Stress Calibration from Drilling Data
Possibilities and Limitations
October 6th 2011 – FKPE Workshop Hannover
Stefan Wessling, Anne Bartetzko, Thomas Dahl
© 2011 Baker Hughes Incorporated. All Rights Reserved.
Overview
• Introduction wellbore stability model & calibration
• Calibration sources in detail
• Summary
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Wellbore Stability – Pressure Window
Pressure
Fracture gradient (FG)
Breakouts
Pressure window
Mud weight / ESD
3 © 2011 Baker Hughes Incorporated. All Rights Reserved.
Dep
th
Pore pressure gradient (PPG)
Collapse gradient (CG)
Breakouts
ECD
Kick
Losses
Calibration Sources
Formation
pressure
testKick
Connection
gas
LossesLeak-
off test
Ballooning
Pressure
Dep
th
Pore pressure gradient (PPG)
Collapse gradient (CG)
Fracture gradient (FG)
Breakouts
Pressure window
ECD
Mud weight / ESD
Kick
Losses
FG
SFG
PPG
4
intentional
accidental
test
Differential
sticking
Kick
Drilling-induced
tensile fracture
Fracture
test
Breakouts
Cavings
Pack-off
Stuck pipe
© 2011 Baker Hughes Incorporated. All Rights Reserved.
Real-Time Wellbore Stability Procedure
Processing
Alerts & advices
Acquisition
Alert Traffic light No breakout observed, as
expected
Small breakout observed,
small breakout expected
Observed and expected
breakout orientations coincide
Small breakout expected but
not observed
Observed and expected
breakout orientations do not
coincide
Large breakout observed, but
not expected
Observed breakout width
larger than expected
Very large breakouts observed
Control
5
Acquisition
Processing
Analysis
Interpretation
Telemetry
ProcessingAnalysis
Interpretation
© 2011 Baker Hughes Incorporated. All Rights Reserved.
Calibration Sources
Formation
pressure
testKick
Connection
gas
LossesLeak-
off test
Ballooning
Pressure
Dep
th
Pore pressure gradient (PPG)
Collapse gradient (CG)
Fracture gradient (FG)
Breakouts
Pressure window
ECD
Mud weight / ESD
Kick
Losses
6
accidental
© 2011 Baker Hughes Incorporated. All Rights Reserved.
FG
SFG
PPG
intentional
accidental
test
Differential
sticking
Kick
Drilling-induced
tensile fracture
Fracture
test
Breakouts
Cavings
Pack-off
Stuck pipe
Calibration: Formation Pressure Tests (FPT)
• Calibration of pore pressure
• Only possibility to measure porepressure
• Only in permeable
Pore Pressure
Shale
Shale
• Pore pressure modeled
• Exponential
vs• Only in permeable
formations (e.g., sand)
7
Depth
Shale
Sand
Sand• Pore pressure measured• Linear• Gradient controlled by
pore fluid density
© 2011 Baker Hughes Incorporated. All Rights Reserved.
FPT
Calibration Sources
Formation
pressure
testKick
Connection
gas
LossesLeak-
off test
Ballooning
Pressure
Dep
th
Pore pressure gradient (PPG)
Collapse gradient (CG)
Fracture gradient (FG)
Breakouts
Pressure window
ECD
Mud weight / ESD
Kick
Losses
8 © 2011 Baker Hughes Incorporated. All Rights Reserved.
FG
SFG
PPG
intentional
accidental
test
Differential
sticking
Kick
Drilling-induced
tensile fracture
Fracture
test
Breakouts
Cavings
Pack-off
Stuck pipe
Calibration: Drilling-Induced Tensile Fractures
• Observed in downhole electrical images
• Stress direction, magnitude
• En-echelon in deviated wells
Memory
(120 sectors)
Real-time
(32 sectors)
9
Weng, 1993
© 2011 Baker Hughes Incorporated. All Rights Reserved.
Image Interpretation – Annular Pressure
Uncertainty
10 © 2011 Baker Hughes Incorporated. All Rights Reserved.
Image Interpretation – Annular Pressure
Uncertainty
Scenario1:
Feature @2800 ft
Wireline image
Feature @3280 ft
While-drlg image
Scenario2:
© 2011 Baker Hughes Incorporated. All Rights Reserved.
cf. Pei et al., 2009. Constraining in-situ stresses at BETA by analysis of borehole images and downhole pressure data. Paper IPTC 13773 presented at the International Petroleum Technology Conference held in Doha, Qatar, 7–9 December 2009.
Image Interpretation – Annular Pressure
Uncertainty
Wireline
While Drilling
© 2011 Baker Hughes Incorporated. All Rights Reserved.
Calibration: Drilling Fluid Losses
Pressure
Dep
th
Pore pressure gradient (PPG)
Collapse gradient (CG)
Fracture gradient (FG)
Breakouts
Pressure window
ECD
Mud weight / ESD
Kick
Losses
13 © 2011 Baker Hughes Incorporated. All Rights Reserved.
cf. Wessling et al., 2009. Calibrating Fracture Gradients - An Example Demonstrating Possibilities and Limitations. Paper IPTC 13831 presented at the International Petroleum Technology Conference held in Doha, Qatar, 7–9 December 2009.
Calibration: Drilling Fluid Losses
1. Detect losses (surface logging)
2. Locate thief zones (MPR)
3. Constrain ECD causing losses
4. Calibrate fracture gradient
14 © 2011 Baker Hughes Incorporated. All Rights Reserved.
Calibration Sources
Formation
pressure
testKick
Connection
gas
LossesLeak-
off test
Ballooning
Pressure
Dep
th
Pore pressure gradient (PPG)
Collapse gradient (CG)
Fracture gradient (FG)
Breakouts
Pressure window
ECD
Mud weight / ESD
Kick
Losses
15 © 2011 Baker Hughes Incorporated. All Rights Reserved.
FG
SFG
PPG
intentional
accidental
test
Differential
sticking
Kick
Drilling-induced
tensile fracture
Fracture
test
Breakouts
Cavings
Pack-off
Stuck pipe
Calibration: Breakouts
• Uncertain parameter determination
• Reduction by automation
12030
35Intervals right
Intervals left
16 © 2011 Baker Hughes Incorporated. All Rights Reserved.
Manual
(geoscientist and non-scientist probands) automated
cf. Wessling et al., 2011. Challenges and Solutions for Automated Wellbore Status Monitoring - Breakout Detection as an Example. Paper SPE 143647-PP presented at SPE Digital Energy Conference and Exhibition, The Woodlands, Texas, USA, 19–21 April 2011.
50
60
70
80
90
100
110
1 2 3 4 5 6 7 8 9 10 11
Bre
ako
ut
wid
th, d
eg
ree
Sample
Interval 1
Interval 2
0
5
10
15
20
25
1 2 3 4 5 6 7 8 9 10 11
# In
terv
als
Sample
Intervals left
Summary
• Advanced technology: wellbore stability prediction and monitoring while drilling
• Calibration is essential; requires data / information from different sources
• Uncertainties
– Models and assumptions (pore pressure gradient)
– Location
– Data resolution (images)
– Time interval (ECD; time-depth analysis necessary)
– Interpretation (Breakouts)
17 © 2011 Baker Hughes Incorporated. All Rights Reserved.
