to try to align the traces by making minor up/down shifts so that a reflector that appears continuous and smooth takes on this appearance. This situation shifts some traces in a way that moves them above the 0.0 time point into negative time.

Similarly, larger shifts occur when data is shot beneath a water body (lake, river) or other feature with velocities that depart significantly from the seismic velocity model.

Some geophysicists (and some software systems) do not like the idea 382 •Sonic calibration

Petrel Geophysics

I <

Q. 3

of negative time. The solution is to move SRD far above the point that any trace is reasonably expected to be shifted. Often, this solution puts SRD somewhere up in the sky, especially in mountainous areas where surveys are shot over large changes in elevation.

>

In West Texas, SRD often is set at 3,000 ft MSL, although ground level often is closer to 2,300 ft MSL.

In this case, the thickness of the air gap between the SRD and the ground surface is used to compute a replacement velocity so that the first live sample on the seismic trace is located at the surface. Any subsequent static shifts are small enough that data remains in positive time. A similar situation occurs with what is known as the weathering layer. This layer is the region between the ground surface and the portion of the seismic that the geophysicist can understand. The time thickness of weathering layer velocity anomalies is estimated and weathering statics are applied that compensate for the associated timing shifts. These weathering static shifts must be taken into account when trying to align land seismic data with VSP traces that typically DO NOT have weathering statics applied. In most cases, land VSP and checkshot data are datumed (0.0 time set) at the ground surface. In areas with elevations relatively close to sea level, the data can be datumed beneath the ground surface at MSL. With third-party contractor data libraries, checkshot data is datumed at some arbitrary subsurface elevation. For example, in West Texas, this elevation is 1,000 ft MSL.

This means that 0.0 time for VSPs and checkshots often are at a different elevation than 0.0 time for the seismic data. In cases where this datum elevation is below ground level, a VSP/checkshot replacement velocity often is computed and applied so that 0.0 time is shifted to ground elevation even though the data remains positioned correctly in the subsurface. Figure 9 shows Land datum and its parameters selection in the Seismic well tie dialog box.

Petrel Geophysics

Sonic calibration •383

a

•

Land datum Marine datum Chackshot Otcund

<

KB ■ 20m above ground

Ground!

r Time datum ISRM

Vr

Weathering layer

■ 1000m

Vw = 1800 fTl/S

>

Ba*e of

..ill! kliL Datum elevation Chcckshot time- zero (b)

000 ft

□ Ute SRD

Output tona (TWT) (c):

0 00 ft

□UaoSRD

Aboveground surface

Elevation of sonic log (a):

11800 ft

Replacement velocity (Vr)

1115 00 ft/s

Elevation of ground surface (d)

3280 00 ft

Velocity (Vw)

5905 00 ft/s

Below Weathering layer

a

a

Below weathering Elevation at the base of the weathering (e)

1312 00 <1

Velocity (Vb)

5890 00 ft/s

-3RD «-400m

a

a

[•1

m 0

Va = 340 fTl/S A

,100 depth datum (KBI

depth i

Sietsce

Above surface replacement

,

T(JP

I 1

Vw = 2100 ITl/S

-Choctohot -200m

v -CftKttfiet

M3L ■ Om

Vi = 2300 m/s V -Chackabot

900m

V, = 2500 m/s V -Choetahot

Figure 9 Land datum and its parameters selection in the Seismic well tie process dialog box

384 •Sonic calibration

Petrel Geophysics

B Seabed : Water velocity With the seabed and the water velocity options (Figure 10), you can include a new data point (time-depth pair) into the checkshot survey. :

<

>

■

Q.

a jo

'1

.

.

—

=

-4

* «

*

:

r

Water layer Elevation o? water surface (d) Velocity (Vw)

0 00 II 4862 20 ft's

Bekr* seabed

Depth of seabed (from MSL) (e):

Velocity (Vb)

60000 II 486220 Its

Figure 10 Seabed not taken into account (left) and seabed taken into account (right)

Petrel Geophysics

Sonic calibration •385

Time-depth tab The Time-depth tab tab (Figure 1 1 ) is divided into three main sections: • Checkshots and interpolation above TOL • Top of log time • Below of log time. This tab works with the Datuming tab to control how checkshots are used above the top of the log (TOL). It allows you to control how time values are derived and which interpolation method is used.

<

[•]

Input

Output

Datuming Time-depth

I Options |

Statistics

Track manager

All depths in this tab are measured from KB in TVD

0

a

Checkshots and interpolation above TOL Checkshots threshold depth

Just above shallowest checkshot

Interpolation type (time)

Linear

Velocity to use at start of interpolation:

Calculate automatically

Interpolation velocity at top of log.

Calculate automatically

;

■

a

Top of log time

© TVTc

■

0 at the first checkshot sample after the top of the sonic log (TOL)

o Interpolate between the two closest checkshot samples at TOL for Tl-Tc = 0

© Two-way time at the top of sonic log:

122349

a

Below of log time Maximum TVD of output time/depth

0 00] +1500ft

Below sonic replacement velocity:

0 00

m Default

Figure 1 1 The Time-depth tab in the Seismic well tie dialog box

386 •Sonic calibration

Petrel Geophysics

>

I Checkshots and interpolation above TOL This section gives you control when working with checkshots above the top of the log, that is, above the first measured sample of the log. <

These options establish how far above the top of the log (first sample of the log) the checkshots are used to define the shallow interval velocity trend.

>

Checkshots threshold depth This field can be set to one of several predefined values or entered manually if you select User from the list. This field controls the boundary between the values calculated on the Datuming tab and the values calculated from the checkshots.

Q. 3

<

Above this depth, the output time-depth is calculated from the Datuming tab. Between the Checkshot threshold depth and the Top of sonic log (TOL), the checkshots are used. Depending on the value selected, the settings on the Datuming tab are not used.

>

You can select one of these predefined values for the Checkshots threshold depth field: • Only use checkshots: The interval velocity trend comes entirely from the checkshot. above shallowest checkshot: The interval velocity trend Just • comes from the Datuming tab down to a point just above the shallowest checkshot point. From that point downward until the top of the sonic log, checkshot velocities are used. • Up to sea surface (for marine)/Up to ground surface (for Land): The interval velocity trend comes from checkshots up to sea surface in the marine case, then the values specified on the Datuming tab are used. Up • to sea bed (for marine)/Up to base of weathering (for Land): The interval velocity trend comes from checkshots up to sea bed in marine case, then the values specified on the Datuming tab are used. • Do not use checkshots above TOL: The interval velocity values specified on the Datuming tab are used regardless of the checkshots. • User: User-defined threshold depth value to start using the values specified on the Datuming tab. Petrel Geophysics

Sonic calibration •387

I Interpolation type (time) The interpolation type between the lowest datum layer and the first checkshot sample or top of log can be set to Linear, Quadratic, or Cubic spline.

<

The fields Velocity to use at start of interpolation and Interpolation velocity at top of log are available only for the Cubic Spline method. For these fields, you can select Use datuming velocity or Calculate automatically. Q. 3

Top of Log time This section controls how the time for the top of the sonic log is calculated. It has these options: • Tl-Tc = 0 at the first checkshot after the top of the sonic log (TOL): This calculation is the time of the first checkshot sample below the TOL minus the time integrated up the sonic log from this depth to the top of the log. • Interpolate between the two closest checkshots at TOL for Ti-Tc = 0: The time at the top of the sonic log is calculated by interpolating linearly the two closest checkshot samples to get the corresponding sample at the same depth at the top of sonic log. • Two-way time at the top of sonic log: When checkshots are not available, this field can be used to set the two-way time to the top of the sonic log. The time is measured from the Output TWT Datum. You can use this option when checkshots are available to set this time manually.

388 •Sonic calibration

Petrel Geophysics

>

I Below of Log time

<

Q. 3

This section controls how the time/depth curve is calculated below the bottom of the log. It has these options: • Maximum TVD of output time/depth: The maximum TVD to use for the output time-depth. The time-depth is extrapolated using the Below sonic replacement velocity. +0: • Use the maximum depth of the sonic log or time-depth. • +500 m (+1500 ft): Add 500 m (1500 ft) to the maximum depth of the sonic log or time-depth. +1 • 000 m (+3000 ft): Add 1000 m (3000 ft) to the maximum depth of the sonic log or time-depth. • User: Enter a maximum depth. • Below sonic replacement velocity: The velocity to use when extrapolating the output time-depth below the sonic log. You also can select the option Default (by default, set the replacement velocity to the velocity at the bottom of the sonic log). In Figure 12, Figure 13, and Figure 14, you can see the effect of the various interpolation options above TOL. D;ar-ond-14

>

B

[SST\'D]

/o».

4862ft/s

I

a

V**

-a

ffl la—lawal

-

T|

6000H/S

J

0

Drift

DT

V-CS

Velocity (Vw):

Below seabed

J

V 486220 ft/s

-

Depth of seabed (from MSL) (e):

Velocity (Vb):

60000 ft 6000.00 ft/s

Figure 12 Cubic Spline interpolation method above TOL (time of first log datum) Petrel Geophysics

Sonic calibration •389

In Figure 13, the Quadratic interpolation method is used above TOL (time of first log datum). For this dataset, the Quadratic interpolation method is not flexible. Diamond-14 [SSTVD]

<

-155

’

Calibrated sonc ms 14 20 5000 osffi 250 00 TcmTl

500 00 1b> 9 000 00

: a«aw

>>ai veioct.

4862ft/s

a

HC

>

V Cahb

Interval velo cty 4

I

6000ft/s

a

i

/

•

CNwaar Eat Mr

(54
d

TfTenMe S (Sfady 1) Damond-14 Sane < | Swot > Owon*|¿ ** i

kVU | OutBU

I kan KB

•ooe

■

rucfc

TVO

a

I TOL

H

■*K

Vetoed* lo WM ■ ooort <4 <

m M0C

aoe

a

T«a«n«aM O TWTc •0 « *># «nt

-o

)

©

o o ©

o Drift o

R

DT

V-CS

■>

b

m

'

i

i

: to9 (TOO

o4or *<•»09 of tm I

IMTatotTVTc-0 Too —y Oma otto lop oft

:to«

177349

B— n. odogm

HMwTVOriMill

•isoc* J

a

.

Mu*

V I 4862 20 ft's

Velocity (Vw):

Below seabed Depth of seabed (from MSL) (e)

Velocity (Vb)

600 00 ft

6000 00 ft*

| V 499»

II V

OK

][* CandJ

Figure 13 Quadratic interpolation method above TOL

390 •Sonic calibration

Petrel Geophysics

B In Figure 14, the Linear interpolation method is used above TOL (time of first log datum). The Linear interpolation method CANNOT take into account the velocity below the seabed (6000 ft/s). Diamond-14 [SSTVOf

<

*<

> Mr1)IWUStK<

4862ft/s

I

Q

T„.otMr

lDm~+U TfTiwpMi

»u«*<

t*

6000ft/s

•a

gB>idr1)DwwM i

a

Q.

0

id

Tecrftoa«m*

.«-cwaou

jo

■ MTOIIMTVTC.O

!»•

<

o o

a

>

❖ O

«

Drift

DT

V-CS

Velocity (Vw):

4862 20 ft/s

Below seabed Depth of seabed (from MSI) (e):

Velocity (Vb)

600 00 ft

6000 00 ft/s

I*

«ÿ»

II <

<*

*

Figure 14 Linear interpolation method above TOL

Petrel Geophysics

Sonic calibration •391

I Options tab The Options tab (Figure 1 5) allows you to define how knee points and residual drift curves are interpolated. <

Input | Output | Damning | Time-depfh | Options

>

[ Statistics| Track manage» |

a

Automatic adjustments Knees:

a

Cubic

Polym

Q.

Residual drift

Linear

Interpolations

Residual drift

3

I Linear [Cubic

ii

Figure 15 Options tab in the Seismic well tie process dialog box

The tab has these fields. Knees Set the type of function that is used to interpolate the knee points. The interpolation function can be set to Linear or Cubic. The Polynomial fit function is recommended when the checkshots are used to calibrate sonic that is noisy.

This correction smooths the differences between checkshot (time-depth) pairs and the integrated sonic log, estimating a polynomial drift curve to honor the knee points without fitting the noise. Residual Set the type of function that is used to interpolate the residual drift. The interpolation function can be set to drift Linear or Cubic. Refer to Figure 16, Figure 17, and Figure 18 for examples of the various interpolation options.

392 •Sonic calibration

Petrel Geophysics

B hamood-14 Sonic calibration [TVD]

fl SMIAK wHI tw rÿOmÿUSoici

(SMv 1) OmmcntU Sene ctfknfton

J

Ttvarfi

<

Tfj *4>nfM*

*9* 1 Owl P«—

ITM im* ;

a

a

.

>

B

-•

a

c V /

Q.

0

in

mu:

■

NH

..

jo

i.

/IUJ

m

m -

,

?UK

ni

(

y *» it'

Figure 17 Interpolation in knee and residual points using the Cubic function Sonic calibration •393

Petrel Geophysics

i

J T|1

Ei

1 IISUMIC

:

’S)

a a

/

3

<

>

V

/

,

'-i'-:

in

{

H

'ÜSMMCMII*

«amond-14 Some calibration (TVD]

O C (Si* i> OMMM-14 SOW «HéNMH

a V*

J,0Hman*M

■(SMyt)Dn. , ton1 Punt iPanaw iTaitna i T|T«n*l.

EE

la—mlTwn— 2

—

■

I

m a a

Uu 5000

••» >

MOO MOO

\

■M..MOO

”«• 0200

•

0000

111*

2000-

bmo

2000-

pi±

SOL

r* ™

rFigure 18 The Polynomial fit estimates a polynomial drift curve to honor the knee points without fitting the noisy checkshots

[function

drift

lint Vallfl Int Vel

I

input

[I

output

b D~i! function

drm

br_

lini I

ni M ini ii»i

input

| I

output

/

Int.Vef output

!

3

)

Cub,,

[iñtVeil l input I

RMMMI Drift drift DT function

4p

polynomial

1

Figure 19 Comparison of different methods for modeling the drift curve

394 •Sonic calibration

Petrel Geophysics

Petrel Geophysics

Aa

©

I <

Q.

Statistics tab On the Statistics tab (Figure 20), the depth and time of the first sample of the log is known as Top of the log (TOL). This tab has these fields: • Depth reference (DREF): Displays the MD and TVD values of the top of the sonic log. • Time reference (TREF): Displays the two-way time calculated for the top of the sonic log. How this value is calculated is

>

defined on the Time-depth tab. Click Save to save this information as a log.

3 Input | Output | Datuming

| Time-depth | Options I

Statistics

I Track manager

Top of the sonic log (TOL) Depth reference (DREF) : 3983 00 MD

Ü

3982 84 TVD

Time reference (TREF): 1223.49 TWT

TREF

@

Figure 20 Statistics tab in the Seismic well tie dialog box

Sonic calibration study template After defining the inputs and datums correctly, click Apply in the Seismic well tie dialog box. Automatically, some output data is created virtually (but it is not stored yet in the Input pane). Also, a Well Section window opens with a default template, showing the tracks described in Figure 21.

Petrel Geophysics

Sonic calibration •395

1 TVD

•

g (Study 1) Diamo

*

H, ft VtI I">

Undef

0 Diamond-14 [TVD] dnfl

~U20

1 14733 •185

<

, Average v#k>c*y 4 T

' j 4>j

147 00

u«/fl

0

T.'. T p eked , me 2,686 97

24 00 1.369.95 ft/a 28.150 73 14.606 66 ft/'* 9W 50 1800 02 ft/s 7 560 54 •244 27

o o

2

©

o r

Q. 1492 1

5000

4

:

©

a 1741 7

■

5

: r

1979 4

o o

o o o

o o

o

o

8

3 o o

O

©

- -6000

:-7000:

o

o

o

o

o

o

o

o

o

o

o

o

o o

o o o o o

2208 3 •-8000; r

2427 4 (2503 6)

9000; I,,»,,:

>

o

o 12282- -4000-

ft

1

9574 30184;

o

o o

o

o o

0

o o

o

o

o

o o

o

o

o

o

III

Figure 21 Well section window showing these tracks:

1

2 3 4

5

6

7 8 9

396 •Sonic calibration

Checkshot Initial knee point (Blue) Drift (Red) Residual drift Original Sonic (Red) / Calibrated Sonic (Blue) Output interval velocity (RED)/ Input interval velocity (Blue) Two way time of TDR used as input Interval velocity of the TDR used as input Average velocity of the TDR used as input

Petrel Geophysics

I Checkshot, drift, and knees

<

By default, this track contains checkshots and a proposed drift curve. The red line is made as a 2-point straight line from the start to the end of the well data.

>

To edit the drift curve, you can insert knee points interactively.

Q. 3

The drift curve is derived by integrating time values from the calibrated sonic log. In other words, the drift curve times quantify how much the sonic log is corrected. The drift curve is used to adjust the overall time-depth relationship of the sonic log to the checkshot data, while retaining the high-frequency data from the sonic log data. Because the drift curve represents a relationship between the checkshot values and the sonic log, any edits to the checkshot also update the drift curve.

The reverse, however, is not true. If you edit or change the drift curve, the checkshot is not updated or changed. The horizontal axis is the difference between Tc (Time from Checkshot) and Tl (Time from sonic log integration). Residual drift The difference in time between the checkshot and drift curve is the residual drift (curve). The closer it is to zero, the more accurately the sonic matches the checkshot.

If the residual drift curve does not deviate from the zero line, it means that the log times are fully consistent with the checkshot times and the drift curve coincides with the checkshot points. Two-way time and input velocities

This data is derived from the input checkshots.

Knee points The Petrel Sonic Calibration workflow includes the ability to edit a knee curve interactively based on checkshots. The knees can be added at specific locations (using well tops, for example). You can view the calibrated sonic log while editing the knees. It also is possible to redefine the datum in the process and specify the outputs after calibration. Petrel Geophysics

Sonic calibration •397

Procedure — Use the Seismic well tie Tool Palette 1 . On the Seismic interpretation tab, in the Seismic-well calibration group, click Well tie editing to launch the Seismic well tie Tool Palette.

<

File

Home

m

■

Managers

]

Seismic Interpretation

Stratigraphy

sa

Seismic (default)

Houston.Restorat

QQ

Setup

m

Seismic well tie

Petn

Wavelet toolbox Log conditioning

Well tie editing

Seismic-well calibration

2. From the Seismic well tie Tool Palette, you can access a set of tools to manipulate the knees.

1 ¡a

3D grid Completions design

_] Edit fault properties

>2

Facies

'2 ¿2 ?ii

Fault model

fH

Geopolygon editing

<3

Geobody interpretation

Geomechanics tools tog conditioning

Mesh editing Microseismic Pad editing

TodPaMt*

¡33

Edit mode

* Seismic weH tie

3s if 2 3 T: > 4- $ £ E

:: rl

Point editing

¿2

Polygon editing

£2

Prestack seismic

hfi

Q1 tools

i W\

Seismic well tie

Seismic interpretation Stratigraphic chart editing

&

Surface editing

12

Well correlation Well design

12

398 •Sonic calibration

X-section editing

Petrel Geophysics

>

I This figure shows the tools that you can use to edit knees.

»

Select

© ©

Seismic well tie

■3

Ss

*1 /E3

'E3

s4" 3 ¡3

j¡4-

@

i Is 31

©

Q.

1 jo

▼

2 3

4 5

Edit mode Knees at checkshot Knees at markers Delete knee point Delete all knees

3. Edit the drift curve by interactively inserting, moving, or deleting knee points. Click Edit mode in the Seismic well tie Tool Palette and use the left mouse button to edit the drift curve. You can create knee points at checkshots or at well tops (markers). In the figure, the positions of the well tops have been used to create knee points.

Petrel Geophysics

Sonic calibration •399

Before you can use well tops, they must be displayed in the Well section window.

|& k TVt)

TWT

.1 90

:

l»ll

|*n—

1

¡jf

(Study 1) Diamo

& 1*1 V 8 I10

*

üs

602 147 00 us/n Sonic

-

I" :

«ÿ

*

■

:i: :c

-ÿ

o

o

o

o

o

o

o

c

o

5

8

o

o

f

t

■o


- - 9000 -

-o o o o

tr»*

o

«

22*»

Select Seismic wen tie

¥] > - - *000 -

400 •Sonic calibration

Petrel Geophysics

0

u

o o

Ü >ÿ

o

o

o

o o

o

o o

o o

o

o o

9

o o o

Tool Palette

1ÿ

*

2*3I

o

o o

■

- 8000

-ÿDALLAS

§

- - «00 -

- - rooo

-

o o

*J

%

r O

- - *000 -

t?«i*

M>tw(

TJ


*

»

intefvalverocly LtAvefaoev rel="nofollow">clc«4-, »M r 4,607 ft/s 9 688M 7» M«f» 7 340 59

24 00

—

M

Undef

.

Residual dnt

14X1-3 34

ms

rimn 1 314

939 6 ?999 3

'•]

*

jUiCt.wwwi 1

TgfTl-X;

1 Man

TVD

X

& P 5?

»+ $ a■

HOUSTON HOUSTON BASE

■0KOBE

o o

o

o

o

o

o

0

9 0

0

o

o o

o

PARIS PARIS BASE

o

Petrel Geophysics

Aa

©

ITg

I Customize the template display settings The display settings (Figure 22) can be changed in the well section template Settings dialog box for all data: sonic, calibrated sonic, residual drift points and curve, checkshots, knee points, and the drift curve. Settings for '(Study 1) Diamond-14 Sonic calibration'

O Info [ [®

Well Mctwn template

L3

Template objects

Q.

(Ü &

3

l

Vertical tracks (a)

I -

@Q

Info

SSTVt Index track TcmTl (SWT) TcmTl (SWT)

El Show

Limits

V Style

a

Color

Selected

© Some Deepiked/Catbrat

I!

lOjitp Calibrated some log

laj

[Jj Definition

Line

± ffl

0

-a

Objects settings

0A

Input rterval vekxdty y* input rterval vstoat y* Output rterval vekx a Hetval vdodty (AtIChec EIÿHenral vetoed (AK Average velocity (AKhe E 0 Average velocity (AH VIA TWT picked (AtOieckS TWT picked (AK>e -

✓

ivifl

- Sold

Une type

Sonic Despiked

Block type:

a

■

Porta

® Show Port sue

5

A 0v*H

Background

Deviated tracks (0)

O Orele

a

Bade

©

Automatic Specified

□ • Bto

□•

-

N

| /Aw» | [

O*

Bta

lOv

No.

v' OK

] IÿCencet

|

Figure 22 Display settings can be changed in the Well section template

You can change the minimum and maximum values, the colors and sizes of the curves/points, and the type of line (dashed, solid). It also is possible to use additional logs or modify the order of tracks. The Well section window template settings (Figure 22) control the order of tracks. The overall display, with auxiliary logs, can provide the interpreter with many pieces of additional information. In addition to the residual drift, you can identify lithologic changes from the gamma log, washout from the caliper, and velocity abnormalities from the interval velocity log. Petrel Geophysics

Sonic calibration •401

Aa

IT8

I When the time-depth relationship is output, you can display the interval velocity derived from the calibrated sonic and quality check the output. See Figure 23. 4' i

<

M4 [TVD1

>

ICO

: Q. 3 «0ÿ

: <

m

I \ t>r

;«

L e

■

:>

t>- :

w

&Z-

m

IIr v

í-

i Figure 23 Use additional logs or modify the order of the tracks

402 •Sonic calibration

Petrel Geophysics

I Lesson 2 — Sonic calibration through the Global well logs folder <

Q.

jo

The approach available in the sonic calibration workflow of Seismic well tie allows you to work with only one well at the time. You can use the method described here to calibrate multiple wells simultaneously.

