Drilling Optimization Workow Vibrations—Recognize the Symptoms SURFACE MEASUREMENT OR SYMPTOM
Conventional Cures While Drilling AXIAL VIBRATION (bounce)
Vibrations—Recognize the Symptoms SURFACE MEASUREMENT OR SYMPTOM
Conventional Cures While Drilling
Vibrations—Recognize the Symptoms SURFACE MEASUREMENT OR SYMPTOM
LATERAL VIBRATION (bit/BHA whirl)
• Increased mean surface torque
• Large WOB uctuations Increase WOB by 1 ton
• Rig/topdrive shaking • Loss of toolface
• Reduced ROP
Decrease rpm by same percentage
• Reduced ROP
TORSIONAL VIBRATION (stick/slip)
• Topdrive stalling
• Loss of toolface
Conventional Cures While Drilling
Decrease rpm by 10%
• Increased delta surface torque
Increase WOB by 10%
• Loss of toolface
Place topdrive in high gear; ensure soft torque operational.
• Rpm/torque cycling
Decrease WOB by 5% Increase rpm by 10%
• Reduced ROP Repeat three times unless WOB limit is exceeded
Repeat three times unless WOB limit is exceeded Yes
No
Yes
Does vibration continue?
No
Pick up off bottom and allow string torque to unwind
• Loss of real-time data/ measurement
Set rpm at 40 to 50% of original
• Increased shock count
Increase WOB by 10 to 20% of original
• Increased axial vibrations
Gradually return rpm to original No
Vibration resumes?
DOWNHOLE MEASUREMENT
• Early bearing failure • Broken/chipped cutters and inserts—no specic location
Pick up off bottom and allow string torque to unwind Set rpm at 40 to 50% of original
• BHA failure Increase WOB by 10 to 20% of original Gradually return rpm to 25% below original
Yes
• High-frequency downhole shocks—10 to 50 Hz
Restart drilling with 70 rpm
• Increased lateral shocks
Increase WOB by 10% of original
• Increased torsional acceleration
No
Does vibration continue? Yes Pick up off bottom and allow string torque to unwind
• Increased delta downhole torque • Increased torsional acceleration
Increase rpm to original value
• Loss of real-time data/measurement • Increased shock count
No
DOWNHOLE MEASUREMENT
Pick up off bottom and allow string torque to unwind
• Increased mean downhole torque
• Increased stick/slip indicator
Restart drilling with 10% increased rpm
• Downhole collar rpm greater than surface rpm
Decrease WOB 15 to 20%
• Loss of real-time data/measurement • Increased lateral shocks
Vibration resumes?
• Increased shock count
No
Vibration resumes? Yes
Yes
Yes
POSTRUN EVIDENCE
Does vibration continue? Yes
Yes
DOWNHOLE MEASUREMENT
Repeat three times unless WOB limit is exceeded
POSTRUN EVIDENCE • Cutters/inserts damaged typically on shoulder or gauge • Broken PDC blades • Worn hybrids (equivalents) with minimal cutter wear
POSTRUN EVIDENCE
Pick up off bottom and allow string torque to unwind
• Cutters/inserts damaged typically on nose and taper
Restart drilling with 70 rpm
• Overtorqued connections • Twistoffs and washouts
Increase WOB to original value
• BHA failure
• Overgauge hole from calipers • One-sided wear on stabilizers and BHA
Pick up off bottom and allow string torque to unwind Restart drilling with 70 rpm Increase WOB to 25% below original value
Increase rpm to 25% below original value
Gradually return rpm to 15% above original
CONTINUE DRILLING
CONTINUE DRILLING
• BHA failure CONTINUE DRILLING
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Shock and Vibration Information 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
BHA whirl
Large downhole shocks,increased STOR
Stick/slip
Large surface torque and rpm fluctuations, MWD peak-peak rpm
i Bit Bounce
DRILLING DYNAMIC GUIDELINES
FACTORS AFFECTING VIBRATIONS
Lateral vibration, g n RMS (cumulative during a bit run) Vib Lat (gn R MS)
Risk
Time limit
<1
Low
None
1–3
Medium
Recommended to mitigate. More than 24 h, medium risk of tool failure.
STOP Increase WOB and decrease rpm
Change bit, use full-gauge NB stabilizer
3–6
High
Mandatory to mitigate. More than 12 h, high risk of tool failure.
