Molecular Simulation Study of Rock-Water-Oil Systems

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Oil recovery is an important world-wide enterprise with significant social, economic, and environmental impacts. When oil is extracted from an underground reservoir, only about 10% is removed via pressure and pumping. Secondary and tertiary recovery methods are used to extract the remainder of the oil, and these involve physical and chemical stimulation of the oil well, respectively. One such stimulation technique is the injection of a high salinity brine or surfactants (soaps) into the subsurface. These chemicals not only displace the oil, but also alter the chemical interaction, or "wetting", of the oil with subsurface rock. Decreasing the chemical interaction by which the rock "holds onto" the oil facilitates oil recovery. How wetting behavior evolves with changing reservoir conditions is not fully understood. This project uses computational tools to probe molecular interactions that dictate the wetting behavior and to elucidate the connection between the larger environment of the reservoir with the microscopic details of the rock, oil and brine/surfactant. This research project uses molecular simulations to probe wetting phenomena, including molecular interactions at the brine-oil and brine-mineral interface. These interfacial properties are known to affect capillary pressure, which is the key determinant in the wettability of porous rock. The project also quantifies the extent to which acids, bases, and asphaltenes adsorb onto the rock surface, and the potential of this adsorption to change both rock surface chemistry and rock-brine-oil interfacial interactions. The extent to which wettability evolves with temperature, surface concentration, and the chemical identity of the surface will elucidate how wettability evolves with changing reservoir conditions. The role of surfactants in altering interfacial interactions is also being explored. As this system is quite complex, the project goal is to develop quantitative relationships that connect macroscopic properties to microscopic structure. These relationships will enable the rational design of safe, efficient, and environmentally friendly solutions for oil extraction. Students are being trained on surface thermodynamics, statistical mechanics, and computer simulations. Outreach activities to area high schools are educating students about the impact of engineering studies on society and everyday life.