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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


Stress concentrations and shear failure at the wellbore walls.


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Coupled linear elastic mechanics and Darcy flow

Examples: Multilateral wellbore stability



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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


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


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

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