Summary
We present the first 1D simulations of dynamic foam displacements with a
population-balance model incorporating bubble creation controlled by pressure
gradient. For the first time, a population-balance model is fit to steady-state
experimental data for both the three foam states (coarse foam, intermediate,
and strong foam) and the two strong-foam regimes (low-quality and high-quality)
observed in laboratory studies. Simulations confirm the stability of the
coarse-foam and strong-foam states to small perturbations, and the instability
of the intermediate state, at fixed injection rates.
In dynamic displacements, the model shows foam generation as injection rates
increase, or as liquid fraction of injected fluids increases, in agreement with
laboratory observations.
When coarse foam is created instead of strong foam, there is a narrow region
of finer foam predicted near the gas displacement front. This region appears to
play a role in foam generation. However, in the limited cases examined here,
foam generation occurs at roughly the same injection rate as predicted by
local-steady-state theory. Because of this narrow region of finer-textured
foam, fronts can be sharper than estimated from fractional-flow theory assuming
a constant effective gas viscosity at its steady-state value behind the
displacement front.
If a strong foam forms in the low-quality regime, the kinetics of foam
generation and destruction affects the length of the entrance region in which
foam forms. Therefore, the length of the entrance region can be used to
calibrate the kinetic parameters in the model. The displacement front and the
bank behind it, however, are essentially what one would have predicted from
local-steady-state modeling. The complexities of population-balance modeling
are not necessary, if it is known that strong foam will be created.
Introduction
Foam can improve sweep efficiency in gas-injection improved oil recovery
(IOR) processes (Schramm 1994; Rossen 1996; Terdre 2003), redirect acid flow in
matrix acid stimulation (Gdanski 1993; Cheng et al. 2002; Nguyen et al. 2003),
and increase the efficiency of environmental remediation of aquifers (Hirasaki
et al. 2000; Mamun et al. 2002). A continuing goal of foam research is the
development of a fully mechanistic, predictive model. This paper describes
efforts toward such a model and insights gained from application of the model
to dynamic displacements. Before providing a detailed description of the model,
it is worthwhile to review the mechanisms of foam in porous media and the
experimental observations that the model attempts to reproduce.
© 2007. Society of Petroleum Engineers
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History
- Original manuscript received:
7 June 2004
- Meeting paper published:
26 September 2004
- Revised manuscript received:
4 April 2006
- Manuscript approved:
5 May 2006
- Version of record:
20 March 2007
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