Shaly Sand Petrophysics.pdf

Evaluation Techniques for Thinly Bedded Sandstones Petrophysics Jan van der Wal, Senergy

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Outline • What are Thin Beds? • Part 1: Evaluation Techniques • Part 2: Revisiting Normalised Qv of Juhasz

• Example

(NL: Spekkoek) The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

• Introduction

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Introduction

Thin Beds Concept • What are ‘Thin Beds’? • Laminations of sand and shale, with.. • .. beds so thin that logs do not read true properties. • Why do we care? In Thin Beds.. • .. conventional evaluation can miss pay, • .. phi & perm are too low, • .. resistivity reads too low, and • .. saturation height functions give too low HC.

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Introduction

When to Apply? • Consider • Bed thickness • Shale percentage, ~50 %? --• Laminated, or dispersed? • Depositional Environments, can we model it?

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Introduction

What is Thin? • Depends on logging tool as well, < 1m? Thomas Stieber paper Sabah

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Introduction

What is Thin? • Porosity

• Resistivity • Old indution < 2m • Recent < 0.8m?

R corr

• Old logs < 0.5-1 m • High res < 0.4 m? R meas

2 Bed Thickness The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Introduction

How much shale • Porosity in Thin Beds • Not OK: ‘Effective Porosity’ = PhiT – Vsh*PhiShale • NTG variable with PHIsand • Problems (missing reservoir) when Vsh > ~40%

• Resistivity • Water bearing: resistivity contrast small, little effect • HC bearing: resistivity contrast large, 25% Shale obscures high resistivity. HC underestimated.

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

• Part 1. • Techniques • • • • • •

Cuttings Images Volumetric/Probabilistic NMR 3-D res SHF

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Techniques

Vshale from Images • Core Photos in XLS • detailed Sand flag (0,1) • Smooth to log resolution (por ~1ft, res 1m)

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Techniques

Vshale from Image Logs

NEU/DEN/SON The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Conductive Dark Resistive Light

Techniques

Vshale from NMR (1/2) • Assumes ClayBoundFluid relates to Vshale • Shale volume • Vshale = (CBFV/ClayPhiShale) • Vshale = (BFV/PhiShale)

• Complications: • dispersed components with additional BF

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Techniques

Vshale from NMR (2/2) • Clay bound • Laminated: Cap.BF and FFV • Clean sand

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Techniques

Vshale from 3D-res • 2000’s, revived thin beds • Tensor Model • Horizontal and Vertical, or • Parallel Conductivity and Serial Resistivity Res HOR

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Res VER

+

Techniques

Volumetric / Probabilistic • Probabilistic • Allows for more components, glauconite? • Cementation? • Requires more input curves

• Deterministic: Thomas Stieber (1975) • Input: Phi and Vsh, • Outputs: Phi_sand, Vsh_lam, Vsh_disp

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Techniques

Core Porosity – of sands!

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Techniques

Saturation from core • Dean Stark • Capillary Pressures 1. Get Swirr. 2. What is max Rsand? 3. Optimize shale model

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Techniques

Saturation - Height Function • Derive SHF from thick beds • Apply to thin beds • But is rock quality the same?

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Techniques

Summary – part 1 • Fairly common, also in North Sea • Vshale: Cuttings, Core, Image logs, NMR, 3D-res • NTG curve

• Porosity: Core Phi <-> sand lamination • Porosity of sand

• If Resistivity still problematic -> SHF

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

• Part 2. 3D resistivity workflow • Thomas Stieber • Conductive dispersed components

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

3D-resistivity workflow

Case Study data – where is the HC? Vshale Original Publication

Neutron & Density

Deep Res

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Case Study, Clavaud, 2005

3D-resistivity workflow

steps • Aim: properties of sand lamination 1. Thomas Stieber (1975) •

Φ, Vsand, Vsh.disp

2. Resistivity of the sand lamination • •

3D-res 2000’s Rsand

3. Saturation computation (SwRT) •

Juhasz 1981

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

3D-resistivity workflow Thomas Stieber Definitions

• Shale (not clay) • Shale types:

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

3D-resistivity workflow - Step 1 Thomas & Stieber, 1975

• 2 endpoints + 1 Clean Sand

Porosity

‘Pure Shale’

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Volume of Shale

3D-resistivity workflow - Step 2: Resistivity of Sand Laminations 3D-res

• 2a) Tensor Model • Horizontal and Vertical, or • Parallel Conductivity and Serial Resistivity Res HOR

• 2b) Anisotropy Model • Smart Tensor Model; • Inputs Thomas Stieber The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Res VER

+

3D-resistivity workflow - Step 3 Saturation Calculation

• Which equation?

