Directional Drilling

Directional Drilling And Surveying

What is Directional Drilling? Directional Drilling is the process of directing a well bore along some trajectory to a predetermined target. Basically it refers to drilling in a non-vertical direction. Even “vertical” hole sometimes require directional drilling techniques. Examples: Slanted holes, high angle holes (far from vertical), Extended Reach Holes, and Horizontal holes.

Non-Vertical Wellbore

θ, α or I Inclination Angle

n o i t a n i l Inc e Y n a l P

Z Axis (True Vertical Depth) North Direction φ, ε or A Angle Direction Plane X

Lease Boundary Surface Location for Well No. 2

Surface Location for Well No. 1

Bottom Hole Location for Well 2 Houses

Oil-Water Contact

Figure 8.2 - Plan view of a typical oil and gas structure under a lake showing how directional wells could be used to develop it. Best locations? Drill from lake?

Top View

NOTE: All the wells are directional

5 - 50 wells per platform

Figure 8.3 - Typical offshore development platform with directional wells.

Drilling Rig Inside Building

Figure 8.4 - Developing a field under a city using directionally drilled wells.

Why not drill from top of mountain ?

Maximum lateral displacement

Fig. 8.5 - Drilling of directional wells where the reservoir is beneath a major surface obstruction.

Cement Plug

Fish Lost in Hole and Unable to Recover Sidetracked Hole Around Fish Figure 8.6 Sidetracking around a fish.

Figure 8.7 Using an old well to explore for new oil by sidetracking out of the casing and drilling directionally.

Oil Producing Well Ready to Abandon Sidetracked Out of Casing Possible New Oil Old Oil Reservoir

Horizontal Departure to Target

Type II Build-hold and Drop (“S Type”)

Type I Type III

Build and Hold Type

Build-hold Drop and/or Hold (Modified “S” Type)

Continuous Build

Figure 8.8 - Major types of wellbore trajectories.

Figure 8.10 Geometry of the build section.

Build Section θ

Build Radius:

18,000 r1 = π * BUR

Build Section: Length of arc, L = r1θ1 Vertical depth = C’D’ = r1 sin θ1 Horiz. Depart. = DD’ = r1 (1-cos θ1 ) r1

L = θ

1

100

=

1

↑

rad

18,000 r1 = π * BUR

θ

π * 180

1 ↑

deg

BUR = build rate in deg/100 ft

Start of Buildup End of Build

Type II

Drop Off Target

Build-hold-and drop for the case where: r1 < x 3 and r1 + r2 < x 4

Kickoff Type II

End of Build Maximum Inclination Angle

Build-hold-and drop for the case where:

r1 < x3 and r1 + r2 > x4

Drop Off

Target

Projected Trajectory

Projected Trajectory with Left Turn to Hit Targets

Target 1 Target 2 Target 3

Fig. 8-14. Directional well used to intersect multiple targets

N18E

S23E A = 157o

Fig. 8-15. Directional quadrants and compass measurements N55W S20W A=?

A = 305o

Lead Angle

Projected Well Path

Surface Location for Well No. 2 Lake

Figure 8-16: Plan View

Target at a TVD 9,659

Well profile

Directional Drilling Operation

Deviation due to Formation Dip

Deviation due to Hardness of Formation

Deviation due to Miniature Whipstock Theory

Directional Tools • (i) Whipstock • (ii) Jet Bits • (iii) Downhole motor and bent sub

Whipstocks

Standard retreivable

Circulating

Permanent Casing

Setting a Whipstock • Small bit used to start • Apply weight to: – set chisel point & – shear pin

• Drill 12’-20’ • Remove whipstock • Enlarge hole

Jetting Bit • Fast and economical • For soft formation • One large - two small nozzles • Orient large nozzle • Spud periodically • No rotation at first

Small Jets

Jetting • Wash out pocket • Return to normal drilling • Survey • Repeat for more angle if needed

Mud Motors Drillpipe Non-magnetic Drill Collar Bent Sub Mud Motor Rotating Sub

Increasing Inclination • Limber assembly • Near bit stabilizer • Weight on bit forces DC to bend to low side of hole. • Bit face kicks up

Hold Inclination • Packed hole assembly • Stiff assembly • Control bit weight and RPM

Decrease Inclination • Pendulum effect • Gravity pulls bit downward • No near bit stabilizer

