Oil & Natural Gas Projects
Exploration and Production Technologies
Mechanistic Studies of Improved Foam EOR Processes
This project was selected in response to DOE's Oil Exploration and Production
solicitation DE- PS26-01NT41048 (December 1, 2000). The objectives of this part
of the solicitation were to access oil not recoverable by conventional methods
by developing improved methods of gas, chemical, and microbial flooding for
light oil recovery.
The project goal was to provide the scientific and engineering basis for improved
design of foam processes for enhanced oil recovery, by studying polymer-enhanced
foam, gas trapping in the presence of foam, and mechanisms of foam generation.
University of Texas
Numerical models and simulation studies of foam mechanism were developed to
improve prediction of foam movement through the reservoir. An area of unstable
foam generation was identified that provides important information for foam
design in field applications.
This research provides the foundation for more-accurate predictive modeling
of foam processes to improve oil recovery, improve process design, enable wider
application of foams and gas injection, and increase domestic oil production.
Injection of gases, including steam, carbon dioxide, and produced field gas,
accounts for nearly all the enhanced oil recovery production in the United States,
or about 12% of total U.S. oil production. The processes are efficient in recovering
oil in portions of the oil reservoir where the gas flows, but the failure of
gas to sweep through much of the reservoir reduces both the number of projects
attempted and the rate of oil recovery in ongoing projects. Creating foams with
gas, water, and surfactant (detergent) solution within the oil reservoir offers
one means to increase this "sweep efficiency." The proposed research
aims to improve foam processes through studies of their mechanisms, leading
to more-predictive computer modeling of foam processes and improved process
The model for gas trapping incorporated into the UTCHEM simulator was used to
fit data on gas trapping during liquid injection after foam. The model predicts
mobilization of gas near an injection well during liquid injection in an alternating-slug
process, enhancing liquid injectivity. University of Texas experiments verified
the model for foam generation based on foam mobilization at a critical pressure
gradient. Their data also identified an unstable foam-generation regime that
may dominate field applications of foam constrained by moderate injection pressures.
Researchers incorporated a simple model for this mechanism into the "population
balance" framework for foam simulation. The model confirms the existence
of an unstable regime at intermediate pressure gradients. Researchers drafted
a manuscript on the foam-generation work.
Conclusions from the project are as follows:
- Interactions between foam and polymer.
-For the polymers, oils, and surfactants tested, it appears from coreflood pressure
gradient that polymer destabilizes foam somewhat, raising water saturation and
water relative permeability. Increases in observed pressure gradient resulted
from the increased viscosity of the aqueous phase.
-For the same polymers and surfactant, polymer does not stabilize foam in
the presence of decane or 37.5 API gravity crude.
-Complex behavior, in contradiction to the expected two steady-state strong-foam
regimes, was sometimes observed.
-Theory predicts that polymer should make the flow of foam more shear-thinning
than without polymer. In the high-quality regime, where pressure gradient
is controlled by water transport at fixed water saturation, the shear-thinning
nature of the aqueous polymer solution would make flow shear-thinning. In
the low-quality regime, where the rheology depends on the resistance to movement
of gas bubbles, flow is predicted to be more shear-thinning because of the
presence of polymer.
- Gas trapping.
-A new model for gas trapping has been incorporated into a foam simulator. This
model can fit steady-state data for the two strong-foam flow regimes. In limited
trials, it also fits the transition period between foam injection and injection
of liquid following foam. The simulator will be most helpful in modeling liquid
injectivity in SAG foam processes.
-Coreflood experiments measured the average liquid saturation in a core during
liquid injection following foam. Data implied that liquid does not uniformly
sweep the core but only contacts a portion of the trapped gas.
-CT studies confirm that liquid fingers through foam rather than displacing
it. Because of this fingering, surfactant-free brine injected after foam does
not displace the surfactant solution initially present or destroy foam as
rapidly as predicted in one-dimensional (1-D models.
-The yield stress of foam is the origin of gas trapping and relative premability
effects with foam.
-CT imaging showed that the 1-D model used to infer trapped- and flowing-gas
fractions from gas tracer effluent data have several shortcomings. They are
noted in the report. In spite of the uncertainty, some trends are still evident.
- Foam generation
-The consensus view in foam research has been that foam is created by roof
snap-off, governed liquid and gas velocities, and the geometry of the pore
throats and pore bodies. A review of these individual studies cited in support
of this mechanism shows there is no substantial support for this mechanism
for steady-state foam generation in homogeneous porous media.
-If pressure gradient is fixed, rather than injection rates, one observes
an unstable state between coarse foam (or no foam) and strong foam. This state
may have practical importance in field applications with limits on injection
-A population-balance model incorporating a lamella-creation function that
depends on pressure gradient fits numerous features observed in foam generation
experiments. This model indicates that the details of the lamella-creation
function have little effect on the high-quality and low-quality strong-foam
regimes, if strong foam is formed.
-The population-balance foam simulator, applied to dynamic foam displacements,
confirms the stability of the coarse- and strong-foam states and the instability
of the intermediate state. The model predicts a transition from coarse foam
to strong foam as injection rates increase, in agreement with experiments.
-Fractional-flow models can be modified to account for sudden changes in
properties such as foam generation and foam collapse.
-A pore-network model for foam generation resolves two paradoxes troubling
researchers' finding that foam is created by mobilization and division of
lamellae by pressure gradient. First, the network model shows how new lamellae
are created near the inlet of the porous medium to replace those mobilized
and transported downstream. Second, the model reconciles the two halves of
the theory of Rossen and Gauglitz (1990) at the percolation threshold.
-A series of experiments in sandpacks found several effective ways of enhancing
foam generation. Other studies indicate the same trends in foam behavior are
observed in sandpacks as in consolidated core, but at lower pressure gradients.
Current Status (October 2005)
This project has been completed.
Project Start: September 1, 2001
Project End: December 31, 2004
Anticipated DOE Contribution: $639,525
Performer Contribution: $172,163 (21% of total)
NETL - Sue Mehlhoff (email@example.com or 918-699-2044 )
U. of Texas - William Rossen (firstname.lastname@example.org or 512-471-3246)
Final Report [PDF-4.46MB] - March, 2005
Kim, Dong, and Rossen, Steady-State Flow Behavior of CO2 Foam, SPE 89351,
presented at 2004 SPE/DOE IOR Symposium, Tulsa, OK, April 2004.
Rossen and Bruining, Foam Displacements With Multiple Steady States, SPE
89397, presented at 2004 SPE/DOE IOR Symposium, Tulsa, OK, April 2004.
Kam and Rossen, A Model for Foam Generation in Homogeneous Porous Media,
SPE Journal 8, 417-425, December 2003
Cox, Neethling, Rossen, Schleifenbaum, Schmidt-Wellenburg, and Cilliers,
A Theory of the Effective Yield Stress of Foam in Porous Media: The Motion
of a Soap Film Traversing a Three-Dimensional Pore, Colloids Surfaces A: Physicochem
Eng. Aspects 245, 143-151, 2004.
Rossen and Van Duijn, Gravity Segregation in Steady-State Horizontal Flow
in Homogeneous Reservoirs, Journal of Petroleum Science Eng., 43, 99-111,
Shan and Rossen, Optimal Injection Strategies for Foam IOR, SPE Journal 9,
Kam and Rossen, A Model for Foam Generation in Homogeneous Media, SPE 77698.
Mamun, Rong, Kam, Liljestrand, and Rossen, SPE 77557, Extending Foam Technology
From Improved Oil Recovery to Environmental Remediation.