Washed out hole, BHA pendulum or unstabilized
STOP Increase WOB and reduce rpm
Use a stiffer BHA
>6
Severe
30 minutes (formal notification)
Aggressive PDC bits, high wellbore BHA friction
STOP Reduce WOB and increase rpm
Increase mud lubricity, use less-aggressive bit, improve hole cleaning
Bending
i Stick/Slip
Lateral vibration, g n RMS (cumulative during a bit run) Vib X (g n R RM MS)
Risk
Time limit
<1
Low
None
1–2
Medium
Recommended to mitigate. More than 24 h, medium risk of tool failure.
2–4
High
Mandatory to mitigate. More than 12 h, high risk of tool failure.
>4
Severe
30 minutes (formal notification)
BHA Whirl
IWOB torsional vibration, ft.lbf
Axiail l
Lateral l
Torsioinall
Eccentered
Vib Tor 6 3 ⁄ 4-in
Vib Tor 8-in
Vib Tor 9 1 ⁄ 2-in
Low
< 1,500
< 1,650
< 1,750
Medium
1,500–2,500
1,650–2,600
1,750–2,800
High
2,500–3,000
2,600–3,100
2,800–3,200
Severe
> 3,000
> 3,100
> 3,200
Generalizations only—vibrations often result from complex interplay of factors Inclination—more axial vibrations closer to vertical; tendency for more vibrations as angle increases, increases, but can also be dampened by angle
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BHA design—higher vibrations with slick and pendulum assemblies
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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
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Bits—PDC bits generate higher vibrations, as do aggressive features like larger cutter size, lower number of cutters, fewer blades, and low backrake angle
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Higher friction factors will generate higher vibrations
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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
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Large ratio of hole size to BHA/tool OD size will generate more vibrations
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Poor hole conditions, such as poor hole cleaning, washouts, and ledges, can sometimes generate vibrations
Stick/slip severity levels (consecutive) Stick/slip (Stick_RT) = Maximum Downhole RPM – Minimum Downhole RPM Stick/slip % = [ (Stick/slip) / (2 x Average Surface RPM) ] x 100 Stick/slip %
Mode
Severity le level
Time lilimit
Low
None
Torsional oscillations
Medium
None
Medium
Recommended to mitigate
80–100
Stick/slip
High
Onset of of fu full stall st stick/slip, mandatory to mitigate
100+
Stick/slip
Severe
30 minutes (formal notification)
0–40 40–60
60–80
Shock risk levels (consecutive) PowerPulse,TeleScope,ImPulse, LWD, and RSS tools
99
100
Total shock levels (cumulative only reset after appropriate tool service levels)
S ho ho ck ck ri ri sk sk
R is is k l ev ev el el
Sho ck s> 50 gn
Value Va lue
Number of shoc shocks > 50 gn
0
No risk
cps < 1
0
0—tshk—50,000
1
Medium risk
1 ≤ cps < 5
1
50,000 ≤ tshk < 100,000
2
High risk
5 ≤ cps < 10
2
100,000 ≤ tshk < 200,000
3
Risk of tool failure
cps ≥ 10
3
> 200,000
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Shock and Vibration Mitigation VIBRATION PREVENTION •
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Run DOX software/BHA-V—This software analyzes BHA and predicts resonant frequencies—stay away from bad rpm; compare calculated with actual values Always run multivibration chassis (MVC) in MWD tools for real-time vibration communication
Within limitations, design BHA, especially stabilization, and select PDC bit with vibration prevention in mind
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Help train drillers in vibration reduction—ensure LWD engineers have vibration training Be aware of high-vibration operations—backreaming, opening a pilot hole, reaming, hole opening while drilling, drilling out of casing/liner Know vibration reduction procedures for each type of vibration Know procedures for dealing with high vibrations from drilling hard streaks and reaming Identify vibration generation mechanism—bit, BHA, formation, drilling parameters, on or off bottom—and use counteractive measures Optimize correct real-time shock/vibration variables from MWD tool for predicted vibration environment Set tight alarms on all vibration variables and monitor closely—display for driller to see Optimize drilling parameters—WOB, rpm, flow rate— for vibration prevention/reduction and ROP Torque feedback—soft-torque system (may mask stick/slip)
Increase mud lubricity to reduce friction and, thereby, vibrations vibra tions
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Keep offset log of formations if available—track lithology for upcoming vibration risks
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