Schlumberger Shock Guide

Shock and vibration mitigation Factors Affecting Vibrations

Vibration Prevention

Generalizations only—vibrations often result from complex interplay of factors

✓ Run Drilling Office/BHA-V—This drilling office application analyzes BHA and predicts resonant frequencies—stay away from bad rpm; compare calculated with actual values

✓ Identify vibration generation mechanism—bit, BHA, formation, drilling parameters, on or off bottom—and use counteractive measures

✓ Always run multivibration chassis (MVC) in MWD tools for real-time vibration communication

✓ Optimize correct real-time shock/vibration variables from MWD tool for predicted vibration environment

✓ Within limitations, design BHA, especially stabilization, and select PDC bit with vibration prevention in mind

✓ Set tight alarms on all vibration variables and monitor closely—display for driller to see

✓ Bits—PDC bits generate higher vibrations; aggressive features like larger cutter size, lower number of cutters, fewer blades, and low backrake angle

✓ Help train drillers in vibration reduction—ensure LWD engineers have vibration training

✓ Optimize drilling parameters—WOB, rpm, flow rate— for vibration prevention/reduction and ROP

✓ Higher friction factors will generate higher vibrations

✓ Be aware of high-vibration operations—backreaming, opening a pilot hole, reaming, hole opening while drilling, drilling out of casing/liner

✓ Torque feedback—soft-torque system (may mask stick/slip)

✓ Inclination—more axial vibrations closer to vertical; tendency for more vibrations as angle increases, but can also be “dampened” by angle ✓ BHA design—higher vibrations with slick and pendulum assemblies ✓ BHA components—undergauge stabilization generates vibrations; straight-blade stabilizers, smaller drill collars usually have higher vibrations; high-torque and aggressive mud motors may have higher vibrations

✓ Expect higher vibrations in formations that are hard/abrasive and/or have high coefficients of friction and restitution—conglomerates, boulders, cherts, interbedded/intercalated formations, sandstones, and limestones

✓ Know vibration reduction procedures for each type of vibration—see Cures below

✓ Large ratio of hole size to BHA/tool OD size will generate more vibrations

✓ Know procedures for dealing with high vibrations from drilling hard streaks and reaming

✓ Poor hole conditions, such as poor hole cleaning, washouts, and ledges can sometimes generate vibrations

Detection/Symptoms AXIAL VIBRATION

Perform Engineer

Driller

LATERAL VIBRATION (bit/BHA whirl)

SURFACE • Large WOB fluctuations • Rig/topdrive shaking • Loss of toolface, steering problems • Reduced and inconsistently slow ROP

SURFACE • Increased mean surface torque • Loss of toolface, steering problems • Reduced and inconsistently slow ROP

DOWNHOLE • Increased axial vibrations • Increased shocks • Intermittent transmission or loss of MWD signal and downhole data

• • • • •

POSTRUN

• Early bearing failure • Broken/chipped cutters/inserts—no specific location • MWD/LWD failure

Cures

AXIAL VIBRATION (bounce)

Perform Engineer

✓ Increase mud lubricity to reduce friction and, thereby, vibrations ✓ Keep offset log of formations if available—track lithology for upcoming vibration risks

Driller

DOWNHOLE Increased mean downhole torque High-frequency downhole shocks (10 to 50 Hz) Increased lateral vibrations Increased torsional vibrations and shocks Intermittent transmission or loss of MWD signal and downhole data POSTRUN Cutters/inserts damaged on shoulder or gauge Broken/damaged PDC bit blades Worn hybrids with minimal cutter wear Overgauge hole from calipers One-sided/eccentric wear on stabilizers and BHA components MWD/LWD failure

• • • • • •

LATERAL VIBRATION (bit/BHA whirl)

STICK/SLIP TORSIONAL VIBRATION

Perform Engineer

Driller

SURFACE • Topdrive stalling—increased and erratic surface torque • rpm/torque cycling • Loss of toolface, steering problems • Reduced and inconsistently slow ROP DOWNHOLE • Increased/erratic downhole torque • Increased torsional vibrations, from MWD tool • Increased stick/slip • Collar rpm greater than surface rpm • Intermittent transmission or loss of MWD signal and downhole data • Increased lateral vibrations and shocks POSTRUN • Cutters/inserts damaged on nose or taper • Overtorqued/damaged pin/box connections • Drillstring damage—twist-offs and washouts • MWD/LWD failure

TORSIONAL VIBRATION (stick/slip) Place topdrive in high gear. Ensure soft torque operational

Repeat three times unless WOB limit is exceeded Yes

Increase WOB by 1 ton Decrease rpm by same percentage

Does vibration continue?

