The goal of this project was to devise effective surfactant packages and a mechanism-based simulator of foam displacement in porous media for mobility control in improved oil recovery (IOR) processes.

Program
This project is part of the Natural Gas and Oil Technology Partnership, Oil and Gas Recovery Technology. The program partners the National Laboratories with petroleum industry organizations to develop advanced technologies for improved natural gas and oil recovery.

Lawrence Berkeley National Laboratory (LBNL)
Berkeley, CA

Increasing oil recovery is a crucial problem, since many domestic reservoirs are nearing depletion with standard production techniques. Modern IOR practice is well-developed in the area of dislodging trapped oil, for example, by establishing ultralow tensions with exquisitely designed surfactant formulations. However, mobility control is not well-developed, even though the basic principles are understood. Because reservoirs are naturally heterogeneous, all current enhanced oil recovery processes (including steam flooding, hydrocarbon injection, CO2 flooding, alkaline flooding, and surfactant flooding) require mobility control. This work focuses on use of gas-aqueous surfactant dispersions (also called generically "foams") as a general mobility control agent both in establishing macroscopic sweep efficiency and microscopic displacement efficiency and for a range of IOR processes. Foams for both in-depth sweep improvement and local well profile modification are under development.

Project Results
A fully 3-D, mechanistic population-balance foam simulator has been developed, including the kinetics of oil destabilization of foam. A mechanistic description of oil destabilization of foam by the rupture of lamellae as they encounter oil has been successfully implemented.

Benefits
The simulation tool developed in this project will enable operators to predict where the use of foam mobility control is advantageous and thereby increase oil recovery.

Project Summary
Project milestones include the following:

• A fully 3-D, mechanistic population-balance foam simulator has been developed, including the kinetics of oil destabilization of foam. The new foam simulator is constructed to be compatible with currently available state-of-the-art reservoir simulators. Its advantage over available treatments of foam flow is that verifiable physical phenomena are incorporated so that scaling from laboratory to reservoirs can be accomplished. The simulator has been updated to predict foam generation based on snap-off in constricted cornered pores and on effective-medium theory. Also, the basic principles by which bubbles trap, coalesce by gas diffusion, and remobilize into the flowing regime have been elucidated.


• A mechanistic description of oil destabilization of foam by the rupture of lamellae as they encounter oil has been implemented successfully. To improve understanding of surfactant design, a novel thin-film balance is being employed that allows simultaneous measurement of disjoining pressures and longitudinal electrical conductivities and seconds an atomic force microscopy (AFM) that presses bubbles against solid surfaces to measure reservoir wettability and aqueous film rupture pressures. In particular, how drops are configured at solid/liquid interfaces in the presence of thin films has been determined (Colloids and Surfaces, 1999), a new theory for how foam films are stabilized has been derived (Adv. Coll. Int. Sci. 2001), and a new understanding of oil spreading (JCIS, 2000; Langmuir) has been devised.


• A new theory to garner disjoining forces from AFM was accomplished. Molecular simulations of the disjoining pressures in thin foam films using MD and MC algorithms have been conducted. An oscillating drop tensiometer to gauge the film-forming behavior of the crude oil/water interface has been constructed. An adhesion test of crude oils against mica surfaces, including AFM examination of the molecular architecture of the deposited films, has been performed.

(October 2005)
The project has been completed.

Publications
Bhatt, D., Newman, John, and Radke, C.J., Molecular Simulation of Surface Tensions of Aqueous Electrolyte Solutions, J. Phys. Chem. B, 2004.

Bhatt, D., Chee, R., Newman, John, and Radke, C.J., Molecular Simulation of the Surface Tension of Simple Aqueous Electrolytes and the Gibbs Adsorption Equation, submitted to Current Opinion in Colloid and Interface Science, 2004.

Bhatt, D., Newman, John, and Radke, C.J., Monte Carlo Simulation of Disjoining-Pressure Isotherms for Lennard-Jones Surfactant-Stabilized Free Thin Films, submitted to J. Chem. Phys. B, 2004.

Freer, E.M. and Radke, C.J., Relaxation of Asphaltenes at the Toluene/Water Interface: Diffusion and Surface Rearrangement, J. Adhesion, 2004.

Kovscek, A.R., and Radke, C.J., Pressure-Driven Capillary Snap-Off of Gas Bubbles at Low Wetting Liquid Content, Colloids and Surfaces A, 212(2-3), 2003, pp. 99-108.

Svitova, T.F., Weatherbee, M., and Radke, C.J., Dynamics of Surfactant Adsorption at the Air/Water Interface: Continuous Flow Tensiometry, J. Coll. Int. Sci., 2003.

Yaros, H.D., Newman, John, and Radke, C.J., Evaluation of DLVO Theory with Disjoining-Pressure and Film-Conductance Measurements of Common Black Films Stabilized with Sodium Dodecyl Sulfate, J. Colloid Int. Sci., 2003.

Freer, E.M., Svitova, T., and Radke, C.J., The Role of Interfacial Rheology in Reservoir Mixed Wettability, J. Petroleum Science and Engineering, 2003.

$4,597,000

$0

NETL - Sue Mehlhoff (sue.mehlhoff@netl.doe.gov or 918-699-2044)
LBNL - Clayton Radke - (radke@cchem.berkeley.edu or 510-642-5204)