MECHANISTIC STUDIES OF IMPROVED FOAM EOR PROCESSES

Rossen, William R.

The University of Texas (United States)

关键词: Trapping;    Sweep Efficiency;    02 Petroleum;    Flow Rate;    Polymers;   

DOI  :  10.2172/808965
RP-ID  :  NONE
RP-ID  :  FC26-01BC15318
RP-ID  :  808965

美国|英语

来源: UNT Digital Library

【 摘 要 】

The objective of this research is to widen the application of foam to enhanced oil recovery (EOR) by investigating fundamental mechanisms of foams in porous media. This research will lay the groundwork for more applied research on foams for improved sweep efficiency in miscible gas, steam and surfactant-based EOR. Task 1 investigates the pore-scale interactions between foam bubbles and polymer molecules. Task 2 examines the mechanisms of gas trapping, and interaction between gas trapping and foam effectiveness. Task 3 investigates mechanisms of foam generation in porous media. The most significant progress during this period was made on Tasks 2 and 3. Research on Task 2 focused on simulating the effect of gas trapping on foam mobility during foam injection and during subsequent injection of liquid. Gas trapping during liquid injection is crucial both to injectivity during liquid injection in surfactant-alternating-gas foam (SAG) projects and also provides a window into trapping mechanisms that apply during foam flow. We updated our simulator for foam (Rossen et al., 1999; Cheng et al., 2000) to account explicitly for the first time for the effects of gas trapping on gas mobility in foam and in liquid injected after foam, and for the effects of pressure gradient on gas trapping. The foam model fits steady-state foam behavior in both high- and low-quality flow regimes (Alvarez et al., 2001) and steady-state liquid mobility after foam. The simulator also fits the transition period between foam and liquid injection in laboratory corefloods qualitatively with no additional adjustable parameters. Research on Task 3 focused on foam generation in homogeneous porous media. In steady gas-liquid flow in homogeneous porous media with surfactant present, there is often observed a critical injection velocity or pressure gradient {del}{sub p}{sup min} at which foam generation occurs. Earlier research on foam generation was extended with extensive data for a variety of porous media, permeabilities, gases (N{sub 2} and CO{sub 2}), surfactants, and temperatures. For bead- and sandpacks, {del}{sub p}{sup min} scales like (1/k), where k is permeability, over 2 1/2 orders of magnitude in k; for consolidated media, the relation is more complex. For dense-CO{sub 2} foam, {del}{sub p}{sup min} exists but can be less than 1 psi/ft. If pressure drop, rather than flow rates, is fixed, one observes an unstable regime between stable ''strong'' and ''coarse'' foam regimes; in the unstable regime {del}{sub p} is nonuniform in space or variable in time. Results are interpreted in terms of the theory of foam mobilization at a critical pressure gradient (Rossen and Gauglitz, 1990).