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A MODELING APPROACH FOR ANALYSIS OF COUPLED MULTIPHASE FLUID FLOW , HEAT TRANSFER, AND DEFORMATION IN FRACTURED POROUS ROCK

指導教授 : 陳瑞昇、董家鈞 老師學生 : 楊慶中

日期 :99.12.301

International Journal of Rock Mechanics & Mining Sciences 39 (2002) 429-442

J. Rutqvist ,Y.-S. Wu , C.-F Tsang , G. Bodvarsson

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Outline

Introduction FLAC3D

TOUGH2 Coupling module Examples Results Conclusion

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Introduction

Coupled thermal–hydrologic–mechanical processes under multiphase flow conditions are prevalent in geoscientific applications.

A few of the most important include nuclear waste disposal in geological media, deep underground injection of hazardous waste and underground storage of carbon dioxide into permeable aquifers.

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Introduction

However, there is no single computer code that handles general coupled thermal–hydrologic–mechanical processes .

The two codes—TOUGH2 and FLAC3D are linked using sequential execution and data transfer through nonlinear coupling functions.

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FLAC3D

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FLAC3D

FALC (Fast Lagrangian Analysis of Continua ), the finite difference code is developed by the United States Itasca Consulting Group Inc in 1986 ,and FLAC3D developed in 1994.

Code is developed for rock and soil mechanics and can also handle thermomechanical and hydromechanical problem for single-phase fluid flow.

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Cauchy’s fomula

Motion equations

idvF mdt

iij i

dvb

dt

FLAC3D

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FLAC3D

' ( ', )H t

'

e p T

T I T

I P

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TOUGH2

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TOUGH2

TOUGH(Transport of Unsaturanted Groundwater and Heat) developed in the Earth Sciences Division of Lawrence Berkeley National Laboratory in 1987.

TOUGH2 is a simulator for multiphase, multicomponent , non-isothermal flows in fractured-porous media.

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1111

n n n

K K Kn n n

V V

K K

K K K

adv dis

dM dV F nd q dV

dt

M S X

F F F

TOUGH2

Governing equations

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Coupling module

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(1- )

l

l

a

l l l a

P pore pressure

S saturation of liquid

P pressure of liquid

P pressure of air

P S P S P

Biot's effective

stress parameter

pore pressure.

unit tensor

'

P

I

I P

Coupling module

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0

0

residual porosity at high stress

porosity at zero stress

' mean effective stress

exponent

( ) exp( ')

r

r r

a

a

0

0

0 0

porosity at zero stress

permeability at zero stress

exponent

exp[ ( / 1)]

k

c

k k c

0 00

=capillary pressure

/( )

/

c

c c l

P

kP P S

k

Coupling module

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Examples Results

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Examples Results

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Examples Results

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Examples Results

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Examples Results

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Examples Results

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Examples Results

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Examples Results

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Examples Results

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Conclusion

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Conclusion

We have linked two codes—TOUGH2 and FLAC3D—for analysis of coupled thermal-hydrologic-mechanical processes.

The coupling modules contain nonlinear stress versus permeability functions.

Conclusion

In both these examples, the hydromechanical changes are relatively slow, which is most suitable for the sequentially explicit solution.

Problems with higher strain rates relative to fluid mobility may require the sequential implicit approach or ultimately a fully implicit coupled approach.

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Thank for your attention

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