Packed Hole Assemblies

Drill pipe

String String NB Stabilizer Stabilizer Stab Monel Steel DC Steel DC DC

String Stabilizer HW DP

Vertical Calculation

Horizontal Calculation

3D View

Dog Leg Angle

Deflecting Wellbore Trajectory 0

270

90

180

Bottom Hole Location Direction

: N 53

Distance

:

TVD

:

2,550

o

E ft

10,000 E = 2,550 sin 53 o = 2,037 ft N = 2,550 cos 53 o = 1,535 ft

Closure = 2,550

=

E 2 + N2

⎛E ⎞ Closure Direction = tan ⎜ ⎟ = 53 o ⎝N⎠ -1

Horizontal N View Vertical View We may plan a 2-D well, but we always get a 3D well (not all in one plane)

MD, α1, ε1 ∆MD β = dogleg angle

α2 , ε 2

Fig. 8-22. A curve representing a wellbore between survey stations A1 & A2

Bottom Hole Location Direction : N 53o E Distance : 2,550 ft TVD :

10,000 E = 2,550 sin 53 o = 2,037 ft N = 2,550 cos 53 o = 1,535 ft

Closure = 2,550

= E 2 + N2

⎛E⎞ Closure Direction = tan ⎜ ⎟ = 53o ⎝N⎠ -1

Survey Calculation Methods 1. Tangential Method = Backward Station Method = Terminal Angle Method

Assumption: Hole will maintain constant inclination and azimuth angles, IB and AB , between survey points.

A

Known : Location of A Distance AB Angles IA , IB

IA IB

Angles A A , A B Calculation : VAB = AB cosIB HAB = AB sinIB B IB

Poor accuracy!!

Average Angle Method = Angle Averaging Method Assumption: Borehole is parallel to the simple average drift and bearing angles between any two stations. Known: Location of A, Distance AB, Angles I A , IB , A A , A B

A

Average Angle Method (i) Simple enough for field use

IA

(ii) Much more accurate than “Tangential” Method

IB IAVG

Iavg B IAVG

A avg

⎛ I A + IB ⎞ =⎜ ⎟ ⎝ 2 ⎠ ⎛ A A + AB ⎞ =⎜ ⎟ 2 ⎠ ⎝

A

Average Angle Method Vertical Plane:

IA IB

Iavg

IAVG B IAVG

⎛ I A + IB ⎞ =⎜ ⎟ ⎝ 2 ⎠

V AB = AB cos Iavg H AB = AB sin Iavg

Average Angle Method

N

Horizontal Plane: AB

B AAVG

∆N

AA

∆E

A

H AB = AB sin Iavg

∆ E = AB sin Iavg sin A avg ∆ N = AB sin Iavg cos A avg ∆ Z = AB cos Iavg E

Change in position towards the east: ⎛ IA + IB ⎞ ⎛ A A + AB ⎞ ∆ x = ∆ E = L sin ⎜ ⎟ sin ⎜ ⎟..(1) 2 ⎝ 2 ⎠ ⎝ ⎠

Change in position towards the north: ⎛ I A + IB ⎞ ⎛ A A + AB ⎞ ∆ y = ∆ N = L sin ⎜ ⎟ cos ⎜ ⎟..( 2 ) 2 ⎝ 2 ⎠ ⎝ ⎠

Change in depth: ⎛ I A + IB ⎞ ∆ Z = L cos ⎜ ⎟ ⎝ 2 ⎠

..( 3 )

Where L is the measured distance between the two stations A & B (∆MDAB).

Example The coordinates of a point in a wellbore are: x = 1,000 ft (easting) y = 2,000 ft (northing) z = 3,000 ft (depth) At this point (station) a wellbore survey shows that the inclination is 15 degrees from vertical, and the direction is 45 degrees east of north. The measured distance between this station and the next is 300 ft….

