Volume 34: CCUS Technologies for the Carbon Neutrality: Part II

Effect of CO2 sequestration on multi-phase multi-component fluid transport and gas production in shale Chenhao Sun, Jun Li, Jiawei LI, Sailiang Dong

Abstract

CO2 injection into shale and coalbed reservoirs to enhance methane (CH4) production is treated as a better way to promote gas recovery efficiency as well as easing carbon emission by CO2 sequestration. Most CH4 is adsorbed inside the organic micropores and mesopores (≤ 50 nm), enjoying large surface areas and serving abundant adsorption sites. And another key structure factor is the slit, which is usually treated as a sequestration medium. To better understand the microscopic mechanism of enhanced CH4 recovery by CO2 in nanopores and slit becomes necessary. Thus, Molecular Dynamics (MD) supports a solid foundation for constructing the nanosized kerogen frameworks to investigate the gas adsorption behavior on the kerogen-accessible surface. This study innovatively introduced a new method of constructing kerogen slit nanopores, making the model more practical and approaching real underground environments. The grand canonical Monte Carlo (GCMC) method is employed to uncover the gas adsorption and sequestration practices within the kerogen nanopores and slit at various subsurface conditions. According to our results, the previously overlooked slit particularly impacts gas adsorption and recovery efficiency. This study also examines the widespread water encroachments, including various pure water and saline environments. Pure moisture has an overall negative on gas adsorption and sequestration, promoting the recovery efficiency of CH4 by CO2 injection. Moreover, saline has a further enhanced negative influence on gas adsorption, whereas it advantages the displacement process. Ethane (C2H6) influences the CH4 adsorption negatively but favors the recovery process. This work shows significant importance in underlining the kerogen slit nanopores structure and develops the knowledge of the comprehensive underground conditions work on gas adsorption and recovery mechanisms at a thorough level to enhance CH4 extraction and CO2 utilization and sequestration.

Keywords CO2 sequestration, fluid transport, shale, molecular simulation