Zhiyue Liang's dissertation
by
Zhiyue Liang, Ph.D.
University of Texas at Austin, 1997
Supervisors: Mark A. Miller
Kamy Sepehrnoori
A distinguishing characteristic of naturally fractured reservoirs is that
fractures have high permeability with very small pore volume while the matrix
blocks between fractures have low permeability with large pore volume. Because
of the extreme differences in properties between the two media, fluids tend to
channel through fractures to production wells, leaving much oil behind in
relatively low permeability matrix blocks, typically resulting in very low oil
recoveries.
One method proposed to increase recovery from naturally fractured reservoirs
is steam injection. Heat transfer, imbition, gas generation, and other
mechanisms have the potential to expel fluids from matrix blocks at sufficient
rates and in sufficient quantities to be feasible. The objective of this study is to
develop an accurate 3D three-phase dual porosity thermal simulator to study
steam injection processes in naturally fractured reservoirs.
A new dual porosity thermal simulator, UTDUTHM, has been developed
for modeling steamflooding in naturally fractured reservoirs. An implicit
algorithm is used to solve the equations for the combined fracture/matrix system.
The new simulator can model reservoirs with vertical fractures, horizontal
fractures and their combination by appropriate subgridding of matrix blocks. The
new simulator can also handle gas generation in the matrix, a capability not found
in other simulators.
A new set of correlating equations for saturated steam/water properties has also been
developed for inclusion in the simulator. These correlations are better
than those previously reported in terms of accuracy, continuity, range of
applicability, and simplicity.
The new simulator is verified by test runs against a commercial simulator, STARS, and a
research simulator, UTDUAL. Excellent agreement is achieved.
The procedure for implementing a dual porosity model was also
implemented into UTCHEM, a chemical flooding simulator developed at The
University of Texas at Austin. This implementation shows that the method
can easily extend an existing single porosity simulator to a dual porosity simulator
with very few changes to the existing code.
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