17-BHAs

Sperry Drilling Services

2007.1

Buoyancy Factor

Directional Drilling

BF = 1− MW 65.4 BF = 1− SGmud 7.85

Bottom Hole Assemblies

where : MW (lb/gal) 65.4 (lb/gal) SGmud (--) 7.85 (--)

Sperry Drilling Services 2007

Force Components

Weight Correction BF = 1− MW 65.4

Buoyancy factor

Buoyed unit weight

Wbuoy = Wair x BF

Axial weight force

Fa = L x Wbuoy x cos IN

Normal weight force

Fn = L x Wbuoy x sin IN

Notes : IN hole inclination, degrees wair from pipe tables, lb/ft

mud weight density of steel specific gravity of mud specific gravity of steel

DC axial

Fa

WOB

normal

Fn

torque and drag

Fn normal force

α Fa weight on bit

weight of DC Use only the 75-80% of the available BHA weight for WOB for keeping the neutral point of tension within the DC column

MW mud weight, lb/gal L length, ft

Effect of Hole Inclination

Note !

The weight of the DC DC Fnormal = 0

F = L x W buoy

Axial weight force Fa Normal weight force Fn

Faxial = 0 Fnormal = Wbuoy x sin IN

Fnormal = Wbuoy

Fn

α

Faxial = Wbuoy x cos IN

F =

2 2 (Fa + Fn ) [ lb ]

Fa F

Faxial = Wbuoy Friction Force : Ff = Fnormal x ff

Directional Drilling – BH Assemblies

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Sperry Drilling Services

2007.1

Basic Rotary Assembly Types

The Pendulum Principle

Dropping Assembly

Pendulum assemblies drop angle as a pendulum creates negative

• Dropping Assembly (Pendulum)

side force

• Building Assembly (Fulcrum)

1 F = W × BF × L × sin IN s 2 c t

• Holding Assembly (Packed Hole)

tangency point (welllbore contact)

Lt

Fs Side force on bit (lbs) Wc DC weight below tangency point (lbs/ft) Lt Length of pendulum (ft) IN Fs

Inclination at tangency point (deg)

BF Buoyancy factor (-)

Pendulum Assembly - Tally Generic Angle Dropping (Pendulum) Assembly • • • • • • • •

Bit Drill collar, 30-90ft String stabilizer, full gauge Drill collar, 30ft String stabilizer, full gauge Drill collar,90ft HWDP, 90ft min. Drill pipe

Drilling Parameters Used in BHA Analysis

Directional Drilling – BH Assemblies

Pendulum Assembly - Performance

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Sperry Drilling Services

2007.1

The Fulcrum Principle

Slick Angle Dropping Assembly

• The fulcrum uses a near-bit stabilizer WOB

• WOB (if sufficient) will cause the bottom DC to bend

To increase drop rate :

• In holes with inclination > 5°, DC will bend towards the low side of the hole – due to the gravity

• Increase stiffness • Increase bit/DC size ratio • Increase DC weight • Decrease WOB • Increase rotary speed length of pendulum

wellbore contact Lt

Problems ? This bend will cause bit to exert a side force against the high side of the hole, resulting in a build of angle as drilling progresses

Fs side force (negative)

Generic Angle Building (Fulcrum) Assembly

• • • • • • • • •

a

Fulcrum Assembly - Tally

Bit Near-bit Stabilizer, full gauge Drill collar, 30-90ft String stabilizer, full gauge Drill collar, 30-60ft String stabilizer, full gauge Drill collar,90ft HWDP, 90ft min. Drill pipe, as required

b

Fulcrum Assembly - Performance

Packed Hole Assembly • The packed hole assembly is used to maintain angle or build/drop at mild rates • 3 or more stabilizers are placed at specified points to control the deflection of the drill collar string

1-2 jts dc

1 jt full length dc ~ 30 ft short dc • The increased straightness of the drill collar string reduces or eliminates the bit tilt

Directional Drilling – BH Assemblies

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Sperry Drilling Services

2007.1

Packed Hole Assembly - Tally Generic Packed Hole Assembly • • • • • • • • •

Bit Near-bit Stabilizer, full gauge Short Drill collar, 6-20ft String stabilizer, full gauge Drill collar, 30ft String stabilizer, full gauge Drill collar,90ft HWDP, 90ft min. Drill pipe, as required

