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Underbalanced Coiled Tubing Drilling Case Study:
Drilling Larger Hole Sizes in Underbalanced Conditions and Ensuring Hole Cleaning
SPE ICoTA 20th European Well Intervention Conference – Aberdeen, 12-13 November 2014
Toni Miszewski, Managing Director, AnTech Ltd
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 1
Well Description
> Well located in the Paris basin, France
> Wells in the field are depleted oil wells in a carbonate reservoir and have to be pumped.
> Wells produce with a high water cut
> Thin payzone
> Barefoot completion
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 2
> Tap into an un-drained pocket of the reservoir
Why CTD:
> Only drilling method that can offer continuous underbalance
> Higher ROP
> Well fully contained during drilling
> Based on a successful 4-well CTD program in 2007
Overall Objective and rational for CTD
Plan Plot
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 3
Specific Program Objectives
> Perform all work with zero HS&E incidents
> Initiate open hole side-track inside the porous reservoir boundaries, 4m thickness
> Drill at least 300m long drain
> Keep the well underbalanced and drill in one run
> Capture technical learning and best practices
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 4
Different Well Geometry
PREVIOUS WELL THIS WELL
7” Casing 7” Casing
6-1/8” OH4-1/8” OH
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 5
Planning for success
> Tubing Forces
> Getting weight to bit> Hook load
> Hydraulics
> Bottom Hole circulating pressure (BHCP)> Hole cleaning ability
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 6
Previous well: 2-3/8” CT, 3” BHABHCP vs Injection Rates 2-3/8 CT, 3” CTD BHA
Gas Injection Rate (Ncum/min)
BH
CP
(Bar
)
Formation Pressure
Target BHCP
Liquid Phase 223.6 l/min
Cleanability
Liquid Phase 260.4 l/min
Cleanability
Liquid Phase 297.2 l/min
Cleanability
Liquid Phase 334.0 l/min
Cleanability
Liquid Phase 370.8 l/min
Cleanability
Motor Max Rate 140 USGPM
Motor Min Rate 60 USGPM
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 7
New well: 2-7/8” CT, 5” BHA
BHCP vs Injection Rates 2-7/8 CT, 5” CTD BHA
BH
CP
(Bar
)
Gas Injection Rate (Ncum/min)
Formation Pressure
Target BHCP
Liquid Phase 315.6 l/min
Cleanability
Liquid Phase 378.7 l/min
Cleanability
Liquid Phase 441.8 l/min
Cleanability
Liquid Phase 505.0 l/min
Cleanability
Liquid Phase 568.1 l/min
Cleanability
Liquid Phase 631.2 l/min
Cleanability
Motor Max Rate 240 USGPM
Motor Min Rate 120 USGPM
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 8
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen
9
Results
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 9
Drilling Results: Plan View
Plan Plot
-400
-300
-200
-100
0
-1000 -900 -800 -700 -600 -500 -400 -300 -200 -100 0
N-S
(m
)
E-W (m)
Original Well Plan Existing Drilled 140927 Updated Well PlanUpdated Well Plan
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 10
1840
1845
1850
1855
1860
1865
1870
1875
1880
1885
1890
1895
1900
250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100 1150 1200
TV
D (
m)
Vertical Section (m)
1
2 3
Drilling Results: Section View
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 11
Underbalance
Lesson learned: separator capacity needs to match ROP capability
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 12
Weight-on-Bit Comparison
Comparison of Predicted Max WOB and Measured WOB
Measured Depth (m)
Wei
gh
t on
Bit
(N)
Measured
Predicted
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 13
0
20
40
60
80
100
120
140
160
180
0 10 20 30 40 50 60
BH
CP
(B
ar)
N2 Rate (Ncum/min)
Comparing Predicted & Observed Steady State BHCP for 2-phase Circulation Liquid rate fixed at 400 l/m, 3 N2 rates
Formation Pressure
Target BHCP
Predicted Steady State
BHCPObserved BHCP (10500
data points)
Liquid Properties:
Diesel
BHCP Comparison
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 14
Objectives vs Results
Objective Result
Perform all work with zero HS&E incidents Achieved
Initiate open hole side-track inside the porous reservoir boundaries 4m thick Achieved
Drill at least 300m long drain Achieved (438m)
Keep the well underbalanced and drill in one run. Not achieved
Capture technical learning and best practices. Achieved
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 15
With thanks to Lundin Petroleum
© AnTech 2014 SPE ICoTA 20th European Well Intervention Conference – Aberdeen 16
