Laboratory Studies of Parameters Involved in Modeling Microbial Oil Mobilization

Abstract

ABSTRACT Microbial methods for increasing oil recovery are potentially cost-effective even at relatively low crude oil prices. Microbial formulations can be applied in a variety of methods including permeability modification treatments and microbial-enhanced waterflooding. The flexibility and potential cost-effectiveness of the technology make it attractive, but further understanding of the transport mechanisms of microorganisms and the development of a sound engineering methodology for optimizing microbial formulations and injection strategies are needed to realize its potential. Work on this project has included the continuing development of a three-dimensional, three-phase, multiple-component numerical model to describe microbial transport phenomena in porous media. Laboratory data were used to develop correlations and mathematical models for specific phenomena; linear coreflooding data were used to test the simulator in an iterative process. The simulator development and laboratory testing aspects of this project were coordinated so that the results could be used to design other laboratory experiments to clarify and quantify certain physical and chemical effects. An accurate reservoir simulator for MEOR methods can best be developed through an integrated program of acquisition of laboratory and field data with the feedback loop being the reservoir simulation model. From our concepts of the hydrodynamics, physics, chemistry and microbiology of MEOR processes, microbial parameters incorporated into the microbial transport model include: (1) microbial growth and decay; (2) microbial deposition; (3) chemotaxis; (4) diffusion; (5) convective dispersion; (6) tumbling; and (7) nutrient consumption. Laboratory experiments were conducted to obtain actual data for the simulator regarding microbial growth and decay, nutrient consumption, microbial deposition, convective dispersion, and diffusion. Unsteady-state relative permeability measurements using microbial formulations were made to determine the effects of microbial metabolites on fractional fluid flow in porous media. Mechanisms considered to be important for oil recovery include changes in microscopic properties such as interfacial tension, wettability, and adsorption that govern oil mobilization and affect fractional flow and relative permeabilities. Other oil recovery, mechanisms traditionally associated with fluid flow changes include polymer and biomass production by microorganisms. This paper describes the laboratory investigations conducted in our ongoing efforts to incorporate oil recovery mechanisms by microorganisms into the simulator. Computer tomography studies demonstrated that gas production by microorganisms can reduce residual oil saturation in porous media. After conducting field-scale numerical simulation studies using data from relative permeability experiments, it was determined that microbial treatment could improve oil recovery over waterflooding alone.