Packed Hole Assembly - Performance

Packed Hole Assembly - Performance

The table shows the inclination and DLS values through the transitional period

Packed Hole Assembly - Performance

Typical Configurations - Summary

30-90 ft (9-27m)

the equilibrium is reached here

30 ft (9m)

30 ft (9m)

5-20 ft 1.5~20m

Directional Drilling – BH Assemblies

30 ft (9m)

30 ft (9m)

30-60 ft (9-18m)

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2007.1

Three – point Geometry Directional Assemblies Top stabilizer

• Traditional Assemblies : » straight motors or turbines with bent subs

3 points, which are not on the same straight line …

• Steerable Assemblies : » bent housing motors or turbines

R

– Stabilized – Slick

… defines only 1 circle

• Rotary Steerable Systems : – Indirect side force (Appleton, DDD) – Direct side force (Camco, BHI) – Bit pointing (SSDS, Amoco,Precision Drilling/Computalog)

Motor stabilizer or bend

Bit

Theoretical DLS

3-p Geometry Calculation vs. PLANIT BHA Analysis

R

9-5/8” SperryDrill 6/7 – 5.0 Top stabilizer

Θ Bend angle

DLS =

L2

From 3-p calculations the build rate is 7.94°/100 ft 200 × Θ (o / 100 ft ) L1 + L2

Motor stabilizer Curved borehole L1

Bit

For comparison, these data were used in PLANIT

Based on the assumption that the stabilizers are full gauge, and the bend is at the motor stabilizer

3-p Geometry Calculation vs. PLANIT BHA Analysis (7.94 vs. 7.20 – 8.40 °/100 ft)

dc or nmdc

Conventional Straight Mud Motor / Bent Sub

bent sub • Uses (straight) motor (turbine) and bent sub • Usable with single shot orientations, too • Smoothest curvature

IN = 5°

IN = 35°

• The BHA must not be rotated • Must be tripped when EOB reached or correction finished

PDM or turbine

Directional Drilling – BH Assemblies

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2.stab UG

2007.1

Steerable Motor Assembly

1.stab UG

Generic Stabilized Steerable Assembly • • • • • • •

nmdc

Bit and 2 stabilizers provide 3 contact points Sliding and rotating are both possible Bend might be adjusted on site More tortuous hole Float valve and 2nd stabilizers are optional

• • • • • •

Bit Mud motor with bent housing, w/ sleeve stabilizer, 1/16-1/4” undergauge String stabilizer on top of motor, 1/8-1/2” undergauge Drill collar, or MWD hang-off collar, 30-40ft String stabilizer, full gauge to ½” undergauge Drill collar, 90ft HWDP 30-90ft Drill pipe, as required

UG float valve toolface direction

Steerable Assembly Performance

Steerable Assembly - Tally

MWD

Note, this performance is true only at 30° inclination PDM

bend

“control ” stabilizer

optional

Steerable Assembly – Performance Change

Directional Drilling – BH Assemblies

Steerable Assembly – Equilibrium Rate

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2007.1

Steerable Assembly with AGS - Tally

Steerable Assembly with AGS - Performance

Bent Sub Alignment

Double Bend Assembly

2.stab UG

bent sub The motor toolface and bent sub scribeline has to be lined up

nmdc

•

Increased dogleg capability

•

Bent sub needs to be aligned to motor toolface using shims btw bent sub and motor for correcting scribeline position cut off direction of bend on bent sub

UG float valve direction of bend on motor

toolface direction

Kick Pads

Offset Pads •

nm dc

Increased dogleg capability with same bend angle compared to slick assemblies

At higher build rates (e.g. short radius wells) pads are used in the place of stabilizers

•

Behaviour is sensitive of WOB

Pad sizes and correct alignment to HS and LS are critical !

