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Multiphysics Modeling forPetroleum Geomechanics
Comsol Conference, Las VegasOct 26 27, 2006
by Roberto Suarez-RiveraTerraTek a Schlumberger Company
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What is petroleum geomechanics?
Why is petroleum geomechanics important?What type of problems are relevant to
Comsol Multiphysics?Examples
Potential and relevance of coupled physics
Outline
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What is Petroleum Geomechanics?
Petroleum (related)
geomechanics applies the
principles of engineeringmechanics to predict the
failure of porous,
discontinuous, granular,heterogeneous, and
anisotropic, materials,
whose properties vary with
the type and the degree of
loading.
It is the mechanics for
difficult materials
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Why is Important?
Shale-related problems
$400 - $500 Million/year (Bol et al.,1992)
Borehole stability
$80 - $110 Million/year (SPE-Bali, 1994)
Compaction/Subsidence
in excess of 1 Billion Dollars (Ekofisk Field) Cusiana field in Colombia
$23M/well -> $17M/well (Hagan, 1998)
Completion (GOM): Horiz. Well + GP Completion $2.5 M/well
Casing Integrity (Loss of access to the well): 150M$ excluding loss
due to deferred production. (Conoco Phillips, 1999)
H=h h=H
H=h h=H
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Relevant problems?
Mechanical stability
Compaction and subsidence (coupled mechanical/fluid flow)Fluid flow in fractures
Two phase flow in porous media
Electro-osmotic flow in porous mediaFree convection in a porous medium
Groundwater flow and solute transport
Transport and adsorption
Darcy-Brinkman flow (wellbore to reservoir flow)Elasto-plastic analysis on a plate with a hole
Hertzian contact
TWC Benchmark problem
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Examples: Single well stability
(Mechanics coupled with fluid flow)
1 3
Failurepp
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Examples: Multilateral wellbore stability
(Mechanics coupled with fluid flow)
Stress concentrations and shear failure at the wellbore walls.
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Coupled linear elastic mechanics and Darcy flow
Examples: Multilateral wellbore stability
(Mechanics coupled with fluid flow)
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Some Aspects of Multilateral Junction
Modeling
Sig_y
Sig_x
Comparison of 2D plane-
strain modeling with 3Dmodeling
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Example: The Effect of Strength Anisotropy on
the Perceived In-Situ Stress Orientation
Tight gas sand
H=h h=H
Wellbore in an anisotropic medium (i.e., slightly inclined beds) and subjected to hydrostatic
in-situ stress. Borehole breakouts result from the anisotropic nature of the material and not
to the anisotropy in the in-situ stress.
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LQ Res.
LQ Res.
HQ Res.
Stre
ss
Profile
How do the in-situ stress and
the material properties affectfracture propagation?
Hydraulic Fracturing Design
Example: Hydraulic fracturing and fracture
containment
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Example: Hydraulic fracturing and fracture
containment stressing a pre-existing fracture
A fracture will propagate from the pre-existing fracture once the stress concentrations
overcome the tensile rock strength of the minimum horizontal stress. The ports measure the
fluid pressure during fracturing.
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Change in pore pressure ( z coordinate), and fluid penetration into the porous mediaduring fracture flow with low damage in permeability along the sand face. (k1(sand) =
100 mD, k2(transition) = 10 mD, k3 (shale) = 1 mD).
Sand
TransitionShale
Example: Coupled fracture flow- and porous
media flow
Darcy flowBrinkman flow
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Induced flow in the porous media by a Power Law viscous fluid flow along a hydraulicinduced fracture. High fluid penetration occurs along the sand face. (k1(sand) = 100 mD,
k2(transition) = 10 mD, k3 (shale) = 1 mD).
Sand Transition Shale
Example: Coupled fracture flow- and porous
media flow
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k1 k2 k3
Induced flow in the porous media by a Newtonian viscous fluid flow along ahydraulic induced fracture. High fluid penetration due to low permeability
impairment along the fracture face ( k1 = k2 = k3 = 100 mD).
k1 k2 k3
k1 k2 k3 k1 k2 k3
Example: Coupled fracture flow- and porous
media flow
k1 = 10 mD, k2 = k3 = 100 mD
Newtonian
Power Law
k1 = k2 = k3 = 100 mD
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Traditionally in petroleum geomechanics, the computational
capacity has always exceeded the availability of data (material
properties and in-situ stress)This has resulted in simplified models (LE) and partially
coupled behavior.
As data becomes more readily available, there is a growingneed for better modeling capabilities.
Comsol multiphysics, with its powerful computational
algorithms, its coupled-physics capabilities, its user friendly
interface and its outstanding graphics has the potential for
becoming the software of choice in geomechanics.
Current limitations are the absence of sliding contacts and
capabilities for propagating fractures.
Final remarks