John Macpherson - Stick Slip Presentation

The Science of Stick-Slip IADC Stick-Slip Mitigation Workshop July 15, 2010 John Macpherson Baker Hughes Inc.

1

Three Modes of Vibration

Lateral Vibration

Bending Bending Whirl Whirl

Torsional Vibration

Stick -Slip Stick-Slip

Bit Bit Bounce Bounce Axial Vibration Jarring Jarring (impact) (impact)

2

Torsional Vibrations • Drillstring is a Spring-Mass System (Torsional Pendulum) • Torsional Oscillation frequency

is the first natural torsional frequency for the drillstring System

• Frequency is very low, usually

less than 1/2 Hz, for a drillstring of any length.

Torsional Oscillation Period Torsional Oscillation Period, seconds

14 12 10 8 6

6-3/4 x 200 ft BHA 8-1/4 x 200 ft BHA

4 2 0 0

5000

10000

15000

20000

25000

30000

Drillstring Length, feet • Analytic Calculation: Bailey J.J., and Finnie I., "An Analytical Study of Drill-String Vibration",

Trans. ASME, May 1960, pp 122-128 • Empirical: period of oscillation increases by 2 seconds per 1,000m of 5” pipe (Dufeyte and Henneuse, 1991, IADC/SPE 21945)

Torsional Vibrations Smooth rotation

Torsional Oscillations

Stick-Slip

Bit Rotation Rate

Field Example, downhole rotation measurements

A

B

C

Time (secs)

• A – Increase RPM, B – Torsional Oscillations, C – Stick-Slip (period = 4.5s)

Stick -Slip: bit Stick-Slip: bit rotation rotation periodically periodically stalls stalls during during continuous continuous surface surface rotation. rotation.

Severe Stick Slip Maximum DRPM 645; Surface 70

Stick periods 24 s rotation periods 2.5s

Increase RPM

600 400 200 0 -165 RPM for 1.4s

kN.m 30 20 10 0 kN 150 100 50 200

250

300

Vertical Well (2.5 deg), about 10,300 feet, measurements 8 feet above bit.

350

Time (seconds)

400

Stick-Slip Example Roller Cone Bit

Torque, kN.m

15 10 5 0

Weight, kN

-5 400 300 200 100

RPM

0 -100 100 50 0 320

330

340

350

Elapsed Time, seconds

• Downhole Rotation Rate • Stick-slip period = 3.3 seconds

360

370

Modeling: Stick-Slip Visualization • Drillstring Simulation – Finite Element Model – Arbitrary curved and straight boreholes – String can move freely in wellbore – Wall contact penalty formulation – Friction during drillstringwall contact – Torque on bit from a coupled bit model

Downhole -slip behavior Downhole torsional torsional oscillations oscillations and and stick stick-slip behavior are are visible visible as as periodic periodic torque torque fluctuations fluctuations on on surface surface

Comparison Comparison of of measurements measurements and and simulation simulation for for the the Stribeck Stribeck type type bit bit model model

TB  5231.608  100.658  n B  49.91  n B

Torque on Bit [Nm]

properties) important • Validated with high frequency downhole measurements • “Falling friction” characteristic • Stribeck type bit-friction model

Rotational Speed [RPM]

• Bit interaction with rock (rock

Torque on Bit [Nm]

Bit and Drillstring Coupled Modeling 9000

Measurement

6000

Simulation

3000 0 0

50 100 150 Rotational Speed [RPM]

200

9000 6000 3000 0 0

5

10 T ime [s]

15

20

0

5

10 T ime [s]

15

20

200 100

0

Reckmann, Jogi, Herbig, 2007, “USING DYNAMICS MEASUREMENTS WHILE DRILLING TO DETECT LITHOLOGY CHANGES CHANGES th AND TO MODEL DRILLING DYNAMICS” DYNAMICS”, paper 29710, OMAE, 26 International Conference

