CO2-kerogen interaction dominated CO2-oil counter-current diffusion and its effect on ad-/absorbed oil recovery and CO2 sequestration in shale

The affinity of CO2 to kerogen represents an opportunity to increase shale oil/gas recovery using CO2, and as well represents great potential for CO2 sequestration in shale formations. In this study, the CO2-kerogen interaction dominated counter-current diffusion was investigated using molecular dynamics simulation. Molecular models of ad-/absorbed hydrocarbons extraction from kerogen using CO2 were constructed, and the CO2-hydrocarbon counter-current displacement processes were simulated. Results showed that the stronger interaction between kerogen and CO2 than that between kerogen and hydrocarbons results in a spontaneous counter-current diffusion process. That is, the ad-/absorbed hydrocarbons in kerogen can effectively be extracted out and CO2 can flow into and be stored in kerogen simultaneously. Effects of pressure, temperature, hydrocarbon, and the type of kerogen on the efficiency of hydrocarbon extraction, and CO2 storage capacity were analyzed. Further, in field applications, methods of evaluating the enhanced hydrocarbon recovery and the CO2 storage capacity of shale formations were proposed. Results obtained from this study provide guidance for enhancing shale oil/gas recovery using CO2 and for CO2 sequestration in shale formations.