Investigations on CO2 migration and flow characteristics in sandstone during geological storage based on laboratory injection experiment and CFD simulation

CO2 geological storage in tight sandstone reservoirs is an effective method of CO2 capture, utilization, and storage (CCUS). CO2 migration and flow characteristics in sandstone during geological storage affect the physical and mechanical properties of rocks significantly. In this study, laboratory injection experiments combined with X-ray computed tomography (CT) scanning and scanning electron microscopy (SEM) tests, and computational fluid dynamics (CFD) numerical simulation have been conducted to investigate the effect of geological and engineering parameters on CO2 migration and flow characteristics. The results show that: (1) The injection rate and injection pressure affect the Sc-CO2 migration path. Moreover, the fluid velocity and fluid pressure affect the pressure distribution in pores significantly. Limiting the injection rate and pressure during the CO2 geological storage is beneficial for the stability of the storage. (2) The pressure distribution of the fluid changes with orders of magnitude depending on the injection pressure. However, the overall transient relative pressure is almost consistent and the fluid pressure in the bending section of the bending pores exhibits a linearly decreasing trend. (3) SEM tests provide a connection between laboratory experiments and CFD simulation on microscopic scale. The injection pressure and the acoustic emission (AE) energy have a positive correlation to a certain extent. The Sc-CO2 migration path could be forecasted preliminarily through the fluctuation of the injection pressure-time curves and AE response. The results enrich the theory of CO2 migration and flow characteristics during CO2 geological storage.