• Conventional (deterministic) • Laminated Shaly sand eqs: • Poupon, Indonesia, Simandoux

Poupon, parallel conductor

1  V sh V sh 1 m n     Sw  Rt Rw R sh



• Thin Beds (dispersed clay/shale in sand lamination) • Dispersed Shaly sand eqs: • Dual Water, Waxman Smits, Normalised Qv Juhasz The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway



3D-resistivity workflow

Saturation from Resistivity

• Waxman Smits equation Archie

Shale corr

• For waterleg assume SWT = 1, (and a*=1):

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

3D-resistivity workflow

Waxman Smits in Xplot

Y

= aX +b Y=

Slope B

X=

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

(cousin of Pickett-plot)

3D-resistivity workflow

Juhasz • Juhasz: if no core Qv available, • Qv = f(Vshale)

~ Conductivity

1/Rw_shale 1/Rw_shale

= shale conductivity + 1/Rw

1/Rw

Qv_shale

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

100% Shale

3D-resistivity workflow

Juhasz Normalised Qv • Juhasz: Qv = f(Vsh), or Qv = f(Phi), f(1/Phi) • Qv = f(1/Phi, Vsh) = f(RPD), (similar to ~Qvn) • Relative Porosity Difference

• Assume Qv = RPD*C, substitute

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

3D-resistivity workflow

To better pick BC

= CWA

Slope B*C 1/Rw

RPD The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

3D-resistivity workflow

To better pick Rw • Terms divided by RPD: CWA/RPD

Slope 1/Rw BC

1/RPD The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

3D-resistivity workflow

Data Example BC

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Rw

3D-resistivity workflow

RPD in Thin Beds? • RPD of Bulk not good enough • => RPD of Sand lamination (RPDs) • RPDs = f(1/PHIs, Vsh.disp), or

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Vshale Original Publication

Neutron & Density

H+V Res & Parallel Conductor

POROSITY Conv

BVirr

CPI with eval

The Study, 20th SPE Bergen One Day Seminar Case data of Clavaud April 10th 2013 | Bergen, Norway

HC

H20

POROSITY Conv & Par.Cond.

POROSITY Thin Beds & 3D-Res

3D-resistivity workflow

Summary • In case of: 3D resistivity, no core, water leg • • • • •

Optimise Thomas Stieber with Tensor Model Resistivity Sand from Anisotropy model Relate Qv to RPD Compute RPD for sand lamination only New Xplots for picking Rw and ‘BQv’

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

References • • • • •

•

Cao-Minh, C., Clavaud, J., Sundararaman, P., Froment, S., Caroli, E., Billon, O., Davis, G. & Fairbairn, R., Graphical Analysis of Laminated Sand-Shale Formations in the Presence of Anisotropic Shales, 2008, PETROPHYSICS, Vol 49, No. 5, October 2008, pp. 395–405. Clavaud, J. B., Nelson. R., Guru, U. K. and Wang, H., 2005, Field Example of Enhanced Hydrocarbon Estimation in Thinly Laminated Formation with a Triaxial Array Induction Tool: A Laminated Sand- Shale Analysis with Anisotropic Shale, SPWLA 46th Annual Logging Symposium, June 26-29, 2005. Juhasz, I., 1981, Normalised Qv. The Key to Shaly Sand Evaluation using the Waxman-Smits Equation in the Absence of Core Data. SPWLA 22nd Annual Logging Symposium, June 23rd-26th, 1981. Passey, Dahlberg, Sullivan, Yin, Brackett, Xiao, Guzman-Garcia, 2006,Petrophyscial Evlauation of Hydrocarbon Pore-Thickness in Thinly Bedded Clastic Reservoirs, AAPG Archie Series, No 1 Stromberg S., Nieuwenhuijs R., Blumhagen, C., Edwards, J., Ramamoorthy R., Herold, B., 2007, Reservoir Quality, Net-to-Gross and Fluid Identification in Laminated Reservoirs from a new generation of NMR logging tools. Examples from the Gharif Formation, Southern Oman. Transactions of the SPWLA 1st Annual SPWLA Middle East Regional Symposium April 15- 19. Thomas, E. C., Stieber, S. J., 1975, The distribution of shale in sandstones and its effect on porosity. Transactions of the SPWLA 16th Annual Logging Symposium, June 4-7, 1975.

•

Van der Wal, J., Stromberg S., 2012, Correcting the water saturation calculation for dispersed clay in thinly bedded sandstones, Revisiting the Normalised Qv Equation of Juhasz, Transactions of the SPWLA 53rd Annual Logging Symposium

•

Waxman, M.H. & Thomas, E. C., 1974. Electrical Conductivities in Shaly Sands-I. The Relation between Hydrocarbon Saturation and Resistivity Index; II. The Temperature Coefficient of Electrical Conductivity. J. Pet Tech. 213-23. Trans., AIME, 257. Worthington, P.F., 2000, Recognition and evaluation of low-resistivity pay, Petroleum Geoscience, Vol 6 2000 (as published in Geological Society London, one-day seminar Hidden Hydrocarbons, 2001)