Procedure — Calibrate multiple sonic logs under Global well logs 1. Right-click the Global well logs folder in the Wells folder and select Create corrected sonic log. 2. Click on the Settings tab and select the uncorrected sonic log from the list. 3. Insert the required checkshot data. 4. Define the correction curve using Least squares polynomial (orange curve in Figure 24) or Cubic spline (blue curve in

SI >

m

Figure 24).

Petrel Geophysics

Sonic calibration •403

““ Input i

*A0 Weis -I- □ Gkobahve!ha

&

Log aorta

0ÜCAU

£ □ OLD R« □ CUM

<

R$ □ CSFL
*n Q NPHI □ PHIT P r I I RH08

Calculator

55

Log attributes

[aj

Export multiple Items

Expand (recursive)

Sort by names

y*|

sort by property templates

./< “ IP

j

Bi D OwT I

Sorsc Desi (Study 1)C

Style

Histogram

©

Auto name all (recursive)

C©

Info

Uncomected sonic log:

At

Use checkshots:

«V>

DT AJICheckShots cs

Correction curve

0

3 Order:

9

3

Cubic spline

Delete empty global well logs

Insert 0lobal

Settings

calculated logs

é Least squares polynomial

Auto color all (recursive)

(cont>

Insert 0,obal 20 w<11 *°Q (cont)

Insert global time senes log (cont)

I One-wav

Statistics

* Lock □

$[

>

Settings for Corrected sonic 1'

1

...

*\

Q OamondJ Q

At

At

z-

□ SP

>

Delete content

y£ [¿x]

Fra □ VCl RM U SN

H

§

A i Sort by property templates/name 51 ‘SortOyZ-v'ÿ

RDDRT R»QSFLU

:Í7

Subscribe

<*»»»*«>*»«

«»ÿ10

«i

*«in®s

§¡¿|

Insert new folder

Rn □ ILM

E:

__

&

Insert global well log (disc)

4

Insert global time senes log (disc)

(=)

Insert global comment log

£

Insert global combined log

At

-reate corrected son»c log

Al

Create acoustic impedance Insert estimated global log .

(?)

..

Make log(s) static Make log(s) dynamic

Insert new time folder

BP BP &

Insert new derived discrete log

*{&

Insert global raster log

Insert new derived continuous log

✓ Apply

✓ OK

A Caned

Insert new derived seismic log

Guru

404 •Sonic calibration

Petrel Geophysics

I Well calibration

<

Q. 3

The sonic calibration aligns the derived sonic times to the time values from the checkshot data. This alignment removes drift in the sonic log by adjusting the correction curve to the data points. The Least square polynomial correction curve option fits a smooth curve to the data without matching the points exactly, which results in a residual error.

>

The Cubic spline option matches the checkshot points exactly (marked as green horizontal lines in the well section in Figure 24). There is the risk of creating artificial reflectors in a final synthetic trace if the trace is generated. !'!ri

Least squares polynomial

-~ 1

Cubic spline

1

* m

B

=

\m

_

Figure 24 Drift curves and adjusted velocity logs

Petrel Geophysics

Sonic calibration •405

I

m

Procedure — Quality check the Sonic log calibration The correction curve used to fit the drift points can be modified for individual wells. Often, some wells require a different fitting algorithm to approximate the drift points properly. 1. In the Input pane, navigate to the Well logs folder of an individual well and open the Settings dialog box for the Corrected sonic log. 2. Open the Settings tab. 3. Select the Override global settings check box. 4. Select a polynomial function of a different order or a cubic spline function. 5. Check the result in the Well section window.

<

Q. 3

Input

SI Diamond-14 * zta |Wetbgs

lei 4

P

at

Y RD Rn

*n

CALI CILD DPHI DRHO OT GR ILD ILM NPHI

Rp

PHIT RHOB RT

R»O

sau

7»*

SP VCL Sonic Despiked (Sudy 1) Diamond-14 Some calibration Oneway time 1[active] Corrected sonic 1

P

Fra

At

K 0i¿

At

At

Settings for 'Corrected sonic 1'

hi. «

Histcc-e-

|A

'"«o

People

Settings

Statistics

I B Lock calculated logs Uncorrected sonic log: Use checkshots:

At

Sonic Despiked

[HFI Hi AJICheckShots cs

Correction curve

a Least squares polynomial [V] Order

9

© Cubic spline The above settngs are local to wel Otomond-14.

m

3 Ovemde global settings

|

406 •Sonic calibration

[5

V AH»

II

✓OK

I [* Caned

|

Petrel Geophysics

>

I In this figure, the drift curve (black) and the fit curve (red) are shown together in the fit curves track with the calibrated sonic log (second track). •14 ÍSSTVD]

':

"

1

3000

Q. 3

- -0

e-

0-

ii ■0 0" "

00(+>

I ut'E

1

■0 ®-

jfff -0

0>

3X

i

4 J B2

" -0

Exercises — Sonic log calibration Generally, sonic logs are preferred for building velocity models because, unlike checkshot data, they are more densely sampled. However, using the original sonic logs directly delivers incorrect velocities for seismic data conversion because they typically lack data in the upper part of the well.

Sonic logs are measured in a different frequency range than the seismic data (dispersion). They can contain cycle skipping or extreme spikes that accumulate as incorrect integrated time values through the well length. As a result, they must be calibrated with checkshots before velocity modeling.

406 * Petrel Geophysics

Sonic calibration •407

1 0

Exercise 1 — Calibrate a Sonic log using the Seismic well tie process and establishing a time-depth relationship Sonic logs that are calibrated with checkshots as part of the synthetic generation process give a more accurate time-depth relationship. This data can be saved and used later in the time-to-depth conversion. In this exercise, you use the Seismic well tie process to calibrate a sonic log and establish a time-depth relationship. 1. On the Seismic interpretation tab, in the Seismic-well

<

>

IB

Q.

calibration group, click Seismic well tie

□I Seismic Interpretation

Petroleum Systems

<

3

Seismic well tie

IS Log conditioning

Insert

Well tie editing

interpretation * 2D/3D interpretation

Seismic-well calibration

2. 3. 4. 5.

n

The name of the study is updated based on the name of the well that you select. You can change the name of the study.

m

4

Mesh editing

Seismic ■

Mesh

.

Structural Modeling

Decision Support

®í Ü

jfr Wavelet toolbox

Seismic well tie

|

Volume attributes

r,|

Property Modeli

:! QH] Mixer

,

5**

Surface attributes

Calculator

>

Neural net

Attributes

In the Seismic well tie dialog box, click Create study. In the Type of study field, choose Sonic calibration. In the Well list, select the well Diamond-14. In the Input tab, make these selections from the lists, as shown in the figure: • Sonic Despiked for Sonic log • Diamond-14/Diamond_14.cs for TDR.

I I» Seismic well tie Seismic well be

[~H¡ñis1

# Create study:

(Study 1) Diamond-14 Sonic calibration

O Edit study

| Type of study: |

Sonic calibration

ffl A

Diamond-14

Sonic calibration default template TQ Copy template: Input |Output | Datuming | Time-depth j Options | Statistics )

Parameters: Sonic log:

TDR:

408 •Sonic calibration

[ifr c£>]

Track manager

TB

a

At Sonic Despiked Diamond- 14/Diamond_14 cs

□ Orop from other well

Petrel Geophysics

1 6. On the Output tab, observe the different output options. Select Auto save to save all changes in the Input pane automatically and update the output in real time. If you use this option, you do not have to save the study every time you adjust the parameters. 7. For the Time-depth relationship (TDR), select the Auto save check box and click Set as active TDR.

<

'

Q.

a

|i Seismic well tie Seismic well tie

!'

Hints1

•Create study:

□I

>

(Study 1) Diamond-14 Sonic calibration

O Edit study Type of study

Q

\ Wed: <

TB Copy template: Input | Cutput

Sonic calibration

A Diamond-14

-

Sonic caibration default template

[ Datuming ] Time-depth | Options | Statistics

Tl

Track manager

@ Calibrated sonic Calibrated sonic:

Calibrated sonic

□ Autosave (
TDR name:

¿

Calibrated TDR Sample interval:

16.40

~ ft

a

□All samples

17 Auto save [Set aa active TDR||

© Integrated sonic © TcmTI ( v Knee points

© Knee curve v

Residual drift

Petrel Geophysics

Sonic calibration •409

8. On the Datuming tab, the entries are filled in automatically from the project and well settings. Using the Seismic reference datum (SRD), the Seismic well tie process in Petrel automatically assumes offshore data for SRD=0 (Marine) and onshore data for other SRD values (Land). Datuming is key here. All settings are correct. Do not change the parameter values; keep the default parameters as they are for now.

<

rJI Seismic well tie Seismic well tie

Hints (Study 1) Diamond-14 Sonic calibration

9 Create study:

f

1 ¡a

C Edit study: Type of study:

4k

iÿJ

Wei:

TU Copy template: Input

j

Output

1

Sonic calibration

*

Diamond-14

-

Sonic calibration default template

Datuming

¡ Options

j

Statistics

Track manager

a

0 Land datum 9

TS

Marine datum Checkshot

Log depth datum (KB)

depth daturnÿ

Time datum (SRD)

Vr

Vw Vb

Datum elevation

,b

■!

ii

ira

Checkshot time-zero (b):

OÓÓ|

ft

g] Use SRD

Output time (TWT) (c):

0 00 ft

□ Use SRD

MSL

Seabed

a r

a

Above mean sea level:

Elevation of sonic log (a):

118.00 ft

Replacement velocity (Vr):

4862 20 ft/s

Water layer

a

—

Elevation of water surface (d): Velocity (Vw):

0 00 ft

4862.20 ft/s

a

Below seabed: Depth of seabed (from MSL) (e):

0.00 ft

✓ Apply

410 «Sonic calibration

|V

OK

||

* Cancel |

Petrel Geophysics

>

9.

<

Open the Time/depth tab. On this tab, you control how checkshots are interpolated above the Top of the log (TOL). These options define how far above the top of the log (first sample of the log) the checkshots are used to define the shallow interval velocity trend. It is possible to extend the time-depth output below the log by using a sonic replacement velocity. For this exercise, use the default parameters.

>

1ÿ1

PJI Seismic well tie Seismic well tie O

1 ¡a

Hints (Study 1) Diamond-14 Sonic calibration

Create study:

J O Edit study.

<

|ÿ| ¿ Diamond-14

T&j Copy template : Input

a

Sonic calibration

Type of study:

4ÿ Well:

▼

- TS

Sonic calibration default template

I Output I Datuming]

Time-depth

Options

I

Statistics

>

Track manager

All depths in this tab are measured from KB in TVD

a

Checkshots and interpolation above TOL 0.00 I Just above shallowest checkshot

Checkshots threshold depth: Interpolation type (time):

Linear

Velocity to use at start of interpolation:

Calculate automatically

Interpolation velocity at top of log

Calculate automatically

a

Top of log time

O Tl-Tc = 0 at the first checkshot sample after the top of the sonic log (TOL)

# Interpolate between the two closest checkshot samples at TOL for Tl-Tc = 0

© Two-way time at the top of sonic log

1223.49

a

Below of log time Maximum TVD of output time/depth

Below sonic replacement velocity:

0.00

[

0 CD

j +1500ft

V. Default

✓

Petrel Geophysics

Apply

~|

✓

OK

A Cancel

Sonic calibration »411

1 0. On the Options tab, keep the Knees and Residual drift fields set to Linear. Iÿl

rJI Seismic well tie <

>

Seismic well tie | Hints

o Create study:

f

(Study 1) Diamond-14 Sonic calibration

© Edit study: Sonic calibration

Type of study:

c£> ¿ Diamond-14

4k Well: TÍ] Copy template:

0

Input

¡3

Output

Oatj-ning

Automatic adjustments Knees:

Linear

Interpolations

<

Residual drift:

Sonic calibration default template

"ime-depth Options

Statistics

-

Pin-

a a

Linear

11. Click Apply to create the Sonic calibration study. A new Well section window opens with a default template.

•

412 Sonic calibration

Petrel Geophysics

>

1 This figure shows the default tracks of the Sonic calibration template. • g1 (Study 1) Oi | & no "o n V. 1 t'° •

(jlUiamor

<

\ÿ\ZrZ~~x\ÿF¿Fm 147.00 us/tt

14 [IVD]

>

Interval veloaty UAv erage v el oc rty0 0 1TWT pick

24,00 4.028 11 ft/s

Sonic Desoiked

14.037aj4.606

66 fcs 9.687 50 4,800 02 ft/s 7 560 54 -2441.27 ms 2.6

1061 6+3394:

©

©

©

;©

©

5

Q.

a

:

"if

s

2

6000

::«00 ■;

-i:7000: "7500:

Track 1

Track 2

TcmTI and Drift and Knees: The black points represent the TcmTI (Time of checkshots - Time of log).

In the vertical scale, these black points are at the checkshot depths. A red curve represents the drift and blue dots represent the knee points. Residual drift: Shows the difference between the checkshot time and the integrated calibrated sonic log.

This curve is updated based on the knee manipulations on the Drift and Knees track.

Petrel Geophysics

Sonic calibration •413

I Track 3

Track 4

Track 5 Q.

Track 6

3

Track 7

Sonic: Shows the original and calibrated sonic log.

The last curve is updated based on the knee manipulations on the Drift and Knees track. Output and Input interval velocity: Shows both interval velocities (input and output) in the same track for quality control purposes. Interval velocity: Shows the interval velocity of the TDR used as input (checkshots). Average velocity: Shows the average velocity of the TDR used as input (checkshots). TWT picked: Shows two-way time of the TDR used as input (checkshots).

12. On Seismic interpretation tab, in the Seismic-well calibration group, click Well tie editing to open the Tool Palette. Home

Stratigraphy -

B

Seismic (detault)

Houston.Restorat Setup

*

Seismic Interpretation

a a aj •

O©

}

Petroleum Systems

Decision Support

if U *jjjg -.

Structural

Wavelet toolbox

Log conditioning Seismic | well tie pfl Well tie editing ]

Seismic-well calibration

Insert »

Mesh editing

Seismic interpretation

2D/3D interpretation

r-

Mesh

Volume attributes

-

13. Click Edit mode ‘¿I in the Tool Palette. 1 4. Interactively edit the drift curve using the options available on the Seismic well tie editing Tool Palette.

E

*7$ ▼

Edit mode x

Se:srric well tie

El >

il >« 5a P P.

$13ÿ3

> 4* 414 «Sonic calibration

EQ

Tool Palette

I*,

rl

$ 91 31 Petrel Geophysics

I Sor

<

15. Edit automatically by clicking Knees at checkshots Knees at markers "1(these tools work only if some well tops are displayed in the Well section window). The initial straight red drift curve adopts the checkshot data (black dots) as knee points at all positions or only at the well tops positions. l»»HVO

•

IShdyPftmo

•

an V

j I'°

o**

?

M*

I»»1”

•a '»-0»»—

>

•

an VI

i»

**

•frOW+SH’»1—

Q.

Jo

—

1

pis tt

■

::

ill Petrel Geophysics

>+ . »ÿ_

fill Sonic calibration •415

| & tfr <

TWT

vM0;tt.87

i»;

1491 A

0

fe

T

400)

I TVD

ms 14 36 -1.73

ms

|Tcmf 3 i'T

1061 6+3394;

1=81

1 6. Insert single knee points by clicking directly along the drift curve at a specific location. ' Q Sf »[f <$ £ ! I'D Unde* M * ***** - [Tg (Study 1) Diamo -

------------- ——

--—

.

~ 4500-1

K :

T

i®62 1

- I- 6000 -

.

=

O

O

O

o

o

o

-o-

-o

o

o

o

o

0

o

a...

o

•

o

o

!

O

4

O

O

o

o

O

o

Edit mode

©

o

Se srrlc well tie

O

o

o

o

"6W0-;

■jJ

TOOO-

▼

[31 > 3 >. > 5? 5í S í? I=S ri !‘a 3

*

-•w-

>+ % zzri • goo: *

S5-X :

S 31

HOUSTON HOUSTON_BAS

o

::9000:

V

■ KOBE

o O

c

o

o

o a o

c o

o •

;ü8í

©DALIAS

------

.— -a...

»

+

=189

—

—

o

-j1900 S

>

1-244

a 1T88

!

i interval velocty LAvcrage veloc
■[

-/:K0Q-

•

c

o

o

o

o

o

o

©PARIS

PARIS_BASE

17. Move any knee along the TD relationship using these methods. • To move a knee, click it and drag it to a new position.

•

416 •Sonic calibration

To delete a knee, click Delete knee point Tool Palette and click the knee.

H on the

Petrel Geophysics

I 18. Observe that the original and the calibrated sonic log curves are different. When you move a knee point, the curves are updated, as shown in the figure (third track, red, and blue curves). The result of the calibration creates a new more accurate time-depth relationship for the well.

Q. 3

il

i?

1: $ Inrr 540C

»593

1692

1741.8-J-6000-

HI

19. Open the Output tab of the Seismic well tie dialog box. 20. Rename Calibrated sonic log as Calibrated sonic_l and click Save. ill Seismic well tie

Seiafr*cwellÿll&ftJ O Create study:

S # Edit study: Type of study:

(Study 2) Diainond-14 Sonic calibration (Study 1) Diamond-14 Sonic calibration

Sonic calibration

4k Wei:

¿ Diamond-14

Tj] Template:

¡5 (Study 1) Diamond-14 Sonic calibration

Input Output A

L Datumwg | Time-depth | Options | Statistics | Track manager

Calibrated sonic Calibrated sonic:

Calibrated sonic_1

IFI Autosave

0a

21. For the Time-depth relationship (TDR) field, make sure that the Auto save option is selected and click on Set as active TDR button.

Petrel Geophysics

Sonic calibration •417

I This time-depth relationship is used for the time conversion of the well Diamond_14. The relationship is selected automatically on the Time tab of the Settings dialog box for Diamond_14. These options override the options in the Global settings dialog box. T

Settings for 'Diamond-14' Flow correlatior

O

lnf°

Q.

© Create new

3

•

Edit easing

]

Settings

s

Quality attributes

Time

J

People

Make logs

Report

33

0£ Oneway tine 1

SI Ovenide global settings

ii

Statistics

a

Q Lock calculated log

© From shared TOR: 0 From shared checkshot: # From velocity function

□ Manual a$ustment:

fÿ.] [/

(Study 1) Diamond-14 Sonic calibratiorv'Calibrated TDR

(ÿ] [

IVL |y /ppfr | I

V OK

fta

3

I |,*CMMI |

22. Adjust the knees if necessary and observe the effect on the Interval velocity output. Verify that you are satisfied with its shape. 23. On the Home tab, in the Transfer group, click Reference project tool to open Reference project tool dialog box. 418 «Sonic calibration

Petrel Geophysics

I <

Q.

24. Find Cloudspin_SecondaryProject.petFT\n the Secondary projects folder and open it. (If the Petrel message log appears, view the content and close it.) All available data in the selected reference project is listed on the right side of the Reference project tool dialog box. 25. Select the check box for the Wavelets folder and use the blue left arrow to copy this folder from background project into your working project. You will use this folder in later modules. 26. Save your project.

>

jo

Petrel Geophysics

Sonic calibration •419

I 9

Review questions • Why do you calibrate a sonic log with the checkshot data? • What would you do if checkshot data is not available for a well?

<

>

Summary In this module, you learned about: • calibrating a sonic log • selecting input data and parameters • defining knee points and outputs

o.

jo

420 «Sonic calibration

Petrel Geophysics

I Module 8 — Synthetic seismogram generation

Q.

jo

In this module, you learn about synthetic generation, reflection coefficient calculation, interactive bulk shift or continuous alignments, and the correlation tool and track.

Learning objectives After completing this module, you will know how to: • use the synthetic generation process and input data • calculate the reflectivity coefficient • Use of interactive bulk shift or continuous alignments to adjust the time shifts between synthetic and seismic • use correlation tools and track • model the reflection coefficient (RC) • quality check Interval velocity

Petrel Geophysics

m

Synthetic seismogram generation •421 !ÿ

V

Muchachos, Sé que

-I

estamo*

I

9 <

Lesson 1 — Synthetic seismogram generation workflow Synthetic seismograms are the bridges between geological information (well data in depth) and geophysical information (seismic in time). Synthetic generation involves these steps: 1. Time convert the wells with checkshot data or a sonic log to establish a time-depth relationship. 2. Calculate acoustic impedance and reflection coefficients from different logs (usually density and sonic logs). 3. Generate or extract a wavelet. 4. Generate synthetic seismograms from density logs, sonic logs, and a seismic wavelet by calculating acoustic impedance and reflection coefficients. These calculations then are convolved using a wavelet. The Synthetic generation workflow used in the Seismic well tie process includes the ability to tie a synthetic seismic trace with seismic data.

Q. 3

m

Procedure — Generate a synthetic seismogram 1. On the Seismic interpretation tab, in the Seismic-well calibration group, click Seismic well tie. Petroleum Systems

e

<

Wavelet toolbox

» Seismic well tie

jjjfjj

Log conditioning

<2 Well tie editing

Seismic-well calibration

Decision Support

*&£ ■ Insert

4 11ffi

Mesh editing

Seismic

interpretation

2D/3D interpretation

Structural Modeling

'ÿ

Mesh

Volume attributes

r,

Mixer ,

Property

Modeling

Surface attributes

Calculator

Neural net

Attributes

2. Create a new study. 3. Select Synthetic generation as the Type of study. 4. Select the well.

422 •Synthetic seismogram generation

Petrel Geophysics

>

1 ill Seismic well tie Seismic well tie

<

| Hints"]

# Create study;

(Study 2) Diamond-14 Synthetic generation

O Edit study:

(Study 1) Diamond-14 Sonic calibration

Type of study:

Synthetic generation

lÿl ¿ Diamond-14

4ÿ Well:

>

TÜ Copy template:

0) • TS

Synthetic generation default template

Q.

5. Select the time depth relationship i.e. TDR.

a

Input

| Output |

Time shift Correlation Track manager | Style

ft

JJf Calibrated TDR

ty>

©

0

6. Drop in an existing wavelet or open the wavelet toolbox to create a new wavelet. If you do not have a wavelet available, create new wavelet by clicking Launch wavelet toolbox

w

in the Seismic well tie dialog box.

I Input I Output I

Time shift

Correlation I Track manager

| StyleJ

|efr| -Jj Calibrated TDR )Av Analytical Wavelet

# Wavelet:

I]

(6ÿ

o

0

7. Drop in seismic data. 8. Specify the seismic display position. Seismic display Seismic:

| E£> |

[Realized] 1 9

["I Allow wells outside survey Position:

O Xline

Inline

@(®|®

©

Inline:

622

Xline:

570

Xline window:

Petrel Geophysics

™ :

Synthetic seismogram generation •423

I 9. Choose a Reflectivity coefficient calculation method and associated input data.

