Javier Vilcaez, Boone Pickens School of Geology, Oklahoma State University
Field-scale studies have shown that indigenous microbial communities can adapt to extreme conditions of CO2 injection for geological carbon storage and enhancing oil recovery. This presentation will introduce lab-scale experimental and field-scale simulation results on the utilization of CO2 and protein-rich matter in depleted oil reservoirs to stimulate the microbial conversion of oil and CO2 to methane. Experimental results were obtained using rock, produced water, and crude oil samples collected from the Stillwater and Cushing oilfields of Oklahoma. Simulation results were obtained by simulating the combined injection of produced water supplied with protein-rich matter and CO2 into the Cushing oilfield. Experimental results show that the combined supply of protein-rich matter and CO2 has a synergetic stimulating effect on the activity of indigenous oil degrading methanogenic microbial communities. This is reflected by the production of H2 and CH4, degradation of oil (mostly n-alkanes), and consumption of CO2. Simulation results show that the water-rock interactions and CO2 dissolution in water play a significant role on the activity of methanogenic oil degrading microbial communities. This is reflected by different H2, CH4, and CO2 aqueous and gas concentration profiles around the injection well. One important feature of the proposed carbon utilization method is that methanogenesis occurs preferentially via the reduction pathway of CO2. Therefore, we expect that this carbon utilization method will lead to the establishment of an economically viable industrial method to biogenically convert anthropogenic CO2 and residual oil to CH4 in depleted oil reservoirs.