A Guide to Successful Backreaming: RealTime Case Histories

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A Guide to Successful Backreaming Real-Time
Case Histories
G. Yarim, G.M. Ritchie, R.B. May, SPE,
Schlumberger

• SPE 116555

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Agenda

• Introduction
• Problems with Backreaming
• Case Histories
• Real-time Surveillance
• Recommended Backreaming Approach
• Results
• Conclusions

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Stuck Pipe Statistics
56 of incidents are solid induced pack offs
23 of the Stuck Pipe incidents while
tripping or backreaming
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Differential
Solid Induced Pack Offs
56
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Integrated Project Management data (2005-2008)
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Backreaming

• Backreaming , drilling backwards, to trip out
  of the hole when there is a problem pulling the
  pipe without rotation and circulation
• Backreaming is performed
• when there is a problem to trip out of the hole
  on the elevators
• to clean the hole to eliminate cuttings beds and
  hole cavings
• to pass through plastic formations if mud weight
  is too low
• to eliminate tight hole conditions
• to prepare the wellbore to run logs
• to prepare the wellbore to run casing

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Backreaming and Wellbore Conditions
Lack of industry guidance on conditions where
back reaming should be applied

• Backreaming should be avoided (if possible)
  where
• tripping out of the hole is possible on the
  elevators
• there is pre-existing fractured / failed rocks
  and risk of wellbore instability issues
• the hole is not clean
• cuttings beds exist in high angle wells (risk of
  packoffs)
• rig pumps/mud have insufficient capacity for
  adequate hole cleaning

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How Fast Can Backreaming Be Performed?

• Restricted annular or high amount of cuttings
• High / fluctuating pump pressure
• High / fluctuating torque
• High / fluctuating over pull

• Combination of parameters and downhole conditions
  should dictate backreaming speed
• Do not backream faster than the cuttings can be
  transported out of the hole

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Effect of Backreaming on ECD
Backream
Backream
Circulate
Circulate
Backreaming increases ECD due to solids
incorporated into the flow stream Use
APWD/Surface parameters to monitor the ECD while
backreaming
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Shocks and Vibrations While Backreaming

• BHA in tension and less constrained (no fixed
  end)
• Can lead to high shocks resulting in premature
  failures

Shocks up to 175 G while backreaming with 60 RPM
with a rotary steerable assembly in 12 ¼-in hole
in a 73 tangent
Shock Levels
lt50 G Low50-100 G Medium
100-150 G Highgt150 G Severe
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Backreaming Decision Tree
Drill to target depth monitoring Torque and Drag
Trip out of the hole
Monitor the hole drag
Circulate hole clean and measure TD before and
after circulation
Run back 2-3 stands
Tight spot Excessive over pull based on limit
set
NO
YES
Slowly rotate and break circulation. Circulate,
reciprocate and rotate to clean the hole
Record the depth of the tight spot Record the
over pull
Run back 2-3 stands
Is there well bore instability problem?
Likely cause Well bore geometry or mechanical
YES
NO
Slowly rotate and break circulation. Circulate,
reciprocate and rotate to clean the hole
(Pump a pill if required)
Continue to clean the hole and modify the MW
if required. POOH
POOH with caution to the previous tight spot
Is there still a tight spot?
YES
Backream (away from the tight spot) with
drilling flow rate and RPM
Over pull at the same depth
NO
YES
NO
Likely cause Hole cleaning
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Case History 1
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Case History 1 Findings and Conclusions

• Stuck pipe event due to solids induced packoff
  while backreaming
• Drilled last 996 m with an Avg. ROP of 21 m /
  hour
• Circulated 1.6 x bottoms up prior to POOH
• Drilled 12 ¼ with 550 gpm (constrained by high
  pump pressure using 5 DP)
• Only 253 GPM while backreaming with 150 RPM and
  3,900 psi SPP
• Geomechanics post analysis indicates mechanical
  hole instability (cavings) due to geological
  stress convergence area
• Caliper log shows 40 m of 19-20 washout below 13
  3/8 shoe
• Driller did not follow best practices (exceeded
  overpull limits, backreaming after overpull
  instead of RIH to circulate / clean the well)

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Case History 2

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Case History 2 Findings and Conclusions

• Stuck pipe event was due to solids induced
  packoff while backreaming
• Backreaming with gt planned MW ? wellbore
  instability and cavings
• Clear indication that backreaming parameters
  worsening but driller did not go down and
  circulate to clean the hole
• The best course of action would have been
• to focus on hole cleaning
• to minimize the wellbore instability issue (MW
  selection)
• to observe drilling parameters more closely to
  adjust backreaming speed
• Backreaming should be last resort after other
  options exhausted
• should be avoided when wellbore instability
  issues present

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Real Time Monitoring of Backreaming

• Real time parameters to
• monitor while backreaming
• SPP vs Flow rate
• Hookload
• Torque and Drag
• RPM
• Cuttings / cavings rate
• APWD data
• Backreaming speed

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Backreaming Recommendations - 1

• General
• Backreaming should be the last option
• If tight hole conditions encountered, do not
  start backreaming immediately
• Backreaming should be monitored in real time
• Monitor Torque and Drag and establish a base
  while drilling
• Clean hole with rotation and circulation and
  sweeps (if required) prior to trip
• Monitor the cuttings and caving rates
• Perform pre-trip risk assessment (depths and
  overpull limitations)
• Establish over pull limits
• If there is excess drag while POOH
• Return to bottom (if close to bottom)
• If off bottom, RIH 2 to 3 stands below the tight
  spot

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Backreaming Recommendations - 2

• Backreaming
• Backream (if necessary) with optimum parameters
  monitoring pump pressure, torque and hookload,
  cavings rate, ECD
• Determine the backreaming speed based on the
  parameters above
• Do not backream faster than cuttings being
  transported out of the hole
• Backreaming parameters and practices need to be
  adjusted for hole angle, condition, diameter, etc
• Continue backreaming only if parameters are
  stable or improving
• If parameters are not improving or worsening,
  slow down or stop
• Never force drillstring out of the hole while
  backreaming
• If parameters are not improving, be patient while
  backreaming at the tight spots

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Results
As a result of focus on tripping, backreaming and
stuck pipe prevention, incident frequency and
cost impact has been significantly reduced
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Conclusions

• 23 of IPM stuck pipe incidents tripping or
  backreaming
• Lack of clear backreaming guidelines
• Backreaming should not be practiced as a first
  action
• If there are large amount of cuttings in the
  annular space
• If wellbore instability exists
• Systems approach to improve backreaming
  operations
• Stuck pipe prevention and mitigation training
• Specific backreaming procedures
• Real-time surveillance of tripping and
  backreaming operations
• Stuck pipe incidents due to packoffs reduced 50
• Drilling automation may provide a better
  preventative solution

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Acknowledgement

• We wish to thank who assisted in the writing and
  reviewing of this paper
• Gerard Cuvillier
• Jacques Bourque
• Jose Alarcon
• Eduardo Parra Garcia
• Ember Duran
• Randy Green

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