Primary funding is provided by
The SPE Foundation through member donations
and a contribution from Offshore Europe
The Society is grateful to those companies that allow their
professionals to serve as lecturers
Additional support provided by AIME
Society of Petroleum Engineers
Distinguished Lecturer Program
www.spe.org/dl
Wellbore Deformation in
Unconventional Resources
Trent Kaiser, Ph.D., P.Eng.
Noetic Engineering
Society of Petroleum Engineers
Distinguished Lecturer Program
www.spe.org/dl
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Measuring Deformation
• Multi-finger caliper tools
–Designed to measure casing wear,
corrosion, pitting
–Also used to investigate access issues
• Common conveyance: wireline
• Centralised, although data can
be corrected for eccentering
• Directional instrument: gravity
Weatherford
MSC tool
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Caliper Measures Deformation?
• Direct measurement of casing section
• “Fix” data for tool
string configuration
• Visualise in 3D
–Cool Pictures!
–Risk of mis-interpretation
• Longitudinal deformation patterns might be
inferred, but quantification isn’t possible
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Deformation Interpretations
3D Data View
3D Geometry View
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Caliper Data in 3D
• Measurements are tool-centric
• Tool moves laterally in
deformed well
• Correct interpretation
is “well-centric”
• Beware of data repair
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Caliper Data in 3D
• Measurements are tool-centric
• Tool moves laterally in
deformed well
• Correct interpretation
is “well-centric”
• Beware of data repair
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Well Deformation
Types
• Bending
• Shearing
• Ovalisation
• Combinations
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Deformation Characteristics
• Oilsands Caprock
–Low confinement (shallow)
–“Soft”
–Weak layers localise shear
• Casing has capacity to
redistribute displacements
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Deformation Characteristics
• Unconventional Shale
–High confinement
(deeper)
–“Harder/stronger”
–Highly localised movements in
fractures/faults
• Penetration resistance of shale
to casing at localisation is high
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It’s Not Just About the Well
• First solutions focus on well construction
• Well movement ≈ formation behavior
– Formation/faulting/fracture displacements
– Validate and calibrate simulations
• Get “out of the well” for answers to
formation movements
– Eliminate fruitless solutions, wasted time
– Pursue strategies supported by measurement
– Incorporate into well integrity management
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Case Studies: Shearing in Shale
• Operators experience horizontal well access
problems.
–Compromised stimulation activities
–Pressure test failures
• Case 1:Multiple deformations across
one pad of wells.
• Case 2:Unexpected reservoir response
to frac treatment
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Case 1: Pad-Wide Deformation
Riser Shear Deformations from Caliper Data
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Case 1: Pad-Wide Deformation
Consistent Results with DeformationOptimised Caliper Configurations
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Case 2: Vertical Well
• Good tool centralisation, poor
directional
• Upper deformation minor but
informative
• Deeper deformations: similar nature,
higher severity
• Horizontal frac relieves residual shear
with horizontal movement
Case 2: Vertical Well. Interval 2
• Minor ovalisation: Tensile yield? Shear?
Case 2: Vertical Well. Interval 3
• Major ovality + shift over short interval
Case 2: Horizontal Well
• Large ovality over long
interval
–Well past critical ovality
for collapse
• Horizontal frac relieves
shear, “pinches” casing
Horizontal Frac in Horizontal Well
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Case Study 1 & 2 Learnings
• Formation stress can vary from expectation
– Or be modified by stimulation process
• Anisotropy governs frac direction & movement
– Anisotropic stress:
Predictable frac propagation & motion
– ~Isotropic stress:
Stress shadowing, rock fabric can wreak havoc
– If rock fabric governs?: Unpredictable frac propagation
• Collateral movement can damage well
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Case Study 3: Drilling Application
• Workovers in projects where deformations
are common are often trial and error affairs
• Well access is key to success.
• Logging cost is much than intervention
• Deformation interpretation helps avoid
costly interventions failures
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Access for Workovers
• What if caliper data says
the tool will fit, but well
access is impaired?
• Access is governed by
combination of cross
section and lateral
deformations
• Accurate assessment of
accessibility accounts for
tool length & diameter
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Recent Results
• Deformation in geothermal well impaired
well access.
• Possible annular pressure build-up
mechanism
• Twin 4-arm caliper used to acquire data.
– Tool string configuration is sub-optimal
• Extreme cross section deformation
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Summary
• Multi-finger calipers offer value far beyond the data
they were designed to acquire
– Careful tool setup, thoughtful data processing
– Be vigilant about data cleaning implications,
basic graphic presentation
• Well as an instrument – use well deformations to
understand formation mechanics
• Measured deformation can validate and refute
assumptions about formation response to stimulation.
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