Characterization and Influence Mechanisms of Interfacial Morphology in Multicomponent Thermal Fluid Flooding under Supercritical Water Conditions

Abstract Thermal recovery through steam injection is a vital method for enhancing heavy oil recovery. In recent years, a breakthrough approach for deep heavy oil reservoirs has emerged: multicomponent fluid flooding using media like supercritical water, CO2, and N2. Compared to conventional thermal methods, supercritical multicomponent thermal fluid (SCMTF) flooding offers advantages such as superior heat-carrying capacity and enhanced miscibility. This study utilizes ANSYS Fluent software for numerical solving. A model of SCMTF displacement within a single pore throat is established, defining the diffusion length (LD) and fingering length (LS) to characterize the flow interface morphology. The research investigates the effects of diffusion coefficients and SCMTF composition on both the interface morphology and the displacement pressure differential, analyzing the seepage characteristics of supercritical gas and liquid water phases within the throat. Furthermore, a two-dimensional rock pore model is developed to elucidate the oil displacement mechanisms of SCMTF flooding. A model for residual oil in dead-end pores is constructed, enabling a quantitative evaluation and ranking of the contributions made by various mechanisms─including convection, diffusion, mixing for viscosity reduction, and dissolution and expansion─in mobilizing this residual oil.