Bowei Li's dissertation
by
Bowei Li, Ph.D.
University of Texas at Austin, 2001
Supervisor: Dr. Mark Miller
Transport and flow phenomena in porous media and fractured rock
arise in many fields of science and engineering, including petroleum and
groundwater engineering. Over the past few decades, there are two classes
of models that have been developed for describing flow and transport
phenomena in porous media and fractured rock. They are the continuum and
discrete models. Continuum models include single porosity and dual
porosity models. The latter is popularly applied in simulating flow in
naturally fractured systems.
The dual porosity model, a subclass of the continuum model, is a
favorable approach to study flow in naturally fractured systems. In the
dual porosity approach, it is assumed that the fissured porous media can
be represented by two colocated continua called the matrix and the
fracture system. High conductivity but low storativity typically
characterizes the fracture system, whereas the matrix is usually
characterized as low conductivity but high storativity. The matrix
generally acts as a source that transfers its mass to the surrounding
fractures; then fluid is transported to production wells.
Conventional dual porosity models generally use a diagonal
permeability tensor to formulate and discretize the flow equations for the
fracture system. However, such practice does not always adequately reflect
the characteristics of natural fractures characterized by heterogeneity
and anisotropy ascribed to the fracture's varied orientation, apertures,
and intensity. Therefore, conventional dual porosity models may overlook
the naturally fractured system's directionality and heterogeneity.
This study is designed to develop a novel approach to model fluid
flow in natural fractured systems with a dual porosity approach. In the
study, a full permeability tensor representation of fracture flow is
implemented in the UTCHEM dual porosity chemical flood simulator. The full
permeability tensor feature in the fracture system adequately captures the
system's characteristics, i.e., directionality and heterogeneity. At the
same, the powerful dual porosity concept is inherited. The capability of
modeling the local complex physical phenomena is maintained in the
simulator.
The implementation has been verified through studying
waterflooding in a cylindrical reservoir, and waterflooding in a spherical
reservoir. As an application of the implementation, a study on a naturally
fractured system was conducted. Simulation results were compared with that
generated by the Fracman simulator (Golder Associates, 2000) a discrete
feature model. Another application is waterflooding through a fractured
system using dual porosity approach. A conclusion can be drawn from all
these studies that for a heterogeneous and anisotropic system, full
permeability tensor representation of flow is necessary to accurately
simulate flow in such system.
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