Example The coordinates of point 1 are: x1 = 1,000 ft (easting) o y1 = 2,000 ft (northing) I1 = 15 o z1 = 3,000 ft (depth) A1 = 45 L12 = 300 ft o

At point 2, I2 = 25 Find

o

and A2 = 65

x2 , y2 and z2

Solution Iavg A avg

⎛ I1 + I2 ⎞ ⎛ 15 + 25 ⎞ =⎜ ⎟=⎜ ⎟ = 20 2 ⎝ 2 ⎠ ⎝ ⎠ ⎛ A 1 + A 2 ⎞ ⎛ 45 + 65 ⎞ =⎜ ⎟ = 55 ⎟=⎜ 2 2 ⎝ ⎠ ⎝ ⎠

H12 = L12 sin Iavg = 300 sin 20 = 103 ft ∆E = H12 sin Aavg = 103 sin 55 = 84 ft ∆N = H12 cos Aavg = 103 cos 55 = 59 ft ∆Z = L12 cos Iavg = 300 cos 20 = 282 ft

Solution - cont’d ∆E = 84 ft ∆N = 59 ft ∆Z = 282 ft x2 = x1 + ∆E = 1,000 + 84 ft = 1,084 ft y2 = y1 + ∆N = 2,000 + 59 ft = 2,059 ft z2 = z1 + ∆Z = 3,000 + 282 ft = 3,282 ft

Dog Leg

Problem 3 Determine the dogleg severity following a jetting run where the inclination was changed from 4.3o to 7.1o and the direction from N89E to S80E over a drilled interval of 85 feet. 1. Solve by calculation. 2. Solve using Ragland diagram

α = 4 .3 ε = 89

o

L = 85 ft

o

∆α = 7.1 - 4.3 = 2.8.

α N = 7.1

o

ε N = 100

o

∆ε = 100 - 89 = 11

Solution to Problem 3- Part 1 1. From Equation 8.55 ⎞⎤ ⎟⎥ ⎠⎦

1/ 2

⎡ 2 2 .8 2 11 2 ⎛ 4 .3 + 7 .1 ⎞ ⎤ sin ⎜ β = 2 sin ⎢ sin + sin ⎟⎥ 2 2 2 ⎝ ⎠⎦ ⎣

1/ 2

⎡ 2 ∆α 2 ∆ε 2 ⎛ α + αN β = 2 sin ⎢ sin + sin sin ⎜ 2 2 ⎝ 2 ⎣ −1

−1

β = 3.01

o

Solution to Problem 3- Part 1 1. From Equation 8.43 the dogleg severity,

δ =

β (i) L

δ = 3 .5

= o

3 . 01 85

∗ 100

/ 100 feet

Directional Drilling Measurements • The trajectory of a wellbore is determined by the measurement of: hinclination

θ, α, I

hdirection

φ, ε, A

hmeasured depth

∆MD, ∆L, L

Directional Drilling Measurements - cont’d • A tool-face measurement is required to orient: ha whipstock hthe large nozzle on a jetting bit ha bent sub or bent housing

Directional Drilling Measurements - cont’d • Tools available hsingle-shot magnetic or gyroscopic hmulti-shot magnetic or gyroscopic hmagnetometers, accelerometers, MWD tools

Magnetic Single-Shot Instrument • Records – inclination – direction – tool face position on sensitized paper or photographic film

• Inclination may be determined by – a float on a liquid – a pendulum

Magnetic Single-Shot Instrument • Unit may be triggered by: – clock timer. – inertial timer (after stop).

• Unit may be dropped (pumped down) and later retrieved by wireline or the drillpipe.

Magnetic Single-Shot Instrument • Single-shot instruments are used: – to monitor progress of directional-control well. – to monitor progress of deviation-control well. – to help orient tool face for trajectory change.

Magnetic Single-Shot Instrument - cont’d • Procedure: – load film into instrument – activate timer (activate stopwatch) – make up the tool – drop the tool – retrieve tool (wireline or drillpipe)

Light

Housing Center Post Float Fluid Reference Mark

Main Frame Photographic Disc A. 0-20o Angle-Compass Unit

B. 0-70o Angle-Compass Unit

Fig. 8.41: Schematic diagrams of magnetic single-shot angle-compass unit (courtesy Kuster Co.).

1. Pendulum

Fig. 8.43: Pendulum suspended inclinometer and compass unit for a 0 to oo 17 singeshot unit.

2. Circular Glass 3. Compass 4. Pressure equalization 5. Cover glass

Indicated inclination 5o. Direction of inclination N 45 degrees 0’ or azimuth 45 degrees.