. <

Sonic velocity and density

RC calculation method:

>

| | Alp Calibrated sonic log - (Study 1) Diamond-14 Sonic calibration |s>| PRHOB

Sonic or velocity: Density:

10. Click Apply in the Seismic well tie dialog box. A Well section window opens, showing the output result. Q.

lay™

■nVi

>

---

“nr*

•

AW* a M-

£••• Q

u*

t

ii <

IF

t !

180 i '

.

W~~

0

MMW -* ----— rm 52

m

D

0 ■

>

>

V

--

u bed

it

o

I"

I

-

IIIH— jffiimillIBB muí 1 2

3 4

Input logs track: Logs used for the Reflectivity series calculation. Reflectivity track: Reflectivity series calculated based on the method selected on the Input tab. Wavelet track: Wavelet, power spectrum, and phase spectrum of the wavelet used for the synthetic generated. Seismic track: Seismic section used as a reference to compare the seismic-synthetic track. The extension/orientation of this section is controlled from the Input tab.

The red line on the Seismic track represents the Well trajectory. The display is controlled in the Well section template Settings dialog box. Additional seismic tracks in the Well section window can be added where attributes can be displayed. Well trajectory, logs, and synthetic seismograms can be displayed. 424 •Synthetic seismogram generation

Petrel Geophysics

I 5

6

Q. 3

7 8

Synthetic track: Synthetic seismogram created convolving the reflectivity series and the wavelet. If any of the input data is modified, this track is updated instantly. Correlation track: A tool that helps increase the confidence in matching synthetic seismogram to seismic data. Each trace in the Correlation track represents the degree of correlation between the synthetic and each of the traces contained in the Seismic track as the synthetic is shifted vertically relative to the seismic.

The information from this correlation track is used to determine the correct time shift to be applied to the synthetic or seismic with the goal of achieving an optimal match. Interval Velocity track: The output interval velocity and also the place where the Interval velocity manipulations take place. Input/Output Interval Velocity track: The input and output interval velocities in the same track for quality control.

The input interval velocity is active in the well (from the active TDR); the output interval velocity is the result after the time shifts (bulk and stretch/squeeze) are applied in the synthetic. The default template for the synthetic generation study presents simultaneous display of the time and depth index tracks in Well section window. 9 Drift track: The time shift (in ms) applied in the synthetic to tie with the seismic. This shift comes from the bulk and stretch/ squeeze. 10 Well trajectory

Petrel Geophysics

Synthetic seismogram generation •425

I Seismic well tie dialog box tabs In this section, you get a more detailed look on the options available on the different tabs of Seismic well tie dialog box. >

<

Input tab The Input tab (Figure 1 ) in the Synthetic generation study is used to control the input of logs, time/depth relationship, wavelet, and reference seismic to generate synthetic trace.

Q.

Selecting TDR input

jo

The Seismic to well tie process needs to be, in many cases, very interactive, and different kinds of TDRs must be selected as input in the study. In Petrel 2015.1, any TDR, sonic log, or velocity log contained by the well can be selected as TDR input for the synthetics generation study. For those cases where the sonic log or velocity log are selected, the synthetics seismogram will be posted from 0 TWT. Therefore, it will be out of place and the Bulk shift is a required step in the Seismic to well tie process.

426 •Synthetic seismogram generation

Petrel Geophysics

m Seismic well tie Seismic well tie

Hints |

O Create study:

(Study 3) Diamond-14 Synthetic generation

J ® Edit study:

(Study 2) Diamond-14 Synthetic generation

Type of study:

4ÿ Well

®

*

Tj| Template Input

o Wavelet:

©

¡

Correlation

s

Time varying wavelet

Seismic display _

Seismic:

Diamond-14

5¡ (Study 2) Diamond-14 Synthetic generation

Output I Time shift

TDR:

a

a

Synthetic generation

rv |

iTrack manager I

Style

Calibrated TDR Active from well iji TDR - (Study 2) Diamond-14 Synthetic generation Calibrated TDR ¿w AIICheckShots.cs - v Diamond_14 cs Atp Calibrated sonic log - (Study 1) Diamond-14 Sonic calibration Atp Calibrated sonicjl

w

i

“ÿ¡a \/

Position Inline

Input interval velocity - (Study 1) Diamond-14 Sonic calibration

y* Input interval velocity - (Study 2) Diamond-14 Synthetic generation y* Output interval velocity - (Study 1) Diamond-14 Sonic calibration y* Output interval velocity - (Study 2) Diamond-14 Synthetic generation

At Sonic Despiked

0

Xline Xline window

10

:

570

Reflectivity coefficient

RC calculation method

Sonic velocity and density

Sonic or velocity:

Atp Calibrated sonic_1

Density: v

|=>| PRHOB

Advanced settings

✓ Apply

✓

OK

A Cancel

Figure 1 Input tab

Petrel Geophysics

Synthetic seismogram generation •427

Wavelet

In the Wavelet box, insert the wavelet to be convolved with the reflectivity series to create a synthetic seismogram. If no wavelet is available in the project, open the wavelet toolbox to create a new one by clicking Launch wavelet toolbox

.

See Figure 2.

pjf Seismic well tie Setsmic well be

j

© Create study

[ (Study 3) Diamond-14 Synthetic generation

f

9

Edit study

(Study 2) Diamond-14 Synthetic generation

Type of study:

Synthetic generation

¡a |

Hints

C:

¿ Diamond-14

Tj]Template

{ÿ) (Study 2) Diamond- 14 Synthetic generation

| Output | Time shift j

lrPut

9

a

%yut

Correlation

- \TI\

Track manager I Style

|=>| Calibrated TDR |ÿ| (Av Analytical Wavelet

Wavelet

ft

© Time varying wavelet Seismic display

1ÿ1 £53 mig (Realized] 1

Seismic

© XUne

Inline

9

[r] Allow wells outside survey

lid®

Position Inline

622

ft

Xline Xline window

10

z

570

Reflectivity coefficient

Sonic velocity and density

RC calculation method Sonic or velocity:

| |

Density

1ÿ1 PRHOB

Atp Calibrated sonic log - (Study 1) Diamond-14 Sonic calibration

Advanced settings

a a

RC resampling Sample interval:

1

ms

Gardner's parameters

[Q Use Gardner's equation Constant:

[023

Exponent

1

imperial

0.25

a

Filtenng opb< fyl Use anti-alias filter

|✓

Apply

|| ✓

OK

|

A Cancel

Figure 2 Input tab in the Synthetic generation study 428 •Synthetic seismogram generation

Petrel Geophysics

I <

Seismic display In the Seismic display section, you drop in the seismic that is used as a reference to compare the seismic-synthetic tie. Both 2D and 3D seismic surveys are allowed, so you can use a 3D cube or a 2D line.

>

There are three seismic display positioning methodologies for the Seismic well tie process: Well head location, Deviated well location, and Selected Wavelet: Q.

a

*

Well head location This method sets the Inline, crossline to the location of the wellhead, as shown in Figure 3.

,

m

\

\

1

n®

íílílllfílííl

I

mm ; II I ism ■■

m

mm)

it, Figure 3 The well is displayed in the seismic track according to the position obtained in the wellhead (XY location)

Petrel Geophysics

Synthetic seismogram generation •429

I Deviated well location This method sets the inline-crossline to the location of the well track at the center of the analysis window, as shown in Figure 4. The figure shows how the deviated well is displayed in the seismic track. This method considers the entire trajectory as the display position window, calculating the position point (XY location) as the center of the extraction window.

<

-T

S Q. 3

m

5

[e|®l$

V

\

: : : : i:

il

»111 PIP r- pr

Extraction window

"V

ft ft

P- PÿP*

mnl fn>

K;;

f

ail nnÿn\:“»n\»nn Figure 4 How the deviated well is displayed in the seismic track

The Xline window represents the number of crosslines to be used for seismic reference on either side of the well location. These crosslines are counted from the crossline position that you define.

For example, if you enter 4 in the Xline window, five crosslines are displayed: one that corresponds to the crossline 570 (well position) and four other crosslines after your reference, which is the number that you entered.

430 •Synthetic seismogram generation

Petrel Geophysics

>

I <

Selected wavelet This method sets the Inline-xline to the location of the currently selected wavelet, as shown in Figure 5. The figure shows how the well is displayed in the seismic track according to the position obtained through the wavelet selected on the Predictability map.

j

■

>

e ®f¥|

Q.

íiímüír Í :Hililiiiii rrfrrrrrf;! r?rr;rrrr;rr;; t

Jo

Illlljtiíí}

i::*::::;!:

<

>

::: r r r

■rrrrrrrrr r

t t t • * *

rit

»>

am.

Si

Figure 5 How the well is displayed in the seismic track

Petrel Geophysics

Synthetic seismogram generation •431

Reflectivity coefficient calculation There are several methods for generating reflectivity coefficients, depending on the availability of data (Figure 6): • Acoustic Impedance • Sonic and Density logs • Shear • Porosity • Aki and Richard PP • Aki and Richard PS • Any log

<

1 ¡a

B

$1Seismic well tie Seismic well tie

<

Hints

© Create study

(Study 3) Diamond-14 Synthetic generation

Edit study.

(Study 2) Diamond-14 Synthetic generation

Type of study:

Synthetic generation

S

a

V**

fa Diamond-14

Tfi

(5 (Study 2) Diamond-14 Synthetic generation

Input

Template:

Output

>

|

Time shift

>

¡ Correlation ¡ Track manager | Style Calibrated TDR

Wavelet:

I

I

|4-

Analytical Wavelet

m

© Time varying wavelet: Seismic display Seismic:

iy*

fjjmig [Realized] 1

© Xline [T] Allow wells outside survey

HID®

Position Inline

622

Xline:

570

Xline window

io

:

Reflectivity coefficient

Sonic velocity and density

RC calculation method Sonic or velocity:

g>

Density:

|ÿ| PRHOB

At DT

Advanced settings

a a

RC resampling Sample interval

1

ms

Gardner's parameters

O Use Gardner's equation Constant:

0.23

Exponent

0.25

imperial

]

a

Filtenng options

® Use anti-alias filter

[V

Apply

||

OK

||

A Cancel

Figure 6 Reflectivity coefficient options in the Seismic well tie dialog box 432 •Synthetic seismogram generation

Petrel Geophysics

I Here are some examples of how to calculate the reflectivity coefficient using different types of data:

• <

•

Choose an Acoustic Impedance. It this case, a sonic and density need not be present. The Seismic well tie process calculates a reflection coefficient curve.

•

Use any log curve as a pseudo-Acoustic Impedance curve for apparent reflectivity computation. Gamma logs often work well in this circumstance. Sonic logs also work well, but the polarity typically is reversed from the log derived from true acoustic impedance.

Q. 3

Use sonic and density curves to generate the Al curve as the ratio between the density and the sonic logs. In turn, the RC curve is generated from the Al curve. The Seismic well tie process generates this curve on-the-fly.

n

The original sonic log (or a despiked version of the original input sonic) is used in this calculation. The calibrated sonic log is likely to contain abrupt shifts (at knee point positions) as a result of this calibration. Using the calibrated sonic as input to this process results in the same abrupt shifts in the acoustic impedance log. Because the reflection coefficients are calculated from the acoustic impedance log, the result again introduces reflection coefficients and artificial events in the synthetic trace.

Gardner's patching: Auto-complete reflection coefficient inputs Petrel can automatically complete missing sections of Density or Sonic logs using Gardner's equation. This option fills the gaps where one of the input logs (Sonic or density) is missing. For examples, refer to Figure 7 and Figure 8. One of the logs must exist to compute the other one:

P = aZnpb In this equation, • a = The Constant unit (imperial/metric). It is shown next to the Constant box. For the Exponent parameter, the default value is 0.25. You can change values for these two fields and them as parameters for Gardner's equation. b • = Exponent. If the project is in the Imperial system, the default value is 0.23 for the Constant parameter. If the project is in the metric system, it converts the default imperial value to metric using this equation: a (in metric) = a (in imperial) * (1000/(0.3048 A exponent )) Petrel Geophysics

Synthetic seismogram generation •433

>

B Gardner's equation usually works fine for sedimentary rocks with velocities that are betweenl 500 m/s to 6000 m/s and densities from 2x103 Kg/m3 to 2.8x103 Kg/m3. <

---

ta,


-

>

CCmmmáp

/«Ed*Hud)r

(Study 2) Dwnord-14 Syntabc gmrafeon

Typ.oi.tudy

v«

iDamond-U

TJT.

H (Study 2) Omnd-14 Syrttetc g

a

•

I w ioÿIr-ÿ>|<

o

I

ijfTOR

4C*WedTDR

IA> Anriytaal Wawtat

Q.

B

*

|KJ

l4j CBng|RMlaed|1

a

OXh.

□ Ato.-a.ouW.~vn

BIS®

jo

:

■fl-

570

RriKMycorfnM

<ÿ

a

E

u»1 p™

¥ -a (MT

Ftonngc

a

SBUMI

Figure 7 Patch shows missing section of Sonic log for which RC and Synthetic are not calculated

434 •Synthetic seismogram generation

Petrel Geophysics

B I • *"i

;

m

;Ji Seismic wel tie

: W1

CmmMf -

*

(Study 3) [>amond-14 Syntax generador

J •Ed* study

(Sfcj* 2) Dinnond-USyiAet* generation

Syn*e*ej

Typeofekidr

•

J

•

a

%«•

<

TjTerrpbee Input

(£ (Sbxty 2) ftamond-14 Syntax generation

|(X>wi|T— ajjfcT<

6

I

LVAMlykriWMtel

•

I*

a

I

-

-

OXSne

»:

Xkne vendo*

jo

mg [Resized]'

• n*— mmm

H

Q.

Sonet Sonic or velocity

i and density

I

At:*

P RH06

DenXy

C

-a a

Dee Gartner’* « Constant

025

■a

■u.1

Figure 8 Patch shows that RC and Synthetic can be calculated for missing section of the Sonic log by using Gardner's equation option

Petrel Geophysics

1+ ;-t

Timev»yingwwittet

<

>

Synthetic seismogram generation •435

Output tab Use the Output tab (Figure 9) in the Synthetic generation study to control the output results from the workflow. You can change the name of any output and save it in the Input pane by clicking Save r J. IÿI

f.|! Seismic well tie Seismic well be :

Hints

| (Study 3) Diamond-14 Synthetic generation

(£ I Create study

J $) Edit study:

(Study 2) Diamond-14 Synthetic generation

Type of study

[•]

a

Synthetic generation

*wdt

¿ Diamond-14

TÍ Template

¡3 (Study 2) Diamond-14 Synthetic generation

Inputj

0

'ÿbtpu-

| Time shift

Seismogram

J Correlation j Track manager | Style

-g

[

aa

Diamond-14_mig [Realized] 1_synthetic 1

|r| Auto save Reflectivity

@a

RC

[rj Auto save

* Computed seismogram (depth) Name

@a

Seismogram Depth

[T] Autosave

(X) Time depth relationship (TDR) TDR Name

@a

TDR Sample interval

16 40

C

O Al samples

ft

|r] Auto save

Set as active TDR| Computed acoustic impedance

Name

@a

Al

[T] Auto save A

Resampled acoustic impedance

Name

@a

Resampled Al

[T] Auto save

* Partial seismogram from RC modeling Name:

iA

Partial synthetic

J

|f~| Auto save Seismic trace used in the single trace correlation

Name

(3 a

Verticalized seismic trace

(F] Auto save

| •/

Apply

|[ V

OK

||

* Cancel

Figure 9 Output tab in the Seismic well tie dialog box 436 •Synthetic seismogram generation

Petrel Geophysics

I <

Q. 3

These output types are available from Output tab. All output is saved in the Input pane: • Seismogram: Saved as a seismic log in the Global well logs folder and the well used in the study. • Reflectivity: Saved in the Global well logs folder and the well used in the study. • Computed seismogram (depth)/ Synthetic in depth: The synthetics used to be a time domain object. In Petrel 2015.1, the synthetics that is generated can be saved with depth as the vertical index.

n

You can automatically save all of the outputs, so that after they are saved the first time, any manipulation overwrites the output. If the name of the output is already in the Input pane, a pop-up warning asks you to confirm your decision to overwrite it.

Computed seismogram (depth)

Da

Seismogram Depth

Name:

[ÿAutosave

•

Time depth relationship (TDR): The curve modified by the time shift alignments in Synthetic Generation. It is saved as a TDR only in the Global well logs folder. The specified depth sample interval is used. The TDR generated in the synthetic generation or integrated seismic well tie studies can be directly assigned to the well from the Output tab of the study itself.

(A) Time depth relationship (TDR) TDR Name:

@3

TDR Sample interval:

16.40 |-J-j ft

□ All samples

[ÿAutosave

[Set as active TDR]

• • • •

Computed acoustic impedance: Saved in the Global well logs folder and the well used in the study. Resampled acoustic impedance: Saved in the Global well logs folder and the well used in the study. Partial seismogram from RC modeling: Saved in the Global well logs folder and the well used in the study. Seismic trace used in the single trace correlation: The average or composite seismic trace extracted based on a radius that you define. This option is available only if you choose the option Single trace on the Correlation tab. The seismic trace is saved as a seismic log in the Global well logs folder and the well used in the study.

Petrel Geophysics

Synthetic seismogram generation •437

>

I Synthetic generation template After all of the input data/parameters are selected in the Seismic well tie dialog box and the synthetic is generated, the template shown in Figure 10 opens. It displays the different input data and resultant synthetic seismogram.

< |at>

-

wi

. a, IIVI i» IM

a

-am-sa

Q

>

Analytical Wavalat

0

Q.

I

3

© © I

©

K

K

"

£

6

ntffi

t „

9:

Í1

s Tim, (m,)

; ;

ll

S

J

n

Pm

*

10

i

-

ttfp

ffi

ü

?

\

;

/

$

Figure 10 Default template for the Synthetic generation study.

The Synthetic generation template consists of these tracks, but you can modify them as required. 1 2

3

438 •Synthetic seismogram generation

Input logs track: Logs used for the Reflectivity series calculation. Reflectivity track: Reflectivity series calculated based on the method selected on the Input tab. Wavelet track: Wavelet, power spectrum, and phase spectrum of the wavelet used for the synthetic generated.

Petrel Geophysics

>

I 4

Seismic track: Seismic section used as a reference to compare the seismic-synthetic track. The extension/orientation of this section is controlled from the Input tab.

The red line on the Seismic track represents the Well trajectory. The display is controlled in the Well section template Settings dialog box.

<

Q. 3

5

6

7 8

>

Additional seismic tracks in the Well section window can be added where attributes can be displayed. Well trajectory, logs, and synthetic seismogram can be displayed. Synthetic track: Synthetic seismogram created by convolving the reflectivity series and the wavelet. If any of the input data is modified, this track is updated instantly. Correlation track: A tool that helps increase the confidence in matching the synthetic seismogram to seismic data. Each trace in the Correlation track represents the degree of correlation between the synthetic and each of the traces contained in the Seismic track as the synthetic is shifted vertically relative to the seismic. The information from this correlation track is used to determine the correct time shift to be applied to the synthetic or seismic with the goal of achieving an optimal match. Interval velocity track: The output interval velocity. Also the place where the Interval velocity manipulations take place. Input/Output interval velocity track: The input and output interval velocities in the same track for a quality control. The input interval velocity is active in the well (from the active TDR). The output interval velocity is the result after the time shifts (bulk and stretch/squeeze) are applied in the synthetic.

9

Simultaneous display of the time and depth tracks: The default template for the synthetic generation study shows simultaneous display of the time and depth index tracks in Well section window. Drift track: The time shift (in ms) applied in the synthetic to tie with the seismic. This shift comes from the bulk and stretch/

squeeze. 10 Well trajectory Petrel Geophysics

Synthetic seismogram generation •439

m

Procedure — Change settings for the template and tracks You can edit or change the settings of the Synthetic template and tracks.

<

[ft t*'

1. Click Template settings L- on the Window toolbar. 2. From the Well section template tab in the Settings dialog box, change or modify the settings for different tracks in the template. *©;$## ,§>0'W*.ve S'fl’ Q •HE’S J V K ! IIP

- |g (Study 2) Diamo

TWT

Undgf

to

TVQ I TWT

•

Inline 622

Jr

■

mig (Realized!!

I

50000

•

Inline 622 •mig (Realized! 1

67000

>

Interval «aloe» 680 001« «V 12* » " fiñ |

670 00

DT

Analytical \V avelet

/fW

200:

0

1

"

■

V

■-

<

a

Time ( Power sp

i;

St»:

r

■

I

-

1

9

A «C

I*JA "*0

(*j

90

MA

Frequent

I

2

S

1

0A*

la

Quadratic

>

Scale Seismic plot type

a

V, Wiggle trace

S3 Positive HI C Negative HI

r

J Density HI

Nerpolated

Trace color f*

Lobe

Trace sett ngs

Output Nerval ve (SWT

Wiggle antiataang:

&4t (SWT

Qppmg factor

SB 4

Trace repeal court Nerval

Q 3 1

Deviated tracks (0)

-

Lva»» .II.VOK -I !«ÿ*»« I

400

440 •Synthetic seismogram generation

Interpolation type

5? Background

0

i:

1 rng [Reakred] 1

♦i Borehole markers

Phase sp

■*

Interpolation method and acale

A Co""tabon (SWT)

Correlation (SWT S I*|A Nenral velocity (TDR Nerval velocity f |*jA bpi Nerval velocity (vjy* nput Nerval velo

«.

: -2100:

(Study 2) Dwmor RC (Study 2) Die |VJA Analytical Wavelet Analytical Wavele 0ÿ n»g [Realted] 1 ng [Reakted] 1 ¿/JA SyNhebc (Study 2) C

Style

•

•

E

-90

■2200:

-

«.

0

O'* [3 Definition

•

JJ

-«0

■

inki*jAtDT/RHOB or

Ü

Objects settings

IÿJP RHOB

a

•to

i

Lj

Vertical trades (12) SSTVD We* track

-

m

0

;

•MS

¿

-90

'

•00

-

|

’’HI sector témplale

Template obiecta

á-

•<

I-.-I

Settings for (Study 2) Diamond-14 Synthetic generation'

O Info |[tt

too

0

Frequency (Hz)

Petrel Geophysics

Seismic track

<

The seismic display on the Synthetic template can be customized, depending on the display requirements. • Interpretations (horizon and faults) display • No restriction to inline orientation • Multiple orientation/attributes • Well trajectory, synthetic, and two logs

[•]

Procedure — Display synthetic along a well trajectory in a seismic track 0

>

m

1. Click Template settings [T] -~J in the Well section Window toolbar during synthetic generation study. (§ fe

- Ilf (Study

I 1WT

2) Diamo

-|¡H|n VjM]1 t,D

Undef

'

!i'!l EM’Relative

:

2. Add a new track from Setting dialog box. j]

Index track

£ \

Tadpole track

(=J

Comment track

1

Track

Summation track

OL Settings for '(Study 2) Diamond-14 Sy Well section template 0 Info

a

Template objects

H

jÍQl

Polar frequency plot track

£ 0

Completion track

■o-

Production charts

♦

Vertical tracks (13

TVD (vj [j Index track DT/RHOB ¿jAt DT I VJ p RHOB lv>| A RC • (Study 2) Diamor ¿jJ. RC • (Study 2) Dia

- (3.

a.

