Volume 57

Investigation of Mass Transfer-Flow Coupling Mechanisms and Feasibility of CO2-Enhanced Oil Recovery in Conglomerate Reservoirs YunLuo, Shenglai Yang , Yiqi Zhang, Ziqiang Wang, Gen Kou, Xuewei Zhang, Yang Zhao, Min Wang

Abstract

Carbon dioxide (CO₂) flooding, a critical enhanced oil recovery (EOR) technique, exhibits unresolved miscibility mechanisms and dynamic processes. This study systematically investigates the property evolution of formation fluids and miscibility behavior post-CO₂ injection through comprehensive physical visualization characterization and experiments. Results demonstrate that CO₂ injection markedly reduces fluid density and viscosity, elevates saturation pressure, and induces exponential growth in volumetric expansion coefficients. Concurrently, the phase envelope shifts leftward and upward with expansion of the two-phase region during miscible displacement, while critical parameters undergo dynamic adjustments contingent upon dissolution ratios. Visualization experiments delineate the miscibility process into three mechanistic stages: swelling, mass-transfer zone transition, and miscibility achievement-each exhibiting distinct characteristics. These findings advance fundamental understanding of CO₂ flooding mechanisms and provide a theoretical framework for optimizing field implementation.

Keywords COâ‚‚ Flooding, Miscibility Mechanisms, Property Changes, Phase Behavior, Miscibility Visualization