•

Improved sliding performance (does not hang up)

•

Rotation is limited to lower bend angles 3. HS pad

bit tilt

Only 2 definitive contact points

2. LS pad

Directional Drilling – BH Assemblies

The 3 contact points set the directional performance

1. LS

2. LS pad

bit tilt

HS

1. LS

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2007.1

WOB

Drilling with Slick Assembly Generic Slick Steerable Assembly The WOB could flex the motor opposite to the bend, reducing the build rate – holding or even dropping angle The BHA performance is a strong function of the WOB, because the top contact point is not well defined, moves up or down as the WOB changes

• • • • • •

Bit Mud motor with bent housing, without sleeve stabilizer Drill collar, or MWD hang-off collar, 30-40ft Drill collar, 90ft HWDP 30-90ft Drill pipe, as required

Questions : • Why want we use a slick assembly ? • How can we model its directional behaviour ? • What is the problem with using it in practice ?

Practical Bottom Hole Assemblies 12 1/4" rotary assembly (RHX1214)

• 12-1/4” rotary assembly • 12-1/4” steerable assembly • 12-1/4” wiper trip assembly • 8-1/2” steerable assembly • 8-1/2” wiper trip assembly • AGS application examples

12 1/4" 12 1/4" 8" 12 1/4" 8" 12 1/4" 8" 8" 8" 5" 5"

Bit Integral Blade Near-bit Stabilizer Short Drill Collar Integral Blade String Stabilizer Non-magnetic Drill Collar (for ESS) Integral Blade String Stabilizer Drill Collar, 2-4 jts HMD Drilling Jar Drill Collar, 2 jts Crossover Sub Hevi-Wate Drill Pipe, 3-15 jts Drill Pipe

Note : these assemblies are actual BHAs used for drilling a North Sea directional well

12 1/4" steerable assembly (SXX1214) 12 1/4" 9 5/8" 11 3/4" 8" 12 " 8" 8" 8" 5" 5"

Bit Crossover Sub SPERRY-DRILL Mud Motor w/12” sleeve stabilizer Integral Blade Stabilizer Non-magnetic Hang-off Collar for DWD Integral Blade String Stabilizer Drill Collar, 2-4 jts HMD Drilling Jar Drill Collar, 2 jts Crossover Sub Hevi-Wate Drill Pipe, 3-15 jts Drill Pipe

Directional Drilling – BH Assemblies

12 1/4" wiper trip assembly ( RWX1214) 12 1/4" 12 1/4" 8" 12 1/4" 8" 8" 8" 5" 5"

Bit (milled tooth) Integral Blade Near-bit Stabilizer Non-magnetic Drill Collar (for ESS) Integral Blade String Stabilizer Drill Collar, 2-4 jts HMD Drilling Jar Drill Collar, 2 jts Crossover Sub Hevi-Wate Drill Pipe, 3-15 jts Drill Pipe

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Sperry Drilling Services

2007.1

8 1/2" wiper assembly (RWX 0812)

8 1/2" steerable assembly (SXX0812) 8 1/2" 6 3/4" 8 1/4" 6 1/2" 6 1/2" 8 1/4" 6 1/2" 6 1/2" 6 1/2" 5" 5"

Bit SPERRY-DRILL Mud Motor w/ 8-1/8” sleeve stabilizer Integral Blade String Stabilizer Non-magnetic Drill Collar, 1 jt Non-magnetic Hang-off Sub - DWD Integral Blade String Stabilizer Drill Collar, 4 jts HMD Drilling Jar Drill Collar, 1 jt Hevi-Wate Drill Pipe, 3-10 jts Drill Pipe

8 1/2" 8 1/2" 6 1/2" 8 1/2" 6 1/2" 5" 5" 5" 6 1/2" 5" 5"

Bit Integral Blade Near-bit Stabilizer Non-magnetic Drill Collar, 1 jt (for ESS) Integral Blade String Stabilizer Drill Collar, 1 jt Hevi-Wate Drill Pipe, 3 jts Drill Pipe, 1000m Hevi-Wate Drill Pipe, 2 jts HMD Drilling Jar Hevi-Wate Drill Pipe, 1-8 jts Drill Pipe

Note The above steerable assembly would be modified as hole angle increases, in order to keep the drill collars and the jar inside the 9 5/8" casing when drilling in the horizontal section. Drill pipe and- Hevi Wate drill pipe would be used in the open hole as push-pipes. -

Drillstring Sections Effects of Gravity and Inclination

1. - Bottom Hole Assembly

Normal drillstring - vertical and inclined wells (