!

©

-

m □

ivift Analytical Wavelet

Analytical Wavele mg [Realized] 1 (30 mg [Realized] 1 IÿJA. Synthetic (Study 2) C (V|0 Synthetic - (Study I VI A mg [Realzed] 1/mig [ (30 mo [Realized] 1 mg [Realized] 1 |ÿ|A Correlation (SWT) i igf? Correlation (SWT) (3£ Interval vdoaty (TDR [vrjly Interval velocity C (3£ Input rterval vdoaty |ÿjy* Input interval velo (3"V* Output rterval ve Dnft (SWT) 0AÍ Drtt(SWT) •

E -

-

¡30

♦1 Borehole markers ¡T4 Background Deviated tracks (0)

.

Petrel Geophysics

m

Synthetic seismogram generation •441

3. Right-click the new inserted track under Template objects in the Settings dialog box and select Seismic. ¡TJ Index track

<

£

Track

Tadpole track

[=)

Comment track

O

Summation track

f©i

Polar frequency plot track

Q ®

Completion track Production charts

L°g

£j§ Property

0


0 Info 'fa

-

it»] S; A

““ &

*

1 s .

5®

Bitmap log

gp

Time series log

Raster log Seismic

|1

Prestack gather collection

j

Verticaltracks (13) TVD

0Q

a w ó

!ÿ!

DT/RHOB

£jAt DT

A A

RHOB RC - (Study 2) Diamor RC - (Study 2) Die Analytical Wavelet

Analytical Wave!* rn»g [Reafczed] 1 I y*i n»g [Realized] 1 Synthetic - (Study 2) [ Synthetic - (Study [Realized] 1/mig [ iv>lA rreg [Realized] 1 H»9 [Realized] 1 i*lA Correlation (SWT) Correlation (SWT) i Interval velocty (TDR lÿjly Interval velocty f

f\

(a

-

-

É /-N.

iÿl

a

Objects settmgs

O Info

Style

Curve filling

RRRMI

(*)P

m

Seismic log

2D log

Well section template

Template obtecte

Points attribute

QT

E3

Sittings for '(Study 2) Diamond-14 Synthetic generation

Í !

miáfflca '-'

-=*** «OP"Backgrourd

Specified:

25

Lock

mm

a

Gndbnes

Automatic

[y] Draw vertical lines

[?] Draw honzontal major Ines

PI Draw honzontal minor lines Color

1

a

Background

A Incut rterval velocity ¿jy* Input nterval velo y* Output rterval ve Dr* (SWT) |V) At Drft (SWT)

a

Width

Color Transparency

[

]

a

Value label

®

-

None

Show value leadouta

Deviated tracks (0)

Risk

&

BHA Simulation grid results

|ÿ|

Simulation log

442 •Synthetic seismogram generation

Ky Apply

✓ OK

| 24 Cancel

Petrel Geophysics

>

On the Definition tab in the Settings dialog box, insert ‘V a seismic attribute cube of your choice from the Input pane.

4.

<

i_Bj

Settings for '(Study 2) Diamond-14 Synthetic generation' Info

C©

¿

Template objects Q- ¿ Vertical tracks (13)

00

Definition

sA DT/RHOB

1 0

WAtDT

RHOB RC - (Study 2) Diamor RC- (Study 2) Die 0ÿ Analytical Wavelet 0lL Analytical Wavele É 0Á m'g [Realizedl 1 mig [Realized] 1

0ÿ

m

0ÿ

Synthetic - (Study 2) [ lÿj¿P Synthetic - (Study (=] 0ÿ mig [Realized] 1/mig [

(±)

It'll -

mig [Realized] 1 mig [Realized] 1

0£ Correlation (SWT)

|_)£ÿ Correlation (SWT] (±) 0ÿ Interval velocity (TDR 0|y Interval velocity f 0 (v|¿ Input interval velocity 0y* Input interval vela 0"y* Output interval Á 0 M (SWT)

é A

Verticalization

Style

¿

Well Related

|c¡> Q mig [Realized] 1

Seismic:

-

B ED

Interpretation

||j5j£

Seismic display

0P

-

a

Objects settings

_

™D

; (0 [j Index track

é

>

Well section template

Seismic position

0 Inline

4

£

Xline

a Well her

© User

' me:

500

(

1 360 [

Nuwber of tracer Traces before

5

Traces after

5

: :

/

0A1 .Drift tSWjy B 0ÿ Seismic f

8

Borehole markers Background Deviated tracks (0)

[V Apply | |

Petrel Geophysics

VOK

A Cancel

Synthetic seismogram generation •443

5. On the Well related tab, select the relevant template and drop in synthetic or log of your choice from the Global well logs folder. Click Apply. (ÿ]

<

Settings for '(Study 2) Diamond-14 Synthetic generation'

0 Info

Template objects -)

IZJ g

i

11 I 0

1 0

WA

-

0A

|

Style

|

Verticalization

|A

Wdl Rdated

a

Well trajectory display

a RC - (Study 2) Diamond-'

B

Interpretation

Definition

DT/RHOB 0At DT p RHOB

RC - (Study 2) Diamo aEP Analytical Wavelet

QlJU Analytical Wavelet É 0ÿ rng [Realized] 1 0ÿ m,9 [Realized] 1 Synthetic - (Study 2) Diar B 0 0ÿ Synthetic - (Study 2) B 0ÿ mig [Realized] 1/mig [Re. 0 mig [Realized] 1

m

<

r

TVD

Index track

;

É

a

Objects settings

i Vertical tracks (13)

Sa

*±

>

Well section template

0 mig [Realized] 1 I B klA Correlation (SWT) ¡ \f$ Correlation (SWT) i B 0A Interval velocity (TDR - (! 0 jy Interval velocity (TDF | ¿ |7|A kput interval velodty - (S

0 Show

Color Line width

—

2

▼

a

Logs display Option

0 0 0

Left log Seismogram

Right log

(?)

Styfe

Fiber template

templates

é \h

]J Seismic (default) Log

Synthetic - (Study 2) Diamond-14 SynthetK

■u

0 y* Input interval velodty

0 y* Output interval vdoc

-

0£ Drift (SWT) (SWT>

0 A* Drift 0ÿ mig [Realized] 1

... B

mig [Realized]!

♦A Borehole markers p± Background

1

f

]

Deviated tracks (0)

< l— W-J

ll V Apply

444 •Synthetic seismogram generation

||

V OK

||

* Caned

Petrel Geophysics

>

The figure shows extracted attributes displayed on the Synthetic generation template. <

1 3247

13247

35924

f 1116 1300

4266 4 •i

: 1400

4644 1

0

>

1200

3897

[•]

"57500

|Se5~50~

5031

if 1500

5425 9

if 1600

5829 3

u

-«*»-

6661 1 -

1700

4600-

mv;

1900

•

E-

i

7066 7 1 2000

7521 8 - -2100 7962 71' 2200 »414

2300

8873 4

2400

ilflillli

<9393 5ljgW 3X

Copper 6 [TWT]

PM

-0 09

0 09

ja'oo"

00 Hz 59600

DT

pfnpr

W >6 riMRxkrr Ian

I"

[Hill

...

I

lililí

i

iíBS*Í

Time (ms)

][

mm

IJ

jr

I,

1

Í

Pkat* SftRm

4. ’

Petrel Geophysics

I. f

---

718 00 'Bocio

3 3

Frequency (Hz)

718 00

i •J £5

.

<¿... I

'ÿ

:.i :

I

ff1'

1Synthetic seismogram generation •445

I Interpretation display on seismic track There are many references to be used as a guide during the seismic to well tie process. Usually, the main reference will be markers and horizons; while, in some other cases, it could be faults or other types of identified interfaces. In Petrel 2015.1, horizon interpretations and fault interpretations can be posted in the seismic track, which helps to use them as reference during the tie process.

a

Q.

Procedure — Interpretation display on seismic track in the Well section Window 1. Click Template setting [T] toolbar during the Synthetic generation study.

jo

ja»

TWT

•

TVDITWTI | 1 324

Z

RHOB

(*udy2H>»"0

.

‘

lllCD 4>ii

-rjlrt V K

> U"**

-

oitki

reoIMP 00 Apahtical

«2*0 V 1»0* •2T7 1.

-z

1»0•NO :

•M

e

\

Wavelet

»fl- Mu»»

• SOOOO

570 001

•

e-«-

Q

187000

I

A

1310-i -1320:

? -J tff T

?

!

"

.

■

446 •Synthetic seismogram generation

<»

i i

1 1

I

Petrel Geophysics

2. Add a track from the Settings for <study> Synthetic generation dialog box. [i]

0 Into |[a

<

©

Sai

Settings for '(Study 2) Dwmond-14 Synthetic generaron' Well wctwn tempi»»

Template oCiectt

j

>

Cttjectt Mtngt

Indo track Track

Tadpole track

(?)

FI

Comment track Summation track

Polar frequency plot track

£

Completion track

Production charts -i

&

(*]£

-J (*}

A

Syrthebc • (Study 2) [¡ Synth** • (Study ™g [Rea*rod] 1

"•* [ReafciedJ 1 (kiA Corrdabon (SWT) Correlation (SWT -

[*>1 A hterval vdooly (TDR

5

(Vj

hterval veloaty

f

rterv#l veloaty A knpuiInput

rtetval velo ¿iy* yjy* Output rtervd ve

DrfMSWT)

¿J At Orft (SWT)

**

Borehole master* Background Deviated trade» lO)

IK

r~7

Petrel Geophysics

ir

/ n*

ir

Synthetic seismogram generation •447

3. Right-click to add a seismic. 0

(ÿ) irf: ¡

*/dl section template

1

Template objects

m

<

ESI

Settings for '(Study 2) Diamond-14 Synthetic generation'

Á

Style

Info

0Q

B

a

Objects settings

Vertical tracks (12) SSTVD r 0 |r*dex track B 0ÿ Calibrated sonic_1/RI 0Atp Calibrated sonic_ RHOB $ 0 A RC - (Study 2) Diamor (Study 2) Die RC0|--' !ÿ! A Analytical Wavelet 0li. Analytical Wavele mtg [Realized] 1 - 0 0ÿ rrag [Realized] 1

Curve filling

Q

* 5

a m

□ Specified:

É -

Automatic

Synthetic - (Study 2) [ 0¿P Synthetic - (Study

0 Draw horizontal major Ines O Draw honzontal minor lines

0A ™g [Reaiized] 1

Correlation (SWT) i

Color:

0g# Correlation (SWT]

0 A Interval velocity (TDR 0|y Interval velocity f B 0 A Input nterval velocity

É

Width:

0 At

Drift (SWT)

Borehole ma Background Deviated tra

1

»"

l

A

a ]

Color:

0A Drift (SWT)

/C\ lo) 0& Tr?oiÿ

1

Background

0"y* Input interval velo 0~y* Output nterval ve

4

a

0A

B

<

□ Lock

0 Draw vertical lines

0¿P mig [Realized] 1

%

[25

Gridlines

A.

0]

a

Width

L0P

Transparency:

Track

-

None

a

Index track outs

Tadpole track (EJ

Comment track

O

Summation track

iOl

Polar frequency plot track

i@(

Completion track

IP

Log

Production charts

IV

Apply

j|

✓ OK

l | * Cancel

|

Property

¿S'

Points attribute

Seismic log

|jf 2D log

5® IP -5$

Bitmap log Time series log Raster loq Seismic

Prestack gather collection Risk

448 •Synthetic seismogram generation

>

it

BHA

jfjj

Simulation grid results

\f\

Simulation log

Petrel Geophysics

>

Select this seismic object on the Interpretation tab, which contains the tools to add the interpretation (horizons and faults) in the track.

4.

<

Horizons or Faults from the Input pane to add the 5. Insert interpretation. 6. The format can be edited at bottom of the Interpretation tab.

>

|¥j Settings for '(Study 2) Diamond-14 Synthetic generation'

O Info [©

Well section template

□ Objects

Template objects Q-

¿

Vertical tracks (13) SSTVD | v¡ y Index track E iV A Calibrated sonic_1/RI i @Mp Calibrated sonic |VjP RHOB e ,v>.A RC- (Study 2) 0|P RC - (Study 2) Die E fÿl A Analytical Wavelet 0UU Analytical Wavele ¿ v.A mig [Realized] 1 mig [Realized] 1

j

0 i

II

E]

B

settings

Definition

Verticalizatior

¿

Well Rel ated

Horizon

El

|

©

Fault

Status

Name

Seismic horizon A [2 [y] & Seismic horizon B

V

[y]

Seismic honzon C

✓

[3 & Seismic horizon D

✓

V

|1/| A Synthetic - (9udy 2) [ Synthetic - (Study

(yj¡ÿl

/A

| É

mig [Realized] 1 mig [Realized] 1

i É

. .A Correlation (SWT)

!

Interval velocity (TDR IVlft i-

y

É

$

Style

Interpretation

:m

l±

yjS

ft

Correlation (SWT)

0|y Interval velocity f 6-MA Input interval velocity i

Input interval velo

[J y* Output interval ve Drift (SWT) : Drift (SWT) É Ir/lA Seismic

i Q

i

«

y Display all |Q Name

borehole markers

Background Deviated tracks (0)

IJ

Annotation

Font:

10

Position

Left

©

Interpretation

O Lines

Line type:

Solid

Width: <

I-»' -I

9 Points

4

Size

|

Petrel Geophysics


✓ OK

| | A Cancel )

Synthetic seismogram generation •449

[ij

Sittings for '{Study 2) Diamond-14 Synthetic generation'

0 Info

[a

Well section template

Template otyecJs

<

Vertical tracks (12) B Q SSTVD Indextrack B ir.A Castrated sorac 1/RI (/jitp Calbrated sonc_ RHOB RC- (Study 2) Darner tí RC (Study 2) Da

(uj[j

♦

* 1 ¡3

(3

m

BP

Bl"

■

B-irifi Analytical Wavelet @li. Analytical Wavele B viA mg [Realitedl 1 mg IReefaed] 1 Synthetic (9udy 2) [ Bÿ Synthetic • (Study viA mg |Reabed) 1 n>5 |Reabed| 1 V, A ConeWwn (SWT) Correlation (SWT) V A Interval velocity (TOR BCy Irterval vetocty f rterval veiooty Vi A By* Input nerval veto ¡Vj'y* Output nerral ve

y

Vlÿ,

a

0

a

¿ Objects setlngs

St s" i

•

Deimbon

&

Style

Verbcaliiabon

Well Related

|Interpretation)

fJ

tf

* P,

0

Honton |

#

Tain Status

Name

@1

Fault interpretation 1

✓

0 SB SB 0

Fault interpretation 2

✓

Fault interpretation 3

✓

Fault interpretation 4

✓

& Fault interpretation 5

✓

a

Irixx

< -

¿|£Mt(SWT)

Bit

Ddt (SWT)

H-PIA Seamc

l5T.j8e.5~. |

“

Boreÿoie marker?

Background Deviated track* (0)

• L»-J

> H Display al

a

Annotation

E] Name

Font

10

Position

Left

a

interpretation

Une type

Sotid

\tfdtti

3

|

450 •Synthetic seismogram generation

>

V Apply

I

V OK

A Cancel

Petrel Geophysics

I 7. Seismic cube display and style settings can be changed. 8. Click Apply. •

,o»fa

<

a

¡:as, » * E

ÜÉ IlfSrtSi. -: l*>A

a

ui

i»

p

<

s

A

♦

HrtvMMII

ÍÉ

-fc

-

-

nwiggl.net

1

POMMM

»

íS==s

V

>W rterv* v«tocty

IF

ii

>

a

Q. 3

Setting* for (Study 2) Dnmond-l*Synttr*titgtnet*tion

-s*4lSS

:u*.e

<

>

Interpretation (horizons and faults) will be displayed on the seismic track.

ffll n I

‘

,

L,

Wmm,

I

i

n 1S

} ■■

i -

Petrel Geophysics

s

TT! n

■

'n

aSHHMlijHN mas

m m

sHü A

¡lili is?

«•1*

S'

«

Vv

Synthetic seismogram generation •451

I Correlation track The Correlation tool provides information for a better seismic synthetic match. This tool calculates the cross-correlation between synthetic and seismic, which is achieved by calculating the time shift to be applied to the synthetic.

<

Although the correlation display looks like seismic data and uses similar display mechanisms, it is NOT seismic. Do not look for correlations between this display and the seismic track. Each trace in the Correlation track represents the degree of correlation between the synthetic and seismic, because the synthetic is shifted vertically relative to the seismic.

Q. 3

This calculation is repeated every time, according to the seismic sample rate, and for every seismic trace. Remember that each value represents how well the synthetic matches the seismic trace at a particular point in time over the entire interval that you specified. The result of these calculations is a series of numbers for each seismic trace.

These values are normalized to ±1 and displayed as curves in the Correlation track. These values correspond to the same positions as the seismic traces. When you place the cursor over the Correlation track, you can read the Inline and Xline positions, the correlation value corresponding with the mouse position (Current position), and the Max correlation from the box labeled in the upper right side of the track (see Figure 11 and Figure 12). Irlme 622 & X -e 565 Current posean (-0 116. -30Sms. Odeg) Max correlator (0.504 -Sms. Odeg) Max after rotate (O 4S6 Oms 63deg) Max after rotate and shift (0.513, -4ms. 26degj

Figure 11 A box in the upper right side of correlation track showing correlation values, lag value, and phase rotation

Inside the parenthesis, these values are displayed: • Correlation value • Time value that corresponds to the suggested time to shift (lag value)

• 452 •Synthetic seismogram generation

Degrees

Petrel Geophysics

>

I <

If the Compute phase mistie option (Figure 1 5) is active on the Correlation tab, a new line of information (number 4) is displayed. This information shows the phase rotation to be applied to the wavelet to improve the tie. The time lag for this option is zero, meaning the synthetic was not shifted.

>

If the phase mistie option is active on the Correlation tab, a new line of information (number 5) is displayed. This information shows the phase rotation to be applied to the wavelet to improve the tie. Q. 3

You can see that the time lag for this option is different from zero, meaning that the synthetic was shifted. With this result, the interpreter knows what time shift or what phase applies to get the best correlation. Mint 622

■

miq

570 00]

I00_

-

-

-|Hint 622 rr»a IRtatotdll 570 00 580 001560 00

580 00

f . f

■Si

'

Correlation

560 00

580 00

“iisSIsg Ma

:

J

Figure 12 Correlation track with current cursor position and max correlation values Petrel Geophysics

Synthetic seismogram generation •453

I Correlation lag The lag value at any point in the Correlation track is the time shift applied to the synthetic to move it into the position where it was when the correlation values were calculated.

<

For example, the correlation values at a lag of 0.2 seconds are the result of the correlation calculation made when the synthetic is shifted down 0.2 sec (or 200 ms). The correlation values at lag zero represent the synthetic/seismic relationship as it appears currently. The correlation values reflect a current correlation is not high. In this case, the visual match between the synthetic and seismic is not good.

Q. 3

The largest correlation value on each trace is marked with a symbol. A red diamond marks the trace posted on the Correlation track with the point of highest correlation (Figure 13). This symbol represents the best mathematical match found between synthetic and seismic (in the Time lag window). The lag value at this symbol is the amount of bulk shift that you would need to apply to move the synthetic into this best match position.

An asterisk marks the optimum point of correlation for the entire series of traces used in the correlation generation operation. This symbol is the global optimum correlation value of the best match among all of the traces.

¿SIN

V Time lag window

>200

■L/

Figure 13 The point of highest correlation

454 •Synthetic seismogram generation

Petrel Geophysics

>

I The Time lag window is defined on the Correlation tab in the Window section of the Seismic well tie dialog box (Figure 14). The Correlation tab in a Synthetic generation study is used to define the Time lag window for the Correlation track. For example, if you define a Start time of 1800 ms and an End time of 2200 ms, the time lag window is 400 ms. The Correlation track displays 200 ms below and 200 ms above. ■J! Seismic wefl tie

Q.

/ » Ertstuty TypeofMudy

jo

%Wal TST«ntfale Input | Output

•a

I Tmeihfc| Ccrcia&or [ Tr** manager ¡ Style

Start One:

1800

End tone

2200

a

¿¡¡j

Trace

CUeor defined Start trace

(T

\

2C

Single (race

wlillllllu 1

l/i Compute phaeemsae

IV

Andy

11 V

OK

1 1 A Cancel

Figure 14 The Correlation tab in the Synthetic generation study

Petrel Geophysics

Synthetic seismogram generation •455

Correlation tab This tab controls the display parameters of the Correlation track. It is divided into these three main sections (Figure 1 5): • Window • Trace • Phase mistie

<

|i Seismic well tie

:

Seismic well tie

[•]

'

J

m 0

Herts

£ Create stud/

(Study 3) Diamond 14 Synthetic generation

# Edit study

(Study 2) Diamond-14 Synthetic generation

Type erf stud/

4fcWe*

A D»amond-14

| Output j

(Hi

0 (Study 2) Diamond-14 Synthetic generation j Style

TÍ Template Input

a

Synthetic generation

Tsne shift 1 Corretoboñ~| Track manager

a

Window

Í Automatic set limits Start tome

1800

ms

End tome

2200

ms

a

Trace

© Match setsmic traces © User defined 10

Start trace

End trace

;

10

# Single trace Radius

15

a

Phase misbe

Wl Compile phase mistie

|✓

Apply

|

V

OK

|j

A Cancel

Figure 15 Three main sections of Correlation tab 456 •Synthetic seismogram generation

Petrel Geophysics

>

I Depending on the options that you select, the correlation between the seismic traces and the synthetic are updated. <

Q.

jo

You can specify your preferences, such as Start time and End time. You also can specify visualization of the trace, or compute the phase mis-tie in the wavelet phase to improve the synthetic/seismic tie.

>

Window section To specify a start time (ms) and end time (ms) for the vertical correlation interval, use the Window section on the Correlation tab. You can establish the limits of interest or choose the Automatic set limits option (default). This option takes the complete time window defined by the synthetic.

Every time that you make corrections in time, seismic, and other parameters (such as stretch and squeeze, and bulk shift), the correlation panel is updated. Trace section There are three options to select the number of traces to calculate the correlation: Match seismic traces, User defined, or Single trace.

Petrel Geophysics

Synthetic seismogram generation •457

I Match seismic traces option By selecting this option, you can visualize the generated correlation traces using the entire range of the reference seismic defined in the

Seismic display section of the Seismic well tie dialog box.

<

>

For example, if the number in the Xline window field (Figure 1 6) to be used for reference seismic on either side of the well location is four, five crosslines appear in each track of the seismic: one that corresponds to the Xline 381 (well position in this example) and four other crosslines after your reference (the number that you entered).