Decrease rpm by 10% Repeat three times unless WOB limit is exceeded Yes No

Pick up off bottom and allow string torque to unwind Set rpm at 40 to 50% of original Increase WOB by 10 to 20% of original Gradually return rpm to original

Vibration resumes?

No

Increase WOB by 10%

Does vibration continue?

No Pick up off bottom and allow string torque to unwind Restart drilling with 70 rpm Increase WOB by 10% of original Increase rpm to original value

No

05-DR-125

Produced by Schlumberger Marketing Communications

Does vibration continue?

Pick up off bottom and allow string torque to unwind Restart drilling with 10% increased rpm Decrease WOB 15 to 20%

Vibration resumes?

Pick up off bottom and allow string torque to unwind Restart drilling with 70 rpm Increase WOB to target value Increase rpm to 25% below original value

CONTINUE DRILLING

May 2005

Increase rpm by 10%

No

Yes Pick up off bottom and allow string torque to unwind Set rpm at 40 to 50% of original value Increase WOB by 10 to 20% Gradually return rpm to 25% below original value

Decrease WOB by 5% Repeat three times unless rpm limit is exceeded Yes

No

Vibration resumes? Yes

Pick up off bottom and allow string torque to unwind Restart drilling with 70 rpm Increase WOB to 25% below original value Gradually return rpm to 15% above original value

Shock and vibration information

Conventional Cures While Drilling AXIAL VIBRATION (bounce)

LATERAL VIBRATION (bit/BHA Whirl)

TORSIONAL VIBRATION (stick/slip)

Bit Bounce

Bending

Stick/Slip

BHA Whirl

Axial

Lateral

Torsional

Eccentered

Mode of Vibration

Real-Time Diagnosis

Typical Environment

Potential Cure

Other Solutions

Axial shocks

Topdrive or kelly shaking, downhole shocks

Hard formations, vertical holes, roller cone bits

STOP—Change WOB and change rpm

Change to less-aggressive bit, use a shock sub

Bit whirl

LWD caliper shows overgauge hole but bit is undergauge

Aggressive side-cutting bit

STOP—Increase WOB and decrease rpm

Change bit, use full-gauge NB stabilizer

BHA whirl

Large downhole shocks, increased STOR

Washed out hole, BHA pendulum or unstabilized

STOP—Increase WOB and reduce rpm

Use a stiffer BHA

Stick/slip

Large surface torque and rpm fluctuations, MWD peak-peak rpm

Aggressive PDC bits, high wellbore BHA friction

STOP—Reduce WOB and increase rpm

Increase mud lubricity, use lessaggressive bit, improve hole cleaning

Place top drive in high gear; ensure soft torque operational.

Increase WOB by 1 ton Decrease rpm by same percentage

Yes

Does vibration continue?

No

Decrease WOB by 5%

Increase WOB by 10%

Increase rpm by 10%

Repeat three times unless WOB limit is exceeded

Repeat three times unless WOB limit is exceeded Yes

Decrease rpm by 10%

No

Does vibration continue?

Yes

Vibration resumes?

Yes

Yes

Pick up off bottom and allow string torque to unwind Set rpm at 40 to 50% of original Increase WOB by 10 to 20% of original Gradually return rpm to 25% below original

Pick up off bottom and allow string torque to unwind Restart drilling with 70 rpm Increase WOB to original value Increase rpm to 25% below original value

CONTINUE DRILLING

05-DR-125

No

Produced by Schlumberger Marketing Communications

Does vibration continue? Yes

Pick up off bottom and allow string torque to unwind Restart drilling with 70 rpm Increase WOB by 10% of original Increase rpm to original value

No

Vibration resumes?