A/C Units

Plumb-Bob Units

Incl. Only Units

Fig. 8.42: Single-shot film disks (courtesy of Kuster Co.). • Inclination • Direction • Tool Face Angle

Fig. 8.12: Pendulum assembly: a) plumbbob angle unit b) drift arc inclinometer Pendulum Glass ring Piston

(a)

(b)

Fig. 8.13: Schematic drawing of magnetic single and multi-shot instruments.

o

N35 W o I = 5.5

Hole direction with reference to Magnetic North

Compass Inclination Scale

Fig. 8.44: Cardan suspended compass and inclinometer for a single-shot o

o

5 to 90 unit.

Wire Line Socket Overshot

Rope Socket Swivel Stabilizer Stabilizer Fingers

Protective Case Orienting Anchor & Plug Mule Shoe Mandrel

Fig. 8.45: Typical magnetic single-shot tool with landing sub.

Bottom Hole Orienting Sub Bottom Landing Assembly Takes time. Rig time is costly. Temperature limitation. May have to pump down.

Ready to be Dropped

Free Falling to Bottom

Tool seated

Retrieve single shot

Fig. 8.46: Typical single-shot operation.

Timer On 3 min.

Compass Unit *Single Shot Instruments are run on slickline if there is a mule shoe sub in the hole

Single Shot Ready to be Dropped

Single Shot Free Falling in Mud to Bottom

Non Magnetic Drill Collar Orienting Sub Sleeve

Fig. 8.46: Typical single-shot operation.

Fig. 8.46: Typical single-shot operation. Tool seated in orienting sleeve or at stop taking picture

3 min.

10 min.

Overshot Used to Fish Single Shot

Wireline unit to retrieve single shot

Top View Direction of Tool Face Via Bent Sub

Fishing Neck Non Magnetic Collar Single Shot Mule Shoe Orienting Sub Orienting Sleeve Lined up with Bent Sub Bent Sub

Mule Shoe Key Position

New Centerline

Mud Motor

Existing Centerline

Fig. 8.47: Arrangement of the mule shoe for orienting a mud motor.

Magnetic Multishot Instruments • Are capable of taking numerous survey records in one run. • May be dropped down the drillpipe or run on wireline in open hole. • The unit contains a watch that is spring wound and uses the power of the spring to operate a timer cam.

Non-Magnetic Drill Collar(s)

Compass Position Multi-shot Instrument

Landing Plate

Fig. 8.48: Typical arrangement for landing a multi-shot instrument.

Bottom Landing Rope Socket Stabilizer with Rubber Pins Battery Case Battery Connector Connector Shock Absorber Watch Assembly

Protective Instrument Barrel Angle Unit Barrel Lower Ball Plug Aluminum Spacer Bar Bottom Shock Absorber Assembly

Fig. 8.49: Drop multi-shot survey instrument

Watch Section

Motor

Light Switch Lever

Geneva Gear

Knife Geneva Drive Winding Motor Wheel Assembly Switch Stem Lever Watch Switch Terminal Film Sprocket Switch

Time Cycle Cam

Takeup Film Supply Film Spool Spool

Fig. 8.50: Views of the watch and camera unit of a typical multi-shot tool.

Magnetic Multishot - cont’d • The multishot tool is usually dropped down the drillpipe and landed in the nonmagnetic drill collar. • During the trip out, a survey is taken every 90 ft, i.e. every stand.

Magnetic Multishot - cont’d • More closely spaced stations could be obtained by stopping the pipe more often, and waiting for a picture. • A stopwatch at the surface is synchronized with the instrument watch.

Fig. 8.51: Use of the surface watch while running a magnetic multi-shot operation.

Synchronize with instrument watch by starting at the instant camera lights go on.

Time Intervals: A. 10 seconds Lights are on, exposing film B. 15 seconds - Delay before moving. This is an allowance for instrument watch lag during survey.

Time Intervals - cont’d C. 20 seconds - Instrument is idle allowing movement of drill string without affecting picture. Most moves require sufficient time for taking one or more shots while moving D. 15 seconds - Minimum time for plumb bob and compass to settle for good picture, plus allowance for instrument gain during survey.

Fig. 8.52b: Projection of one survey frame for determining inclination and direction.

Steering Tools • Used with mud motors and bent sub • Can either pull every stand or use a side entry sub for continuous drilling

Standard Measuring Cable

Monel DC Probe Mule Shoe Bent Sub Mud Motor

MWD Tools

MWD Tools

Gyroscopic Tools • Non-magnetic drill collars used to prevent magnetic interference from drillstring • Gyros used if magnetic interference is from non drillstring source