Q. 3

[TWTf

id I

I Pal— I ti»<— I *W.v*t

I Till] r i

5)*or ¡glA.IW

-a _

.

Btssi

“

jury

s I

<>

fSnÿ[R..k»dll

t

DID® 4

i

t:

■h 41 u P RH08

«

IJ

!

I

-Li m

i i Xline 381 Well

Figure 16 Define the number in the Xline window field

458 •Synthetic seismogram generation

Petrel Geophysics

I However, the Xline 381 that corresponds to the well location is

duplicated because it is shown in both seismic tracks. It has eight seismic traces to correlate with one trace in the synthetic. <

This means that the correlation track displays nine correlation traces, which correspond to eight seismic traces plus the one that is related to the well position. Each trace displayed in the correlation track is a cross-correlation between the trace in the seismic track and the synthetic.

>

Q. 3 J [OKMI

1 Ciwii*11 lx»*—

|4J ■

""Mi

SIS®

Soncor««too(v

—

0

:

si

i-:

■U4> + > ,

1

r':1

4-4 >4

kit

[+j flOT

® P«Hoe

!

L

■*

1 1 me

”

m

i

Repeated Xline

4 traces

r* MI 39i M3 Mí

n

o»

»

9 correlation traces

(381) Well position

Figure 17 Correlation track with an additional correlation trace

User defined By selecting this option, you specify the range of traces to be used to generate the correlation (Figure 17).

If Start trace is 0, the first seismic trace to be used in the cross¬ correlation is the first one defined in the Seismic track. Following the previous example, this trace is 377.

Petrel Geophysics

Synthetic seismogram generation •459

I Single trace

With this option, a single trace is calculated (Figure 18) following the well trajectory. The traces used in the calculation for this single trace (average trace) are the traces contained within a radius that you determine (Figure 19). Radius=2 traces

Radius=l trace

x

X

X

Q.

X

3

X

X

X

X

x

x

x

x

x

x

x

x

x

x

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Figure 18 Calculation of single trace

In this figure,

• ® represents the Well trajectory at time i • X represents the traces around the Well trajectory. lRadius=5 traces j Radius=10 traces Radius=15 tracesC

Radius 1 trace *ÿ**

t

V

é r-

*•/1

1

•* '

53J5?’

■

**•

■

■

r— -• _ I

"ÿ

:

1.

1

Figure 19 Single trace (average trace) correlation. 460 •Synthetic seismogram generation

Petrel Geophysics

I Figure 20 shows Trace options on the Correlation tab in the Seismic well tie dialog box for trace-by-trace correlation and single trace (average based on a radius) correlation.

110 ~ir V'*

A Owr-6

•a

Q.

SB

3

llllllll

ii

3 H % V

ft

C=3«

> >)) > ' ) I j

1

■SSP =■

| )>»)) ) ))>')))> ) I III

S

al

l'=r

. a

W02!!SSSÿ;::'M I

Figure 20 Trace options on the Correlation tab

1 Trace-by-trace correlation

2 Single trace (average based on a radius) correlation

Phase mistie The previous correlation options consider the time shifts to be applied in the synthetic to improve the synthetic/seismic tie. This functionality calculates the correlation between the synthetic/seismic while considering the phase of the wavelet. See Figure 21. A scan is performed at 360 degrees with a one-degree step. This scan generates the correlation between the synthetic and the seismic for each of the 360 samples. The output of this process is a suggested phase rotation value. You can apply this value at the active wavelet to improve the tie between seismic and the synthetic. Petrel Geophysics

Synthetic seismogram generation •461

1 Because this option is computationally costly, it is not enabled by default. ■;.|1 Seismic well tie Seismic wd tie

<

| Hwte |

Cl 0 Create study Edit study

(Study 4) Copper-6 Synthetic generation

Type of study

Synthetic generation

%We«:

A Copper-6 13 (Study 4) Copper-6 Synthetic generation

TS Template

Q.

Input

> (Study 5) Copper-6 Synthetic generation

| Output | Time shift | Correlation ~[ Track manager |

*(3

Style

a

Window

a

E Automatic set limits Start time: [o"~

ft

End time

3500

B

Trace

# Match sersmic traces © User defined Start trace:

0

End trace:

|20

© Single trace Radius

[HT

a

Phase mw

[Vj Compute phase mistie

|V

Apply

11 V

OK

||

* Cancel

Figure 21 Compute phase mistie on the Correlation tab

Time shift: Interactive bulk shift or continuous alignment The alignment of the well data to the seismic data can be adjusted to improve the tie between the seismic and well data. It also can be used to improve the estimated wavelet. You can apply interactive bulk shift or continuous alignments as discussed in the following sections.

462 •Synthetic seismogram generation

Petrel Geophysics

I Interactive bulk shift

<

After generating the first version of the synthetic seismogram using logs and a wavelet, traditionally, the next step in seismic well tie process is to perform a bulk shift in the synthetic to get a closer match between the synthetics and the seismic.

>

If the quality of the tie between the synthetic and the seismic is good enough, a stretch and squeeze will not be necessary and is not recommended as the first approach. Q. 3

Procedure — Use interactive bulk shift 1. On the Seismic Interpretation tab, in the Seismic-well calibration group, click Well tie editing to open the Tool Palette Seismic Interpretation

5

ill jjjgj

a

Petrq

•J|V Wavelet toolbox

Seismic wed tie

3

|

Log conditioning

Well tie

editing"]

Seismic-well calibration

EM

2. Cl ick Edit mode and then Add bulk shift line the Seismic well tie Tool Palette.

E Tool Palette

Sin

33

Edit mode ▼

Se'smic well tie

: >. : |g|» SB S 2 3 S k 3 > 4* ♦ H 31

1

Petrel Geophysics

Synthetic seismogram generation •463

I 3. Click the position where to add the alignment point (in the seismic track or the synthetic track). Because it is a bulk shift of the entire synthetic seismogram, the position of the Bulk shift line is irrelevant and is used only as a visual reference. 4. Move the line up or down to the corresponding event (in the seismic track or the synthetic track).

<

i Q.

TTTTTTnrmi

IE

k (

<

. flttTSHUlf

ii

¡

ill!

SMfiEMjP 1 -

<

m iiüüüit

ttt" pm ifBHti I I

464 •Synthetic seismogram generation

>

‘

mtm

■

■

\

Petrel Geophysics

>

I 5. On the Seismic well tie Tool Palette, click Apply bulk shift

H. You can edit interactively the bulk shift alignment points <

when Apply bulk shift

SI is switched on.

>

PF »1

m

\ Q.

5}

IE

Edit mode

E

Is 'A 2 3

*

» . m w,

S ;i

■

\

;

IKK'-

ftt

1|

*

lñcÍMÍiiüi'

■Ii li lJI ■*

Petrel Geophysics

Synthetic seismogram generation •465

The interactive bulk shift synchronizes with the Time shift tab in the study; any change made graphically updates the bulk shift box on the fly. 1ÿ1

MI Seismic well tie Seismic well tie '

i

[ Hints 1 (Study 3) Diamond-14 Synthetic generation

Create study:

(Study 2) Diamond-14 Synthetic generation

© Edit study:

4 Diamond-14

Well

¡3 (Study 2) Diamond-14 Synthetic generation

TÍI Template:

m

Input

|

a

Synthetic generation

Type of study:

Output Time shift

Correlation

Track manager

Style

a

Bulk time shift

/] Align bulk shift Bulk shift:

466 •Synthetic seismogram generation

6 68 *

ms

Petrel Geophysics

6. You can modify the format of the bulk shift line from the Style tab of the SWT in the study. 1ÿ1

r.|I Seismic well tie

<

Seismic well tie

Hints

>

ti ( Create study

(Study 3) Diamond-14 Synthetic generation

J »' Edit study:

(Study 2) Diamond-14 Synthetic generation

¿ Diamond-14

V'ell [•]

TjjTemplate: Input

Output

a

Synthetic generation

Type of study:

(ij (Study 2) Diamond-14 Synthetic generation Time shift

j

Correlation

j

Track manager | Style

|

El

Alignment points

0

® Show labels Color

Font size J

8

Show lines

Color

I

Line type

Solid

Line width

a

Bulk shift alignment

V) Show labels

Color Font size

8

/_! Show lines

Color

Line type

Solid

Line width

|

Apply

| [_ÿ_OK

A Cancel

TIP: Best practice is to perform the bulk shift before the stretch and squeeze. Any change in the bulk shift is added to the alignment points but no change to the alignment will affect the bulk shift. 7. Another operation available in the Tool Palette for the bulk shift is Delete bulk shift

Petrel Geophysics

, which resets all the values.

Synthetic seismogram generation •467

I Continuous alignment In the seismic to well tie process, sometimes small adjustments have to be made to match the synthetics with the seismic after the bulk shift is implemented. To perform these adjustments, we use the alignment functionality and this process is interactive.

<

Q.

m

3

Procedure — Use Continuous alignment The basic alignment workflow steps (time domain) are: 1. On the Seismic Interpretation tab, in the Seismic-well calibration group, click Well tie editing to open the Tool Palette.

Petrd

Seismic Interpretation

m

5

Seismic well tie

3

Wavelet toolbox Log conditioning

|

Well tie editing

|

Seismic-well calibration

2. Click Edit mode

m

a.

Tool Palette

ED

Edit mode Se'srric well tie

®

: >* 'o P £ n § 2 3 X ,*!. rl > + $ 31 31

468 •Synthetic seismogram generation

Petrel Geophysics

>

I 3. Click the position where the alignment point needs to be added (in the seismic track or the synthetic track). 4. Drag and drop the line to the corresponding event (in the seismic track or the synthetic track). <

>

iwiinwBwtiinTn

Q.

0 jo

1

(B) 1437.56

maj

(B) 1442.58 m*

ftlMII

Petrel Geophysics

(B) 1442.58 m*

l!

j

n

MU

Synthetic seismogram generation •469

1 5. In step 4, the synthetics is not yet aligned with the analogous event in the seismic. To apply the alignment, Align points

a

from the Seismic well tie Tool Palette must be active and the alignment points can be edited when the Align points

<

H state is switched on.

33

E Tool Palette Edit mode

Q.

▼

Seismic well tie

n>

¡3

iailSL"

>+ (A) 1415.35 ms)

% 9

Q

ps 3 H ;:s % S 31 >B

If A) 1415.35 mi

(B) 1442.58 msl

(A) 141S.35 ms|

1(8)1442.58 m»|

NOTE: You can add as many alignment points as required.

The default for Edit mode L_ÿ“I ¡S to add new alignment points. To perform any edits on the alignment points, the Edit mode

470 •Synthetic seismogram generation

*

X

EMI must be switched on.

Petrel Geophysics

>

I 6.

<

Q.

Use Delete alignment point [Ü3 during a study if an alignment point needs to be deleted. If it is switched on, the alignments points can be deleted by clicking the alignment point line. In the case where the study needs to be reset, you can use the

>

. However, it must be tool Delete all alignments points used very carefully because this option will delete all the selected alignments points instantly.

33

E Tool Palette Edit mode jo

▼

Seismic well tie

M

;§ )B

=ÿ

PW

ülHlgal o :•* ri > + $ si m

NOTE: The continuous alignment in the depth domain works the same for the Tool Palette, except that the tool to add new alignment points is not available. The alignment points are tied to an existing well top in the Well Tops folder selected in the study. The depth for the markers are considered real, so the drag-and-drop functionality must be performed only in the seismic tracks.

Petrel Geophysics

0

Synthetic seismogram generation •471

7. The values of the alignments are reported through the alignment line. You also can modify the format of the alignment line on the Style tab of the study. ¿11 Seismic well tie Seismic wel be

["Hints ]

Create study

f

(Study 3) Diamond-14 Synthetic generation

(Study 2) Diamond-14 Synthetic generation

0 Edit study Type of study

a

Synthetic generation

Diamond-14

Tfi Template

(*) (Study 2) Diamond-14 Synthetic generation

Input | Output | Time shift

i

Correlation

•

_

@

| Track manager | Style |

Alignment points -

1 ¡a

® Show labels Color

Font size

8

@3 Show lines Color Line type

Solid

Line width

a

Bulk shift alignment

® Show labels

-

Color

Font size

8

@3 Show lines Color Line type

Solid

Line width

[ •/

472 •Synthetic seismogram generation

Apply

j|V

OK

A Cancel

Petrel Geophysics

I <

Q.

Quality check interval velocity The Synthetic generation process has two tracks for quality checking. The first track displays the Input Interval Velocity vs. Output Interval Velocity. The second track displays the Drift curve in time for the shifts applied (Figure 22).

>

When time shift is applied to tie the synthetic with the seismic, this tool gives the information about the resultant interval velocity and the time shift applied to the alignment points. These tracks act as guides for the synthetic generation process and velocity editing.

3

■4- Copper-6 [TYvT]

t n L.

J

*

It

> mrm31•

»

=

■U » » ¡ > M i t P urrm

f MHIa

©

=

* •

■

. YM

i

*

©

i

. I—

■

I. liiyjjj, IT

I

BWHSyÿiwii T Figure 22 Synthetic generation process tracks for quality checking

1 Input Interval Velocity vs. Output Interval 2 Drift curve in time for the shifts applied Petrel Geophysics

Synthetic seismogram generation •473

I Interval velocity manipulation Editing/manipulating the interval velocity can be done on-the-fly to check the impact on your data.

You can edit the velocity values visually in a Well section window. Use the Seismic well tie Tool Palette to manipulate and delete velocity points. You also can lock the velocity manipulation into vertical and horizontal directions. Figure 23 shows the Seismic well tie Tool Palette where you can click different tools to perform these functions:

<

Q.

33

Tool Palette

3

Edit mode ▼

Seismic well tie

El

iS >.

P

$ss>"

<

+

*

Si 31

s

n>

Figure 23 Seismic well tie Tool Palette

| )i; |

Manipulate interval velocity

Delete interval velocity knee rl

Vertical interval velocity manipulation

>

Horizontal interval velocity manipulation

[4Ü Edit mode

474 •Synthetic seismogram generation

Petrel Geophysics

>

I Figure 24 illustrates the Interval velocity track. In the Interval velocity profile, you can manipulate the points when the Edit mode and Manipulate interval velocity tools are switched on in the Seismic well tie Tool Palette. >

<

1

Q.

jo

rt Figure 24 Interval velocity manipulation in the velocity track.

The sampling of the interval velocity can be set on the Output tab of the Seismic well tie dialog box in the Time/depth relationship (TDR) section (Figure 25). Remember that the interval velocity is an attribute of the checkshot.

Petrel Geophysics

Synthetic seismogram generation •475

1

;J1 Seismic well tie wel tie

Hints

C Create study

<

(Study 4) Copper-6 Synthetic generation

J•

Edit study

(Study 3) Copper-6 Synthetic generation

Type of study:

Synthetic generation

V/eM

A

T$1 Template Input | Output

fl

Copper-6

- (TB)

[§} (Study 3) Copper-6 Synthetic generation Time shift | Correlation

Seismogram

[

Track manager

|

Style

Copper-6_rmg [Realized] 1_synthetic 1

□ Autosave

[m Reflectivity

@0

RC

□Autosave

%

v

Computed seismogram (depth)

Time depth relationship (TDR)

TDR Name

aa

TDR Sample interval

150 00

~

□ Al samples

ft

□ Autosave Set as active TDR | v

Computed acoustic mpedanee

v

Resampled acoustic impedance

v

Partial seismogram from RC modeling

v

Seismic trace used in the single trace correlation

Apply

✓

OK

*

Cancel

Figure 25 Sample interval option in the Seismic well tie dialog box

476 •Synthetic seismogram generation

Petrel Geophysics

>

I The interactive manipulation feature can be an important tool for quality control purposes, especially if you have information about the lithology (from the driller or geologist, for example) because you know what range of velocity to expect (Figure 26). <

>

For the top of the logs, this tool can be a good option for creating a more realistic (geologically speaking) velocity trend. _£CoEEer-6 ÍTWT

Q.

-

HOU8T4 HOUST*

.BASE

il

+ c

man 2

I

M3

¿T

"3"

i

¡¡¡MU

t

K

::S i

ruon2

a

i-Í

0

SUQ

<

rntrniü

r

.BASE

1

''

1

'

1

»

l

ESS

'ÿ3

A

i

1

t

Hortion

4—1

|

-

PAMS

PAMSJ

. ♦

2.

Figure 26 Interactive manipulation of interval velocities

Petrel Geophysics

Synthetic seismogram generation •477

I Reflection coefficient (RC) modeling The Reflection Coefficient (RC) modeling tool is used for studying tuning effects. This tool can help you better understand the correlation between depth logs and seismic data.

<

You can access this tool during the Synthetic generation process. Accessing it in this way allows you to select/clear RC areas or individual coefficients and see the results as a partial synthetic. This process helps you better understand how these coefficients can impact the synthetic response and allows you to filter problematic areas from your synthetic.

Q. 3

Figure 27 shows buttons available for Reflection Coefficient (RC) modeling on the Seismic well tie Tool Palette.

33

B Tool Palette <¿2 ▼

Edit mode

Seismic wen tie

D > « >B

'E3

PP

aaaaEl*. a >

S$

ü ai

Figure 27 Buttons available for Reflection Coefficient (RC) modeling on the Seismic well tie Tool Palette

[ÿ1

Activate RC modeling Invert the RC selection

Ü Delete single RC selection Delete all RC selections By using the RC modeling process, you can select/deselect reflection coefficients and see the impact in the new synthetic created through RC modeling (Figure 28).

478 •Synthetic seismogram generation

Petrel Geophysics

>

ggaasam Al

✓

l

"

AV

■

>

RC

Negative

Positive

component

component

iw <

I

Partial Synthetic V

•i

Figure 28 Schematic representation of RC modeling workflow

0

Petrel Geophysics

Synthetic seismogram generation •479

I The result appears in the Well section window in the tracks shown in Figure 29.

The Save options of Partial Synthetic can be accessed on the Output tab in the Seismic well tie dialog box.

------

'+ÿ Diamond- U [T.'.r ~ Positive synthetic Negative synthetic •

~o3o|

II

Q. 3

1 2

f-o.io

o.oé

1:

© A

Partial Synthetic (represents the final synthetic from your selected RC values). Positive Synthetic (positive component of your selected RC values).

3

Negative Synthetic (negative component of your selected RC values).

4

480 •Synthetic seismogram generation

RC track

Petrel Geophysics

I Procedure — Perform Reflection coefficient (RC) modeling

5

<

Q. 3

in the Seismic well tie Tool 1. Click Activate RC modeling Palette. Three more tracks appear in the Synthetic display of the Well section window (WSW). The first track is the Partial Synthetic, the second track is Positive component, and the third track is Negative component.

m >

®

2. When the Activate RC modeling tool is switched on, go to your RC series track and select/clear areas of your log to see the impact on your Synthetic. Click to select the positive reflectivity. You see a component in the positive track and the resulting synthetic (that is, in the partial synthetic track). You can select multiple areas (positive reflectivity as well as negative reflectivity) in the RC series track for your synthetic.

------

® Díamond-14 [TWT] 030

'

Positive synthetic Neg¡stive synthetic -0.10

/

Petrel Geophysics

Synthetic seismogram generation •481

3. Save your partial synthetic. On the Output tab of the Seismic well tie dialog box, click Save or select the Auto save check box, as shown in the figure. ;JI Seismic well tie

j Hints

Seismic well tie

J [•]

O

S3

Create study

(Study 3) Diamond-14 Synthetic generation

Edit study:

(Study 2) Diamond-14 Synthetic generation

Type of study

Synthetic generation

%Wefl:

¿ Diamond-14

TÍTemplate

(3 (Study 2) Diamond-14 Synthetic generation

Input | Output

| Time shift ] Correlation ] Track manager

Seismogram

0

Style

@0

Diamond-14_m»g [Realized] 1_synthetic 1

n Auto save Reflectivity

ia

RC

0 Auto save v

Computed seismogram (depth)

v

Time depth relationship (TDR)

v

Computed acoustic impedance

v

Resampled acoustic impedance

* Partial seismogram from RC modeling Name

A

Partial synthetic

A

@1 Auto save v

Seismic trace used in the single trace correlation

■J

482 •Synthetic seismogram generation

Apply

■/

OK

A Cancel

Petrel Geophysics

I Track manager The Track manager tab provides a shortcut to help you manage the tracks that you want to display within the study. <

Q. 3

When you generate a study, the default tracks are checked; however, if you consider the visualization of some of them to be unnecessary and want a cleaner window, this operation can help you. Clear the tracks that should not be displayed.

>

You access the Track manager tab in the Seismic well tie dialog box (Figure 30). bH Seismic well tie Create study

Edit study

(Study 2) Diamond-14 Synthetic generation

a

Type of study:

V/e«

4 Diamond-14 ¡3 (Study 2) Diamond-14 Synthetic generation

Input

| Output | Time shift | Correlation | Track manageT~| Style

Synthetic generation tracks display

gllnptflog

a

URCIog @] Wavelet [21 Left seismic reference @] Synthetic seismogram

2! Right seismic reference 2 Correlation □Interval velocity 2 QC interval velodtyS drift

Figure 30 Track manager tab

The tracks can be hidden/posted by selecting the check box. The Well section window template controls the positioning of each track.

Petrel Geophysics

Synthetic seismogram generation •483

9 <

Lesson 2 — Integrated seismic well tie The Integrated seismic well tie study (Figure 31 ) is an integrated process in which Sonic calibration and Synthetic generation are done simultaneously using the same Well section window canvas. The sonic calibration and synthetic generation parameters are defined together to run an integrated seismic well tie study. B

IS Seismic well tie SeiimicwBtee ~l HinU | o Create study

(Study 3) Diamond-14 Integrated seismic well tie

o Edit study

(Study 2) Diamond-14 Synthetic generation

Type of study

4fcWet

0

Integrated seismic well tie

T|j Copy template

-H

Integrated seismic wdlbe default template

Output Timeshr. Datummg Time-depth Options | Statistics | Córrele vn ] Track rra

Inpi*

J

*

s£> i Diamofid-14 Style

a

Parameters

At Sonic log

1 4*

y¡ TDR:

At Some Despiked -'}j Diamond-14/AICheckShots cs

•Wavelet

Drop from other weJ

»

| JA»Analytical Wavelet

*

6 n

© Time varying wavelet Seismic display Seismic

<

CpTig [Reaped] 1 § Inline

©Xkie

Q Alow webs outside survey Position

®|_®

$ 622

Inline

XSne

Xbne window

570 io

;

Reflectivity coefficient

RC calculation method

Sonic velocity and density

Some or velocity

At Some Despiked

Density v

($J P RHOB

Advanced settings

ly

Apply

|| y

OK

A Cancel

Figure 31 Integrated seismic well tie 484 •Synthetic seismogram generation

Petrel Geophysics

>

I Integrated seismic well tie study template

<

Both processes are fully integrated under the same canvas (Figure 32). Operations such as zoom and well top correlations are consistent across the window.

>

Similar to the Sonic calibration and Synthetic generation, you can select a template for the study or use the default template. Synthetic Generatior

SONIC CALIBRATION

Q.