May 2005

Yes

Yes

Pick up off bottom and allow string torque to unwind Set rpm at 40 to 50% of original Increase WOB by 10 to 20% of original Gradually return rpm to original

No

Repeat three times unless rpm limit is exceeded

Pick up off bottom and allow string torque to unwind Restart drilling with 10% increased rpm Decrease WOB 15 to 20%

Schlumberger Drilling Dynamics Guidelines Axial vibrations, gn–RMS (log scales: 0 to 4) 0 to 1

Low

No problem over time

1 3,000

More than 1⁄2 hr, severe risk of failure

Severe

Stick/slip ratio, stick_RT/rpm (log scales: 0 to 200 rpm) < 50%

0 to 0.5

Low

No problem over time

50% < 100%

0.5 to 1.0

Medium

More than 25 hr, medium risk of failure

100% < 150%

1.0 to 1.5

High

More than 12 hr, high risk of failure

>150%

> 1.5

Severe

More than 1⁄2 hr, severe risk of failure

Drilling optimization workflow Vibrations—Recognize the Symptoms

Conventional Cures While Drilling

Vibrations—Recognize the Symptoms

Conventional Cures While Drilling

Vibrations—Recognize the Symptoms

Conventional Cures While Drilling

Surface Measurement or Symptom

AXIAL VIBRATION (bounce)

Surface Measurement or Symptom

LATERAL VIBRATION (bit/BHA whirl)

Surface Measurement or Symptom

TORSIONAL VIBRATION (stick/slip)

• Increased mean surface torque

• Large WOB fluctuations Increase WOB by 1 ton

• Rig/topdrive shaking

Decrease rpm by same percentage

• Loss of toolface

Repeat three times unless WOB limit is exceeded

• Reduced ROP

Downhole Measurement

Yes

• Loss of real-time data/measurement

No

Does vibration continue?

Pick up off bottom and allow string torque to unwind Set rpm at 40 to 50% of original Increase WOB by 10 to 20% of original Gradually return rpm to original

• Increased axial vibrations

Postrun Evidence No

• Early bearing failure • Broken/chipped cutters and inserts— no specific location • BHA failure

Decrease rpm by 10%

• Reduced ROP

Increase WOB by 10%

Downhole Measurement

Yes

• Increased shock count

• Loss of toolface

Vibration resumes?

• Increased mean downhole torque • High-frequency downhole shocks— 10 to 50 Hz

CONTINUE DRILLING

Yes No

• Loss of real-time data/measurement

• Cutters/inserts damaged typically on shoulder or gauge • Broken PDC blades

Does vibration continue?

No

Vibration resumes?

Pick up off bottom and allow string torque to unwind Restart drilling with 70 rpm Increase WOB to original value Increase rpm to 25% below original value

• Worn hybrids (equivalents) with minimal cutter wear • Overgauge hole from calipers • One-sided wear on stabilizers and BHA • BHA failure

Decrease WOB by 5%

05-DR-125

Produced by Schlumberger Marketing Communications

Repeat three times unless rpm limit is exceeded Yes

Downhole Measurement

No

CONTINUE DRILLING

Does vibration continue? Yes

• Increased delta downhole torque

Pick up off bottom and allow string torque to unwind Restart drilling with 10% increased rpm Decrease WOB 15 to 20%

• Increased torsional acceleration • Increased stick/slip indicator • Downhole collar rpm greater than surface rpm • Loss of real-time data/measurement • Increased lateral shocks • Increased shock count

Postrun Evidence • Cutters/inserts damaged typically on nose and taper • Overtorqued connections • Twist-offs and washouts • BHA failure

May 2005

Increase rpm by 10%

• rpm/torque cycling

• Reduced ROP

Yes

Postrun Evidence

• Increased delta surface torque

• Loss of toolface

Pick up off bottom and allow string torque to unwind Restart drilling with 70 rpm Increase WOB by 10% of original Increase rpm to original value

• Increased torsional acceleration

• Increased shock count

Place top drive in high gear; ensure soft torque operational.

Yes

• Increased lateral shocks

Yes Pick up off bottom and allow string torque to unwind Set rpm at 40 to 50% of original Increase WOB by 10 to 20% of original Gradually return rpm to 25% below original

Repeat three times unless WOB limit is exceeded

• Topdrive stalling

No

Vibration resumes? Yes Pick up off bottom and allow string torque to unwind Restart drilling with 70 rpm Increase WOB to 25% below original value Gradually return rpm to 15% above original

CONTINUE DRILLING