Engineering Success in
Extended Reach Drilling
Iain Hutchison
Merlin ERD Limited IADD Houston – 27 Feb 2014
www.MerlinERD.com All Rights Reserved
TODAYS TALK
Making Trouble-Free Hole
Risk, Consequence & Attitude
Key Considerations
• Common Problems
• Hole Cleaning
• Bladed DP
• Tripping & Back-reaming
Options to Reduce Risk
• Hole Condition Monitoring (Trends)
www.MerlinERD.com
Challenge Identified • Planned • Practiced/Trained • De-Risked
WHAT WE WANT
4
Rev 1
If we always do, what we’ve always done we’ll only get, what we always had
IMPROVEMENT
A Journey not a Destination
Industry Experience
Learn from others
• ≈80% of high angle hole problems are avoidable (industry stats)
– Human factors (insufficient planning & practices)
– Assumption that “10°” or “1,000ft” extra doesn’t make a difference.
• Common Problems:
– Inadequate clean-up
– O/pull Tripping
– Backream, pack-offs
– Hole condition worsens
– 1st cavings to surface
– Often in 12¼” hole….
• Swab / Surge
- Highest readings at start of pipe movement
High Angle Wells
Key Risks
Hole Cleaning
Must be Programmed, Implemented
& Monitored
Tripping Practices
ERD wells get stuck TRIPPING
Not Drilling
Back Reaming
Like Drilling Backwards (rpm? gpm?)
Hole Cleaning
Regimes vary with inclination
HIGH angle wells:
• Flow no longer directly opposes gravity.
• Short distance for cuttings to reach low
side & form a cuttings bed.
Downward Force
Gravity
Upward Force
(Buoyancy & Viscous
Drag)
Av > Slip Velocity
Net Result is Cutting Moves Up
LOW angle wells:
• Cuttings have long distance to fall.
• Mud Rheology slows settling.
• Flow will remove cuttings
Annular Velocity
(Flowrate)
Slip Velocity
(Gravity & Mud
Rheology) Resultant
Hole Cleaning
Low & High Angle Wellbores
Tubulars & Hole Size
12¼” Hole
& 9½” BHA
12¼” Hole
& 5” DP
8½” Hole
& 5” DP
Hole Cleaning
Challenges: Annular Space
Generic
Hole Cleaning Theory – Min Parameters
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In high angle wells, the pipe is
eccentric and the TJ will be in
contact with the wellbore wall
(all angles ≥ 1°).
The cuttings are tossed into
the flowing region but begin to
fall as soon as they get
here…Returning to the low
side of the hole within a few
stands
The annular velocity
is highest in the
centre & lower
towards the edges
Rotary < threshold = ineffective hole cleaning
Flowrate < threshold = ineffective hole cleaning
EFFECTIVE HOLE CLEANING = ROTARY AND FLOWRATE > THRESHOLD
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AV ≈ typically 200-300 ft/min
Approximate Distance cuttings will
travel before settling to low side…
200 ft/min A.V. & 1 ft/min Slip Velocity
≈ 2 Stands
Cuttings have to be moved into the high velocity flow above the DP to be transported
OOH. This is accomplished with drillstring rotation >> hole cleaning thresholds.
Bladed DP is more efficient at lifting cuttings and so hole cleaning is achieved at lower
drillstring rpms. Sufficient bladed DP must be run to lift the cuttings again once they
have fallen out of the high velocity flow region. This is typically 200 to 300 ft, which is
recommended spacing between joints of bladed DP.
If rpm > HC thresholds, bladed DP is not
Required
Spacing > 2 or 3 (90ft) stands of DP results in less effective hole cleaning at lower rpm.
HOLE CLEANING
Bladed DP
Risk Reduction
What Can We Do?
What Can We Do to Reduce Risks?
Risk Reduction
Drilling Data Requirements
Roadmap Data Required
• Drag (Hookload no rotation)
• PU/SO/ROB (rotation
• Torque
• Off btm
• Predicted & Actual
• Baseline
• Project Ahead
• REALTIME for Tripping
Risk Reduction
Drilling Parameter Trends
How Can Roadmaps Help?
• Prediction of Loads at TD
• Early Warning of Hole Problems
• Drilling
• Tripping
• Running Casing
Risk Reduction
Engineering Modelling - Drag
Hookload V depth
• Different Friction Factors
• Assumptions (MW, BHA, Traj)
Predicts Load at Section TD
• Still within equipent limits?
Highlights Changes During Drilling
• Hole Condition
Use on Trips
• Early Warning of Poor Hole
• Cuttings Beds
LOOKAHEAD
AVOID Rather than fix Problems
Risk Reduction
Hole Condition Monitoring (HCM)
Risk Reduction
HCM – Drag Superior to Torque
Risk Reduction
Tripping Trends
Mud Logging Data
• Greater uncertainty
Must have accurate data,
use dedicated resource
(ERD Advisor), until
systems updated.
Overpull
Greatest Risk in High Angle Wells
Avoid to Reduce
• Pack-off risk
• Tool failures
• Casing wear
If Required
• Apply parameters ≥ Drilling Hole Cleaning
• Continue to 30° inc & clean-up
BACK-REAMING
Drilling Backwards – Implications?
Risks
• Packing Off
Fatigue of Formation
Lost Circulation
• Stuck Pipe
• Casing Wear
• DP Fatigue
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Tough On Rig Equipment
Biggest Draw On Power
Back-Reaming
Drilling Backwards - Implications
Cuttings Must Be Moved Up Hole
Minimum Rotation to Move Cuttings Up Hole During Back Reaming
• 120+ RPM (hole > 8½”)
• Same As Drilling (Cuttings Behavior Doesn’t Change When the Bit Comes Off Bottom!)
Maximum Back Reaming Speed
• Slower Than Cuttings Move Up Hole…
• Cuttings Don’t Move the Same Speed as the Fluid
• Start With 5 ft / min (300 ft/hr)
Back-Reaming
Fundamentals
If Back Reaming
• Complete Full Clean Up Cycle Prior to:
Starting b/ream OOH
Tripping if inc > 30
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Equilibrium Bed Height is 1 – 2 Stands
Above BHA & Needs to be Reduced to a
Safe Tripping Height After Back Reaming
Back Reaming Equilibrium Height
Safe Tripping Height
Back-Reaming
Drilling Backwards - Preparation
TODAYS TALK
Making Trouble-Free Hole
Risk – we can control
Learn from others
Hole Cleaning to be fit for purpose
Tripping is key risk area
Trends can Provide Early Warning
Back-Reaming is a symptom not a solution
Avoid low bridges via Engineering, not luck!
www.MerlinERD.com
Merlin ERD Ltd
T: +44 1738 627922
W: www.MerlinERD.com
Questions?
Merlin Engineer at play!