© ©I©

3

©©

■

11

13

:4- mm

}

©i

10

E) 3) ©

1

>

t ,

x

\

1

Figure 32 Integrated seismic well tie

Select the default template to display this information: 2 3

Knees and drift curve Residual drift Input logs used in sonic calibration

4

Interval velocity

5

Average velocity TWT Picked Density and Sonic logs for synthetic Reflectivity coefficient

1

6

7 8

Petrel Geophysics

9

10 11 12 13 14 15 16

Wavelet Original seismic Synthetic seismogram Original seismic Correlation Interval velocity Input/output interval velocity Drift curve

Synthetic seismogram generation •485

I The default template Is an integration of the default templates used by Sonic calibration and Synthetic generation studies. The first section is related to the Sonic calibration and the second section is related to the Synthetic generation. >

<

Synthetic seismogram in the Interpretation window The Seismic to well tie process is a stand-alone process; however, all outputs from the process can be integrated with other processes and displayed in different windows.

Q. 3

In an Interpretation window, you can display the wellbore trajectory with the synthetic seismogram to identify the seismic reflectors that represent the geological well tops (markers) before starting horizon interpretation. Display the seismic intersection in the Interpretation window. In the Global well logs folder, choose the Synthetic seismogram.

In Figure 33, a Synthetic seismogram appears along the well trajectory to identify the seismic reflectors that represent the geological well tops (markers). Sffl-B’ T

l&bÿjgiTWT

i.

a

TP

m

«“jr

*T

a

Figure 33 Synthetic seismogram along the well trajectory 486 •Synthetic seismogram generation

Petrel Geophysics

I <

Synthetic seismogram in a 3D window When the time-depth relationship is established, display the inline and crossline at the well position with the synthetic seismogram in a 3D window (Figure 34) in time domain (TWT).

>

Displaying this data in a 3D window provides a visual way to quality control the match between the synthetic seismogram and the real seismic data. L Q.

¿fe?-»-

3

:

ii

r,_

%

wS

SPRIg: v\

:z

'

>5ÿ

m

Jr*

US'

Figure 34 Seismogram and seismic data together in the time domain (TWT) in a 3D window

Obtain a synthetic match Problems can arise when you generate a synthetic that does not match the seismic. It is important to be aware of the issues when generating a synthetic that can lead to such problems.

If seismic data was not processed to an optimum level, data had issues with energy scattering due to surface terrain, or logging shows other problems (too few runs or bad runs), the synthetic might not fit at all. Similarly, if you do not choose the correct datum or you do not edit the logs properly, the synthetic is unlikely to tie to the seismic.

Petrel Geophysics

Synthetic seismogram generation •487

I There are many reasons for a poor match: • Poorly edited log data • Poorly defined reflectivity series • Not enough/poor log data (the logging run is too short to be useful for synthetic) • Issues with data acquisition (acquisition noise, energy scattering, diffractions from fault plane, or gas effects) • Seismic data processing issues (noise, velocity, or multiples) • Not enough depth information • Poorly defined wavelet • Misleading datum information.

Q. 3

Exercises — Generate a synthetic seismogram The result of the previous exercises has produced a calibrated timedepth relationship, which is selected on the Time tab of the well Diamond-14 Settings dialog box. Exercise workflow 1. Generate a synthetic seismogram using a predefined wavelet. 2. Apply interactive bulk shift or continuous alignments to adjust the time shifts between synthetic and seismic. 3. Set synthetic seismogram display settings. 4. Display the synthetic seismogram in an Interpretation window.

0

Exercise 1 - Generate a synthetic seismogram using a predefined wavelet In this exercise, you generate a synthetic seismogram using an existing wavelet. 1. On the Seismic Interpretation tab, in the Seismic well calibration group, click Seismic well tie. Petroleum Systems

m

|

Seismic well tie

V|Sr Wavelet toolbox

£2

|

Insert

Seismic interpretation 2D/3D interpretation

Structural Modeling

Property

Modelmg|

4 W K! S*"""-0

Log conditioning

Seismic-well alteration

488 •Synthetic seismogram generation

Decision Support

,

Mesh

.|

volume itb butts

Mixer

„

Neural net

Attributes

Petrel Geophysics

I <

Q.

2. Create a new study and select type of study as Synthetic generation. 3. Select the well Diamond-14 from the Well list. The study name is updated, depending on the well that you select. You can change the name of the study. 4. Select Calibrated TDR in the TDR list. 5. Select Analytical Wavelet from the list next to Wavelet. This wavelet is a simple Ricker wavelet that is stored in the Wavelets folder in the Input pane. You also can create a new wavelet by clicking Wavelet toolbox ln the Seismic-well calibration group.

I

jo

31 5

Seismic Interpretation

m

Seismic well tie

>

Petrd

Wavelet toolbox

jifl

Log conditioning

"fS WeM tie «W'Hg

Seismic-well calibration

6. Select mig [Realized] 1 next to the Seismic field. 7. In the Reflectivity coefficient section, choose Sonic velocity and the density calculation method. 8. In the Sonic and Density fields, select Sonic Despiked and RHOB.

Petrel Geophysics

Synthetic seismogram generation •489

9. The Seismic well tie dialog box should look similar to the figure. Click Apply to generate the synthetic seismogram. T.|I Seismic well tie

<

Seismic well tie

Hints

•

JC

1

Create study

(Study 2) Diamond-14 Synthetic generation

Edit study

(Study 1) Diamond-14 Sonic calibration

Type of study:

Synthetic generation

4k

©s

Wei:

TÍ) Copy template

Input! Output Time shift

1 0

i

¿ Diamond-14

TB

Synthetic generation default template

Correlation

© |s|

o Wavelet;

>

2

Track manager

I

Style

o

Calibrated TDR

JJAP. Analytical Wavelet

*n

® Time varying wavelet Seismic display Seismic

©

®s

mig (Realized) 1

O Xlme

o Inline

[r] Allow wells outside survey Position

-ft

Inline

622

ft

Xline

Xline window

10

570

2

Reflectivity coefficient

RC calculation method

Sonic or velocity: Density: v

Sonic velocity and density

efr At Sonic Despiked m>| PRHOB

©

©

Advanced settings

Apply

490 •Synthetic seismogram generation

|

✓

OK

A Cancel

Petrel Geophysics

I <

The synthetic seismogram is generated virtually and a new Well section window opens. 10. Zoom inside the well section: a. In Select/Pick mode, place the cursor in the track (TWT), between the gray and the white area. b. Click and drag the cursor to stretch or squeeze the display. •

ISS

snvi i*

--

g :f

»T

■a-a-'Q

i°»

> sm-«H >|

■

mr

Q.

-

jo

J

:

i

3*

Petrel Geophysics

l

»

“

l~

mm

•: :

\

Synthetic seismogram generation •491

1 11. In the Position section of the Input tab in the Seismic well tie dialog box, click Set display position to deviated well <

Input

I Output I T«ne shift I Correlation I Track

*

o

[ÿ1 lA.Analytical Wavelet

Wavelet:

*

4-

n

Time varying wavelet

|4l B0mig [Realized] 1

Seismic:

Q.

>

| Style |

t Calibrated TDR

TOR

# Inline

Xkne

□ Alow wels outside survey

a

Position 622

Inline

Xline:

570

XSne window

10

:

12. On the Output tab, click Save «i next to the Seismogram field. I Input I Output | Time shift | Correlation | Track manager | Style I Seismogram:

Diamond-14_mig [Realized] 1.synthetic 1

0 Autosave

ÜM

The seismogram is stored in the Input pane in the Global wells logs folder in the (Study ...) Diamond-14 Synthetic generation folder. 13. Similarly, save the computed acoustic impedance; you will use it in the next lesson. (Study 2) Diamond-14 Synthetic generation

>

B Visual □ Diamond-14_mig [Realized] 1_synthetic 1 AI U AI

492 •Synthetic seismogram generation

Petrel Geophysics

I Exercise 2 - Make interactive bulk shift and continuous alignments After generating the first version of the synthetic seismogram using <

Q.

jo

0

logs and a wavelet, traditionally, the next step in the seismic well tie process is to perform a bulk shift in the synthetic to get a closer match between the synthetics and the seismic.

>

If the quality of the tie between the synthetic and the seismic is good enough, a stretch and squeeze will not be necessary and is not recommended as the first approach, and all updates are applied as soon as they are required. 1. On the Seismic interpretation tab, in the Seismic well calibration group, open the Well tie editing Tool Palette.

I

Seismic Interpretation

yfa. Wavelet toolbox Seismic well tie

[Ijfll

Log conditioning

Well tie editing

|

Seismic-well calibration

SI

and then Add bulk shift line 2. Click Edit mode the Seismic well tie Tool Palette.

Petrel Geophysics

ISin

Synthetic seismogram generation •493

I 3. Click the position where to add the alignment point (in the seismic track or the synthetic track). Because it is a bulk shift of the entire synthetic seismogram, the position of the Bulk shift line is irrelevant and is used only as a visual reference. 4. Move the line up or down to the corresponding event (in the seismic track or the synthetic track). 4- Diamond- 14 [T'.'.T

I560.00

Q. 3

Inline 622 - mig [Realized] 1

570.00

m

\ _h_i

Inline 622 - mig [Realized] 1

::

580.00

fitmm

>> ml

*

—

j, d'k

1

< <

1412.62 ms (9.18

/ l

ni-Tmm

494 •Synthetic seismogram generation

”

í

% s

ÜÍ

=4

m

Petrel Geophysics

On the Seismic well tie Tool Palette, click Apply bulk shift

5.

You can edit interactively the bulk shift alignment

.

<

points when Apply bulk shift Inline 622

%

0

570 00

m

Inline 622 - mig [Realized] 1

'

1570 00

iiiiW 9.18

>nMn

i >

u-v» 569

i

i

B S

r

n .

<ÿ 1412.62 ms

s

j

i í í I l~f

ifrh 412.62 ms (9.18

nltBfnBg > TTTTTn FiTTf

T?

> s>

1 I

>

is switched on.

T» Diamond-14 [TvVT]

- mig [Realized] 1 i

H

f

1 1

rm 1 1

J

>

b

11 i

I

) )T

»

i

}

m í ni

I

6. The interactive bulk shift synchronizes with the Time shift tab in the study; any change made graphically updates the bulk shift box on the fly.

m Seismic well tie Seismic well be

t.

lÿl

Hints

j (Study 3) Diamond-14 Synthetic generation

Create study;

J 9 Edit study

(Study 2) Diamond-14 Synthetic generation

Type of study:

®

Well:

T{] Template: Input

|

l

a

Synthetic generation

4

Diamond-14

(i) (Study 2) Diamond-14 Synthetic generation

Output Time shift

| Correlation ] Track manager

'0

Style

a

Bulk time shift

® Align bulk shift Bulk shift

Petrel Geophysics

918 * ms

Synthetic seismogram generation •495

7. You can modify the format of the bulk shift line from the Style tab of the SWT in the study. fill Seismic well tie <

Seismic well tie

“

Hints

® Edit study:

Type of study:

(Study 2) Diamond-14 Synthetic generation Synthetic generation

m

4ÿ Well

¿ Diamond-14

T{] Template:

¡3 (Study 2) Diamond-14 Synthetic generation

Input

0

> (Study 3) Diamond-14 Synthetic generation

Create study

(

[•1

]

| Output pirne shift | Correlation [

Track manager | Styfe

a

Alignment points •J Show labels

Color

Font size ■J

8

Show lines

]-

Color

Line type Line width

Bulk shift alignment

Solid

-

4

ÜJ

|y] Show labels

Color

Font size

8

J Show lines

Color Line type

Solid

Line width

|✓

Apply

~| | V

OK

A Cancel

8. Click Delete bulk shift <1 in the Tool Palette, This resets all the values. Now you will perform continuous alignment in the following steps.

In the seismic to well tie process, sometimes small 496 •Synthetic seismogram generation

Petrel Geophysics

1 adjustments must be made to match the synthetics with the seismic after the bulk shift is implemented. To perform these adjustments, we use the alignment functionality and this process is interactive.

<

>

[¿5j

is switched on in the Tool Palette 9. Make sure Edit mode and click on the position where the alignment point needs to be added (in the seismic track or the synthetic track). NOTE: You can add as many alignment points as required.

[¿5l

Q.

The default for Edit mode LÿJ is to add new alignment points. To perform any edits on the alignment points, the Edit mode

a

¿51

L_“iJ

ft

must be switched on. rj? Diamond-14 [TvVT]

Inline 622 - mig [Realized]

>.00

_

_

.

. .

Inline 622 - mig [Realized]

"Loo

i Sir SSL'S?»

i

«ÿÿÿ

H

mmi

U i

>

*

?

>>

/

\

W4

>

m

(

/

I 1 \ \ \ 1 S

v

d

Siii

t|(B) 1598.52

y »-»ÿ i (C) 1723.6 msTT

I.-''.- .

/

inTI

» i» i s s \ 1719.01

m

.6 ms[

U

1

7

» >

>ÿ

IB) 1598.52

|(D) 1772.95

wm

itffliiSI ¡t

Petrel Geophysics

»

1885.4

<

(

rrrTTTTTTT Synthetic seismogram generation •497

I 1 0. In step 9, the synthetics is not yet aligned with the analogous event in the seismic. To apply the alignment, Align points

H in the Seismic well tie Tool Palette must be switched on and the alignment points can be edited when the Align

<

points IM] is switched on. Repeat Step 9 through Step 1 0 as necessary. during a study if an 11. Use Delete alignment point alignment point needs to be deleted. If it is activated, the alignments points can be deleted by clicking over the alignment point line. In the case where the study needs to be reset, you can use

Q.

jo

Delete all alignments points . However, it must be used very carefully because this option deletes all the alignments

498 •Synthetic seismogram generation

Petrel Geophysics

>

12. The values of the alignments are reported through the alignment line and you also can modify the format of the alignment line from the Style tab in the study. til Seismic well tie Seismic well tie

Hints

I

n Q Create study:

(Study 3) Diamond-14 Synthetic generation

J

(Study 2) Diamond-14 Synthetic generation

o Edit study:

Type of study: [•1

0

Synthetic generation

4ÿ Well:

¿ Diamond-14

TE Template

¡2 (Study 2) Diamond-14 Synthetic generation

Input

| Output | Time shift [

Correlation | Track manager Style

Alignment points

[21 Show labels

Color

I

Font size

8

■”

[21 Show lines Color Line type. Line width

Bulk shift alignment

—

Solid 4

□

2] Show labels Color

Font size:

8

J Show lines

Color

Line type

Solid

Line width

[V

Petrel Geophysics

Apply

||V

OK

A Cancel

Synthetic seismogram generation •499

I 13. On the Output tab, change the name of the Synthetic seismogram to Diamond-14_mig [Realized] l_synthetic l_shifted and click Save Í . | Input l Output

<

l Time shift | Conetobon| Track manager I Style |

H

Diamond-14_mig [Realized] 1_synthebe 1_shifted

□ Autosave

1

The edited synthetic trace now can be found in the Input pane in the Global well logs, (Study ...) Diamond-14 Synthetic generation folder.

d

A

M 0 (Study 2) Diamond-14 Synthetic generation C" 0 Visual

Jo

¡P Q

Diamond-14_mig [Resized] 1_synthetic 1

MOM

¡P □ Diamond-14_mig [Realized] 1_syrthetic 1_shifted

0

Exercise 3 - Change the synthetic seismogram display settings 1. Open the Template settings dialog box for the Well section

window by clicking Template settings toolbar.

&k

500 •Synthetic seismogram generation

TWT

- jfj1

(Study 2) Diamo

•

in the Window |

I’t>

Undef

Petrel Geophysics

>

I <

2. Experiment with the parameters and observe the changes. For example, you can clear the interpolated density and density fill check boxes for the surrounding seismic traces and the synthetic seismogram respectively (as shown in the figure). @ Sitting» for ’(Stoidy 2) Diamond-14 Synthetic generation-

hey

•

'*JS

H □

IffT an 00 Bi

™>

Quo

•

Def.mt.or

*

S RC ISU»

&

Q.

am i|¡¡¿

aw»...» HI

"

:áfe¡

jo

<

IP

*

Petrel Geophysics

!ÿ DM,»|

B

—

o*

r.

□

*

-

a

a

I •

RE

*

>

a

0«««.

SpT

|«, Style|

aai we aP

a

± Setting» for (Study 2) Diemond-14 Synthetic generation'

'U

* n**»*

HI

-

Í8S

IP !

>

Synthetic seismogram generation •501

I "3

11

r r

■ Sir'

> >

::. * ) > > 1

;

Q.

a

'

>

... ííffftí

/

*

i

i;;;;;;:;; ) / ?

tü

M FH Ms 1IvM gM MfflW ffi ¡

Pffffff

,

» 1

t!il! IIIl «M|/

0

502 •Synthetic seismogram generation

/

/

(

|(E) 1885.4 m»| /

(

(

( |E) 1886.4 n>l| \

l

I

\

Exercise 4- Display the synthetic seismogram in other windows 1. Open a new Interpretation window and display cross line 560 from the mig Realized] 1 cube. 2. Display the well Diamond-14 in the same window with Dallas, Houston, Kobe, and Paris well tops.

Petrel Geophysics

I 3. Select the synthetic seismogram Diamond-14_mig [Realized] 1_synthetic 1_shifted in the Global well logs folder in the Input pane.

*

<

Ej 0 (Study 2) Diamond-14 Synthetic generation

>

> C □ Visual ¡3p Q Diamond-14_mig [Realized] 1_synthetic 1 AI □ Al

4. With the aid of the synthetic seismogram, identify the seismic reflectors that represent the well tops.

Q. 3

i—wamgiiwf

i

ii

£fi «

«

is

a

a"Tr s s 1 s a

<

a as a a

JUL

-

"f >

4

-

~

- -_•=

_-

5. Open a 3D window and display the inline and crossline at the well position with the synthetic seismogram to quality control the match between the synthetic seismogram and the real seismic data. Make sure that the domain of the window is set toTWT.

Petrel Geophysics

Synthetic seismogram generation •503

I 9

Review questions

• •

<

• • Q.

•

List seven ways to calculate a reflectivity coefficient in Petrel. What is meant by use of interactive bulk shift or continuous alignments to adjust the time shifts between synthetic and seismic? Why do you quality check input and output interval velocities in the Seismic well tie process? What is Reflection Coefficient (RC) modeling, partial, positive, and negative synthetics? Can you save partial synthetic seismograms? If yes, how?

>

Summary

jo

In this module, you learned about: • using the synthetic generation process and input data • calculating the reflectivity coefficient • interactive bulk shift or continuous alignments to adjust the time shifts • using correlation tools and track • modeling the reflection coefficient (RC)

<

504 •Synthetic seismogram generation

Petrel Geophysics

>

I Module 9 — Wavelet generation <

Q.

jo

Seismic-to-well tie is key at any stage of the development of a field and is an essential step of the seismic interpretation workflow, bridging the gap between the time and depth domains. Equally, it plays a key role in the wavelet extraction process as it is involved in seismic inversion for reservoir characterization workflows. In this module, you learn different methods to generate a wavelet in Petrel.

Learning objectives After completing this module, you will know how to: • use the Wavelet toolbox • use the Analytical, Statistical, Deterministic, and Wavelet averaging methods • Multi-well extended white wavelet extraction (MWEW) • Time varying wavelet

Petrel Geophysics

m

Wavelet generation •505

I

flf

Lesson 1 — Wavelet toolbox The Wavelet toolbox (Figure 1) integrates all related processes (Wavelet extraction. Wavelet Builder, and Wavelet viewer) in a single canvas. The toolbox provides an interactive tool that is easy to use.

All methods and their respective algorithms and parameters are available in the Wavelet toolbox. You also can use options in the toolbox to visualize these objects, without creating multiple windows to generate different types of wavelets.

Q

— d>

Wavelet toolbox Wavelets

*

|

*

, (*]

j

/

> Ed* «dating

[ÿ| Ricker 1

&

g 128 ma

u ■23

"5

10

TWM»

”

□ Invert polanty

o

J 180

LI LCoBWit.toaaopliiaa,

ss=

: Figure 1 The Wavelet toolbox window

1

Displayed Wavelet list

2 3

Method and algorithm Parameters of extraction/generation Operations Visualizations

4

5

506 •Wavelet generation

Petrel Geophysics

Accessing the Wavelet toolbox You can open the Wavelet toolbox in one of these ways (Figure 2): On the Seismic interpretation tab, in the Seismic well <

>

calibration group, click Wavelet toolbox (]).

\±\

Click Wavelet toolbox in the Seismic well tie dialog box (2). From any wavelet in the Input pane, right-click the wavelet name and select Open in wavelet toolbox( 3).

[•]

I <&

Petroleum Systems

Seismic Interpretation

m

§

Seismic well tie

0

Wavelet toolbox

iff!

J

Log conditioning

Insert Well tie editing

Seismic-well calibration

Decision Support

m a

▼

Mesh

Seismic interpretation

Volume attributes

editing

2D/3D interpretation

Property Modelirj

Structural Modeling

ifl , “V—

Mesh

ggl [|j

Mixer

Surface attributes Calculator

Neural net Attributes

ill Seismic well tie Seismic well tie

Hints

•

Create study

(Study 3) Diamond-14 Synthetic generation

J O Edit study

(Study 2) Diamond-14 Synthetic generation

Type of study

Synthetic generation

®

%Wel Tfl Copy template Input

Output

*

Diamond-14

- ra

Synthetic generation default template

Time shift

Correlation

Track manager

| Stÿe

o

Calibrated TDR

•

Wavelet:

|~ÿ>]

Analytical Wavelet

a© n rr

■

O Time varying wavelet Seismic display

Seismic:

(Realized] 1

*>> # Inline

XJine

[r| Allow wells outside survey

Position

ü

Inline Xline

m~~

Xline window:

io

:

Reflectivity coefficient

Acoustic impedance

|

| AI Al

Advanced settings

~*

Input

4ÿ0 Wavelets

kV0 Acoustic impedance

RC calculation method

(v

622

X

■

Analytical Waveltj

B

Settings

(1ÿ [=ÿ

Import (on selection)

H

Delete

[j|j)

Copy wavelet (data only)

.. .

Export object

Ed.it global color table

E

.. ,

Open in wavelet toolbox

Guru

Figure 2 Accessing the Wavelet toolbox Petrel Geophysics

Wavelet generation •507

I Types of wavelets A simple 1D synthetic seismogram is computed by convolving a reflectivity series with a wavelet. Amplitude and phase spectra in the frequency domain define a wavelet.

<

The Wavelet toolbox offers five ways to extract wavelets: • Analytical • Statistical • Deterministic • Multi wavelet average • Multi well

Q

Analytical method Analytical wavelets are standard model wavelets. There are five analytical wavelet types available in Petrel: Ricker, Ormsby, Tapered Sine, Butterworth, and Klauder (Figure 3).

508 •Wavelet generation

Petrel Geophysics

>

I ©

I" fi)—

<

’

!§ÿSJ

Q

□9

>

“C5T

i::

J

*

_

@ :

■c:

0]

*

~

— Wr i"

©

Figure 3 Five types of wavelets available for the Analytical method

4

Ricker Butterworth Klauder Ormsby

5

Tanered sine

1 2 3

Petrel Geophysics

Wavelet generation •509

1 Ricker method A Ricker filter requires only one input - the peak frequency (Figure 4). This filter commonly is used for synthetic modeling.

