Sabine Claudia Zeilinger's dissertation
by
Sabine Claudia Zeilinger, Ph.D.
University of Texas at Austin, 1996
Supervisors: William R. Rossen
Foam is used in stimulation treatments and enhanced oil
recovery to aid diversion and to improve sweep efficiencies.
When they are used as diverting agents during matrix-
acidizing treatments, they direct acid flow to low-permeability
or oil-saturated zones. However, foam mechanisms in rock are
complex and not well understood. Foam mobility is controlled
by foam texture, which itself is a complex function of many
variables. Capillary pressure and the relation between the
pore-size distribution of the rock and the texture of the foam,
especially, play important roles in foam behavior.
This work explores the mechanisms of foam diversion in two
ways. The first is mathematical modeling. A theoretical model
of foam in rock can be derived from first principles, using a
material balance on each component and a population balance
on the foam bubbles. However, this method involves the
description of processes that are not well understood. Our
investigation focuses on a simpler approach, which was
introduced in an earlier work and that describes the dominant
mechanism of foams in a rock, applying fractional-flow
methods under the assumption of a limiting capillary pressure.
We show that the predictions of foam flow using this model are
comparable to the other approach, in spite of its simplicity.
A second focus of this work is an experimental investigation of
the bubble-size distribution in foam. Foam-acid treatments in
the field and experimental work published in the literature
suggest that foam texture depends on parameters such as the
permeability and the pore-size distribution of the porous
medium, which reconfigures foam texture. We have built an
apparatus that measures both bubble-size distribution as foam
exits the medium and the pressure drop caused by the foam in
a variety of sandpacks and rock samples.
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