The use of numerical simulation to investigate the enhanced Eagle Ford shale gas condensate well recovery using cyclic CO2 injection method with nano-pore effect

Abstract

The huge reserves of Eagle Ford shale gas condensate reservoirs have drawn great attention. The well productivity analysis indicates that the leading Eagle Ford is in reservoir decline stage. Condensate banking effect induces severer adverse effect on ultra-low permeability reservoirs and shale gas production than conventional reservoirs. The objective of this paper is to investigate the effect of CO2 huff-n-puff injection on mitigating condensate accumulation surrounding the induced fractures. The nano-pore confinement effect on condensate and gas production performance is considered. The nano-meter scale of shale condensate plays exhibit different phase behavior than conventional condensate reservoirs. The influence of nano-pore confinement on liquid phase behavior in shales is similar to adding CO2 in admixture with reservoir fluids, which acts to suppress the phase envelope. The interaction of CO2 injection with reservoir oil at molecular scale was discussed. Two scenarios including a lean gas condensate and rich gas condensate were compared in order to study the CO2 huff-n-puff performance with different reservoir fluids. The simulation results indicated that CO2 is more favorable in improving the rich condensate recovery. Removal of condensate accumulation in rich condensate Eagle Ford shale reservoirs by CO2 huff-n-puff injection results in substantial recovery increment in comparison with the pressure depletion scheme. This paper focuses on studying the influences of nano-pore walls on CO2 injection phase behavior in shale gas-condensate reservoirs.