I With a Ricker wavelet, no side-lobes are

seen in the amplitude vs. time spectrum. The Butterworth, Ormsby, Klauder, and Tapered sine filters all have associated side-lobes.

No bandpass filter is involved. The frequency and phase spectrums are purely a function of the peak frequency input. . _ Wavelet _ 1.0-

Q

0.8-

|

a

f I I

«L

¿

0.&0.4

0.2 0.0-0.2 -04 -60

-50

40

-30

-20

-10 0 10 Time (ms)

20

30

40

50

60

Figure 4 Ricker filter with a 40 Hz peak frequency chosen

Ormsby method The bandpass (Figure 5) of an Ormsby filter can be described using as many as four corner frequencies. Wavelet 1.0-

0 80.6-

|

% I

0.40.2-

0. -0 2-04-

-60

-50

-40

-30

-20

C -10 10 Time (ms)

20

30

40

50

60

Figure 5 Ormsby filter 510 •Wavelet generation

Petrel Geophysics

I Figure 6 shows the four Ormsby filter frequencies in Petrel. 100

2 <

3

75

>

I25

Q

1 o

4

Bandpass 50

75

WO

125

150

175

200

225

Figure 6 Bandpass for an Ormsby filter

<

1 Low cut frequency, where all lower frequencies are filtered out and not used. 2 Low pass frequency where after this frequency, 1 00% of all higher frequencies is used:

>

3 High pass frequency, where frequencies higher than this one are linearly tapered until point 4. 4 High cut frequency, where any frequencies higher than this one are filtered out and not used.

Petrel Geophysics

Wavelet generation •511

I Tapered sine method A tapered sine filter (Figure 7) is defined by a low and a high cutoff similar to a Butterworth filter but applies no further filters. <

A Butterworth filter applies two slopes (refer to the Butterworth method description). Wavelet 1.00 8-

Q

06-

■§

i I

04~ 0.2-

o. -0 2-

-0.4-

-0 6-60

-50

40

-30

-20

10 -10 0 Time (ms)

20

30

40

50

60

Figure 7 Tapered sine filter

512 •Wavelet generation

Petrel Geophysics

>

I <

Butterworth method The Butterworth bandpass consists of two cutoff frequencies taken at 3 dB down from maximum power, or approximately half power (-50% on the amplitude scale in Figure 8). In the example, frequencies are at 1 0 Hz and 50 Hz. The Butterworth filter also requires two slopes.

>

Wavelet 100.8-

Q

<

|

0.6-

1

0.4-

«

0.2-

I o.o-

>

-0.2-0.4-

-60

"

-50" ' 40

-30

' '

-20

' '

-10

"

'0

" '

Time (ms)

Figure 8 Butterworth filter

The slopes are defined as decibels/octave in which an octave is a doubling in the frequency (for example, 10 Hz to 20 Hz). A decibel is a unit of measure for acoustics defined by the formula; dB = 20log(X/Y)

In this equation, X/Y is the ratio of amplitudes. If the ratio of X/Y is 2, it is 6 dB; a ratio of 10 translates to 20 dB (Figure 9).

75

I-

1

2

Bandpass

25

0

25

50

75

100

125

150

175

200

225

Figure 9 Bandpass of a Butterworth filter Petrel Geophysics

Wavelet generation •513

I Klauder method An analytical approximation of the Klauder wavelet is computed through autocorrelation of an actual vibraseis sweep signal. A Klauder wavelet is defined by two frequency cutoff values: a low cutoff and a high cutoff. Figure 10 shows these frequencies set at 10 Hz and 70 Hz.

<

>

A boxcar represents the contributing frequencies. This boxcar assigns the same constant amplitude for all frequency components. Because of sudden discontinuities in the amplitude of frequencies at the beginning and end, the wavelet has some undesirable side-lobe oscillations.

Q

Wavelet

5: 4:

<

1

3'

4

"

1

>

I1

8. 0: -1“

-2: -60

-50

-40

-30

-20

-10 0 10 Time (ms)

20

30

40

50

60

Figure 10 Klauder filter

514 •Wavelet generation

Petrel Geophysics

I <

Wavelet phase The most important decision that you make when using Petrel is to use either a minimum or a zero-phase wavelet. Dynamite and airgun sources produce impulse (minimum phase) source signatures and the resultant data is not necessarily reprocessed to zero phase.

>

Be careful, because the convention for a zero-phase wavelet for the USA and Europe are opposite in phase (Figure 11). Q

0.4-

A

0.8

0 2-

0 b-

0-

0.4-

<

-0 2-

0 2-

>

•0.4-

0-

0 6-

o

o sU*1

-0.4-0 05

-0 025

0

0 025

0 05

-005

0 025

0.025

0.05

Figure 1 1 USA zero-phase wavelet (left) and European zero-phase wavelet

(right)

Petrel Geophysics

Wavelet generation •515

I Statistical method The statistical extraction method (Figure 12) assumes that the embedded wavelet is the same as the truncated autocorrelation of the seismic trace. The average autocorrelation from many traces is used to provide a more representative estimate.

<

>

It is possible to access statistical extraction even if no sonic log exists for the borehole. The statistical method transforms the autocorrelation of all of the input seismic traces into the frequency domain, averages the spectra, and inversely transforms the averaged spectra into the phase specified. Such wavelets are zero-phase by definition.

Q

A statistical wavelet can approximate the correlated source signature used during Vibraseis (non-minimum phase) seismic acquisition. It is useful particularly when the quality of seismic data is high and the quality of the RC series is low.

<

Falca A>“—

’

I:: i-

r

|

* " ""

!: ■

”

4

: a

3I

|

Figure 12 Statistical method of wavelet extraction. Phase and length of the wavelet are supplied. Amplitude spectrum is predefined from the seismic trace.

516 •Wavelet generation

Petrel Geophysics

>

I <

Q

Principles of the Statistical method The statistical methods can be employed as a reliable quality control tool for the deterministic methods, a way of interpolating the wavelet phase between non-matching wells or act as standalone tools in the absence of wells. • Given a borehole trajectory, this method extracts both minimum and maximum values of X and Y: (Xmin,Ymin) and

• • • <

>

(Xmax.Ymax). The auto position (determined automatically) is calculated as the mean between them: ([Xmin+Xmaxj/2, [Ymin+Ymax]/2) It defines the position of the central trace for the extraction. Neighborhood (1x1 , 3x3, 5x5) defines the number of traces to be used for the average.

Figure 13 shows how the statistical method defines the position of the central trace for the wavelet extraction for a given borehole trajectory.

>

+ Xmax]i [Kmin + V'maxjy

Y/

Neighborhood

to *

i

>

.

X

i

Figure 13 Defining the position of the central trace

Petrel Geophysics

Wavelet generation •517

I Deterministic method Deterministic corrections commonly are applied to rectify phase mismatches between final processed seismic data and synthetics created from well logs (Figure 14). For this method, a seismic volume and input logs of interest are required.

<

>

You can change the position of the extraction location interactively, based on predictability, to optimize the wavelet to use. Q

Changing the extraction location automatically updates the extracted wavelet with its corresponding power and phase spectra, as well the resulting synthetic trace. These corrections force the synthetics and seismic to match by assuming that the well logs provide ground truth. However, nearby wells often suggest different phase corrections and well logs are not always available.

<

There are two required parameters: • 2D or 3D seismic data and position for wavelet extraction • Input for reflectivity series calculation. fa Wavelet toolbox

/

Edit existing

r»;

[ÿ] Branded

Ü

SI

l"

li — dH

~ I, □ Use SWT Study tempocwyTDR

’ótó' '-lóo ’

a a

'ÿdo

-r

Sí

f i

"so" ' 100'

mm Si

622

11

■.

N

♦ Phase manipulation

n

P"HOB

I I

) Taweeh*| Hannegttar | Scale facto .

J

—

a 1

Hcl-

maZEdSZc*

I H—Iiwl I

Figure 14 Wavelet toolbox interface for the Deterministic method of wavelet extraction 518 •Wavelet generation

Petrel Geophysics

>

I <

Three algorithms for Deterministic wavelet calculation are available in Petrel: • Extended White • ISIS Frequency • ISIS time.

>

Extended White Conceptually, the Extended Roy White wavelet extraction method (Figure 15) separates the well tie and wavelet extraction problem into

Q

<

these two elements: • Determination of optimal time shift between well log reflectivity and seismic amplitude • Determination of dominant phase. Simply described, the first step is accomplished with a time windowed sliding cross-correlation of the power envelope of the well log reflectivity with the power envelope of the seismic amplitude (both are phase-independent). Optimal time shift from the starting cross¬ correlation point (the optimal lag) is at the maximum cross-correlation point.

>

After determining the optimal time shift, the phase of the wavelet used to create the synthetic is rotated until the maximum cross-correlation between the synthetic amplitude and the seismic trace amplitude (both phase-dependent) is found. At this point, the phase rotation from zero is the optimal dominant phase.

The method provides statistics that are useful in judging well tie quality. Optimal is a relative term - both steps of the method are sensitive to the limits of the analysis windows and velocity errors.

Petrel Geophysics

Wavelet generation •519

I <

General tab From Petrel 2014.3, in an active Well section window, you can use a temporary Time Depth Relationship (TDR) to extract a deterministic wavelet. In previous versions, the TDR had to be assigned to the well to perform the deterministic extraction.

>

If a study Well section window is active, the temporary TDR from that window is considered for the deterministic wavelet extraction. Any change from the bulk shift or stretch and squeeze process in the study is used by the Wavelet toolbox for the extraction. The name of the TDR or temporary TDR used for the extraction will be reported at TDR from in the interface. See Figure 16.

Q

ft

X.

<

Edn trattng

g](

~ li=.

□ UN SWT Study tomporwy TOR

3

■

-

.1 nv.1

!’ÿ

*

«

mm

Q

>

31C1

g)[

V-tofca*» I TDW

I Extwct I Output ]

HlH u Figure 16 Time Depth Relationship (TDR) from an active study WSW can be used in a wavelet tool box to extract a deterministic wavelet

On the General tab (Figure 17), the extraction position can be set at different locations. The number of inlines and crosslines around the center location is specified for 3D seismic data. For 2D seismic data, the center trace and the number of traces on each side define the position. A vertical or deviated well can incorporate this position into the wavelet extraction algorithm.

Petrel Geophysics

Wavelet generation •521

1 General | Verticalization i Taper

1

Output

A Diamond-14

Wei:

Seismic:

TDR from:

<

Extract

mig [Realized] 1

Diamond-14

a a

□ Use SWT Study temporary TDl Q Allow wells outside survey Inline

622

Xline:

570

Q

a

ii®n®ii

Inline window:

10

Xline window:

10

RC calculation method:

Sonic velocity and density

Sonic or velocity:

ty>

|

Density:

<

Atp Calibrated sonic_1

■

»

p RHOB

>

Advanced settings

a

Gardner's parameters

O Use Gardner's equation Constant:

|023

10.25 Filtering options

imperial

a

[2 Use anti-alias filter

Figure 17 General tab of the Wavelet toolbox

To position the well to a new location, away from the actual wellhead,

click Set extract position to the deviated well ® . You also can interpolate seismic data to follow the trajectory or click Set extract position to well head

.

There is an option to enable or disable the anti-alias filter (used before a signal sampler) to restrict the bandwidth of a signal to satisfy the sampling theorem. This filter is recommended when converting the input logs from depth to time. If you are dealing with synthetic data, it is best to disable this feature.

522 •Wavelet generation

>

Petrel Geophysics

I <

Verticalization tab The Verticalization tab (Figure 18) can merge several different traces due to a deviated well trajectory. This option takes segments from each trace the trajectory crosses and projects them (and merges them) into a single vertical seismic trace, which can then be used for wavelet extraction in a deviated trajectory. General | Verticalization

Q

Verticalization type: Smoothing

<

|

Taper

| Extract | Output

No verticalization No verticalization

Smoothing level

Smoothing Truncated sine function

Inline radius:

1

Xline radius:

1

Time smoothing window:

1

Square weights:

>

>

0

Figure 18 Verticalization tab of the Wavelet toolbox

You must use good judgment to determine when a trajectory is so severely deviated that the resulting analysis does not make physical sense. You can control the way seismic data is interpolated using the options Truncated sine function (recommended) and Smoothing in the Verticalization type list.

Petrel Geophysics

Wavelet generation •523

I Taper tab On the Taper tab (Figure 19), you can select the User defined check boxes to customize the length of the taper applied to the cross¬ correlation that is computed and used for wavelet estimation.

<

You also can use this tab to define the length of the taper applied to the cross-correlation used for the deterministic wavelet extraction. General

Q

[

Verticalization I Taper | Extrae*

[ Output

Parameters

a

Length of extraction xcor:

248

Length of extraction xcor taper:

124

O User defined ™ D User defined

:

%

"W

a

White Noise Percentage of white noise:

i.oo

[ Retail

Figure 19 Taper tab of the Wavelet toolbox

The default size of the taper is half of the length of xcor, but it can be changed easily by selecting User defined. The percentage of white noise (used to the prevent instability in the calculation of the coherence function) that is added in the wavelet extraction algorithm also can be defined on this tab.

524 •Wavelet generation

Petrel Geophysics

>

I <

Extract tab The Extract tab (Figure 20) contains options for setting the time window for the wavelet extraction process and the button that begins extracting the wavelet. |

Calculate!

[i~| Auto-calculate

]

| Taper |

General

Verticalization

Extract

>

| Output

RC window

Q

Start (a):

1224 ms

Length (b):

1252 ms 2476 ms

End (c):

J

RC window scan

<

>

0 ms

Offset to center (d):

Length (e):

40 ms

Center (a+d):

1224 ms

Start:

1204 ms

End:

1244 ms

Taper Taper:

Length:

None

[

[Reset]

To] « Percent OTime

Figure 20 Extract tab of the Wavelet toolbox

After defining the parameters, click Calcúlatelo start the extraction. When the extraction is done, you can change its position interactively by clicking the predictability plots. Changing the position can be useful when there is some question about the true position of the well within the seismic volume.

Petrel Geophysics

Wavelet generation •525

I Output tab In addition to generating wavelets, you can use the Deterministic method to generate the Reflectivity, the Acoustic Impedance, and the Dephase Operator as outputs (Figure 21 ). The Dephase Operator is a special purpose wavelet used to dephase amplitude data. Extended White 1

A>“«

♦

BMMM M*1

Q

__ KZ

J

1 .i J

'

i

Phase manipulation

J

Time shrft Hannmg filler| Scale factor

-180

180

0

0 00

;

526 •Wavelet generation

a

*,

Rgyioÿopÿ

-iso

'

'

-160 ' ■ o' ” '6 '

y so'

'

'

'100

lío

l ■

Hi

II

wm

-

!i TT

a

£.«

‘

"

is. 1.

3£ ™

Petrel Geophysics

I <

Isis time/Isis frequency methods for deterministic wavelets The Isis Time/lsis Frequency methods extract wavelets using reflectivity and seismic data, that is, ISIS Time and Frequency. Which method you select depends on the degree of correlation between the seismic data and the reflectivity log.

>

Figure 22 shows the Isis Time and Frequency options in the Wavelet toolbox Q

□ # Create new:

/Q Edit existing:

ISIS (time) 1

Q ISIS

Method:

Deterministic

Algorithm:

Isis Time

m

<

(time) 1

>

IsisTime

Figure 22 Isis Time/lsis Frequency method

Petrel Geophysics

Wavelet generation •527

1 Wavelet extraction displays A PredictabilitysecWon (Figure 23) appears when you set all of the input parameters. Any change in the inputs or in the extraction parameters automatically updates the Predictability.

< •4 Wavelet toolbox

Q

- *11

Wavelet

JO Create new;

'« Edit existing

;«£>

Maximum predictability (top view)

Extended White 1

Method

Deterministic

Algorithm:

Extended White

S:

A Diamond-14

Seamy

ft

560

fvertinwiyatinn | Taper | Exbact | Output]

a TDR from

rJW)

□ Alow wels outside survey Xfine:

570 10

XEne window

10

v

*

I

1

PRHOB

-180

Phase:

‘

! ¡i 8?

:

Phase spectrum

I

___ | Tunc shift ( Hanning filter | Scale factor

Time of maximum predictability

m

¥_rTTTw

Atp Calibrated sonic log - (Study 1) Diamond-14

Advanced settings

Phase manipulation

4

Sonic velocity and density

I

Operations

s:

8'

■

RC calculation method Sonic or velocity.

100

560

* InEne window

Density:

i i

Diamond-14

□ Use SWT Study temporary TDR 622

580

* Maximum predictability (side view)

§] QJmig [Realized] 1

Inline

I

W:

V Auto-calculate

General

>

8

v-

Phase of maximum wavelet

A

Predictability information

*’**618

sr

0

Wa

o oo

-
Relative amplitude

a

“°6Íl

572

a

559

£S5L““*

•20 000M 12040«

¿ Power spectrum in dB scale Phase spectrum in wrapped angles Show envelope

VJ Standard phase convention

□ Aun»

|v

Apply

![ÿ/

OK

11«

Cual

I

Figure 23 Predictability section of the Wavelet toolbox

Predictability in the Seismic well tie process is used to determine the optimal wavelet. The Predictability section opens automatically and shows the calculated predictability spread in the vicinity of the set extraction point and the wavelet shape. It also shows the corresponding Power and Phase spectra.

528 •Wavelet generation

Petrel Geophysics

I <

Q

<

The windows show these Predictability displays: • Maximum Predictability (top view): Calculated correlation between the RC series and the seismic around the well position • Maximum Predictability (side view): Predictability for an inline shown as a function of crossline position and lag time (traces for 2D lines) • Time of maximum predictability: Shows a map of the start time for which the maximum predictability was found. • Phase of maximum wavelet: Shows the phase of the best interval. This option could take considerable time to be calculated. • Predictability information: Data sources, extraction parameters, and predictability values. Initially, a white circle (Figure 24) shows the currently selected wavelet at the maximum predictability of the cube of extracted wavelet. The interpreter can move the extraction point by clicking any predictability display.

>

>

A black X (Figure 24) shows the maximum predictability zone.

The Predictability displays are interactive. By clicking a different location inside a display, the wavelet is updated to the wavelet extracted at that map location and the Predictability for Inline display moves to the selected inline. 1

Maximum predictability (top view)

2'

I-

to

SL

Id)

P

!•!

m I

i

,n :..... ...

o>

■

Position of the currently selected

extracted wavelet.

Maximum predictability zone

CO

8'

o

560

a

580

Figure 24 White circle and black X show the maximum predictability zone

Petrel Geophysics

Wavelet generation •529

I Interpret predictability results The predictability and extracted wavelet displays are used together to determine which of many extracted wavelets are the best to use. Sometimes, the optimal predictability does not occur at the exact location of the well.

<

When this scenario happens, ask these questions: • Where is the well (truly) located? • Was the well location surveyed correctly? • Is everyone using the same cartographic system? • Were cartographic transforms done correctly? • Are we near the edge of a cartographic zone, where errors are often large? • Is the well deviated? If so, where is the downhole location relative to the surface location? Is • the well cataloged as a vertical hole, but is it slightly deviated?

Q

<

Background: Note on predictability information Predictability is calculated using this methodology: An autocorrelation is computed of the Borehole Data and Seismic Data traces Acor1(t) and Acor2(t), and a cross-correlation is computed between them Xcor(t). The

autocorrelations and cross-correlations are tapered from Time zero with a cosine taper up to max-lag samples using:

Max_lag

=

(£-)

*0.5

In this equation: • n is the number of input samples in the window • k has been set from experience to be (n* SR / 100), where SR is the sample rate of the data in milliseconds.

530 •Wavelet generation

Petrel Geophysics

>

>

I The global predictability value now is calculated with this equation, based on the tapered autocorrelations and cross-correlations: Predictability

<

100 '%y'(Acor\(t) *Acor2(t))

>

Predictability values range from 0 to 100, where 100 represents data that matches perfectly. Q

At anytime, these items appear: the maximum predictability map, predictability for a single inline, and the time of maximum predictability or phase of maximum wavelet. The latter two are interactively interchangeable. <

The predictability maps are interactive and linked to the parameters in the Wavelet toolbox. The wavelet for that location is shown and can be edited. The Predictability for an inline window displays the time lag for the position selected in the maximum predictability window. The time of maximum predictability shows the time lag for the best predictability in a map view.

D

Use the envelope peak to work out the time lag. Calculate the instantaneous phase at the envelope peak. This calculation is the reported wavelet phase.

The Phase of maximum wavelet display shows the phase rotation for a maximum predictable wavelet for each trace. The phase is determined by calculating the envelope of the wavelet and, from that calculation, the peak of the envelope.

Petrel Geophysics

Wavelet generation •531

>

I Predictability and correlation Why use predictability? Predictability is a measure of the similarity of the underlying reflectivity, so it is independent of the wavelet on the seismic. It also is fairly insensitive to amplitude scaling differences and wavelet phase uncertainty between the two time series (Figure 25).

<

>

Simple cross-correlation methods do not benefit from these features. SXEtffi

Q /•EtttenMng

[i£j Extended WNe 1

«tato» 1 T«p« lb—

a 1 OKpm

1“

■■

' ‘ i¿¿ ‘' í¿¿ ' ' 2¿¿ " ¿lo

<

fo

>

'

SBM

1»

lr~

58

560

Predictability information Inline: Xlme Lag from RC to seismic Predictability: ;-s tortoise: Start li on seismic Start time onRC:

Li 622

623

569 573 -12000™ -12000™ 17 096 s 19009s 0206 0 235 12120™ 12120™ 1224 0™

a*— /

580

.570

v:

it

¡a:

1252 0™

Figure 25 Wavelet phase and predictability information

532 •Wavelet generation

Petrel Geophysics

I <

Phase manipulation The Seismic well tie process provides comprehensive tools to examine and understand the phase characteristics of the seismic data over a formation of interest.

>

To get correct information, it is necessary to interpret events on the correct part of the seismic waveform. Interpreting on zero phase data is important to assure that the Reflection Coefficients (or impedance changes) from the log interpretation match a peak, trough, or zero crossing wavelet character in the seismic. Only by knowing the phase of the data can you reasonably expect to zero phase it correctly.

Q

<

Zero-phase seismic data is essential for many geophysical analysis techniques including Seismic Inversion. When the phase of the seismic is understood clearly, the seismic can be reprocessed to apply the dephase operator generated from the Seismic well tie process to the seismic. This action creates a zero phase seismic over the formation of interest (Figure 26).

