Page 217 - gas transport in porous media

CHAPTER 12

NUMERICAL CODES FOR CONTINUUM MODELING
OF GAS TRANSPORT IN POROUS MEDIA

KARSTEN PRUESS
Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA

12.1 INTRODUCTION

A variety of techniques and approaches are available for quantitative mathematical
modeling of gas transport in permeable media. Analytical solutions can be obtained
for suitably simplified problems. Numerical simulation approaches are more versa-
tile. They can accurately represent the fundamental physical processes, as well as
honoring non-ideal flow and transport properties, general boundary and initial con-
ditions, and heterogeneities of the medium. Most numerical approaches currently
in use are based on “macroscale continuum concepts,” such as Darcy’s law for
advection, Fick’s law for diffusion, or the “dusty gas model” (DGM). Alternatives
such as numerical solution of the Navier-Stokes equation or lattice gas techniques
are employed for fundamental studies of gas behavior in individual pore channels.
The approach selected for any particular modeling study depends upon the nature
of the flow system, the space and time scales of interest, and on the objectives of
the study.

12.2 CONTINUUM MODELING

Here we review mathematical models and numerical solution approaches that are
currently being used in areas such as oil and gas recovery and storage, geothermal
systems, vadose zone studies, and industrial processing. The mathematical formu-
lation given below makes specific reference to the TOUGH2 numerical simulation
program (Pruess et al., 1999), although similar models and methods are employed
in other commonly used codes. In some cases gas is the only fluid filling the pore
space, while usually additional phases are present (aqueous and non-aqueous), that
may profoundly affect flow and transport behavior in the gas phase.

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C. Ho and S. Webb (eds.), Gas Transport in Porous Media, 213–220.
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