3D Stochastic Reservoir Model and Fluid Flow Simulation of a CO2-EOR Pilot in a Fractured Reservoir

摘要

CO2 sequestration in mature oil and gas reservoirs is attractive due to the possible cost offsets from enhanced oil recovery (EOR). In this work we develop a 3D reservoir model and fluid flow simulation of the fractured Tensleep Formation using geomechanical constraints in advance of a proposed CO2-EOR and sequestration pilot at Teapot Dome Oil Field, WY. The objective is to model the migration of the injected CO2, and to obtain limits on rates and volumes to be injected, without compromising seal integrity. Additionally we want to investigate the effect of fractures on the permeability and mobility of CO2. The pilot planned to inject 1 MMcfd of supercritical CO2 for six weeks. The results indicate that CO2 buoyancy and mobility could pose problems to EOR performance in this highly fractured reservoir. The injected CO2 will rapidly rise to the top layers, above the main producing interval, accumulating in the fractures. It takes almost a year to start saturating the fractures in the target interval and almost two years to penetrate into the matrix. Furthermore a well control strategy would be necessary to improve oil recovery without circulating CO2. Incremental oil production is predicted to be less than 10% or 30% if double the amount of CO2 is injected in twice the amount of time. Regarding storage capacity, the trap could hold up to 2 wells injecting 1 MMcfd each, for 15 years. This could sequester ～5x105 tonnes of CO2 equivalent to a small power plant emitting ～37,800 tonnes/year.