Molecular simulation study on interfacial microstructural changes of CO2 flooding in tight porous environment

Abstract

In this research, the interfacial microstructure dynamics during CO2 flooding in tight porous reservoirs were explored through molecular dynamics simulations. Initially, the study focuses on the structural attributes of the gas–liquid interface in a static state, noting a transition from dissolution to swelling as tightness increases. Subsequently, the research diverges into two distinct areas: the quasi-static and dynamic displacement processes. The analysis of diffusivity and dissolution in the oil phase under quasi-static conditions indicates that the interaction energy between components is influenced by the degree of tightness. In contrast, during dynamic displacement at a constant pressure, tight reservoirs exert an anchoring effect, hindering the movement of the oil phase at 3 MPa. However, at 10 MPa, CO2 is likely to achieve a gas breakthrough in less tight reservoirs, while the adsorption strength of residual oil in the reservoirs concurrently escalates. The study concludes that the stability of the interfacial region plays a dual role in determining the sustainability of liquid exchange in these processes.