>

For more information, refer to the Stretch and squeeze section in the Synthetic seismogram generation lesson. Operations

Phase manipulation

-180

\ Time shift [ Hanning filter [ Scale factor 0

180

■íh Phase:

2.85 * deg

|

Rotate to zero phase |

|

Convert to zero phase |

Figure 26 Phase manipulation tab in the Wavelet toolbox

Petrel Geophysics

Wavelet generation •533

I Time shift A bulk shift can be applied to the entire wavelet using the Time shift feature (Figure 27). Operations Phase manipulation| Time shift

| Hanning filter Scale factor

-242

Cl

a 242

0

Modified time shift:

0.00 * ms

Original time shift:

7.512 ms

a

Petrel Geopf

Figure 27 Time shift tab in the Wavelet toolbox

Hanning Filter: Seismic data frequency characteristics Low frequency is not always good. When high frequency features are obscured because of low frequency noise or natural attenuation of higher frequencies, evaluating well tie details can become problematic. When evaluating a well tie, particularly when using a short extracted wavelet or an analytical wavelet (for example, Ricker), keep in mind that the wavelet can be band-limited relative to the seismic and not fully represent low frequency response.

To assist with frequency evaluation, the Hanning filter subtab (Figure 28) is available for all wavelet types in the toolbox. It is a filter option that applies band limiting to the wavelet and to the synthetic traces built using the wavelet. Phase manipulation

| Time shift |

Hanning filter

| Scale factor

a Low:

High:

Cutoff:

0 Hz

125 Hz

Stopband:

0 Hz

125 Hz

O Apply Hanning filter

Figure 28 Hanning filter parameters in the Wavelet toolbox

534 •Wavelet generation

Petrel Geophysics

A

©

1ÿ

I <

You can use this feature to evaluate if a wavelet extracted in a deep interval is still applicable in a shallow interval. This feature allows you to filter back the lower frequencies and observe the well seismic tie at a shallower interval.

>

You also can use the filter facility to help determine optimal low cut filter parameters to be applied to the seismic data in a later filtering operation. Q

Additional insight into phase behavior is possible because selective filtering allows band-constrained phase behavior to become visible in the wavelet display. Allowing this behavior to become visible is important particularly when working with data acquired with an impulse source (minimum phase). This type of data has the potential for residual minimum phase in lower frequencies after processing.

Scale factor This Scale factor feature (Figure 29) scales the amplitude of the wavelet. For the analytical and statistical normalized method of wavelet extraction in Petrel, the amplitude range varies from -1 to 1. Normally this range does not match the seismic volume's amplitude range. Operations Phase manipulation

Time shift

Hanning filter | Scale factor

a Scale factor:

1

Figure 29 Scale factor tab in the Wavelet toolbox

Petrel Geophysics

Wavelet generation •535

I

9 <

Lesson 2 (Optional) — Multiwavelet, Multi-well extended white wavelet extraction (MWEW), and Time variant wavelet The Seismic well tie process is entirely integrated with the Petrel platform and supports creation of following wavelets:

•

Estimation of an average wavelet calculated from a set of wavelets existing in the project

•

One wavelet representing the combination of RCs and seismic traces from all input wells

•

Applying existing wavelets over different time intervals to generate a synthetic to address the phenomenon of decreasing frequencies and amplitudes at deeper seismic data

Q

536 •Wavelet generation

Petrel Geophysics

>

I Multivavelet

<

Wavelet Average calculates an average wavelet from a set of wavelets that you select. You can define the length and sample interval of the average wavelet, and you can invert the polarity of the resultant wavelet (Figure 30).

>

Wavelet toolbox Wavelet average 1

Q

j

/O Edit existing

Sy> Wavelet average 1

Method:

ill

1 Length Sample nterval Status

z

30 Hz

128

4

✓

lÿtRidoer 20 Hz

128

4

Ricker 13 Hz

128

4

✓ ✓

i

U

a .

128 ms

iftsrl Scale factor

Time shift |

-180

J Average I !

a

Q

0

Í1 Power

Hih 0 01

J

deg

Rotate to zero phase

Phase

| HwUNwnJ

;AU»MV«

V

Apply

V

OK

|

A

Cancel

Figure 30 Calculation of an average wavelet from a set of selected wavelets

In the Parameters area, you select as input a list of wavelets to be used for the average calculation. You can use Analytical, Deterministic, and Statistical wavelets for the average calculation. The input wavelets can have any sample interval between 1 ms and 16 ms and lengths up to 8 seconds.

The Wavelet Average method automatically computes and plots the result just after the first wavelet is selected as input. It is displayed in dark blue. When all inputs are removed, no wavelet is plotted.

Petrel Geophysics

Wavelet generation •537

I Multi-well extended white wavelet extraction (MWEW) In Petrel 2015.1 a multi-well deterministic wavelet extraction is available. <

One of the key elements for the inversion process is the wavelet. You can extract a wavelet from the seismic volumes using different methods. In Petrel, one of them is the deterministic method Extended White that you can use to extract wavelets for a specific borehole. This method works fine when you are interested in just one well, but in many cases, for inversion, more than one well is available to perform the extraction. Now you have a multi-well option.

Q

>

To perform the MWEW, you need an individual deterministic wavelet extraction for every well selected.

MWEW involves these steps: 1. Input: Extended white wavelets where the reflectivity and seismic trace will be retrieved. 2. Extract all wavelets from the same seismic cube. Reflectivity, seismic trace, and time lag used for these wavelets become inputs in the multi-well extraction. Input wavelet amplitudes are not used by this algorithm. 3. Output: Multi-well wavelet extracted. The algorithm uses the extraction window for each one of the input wavelets to get the reflection coefficient (RC) from the logs and the seismic trace from the seismic for all wells. All these pieces from all wells are used to generate just one RC log and one seismic trace log. Between the pieces, a zero interval is added with a length equivalent to the biggest wavelet length.

<

The pseudo log and pseudo seismic trace are used to extract a wavelet using extended white given as result one wavelet representing the combination of RCs and seismic traces from all input wells.

See Figure 31 for a schematic diagram for the multi-well extended white wavelet extraction (MWEW)

538 •Wavelet generation

Petrel Geophysics

>

I Extended white individual extraction

Pseudo-well creation Pseudo well

<

I

Weill

1= P I

Q

Final Wavelet Final wavelet

£>

>

S

Well 2

<

u i %

>

Í

§

Well 3

IJ| 8 7

If

f

Connection with zero as value and equivalent to the largest

Figure 31 Schematic diagram for the multi-well extended white wavelet extraction (MWEW)

Time varying wavelet This tool is useful to address the phenomenon of decreasing frequencies and amplitudes at deeper seismic data. The Time varying wavelet can be useful for applying existing wavelets over different time intervals to generate a synthetic. The character of seismic data varies as time increases, with deeper data generally having lower frequencies and amplitudes. It can be useful to use different wavelets over different time ranges (gates) to generate a synthetic. With the Time varying wavelet option, you can use various existing wavelets and taper types to create a time varying wavelet. Petrel Geophysics

Wavelet generation •539

I This functionality can be accessed on the Input tab on the Seismic well tie dialog box of the Synthetic generation study (Figure 32). >

<

•a VM

•a (eg

B

o

£CaM»mdTDR

-i fcl

Q

Hk s

|ÿ| OB'"* IRsataed] 1 Xine

Taper

®®o

Start time (ms)

End time (ms)

128

1300

1750

128

[TTST

Status Wavelet length (ms)

Trapezoidal

□ Aulo apply [~V~

-fi¬

]L¿_

OK

* Caned |

fi

ej P RHOB

Figure 32 Time varying wavelet in the Synthetic generation study

When the Time varying wavelet option is selected, the Open time varying wavelet tool button is activated. To launch the Time varying wavelet dialog box, click this button.

In the Time varying wavelet dialog box (Figure 33), you specify time ranges or time intervals over which a series of wavelets can be used to generate the synthetic. You can create as many as ten time ranges represented in a dynamic table. -Hr* Status Wavelet length (ms) Start time (ms)

Wavelet

¿IRieka

•

| |Flicker 2 Taper

✓

128

1300

✓

128

p750~

Trapezoidal

Taper length (ms):

□ Aulo apply |V

Apply

|| V

End time (ms) 1750

]

2300

0 OK

|| H

Cancel

Figure 33 Time varying wavelet dialog box 540 •Wavelet generation

Petrel Geophysics

I Each time interval is defined by:

•

from the Input pane. When the A wavelet that you insert wavelet is dropped in, the Ul displays its length. The wavelet can be Deterministic, Statistical, or Analytical. If the wavelet is modified, the system displays a warning icon to indicate that the selected wavelet was modified.

| e¡> | Ricker 20 Hz

Q

!

• Start/end times (in ms) for each individual gate (time ranges) over which individual wavelets generate the synthetic. The minimum time interval is 4 ms. Gaps between time ranges are not allowed.

•

A taper. The supported taper types are • Trapezoidal • Cosine • Cosine squared • Hanning • Hamming • Blackmann • Papoulis • Minimum energy moment • Minimum amplitude moment

Petrel Geophysics

Wavelet generation •541

I Taper length (Figure 34) is a time in milliseconds over which the gate is gradually smoothed to its edges. This parameter is an integer value with maximum limits of the smallest time range. The value should be a multiple of the wavelet sample rate. If you insert a value that is not valid, it updates the Taper length value automatically to the greater valid value. When the taper is applied, it is centered by the transition between two time ranges with half of the Taper length on each side. The start and end times of the RC log crop the Taper length of the first and the last intervals, respectively.

<

Q

k Id

542 •Wavelet generation

z

0}

Taper length

-Taper length

Taper

Taper

Zy

- Taper length

Petrel Geophysics

>

I The synthetic generation is performed for each wavelet with the entire RC log. This process results in n different synthetic seismograms (where n is the number of time ranges). These synthetic seismograms are cut to respect the range that you specify, plus half of the taper length in each boundary (Figure 35).

Q

All the wavelets are resampled to the same sample rate of the one with the lowest sample interval. A synthetic seismogram is generated using the highest resolution.

__

=.1

©Copp«r-STTWTJ saMjn

HWPM

|U

-.-.I

sailgsis

.t..

:

r i

t

z

-{"«I

u

;*

r\i ¿’"'A" "A"".*» '"A"

fir

■Si * * •

'!

m r

1

“PI Lli-g I II

■

E

~riI

■

, £ TTTJTT » » »

.

i

Figure 35 Synthetic seismogram using the highest resolution

Petrel Geophysics

Wavelet generation •543

Exercises — Extract wavelets In these exercises, you extract a wavelet and generate a synthetic seismogram. >

<

Exercise workflow 1 . Create a statistical wavelet. 2. Extract a wavelet. 3. Generate synthetic seismograms and compare wavelets.

0

0

Exercise 1 — Create a Statistical wavelet

Seismic Interpretation

9 9

i

Petroleum Systems

•pjv Wavelet toolbox

?

Log conditioning

Seismic well tie

I

Decision Support

& Insert

Well tie editing

Seismic-well calibration

544 •Wavelet generation

On the Seismic interpretation domain tab, in the Seismicwell calibration group, launch the Wavelet toolbox.

1.

-

m

<4

Seismic interpretation

2D/3D interpretation

Structural Modeling

Volume attributes

Mesh editing IS

Mesh

is

i Mixer

Property Modelira

N;

Surface attributes

Ü]

Calculator

3**

Neural net

Attributes

Petrel Geophysics

I 2. Create a Statistical wavelet with these values: • Length =128 ms • Sample rate = 4 ms • Seismic volume = mig [Realized] 1 • Well = Diamond-14.

<

>

Wavelet toolbox

m Create new SO Edit ensbng U

| c{> ¡ Statistical 1

1

Q 128 ms

1

Hrrvg [Reaped]

A

D

i:

i •»

Diamond-14

Taper

'30' ' '

Time (ms)

40

'50

"

60'

m Detemvneau "ÜT1-

~»11610096-2499] -176239.369915] Time (ms)

í

z

!"

a ■001

; *g

a

1£ □ Amo»™

£

Ik

OK

II»

3. Try different wavelet parameter values: • Length • Sample rate • Neighborhood • Taper • Regions (Position, Inline, Xline, Start time. End time) • Operations (Phase manipulation). The wavelet displayed in the dialog box updates automatically based on any change that you make. 4. When you are satisfied, click Apply and click OK. The wavelet is saved and stored at the bottom of the Input pane. Petrel Geophysics

Wavelet generation •545

I 5. Drag this newly created Statistical 1 wavelet into the Wavelets folder. 6. You again can view or edit the newly created wavelet. Expand the Wavelets folder in the Input pane, right-click Statistical 1 wavelet, and select Open in wavelet toolbox. * C Wavelets

<

IAv

Analytical Wavelet

[@ [|ÿ

Q

>

Settings

Import (on selection)

. ..

[=1,

Export object

&

Edit global color table jgerx

A

H]

<

Delete

.. ,

Copy wavelet (data only)

>

Open in wavelet toolbox

Guru

The wavelet appears in the Wavelet toolbox where you can edit it.

546 •Wavelet generation

Petrel Geophysics

0

Exercise 2 — Use wavelets interactively for a quick synthetic analysis The interactivity of the Seismic well tie process allows quick analysis of a synthetic by using a wavelet for initial assessment. 1. As explained in the previous exercise, create a Synthetic generation study in the Seismic well tie dialog box. 2. Choose the newly created wavelet. 3. Open the Wavelet toolbox from the Seismic well tie dialog box. m 0

Iÿl

U1 Seismic well tie I Seismic well be

Q 1

Hints (Study 3) Diamond-14 Synthetic generation

0 Create study:

f

C

Edit study:

(Study 1) Diamond-14 Sonic calibration

Type of study:

Synthetic generation

|

Well:

THCopy template Output]

Input

©

Synthetic generation default template

Time shift

Correlation

I c£> ®

’

A

-

TS

| A Diamond-14 Track manager

Styfe

O

Í# Calibrated TDR

3 0

|/v- Statistical 1

Wavelet:

1

© Time varying wavelet: Seismic display Seismic:

|

|

(88 m'9 [Realized] 1 9

Inline

C Xline

[H Allow wells outside survey

(D© ®

Position Inline

622

Xline

570

Xline window:

io

:

Reflectivity coefficient

Sonic velocity and density'

RC calculation method Sonic or velocity: Density: v

|

| At Sonic Despiked e>| PRHOB

Advanced settings

|V Petrel Geophysics

Apply

"| | V

OK

|I

A Cancel

Wavelet generation •547

<+> Diamond-14 TWT]

Inline 622 - mig [Realized] 1

Statistical 1

0 00

1.00 560 00

570.00

<

Inline 622 - mig [Realized] 1

580.00 r

J

Statistical 1

570.00

r-*

>

h

-S 3

500000

CL.

-

<

-

0

K!

T

T

T

-50

0

50

Time (ms)

ft

Power spectrum

o

<

*

*

o

%

¡íMMüSIVLLL

-10

m

-

<

3Ü

/

-20

Lj

|

>

i

( »

-30

LL

-40 -50

50

0

100

Frequency (Hz) Phase spectrum 1

0.5

niMI4im«m

■

m

OS Jj i'

0

!/>

J2

CL -0.5

-

-1

0

50

100

Frequency (Hz)

548 •Wavelet generation

Petrel Geophysics

I In the Wavelet toolbox, use the options available in the Operations section to edit the phase and time of the wavelet. 5. Select the Autosave option to save the wavelet and interactively observe the updates in the synthetic when changes are applied. 4.

<

>

Q

r

j.,

|?rr *

■'*

*

*

-fl-

<

r

>

a

I: a

i§|~~ düEEI

Exercise 3 — Extract a wavelet and generate a synthetic seismogram 1. With the Wavelet toolbox open, create a new wavelet using the Deterministic method. 2. Name the new wavelet Deterministic Wavelet

— 0

Diamond-14.

3. Select Diamond-14 from the Well list or insert “v* . 4. Select the mig [Realized] 1 seismic cube from the corresponding field. 5. By default, the extraction position is set automatically to the well location. Because the well has a deviated trajectory, click Set extraction position to the deviated well . This button sets the reference center point at the inline/ crossline location where the TWT of the trajectory matches the Petrel Geophysics

Wavelet generation •549

I TWT at the midpoint of the extraction window. 6. Specify (in the number of inlines and crosslines) an area around the defined position where it is possible to perform wavelet extraction. The predictability between the seismic trace and the RC series will be calculated. 7. For the RC calculation method, choose the Acoustic impedance named Al that you created in previous exercises. It is stored in the (Study ...) Diamond-14 Synthetic generation folder in the Global well logs folder. 8. On the Extract tab, set a start time and window length to define the area of extraction for the wavelet. The interval of interest should be the reservoir interval. You can keep the default value (it uses the whole interval with data). Consider a synthetic to be a valid representation only within the interval from which the wavelet was extracted. After you have configured all of the necessary settings for the extraction to take place, the wavelet is created virtually. The Extracted wavelet display and Predictability display windows are populated. The Predictability display window is divided into five parts: • Maximum predictability (top view): Color-coded display of the maximum predictability in the various inline and crossline positions. • Maximum predictability (side view): Based on the selected inline position in the maximum Predictability display, predictability is color-coded as a function of crossline position and time lag (between seismic and RC series). • Time of maximum predictability: Color-coded display of the lag time for maximum predictability in the various inline and crossline positions. • Phase of maximum wavelet: Color-coded display of the wavelet phase for maximum predictability in the various inline and crossline positions • Predictability information: Values for the current selected extraction position.

<

Q

550 •Wavelet generation

Petrel Geophysics

>

I 4* Wavelet toolbox

/r, Edit existing

g]l

1 0.

>

<

a

02

o:-

1252 ms 2476 ms

End(c)

a

Q

'-260

'

-160'

'

¿

1Ó0

%

~r2M

End:

LZÚ

Taper Taper

GB

i;

1*

Ptieee manipulation

iTanertfcl thnpwnttM I Satohdocl

000 * deg

a

Rotate to zero phase |

“1 "1

...........

a

glE-lE”-

I

V Relative ampitude yj Power spectrum m [ I Phase spectrun Show envelope

n

□ Autosave

\v

Apply

||v_0ÿÿ| [ A Cancel]

9. The default extraction location is at the maximum predictability point calculated in the scan. Interactively change the position for extracting the wavelet. Click somewhere in the window to see the change in the wavelet display section. 10. When satisfied, click Apply to create the wavelet. It is stored in the Input pane. You also can use the Auto save option in the Wavelet toolbox to save the wavelet in the Input pane automatically. With this option, you can see interactively the changes in the synthetic seismogram as you change the wavelet in the Wavelet toolbox. 11. Drag this wavelet (Deterministic Wavelet Diamond-14) into the Wavelets folder.

Petrel Geophysics

Wavelet generation •551

I 12. In the left part of the Wavelet toolbox dialog box, open the Wavelet list by clicking an arrow, indicated by a circle in the figure. 13. In the left part of the Wavelet toolbox dialog box, insert 'v* the other wavelets. 1 4. Click the check boxes to select these wavelets for comparison.

<

,

i-

J

-

>

c~

Q

::

* <

(]£=':

lejffi

.

™!-ÿB

552 •Wavelet generation

|j=-

—

- tel*

>

J

Petrel Geophysics

I 15. In the Wavelet display option section, click the Relative Amplitude check box to compare the power, phase, and amplitudes of the wavelets. Wavelet

<

>

1.0

0.8-

Q

®

0.5-

a.

0.4-

i I

¿

0.2-

I

0<ÿ

-0.2-

—

-0.4-C £•

-250

-200

-150

-100

lo

:

-50

Time (ms)

100

150

200

250

Power spectrum

I

-»ÿ

->

'¿""db" "i'

reo jarov

'ild"iU' 'iü"ii5

Phase spectrum

| 3»

iH “ÿ

100-

i* l

-100-

13

’¿""¿""i"

4j'

Freouencv íHíI

"¿""db" "db "iWiis' 'ito " its' 'iió

"ils

16. Create three synthetic seismograms using the three wavelets and compare the results. Refer to the Synthetic generation lesson exercises. 17. Use the Auto save option in the Wavelet toolbox to see changes in the output synthetic seismogram quickly.

Petrel Geophysics

Wavelet generation •553

1 0

Exercise 4 — Create an Integrated Seismic well tie study 1 . Run a new Integrated Seismic well tie study. a. Continue to work with Diamond-1 4. b. Define the parameters using the same process from the previous exercise and in the Sonic Calibration lesson exercises. c. Choose the type of wavelet. 2. On the Output tab: a. Select TDR: Calibrated sonic. b. Select the Autosave check box. c. Click the Set as active TDR button.

<

Q

a «L

6=3

f® Seismic «vdi tie # Create study

(Study 4) D»mond-14 Integrated Mtsiroc weMte

/©&**dy

(Study 3) Diamond-14 Syrthefee generation

Integrated seismic »

Type of study:

%Wet

©

T|] Copy template

4 Diamond-14 Integrated seam:«elbe defedttmpfaSe

\ Options J Statistics ]

lnpu

_i Oetuming | Tine-deptfi

Al Some log

O At Some Despised y Diamond-14/Calijrated TDR

m

Track manager

-

TB

[fl*]

a]

<>

Output

Drop from other «HI

E

k'V Analytical Wavelet

B

-

1 ün.Ail Dtounwto l TswfrdjB*» 1 Qpta»|StÉíitll C<wWMlTackmuflor 1 SMi l

Calibrated sonic Calibrated sonic

«I

Time varying vraveiet:

A

Tane depth relationship (TDR) From sonic

Xkne

:

A

Calibrated TDR

Samóte interval:

□AloovMas outsidei

11«

Calibrated sonic

B Auloi

16.40

Li

ft

!

ft

[ |AI samples

¡ AM samples

® Autosave From study:

*

TDR

A

Sample interval:

570

1640

%

Li

@] Autosave

!™| Acoustic mpedance

RC catenation method

±

Al-

v

TcmTI

v

Residual drift

Denedy

Name

Diamond- 14_mig (Realized] 1_synthetic 2

IQ

□ Autosave v

Computed setsmogram (depth)

A

Reflectivity

Name V

554 •Wavelet generation

Apply

RC

|Q

□ Autosave

Petrel Geophysics

>

I 3. Click Apply. An integrated Well section window opens where you can perform Sonic Calibration as well as Synthetic Generation.

■■

<

>

r:

A Q

4.

1 i

i

4 £

<

!,

■I :

;

I

■

Calibrate the sonic. Pick individual knee points with a checkshot update and observe the change in the synthetic after each pick. This calibration helps you to identify which checkshot knee points have the most influence over the final depth-time relationship. It also provides insight into which borehole intervals are responsible for the greatest velocity updates. 5. Stretch and squeeze the synthetic. You can output the new time-depth relationship (after stretching and squeezing) and select it on the Time tab of the well Settings dialog box to use it. However, if you used an extracted wavelet, remember to extract it again after the new time-depth relationship has been changed. Perform this task after changing the time-depth relationship, even though the synthetic window reflects these changes. 4.

Petrel Geophysics

>

r

D

Because the time-depth relationship in the sonic calibration and synthetic generation are linked, any change made in the sonic calibration is reflected automatically in the synthetic.

Wavelet generation •555

I 9

Review questions

•

•

<

• Q

What is meant by Analytical, Statistical, and Deterministic methods of wavelet creation/extraction? Is it correct that Ricker, Ormsby, Tapered Sine, Butterworth, and Klauder are Analytical types of wavelets? Are they available in Petrel? Can you create, import, or export a wavelet in Petrel? If yes, how?

Summary In this module, you learned about: • using the Wavelet toolbox • creating different types of wavelets by usinq Analytical,

556 •Wavelet generation

Petrel Geophysics

>