Molecular Insights into Heavy Oil Mobilization Mechanism in Hybrid Thermal Processes: A QCM-D and NEMD Simulation Study

Hybrid thermal processes are promising enhanced oil recovery (EOR) methods integrating thermal and chemical mechanisms. Optimizing these processes requires a clear understanding of multiphase interactions among water, oil, rock surfaces, and additives. This study combined quartz crystal microbalance with dissipation (QCM-D) experiments and nonequilibrium molecular dynamics (NEMD) simulations to characterize the microscopic occurrence and displacement dynamics of heavy oil under hybrid thermal systems. Results demonstrate that surface wettability significantly affects the occurrence and mobilization of heavy oil. Specifically, heavy oil on hydrophobic surfaces is difficult to unlock. However, hybrid CO2-surfactant systems can mobilize this stable oil. During displacement, CO2 and the surfactant synergistically promote tilting desorption of heavy oil, enlarging the oil–water interface and reducing oil-surface interaction, thereby improving recovery. Key operating parameters are assessed for field implementation. This study provides theoretical support for a broader deployment of hybrid thermal processes, demonstrates potential for concurrent CO2 utilization, and supports environmentally responsible oil-recovery practices.