•

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

• Backup

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Logging programs • • • • •

Dip meter Image logs NMR 3D resistivity High resolution, Consider slow logging

• See AAPG Archie series No 1 The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Conclusions • Workflow can be based on log data only • New form of Norm Qv of Juhasz applied to thin beds • Qv estimate refined • Conventional: low HC • Conventional with 3D res (Parallel Res): more HC • Thin Beds with 3D res: most HC The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

What is RPD? • • • •

Middle East for Carbonate stringers (PDO) Shaliness indicator Combines 1/PHIT and Vshale (~ Neu-Den separation) RPD= (Neu + Co – PhiT)/ PhiT

• How to get ‘Co’ • Use ND overlay • For clean sand: RPDs ~ 0 • Clean but conduct: RPDs > 0

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

What if no 3D resistivity available? • Make cases for vertical resistivity • Check with Thomas Stieber • • • •

Simplest: Rv = Rh * C Better: Rv = Rh * C * Vsh_lam, or Rv = Rh + C * Vshl * (Rh – RshH) Rv = Rh + (C* Vshl / ((1/RshH – 1/Rh))

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

What is Parallel Conductor model? • Ct = Vsand * Csand + Vsh.lam * Cshale, or • 1/ RT = Vsand / Rsand + (1-Vsand) / Rsh.hor Res HOR

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

When to apply Thin Beds • Neutron Density Data

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

3 < Density > 2

• Intermediate GR? • Dispersed, Laminated, or Both?

GR

3 < Neutron > 2

When to apply Thin Beds DeepRes

3 < Density > 2

• Conductive dispersed shale?

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

3 < Neutron > 2

What if you do have core? • Are plugs of the sand lamination? • Porosity: • Calibrate Clean Sand endpoint to match the high porosity • Optimise input PHIT

• Calibrate BC & RPD to match the predicted QV curve

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Depositional Environments

Fluvial systems (1/2)

8m

100m

Static Model (25x25x0.5) Dynamic Model The 20th SPE Bergen One Day Seminar (100x100x10) April 10th 2013 | Bergen, Norway

Arbroath, Scotland

Introduction

Also in North Sea Sele and Forties Article: Turbidite reservoirs of the Sele Formation, Central North Sea: geological challenges for improving production M. HEMPTON, J. MARSHALL, S. SADLER, N. HOGG, R. CHARLES and C. HARVEY

From Abstract • Fields: Forties, Nelson, Montrose–Arbroath, Scoter, Pierce, the Gannet cluster, Guillemot A, Mirren and Merganser, Phyllis, Starling and Blane are under appraisal/development.

• ‘Forties’ submarine fan system sourced from feeder channels in northwest and west. From 3D seismic & wells: • Near sources (updip): thicker, higher N/G, and more channelized. • Downdip: thinner, finer grained and stacked lobes and minor channels (controlled by accommodation space and salt movement).

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Introduction

Depositional Environments

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Techniques

Nr of Beds thicker than h

Bed Thickness vs Occurrence

Bed Thickness

• Altered carbon cycling and coupled changes in Early Cretaceous weathering patterns: Evidence from integrated carbon isotope and sandstone records of the western Tethys 20th SPE Bergen One Daya,Seminar , , Jens Olaf Herrleb, , Helmut Weissertb •The Ulrich Georg Wortmann April 10th 2013 | Bergen, Norway

• Where (and when) should we expect Thin Beds issues?

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

How much shale

Sw vs computed Sw

• Theoretical parallel conductor model The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Vshale 0.15; PhiShale 0.18; ShaleRes 3.09; PhiSand 0.2; SandRes from Archie

Techniques

Rock quality • Does NTG correlate to bed-thickness? • Does bed-thickness correlate with quality?

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

• Geo Models

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Depositional Environments Scale - Fluvial systems

8m

Static Model (25x25x0.5) Dynamic Model The 20th SPE Bergen One Day Seminar (100x100x10) April 10th 2013 | Bergen, Norway

100m

Arbroath, Scotland

Depositional Environments Good news: Turbidites

(image from geo ExPro) Kota Kinabalu Sabah, Oligocene deepwater, among most sand-rich outcrops The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

How much shale

Shale vs Sw • In ideally laminated, more than 10% of shale is problem Model: • Sw = 20% in sands • Assumed perfect (theoretical) parallel conductor model

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Workflow • Conventional • Vshale • Porosity • Saturation

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

• Thin Beds • • • •

Vshale Porosity Sand Phi & Shale Rsand & Saturation

Techniques

Vshale from Core (2/2) • Calibrate traditional techniques (GR, ND) to downscaled (i.e. smoothed) core sand/shale flag calcite

calcite calcite The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

Introduction

When to apply Thin Beds GR

• Intermediate GR? • Dispersed, Laminated, or Both?

3 < Density > 2

• Neutron Density Data

3 < Neutron > 2 The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway

The 20th SPE Bergen One Day Seminar April 10th 2013 | Bergen, Norway