Numerical Simulation of Fluid Flow in a Dual Porosity Geothermal System with a Thin Zone of High Horizontal Permeability
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Date
2007
Authors
Ambusso, Willis J.
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
A numerical simulator capable of mode ling fluid flow in layered dual porosity
geothermal systems with high horizontal permeability has been developed. The simulator
can match multiple-peaked tracer profiles from injection tests and reliably predict
temperature and pressure changes caused by injection of brine in these systems. The
simulator was tested and validated using data from Svartsengi geothermal field in
Iceland, a non-layered geothermal field, and Olkaria geothermal field in Kenya, a layered
geothermal reservoir. Simulated results show significant improvement over regular
geothermal simulators and indicate that fluid flow within the horizontal layers with high
permeability are best represented by fracture flow theory where fluid flow between the
matrix-fracture network occurs in both directions rather than what is normally assumed
that fluid flow is governed purely by dual porosity model where fluid flow occurs only
from the matrix to the fracture. The study shows that fluid movement in horizontal
fractures will dominate main fluid flow features in the reservoir and shall uniquely
modify tracer profiles. These horizontal fractures will also lead to high returns of injected
fluid at relatively low speeds in reservoirs with moderate permeability as has been noted
in Olkaria. This simulator makes it possible to extract quantitative values of the
hydrologic parameters of the respective layers. This should lead to better planned and
managed brine injection programs.
Description
A thesis submitted in partial fulfillment of the requirements for the award of the degree of Doctor of Philosophy in Physics of Kenyatta University.