Bit and Drillstring Coupled Modeling Stick-Slip Likely

Stick-Slip Unlikely

• Stick-slip likely when operating in region of “falling friction” • Increase RPM to reduce likelihood of stick-slip Reckmann, Jogi, Herbig, 2007, “USING DYNAMICS MEASUREMENTS WHILE DRILLING TO DETECT LITHOLOGY CHANGES CHANGES AND TO MODEL DRILLING DYNAMICS” DYNAMICS”, paper 29710, OMAE, 26th International Conference

Measuring Stick-Slip Downhole: Stick-Slip Index maxRPM   min RPM  SSI  2  avgRPM  SSI

0.1

0

0.1 inc to 1.0

> 1.0

RPM

A

B

C

• A – Increase RPM, B – Torsional Oscillations, C – Stick-Slip (period = 4.5s)

SSI SSI is is encoded encoded in in aa few few bits bits and and transmitted transmitted to to surface surface

CoPilot Memory Depth Log Surf WOB klbf DH WOB klbf

Surf TRQ ftlb DH TRQ ftlb Surf RPM

Max RPM RPM Avg RPM RPM Min RPM RPM

Min, Max, Average RPM

DH and SURF Torque

DH and SURF WOB

Example Example MWD MWD Memory Memory Log Log showing showing wellbore -slip wellbore friction friction and and stick stick-slip

S Slip Severity

Bit Bounce

Whirl Severity

Tangential Vib gravity

Axial Vib gravity

Lateral Vib gravity

Stick-Slip Severity

Axial Vibration Severity

Lateral Vib Severity

Stick-Slip: Relationship to Failure •

MWD Components – –

•

2010 study, IADC/SPE 127413 Significant relationship to MWD tool failures: 1. Lateral Acceleration Peak Energy 2. Lateral Acceleration 1s RMS Energy 3. Cumulative RPM Variation (revolutions) 4. Cumulative Backward Whirl 5. Cumulative Stick-Slip Index

PDC Bits – – – –

May be damaged during stick-slip Center of rotation off the center of the bit Cutters on some part of the bit move backwards for some portion of a revolution Chipped and damaged cutters

Stick-Slip: Recognition and Control Measurement Downhole

•

Measure rotation rate of drillstring Magnetometers and/or centripetal acceleration Bit periodically stalls (MWD diagnostic transmission)

– – –

Measurement on Surface

• – –

•

Rotary torque & rotary speed Large periodic fluctuations in torque

Stick-Slip Control – Manual (follow flow charts) 1. Reduce WOB, increase RPM 2. Stop drilling, restart with decreased WOB, increased RPM

–

Automatic • •

–

Soft-torque stick-slip control systems Modifies drive speed control to reduce torsional fluctuations

Downhole / Autonomous •

Torque control Subs

Stick-Slip and Lateral Vibrations Downhole Data Distribution for 219 MWD runs

Lateral Vibration (g)

60

40

20

0 0

2

1

Stick-Slip Index

Sliding

1 Fully Developed StickStick-Slip

Reckmann etal 2010, “MWD Failure Rates Due to Drilling Dynamics” Dynamics”, IADC/SPE 127413

Stick-Slip, Lateral Vibrations and ROP Downhole Data Distribution for 219 MWD runs

High ROP Mod Laterals Low SSI

High ROP Low Laterals Moderate SSI

lateral Vibration (g)

60

40

20

0 0

2 Stick-Slip Index

Sliding

Fully Developed StickStick-Slip

Contours showing data sets with average ROP in excess of 45 ft/hr, overlaid on colored surface defined by Stick-Slip Index and Maximum Lateral Acceleration. Reckmann etal 2010, “MWD Failure Rates Due to Drilling Dynamics” Dynamics”, IADC/SPE 127413

The Science of Stick-Slip – Conclusions – Torsional drillstring behavior includes both torsional oscillations and stickslip. In stick-slip the bit periodically stalls in rotation – Stick-slip is detrimental to drill bits, and sustained stick-slip can be damaging to MWD components – Stick-slip behavior is relatively well understood, can be modeled, and can be recognized both downhole and on surface while drilling – Stick-slip behavior can be mitigated manually, automatically, and using downhole subs – Removing torsional oscillations from the system will result in the BHA being susceptible to high lateral vibrations, which could result in rapid MWD failure