Experimental Investigation on Enhanced Oil Recovery and Carbon Storage by Multimedia Synergistic Electrical Heating-Assisted CO2 Stimulation in Developing Medium-Deep Heavy Oil Reservoirs

Summary Carbon dioxide (CO2) stimulation (CS) is a critical method for carbon utilization and storage in developing medium-deep heavy oil reservoirs. However, its efficacy is constrained by CO2 cold damage and limited molecular diffusion at low temperatures, with the incremental oil recovery of CS typically below 15%. Therefore, we propose a novel multimedia (solvent and foam) synergistic electrical heating-assisted CO2 stimulation (MMEH-CS) by integrating solvent, foam, and electrical heating to enhance oil recovery and carbon storage. To clarify the mechanisms of mass and heat transfer improvements by electrical heating, multimedia, and their synergy, six sets of systematic experiments were designed and conducted in an improved 3D radial physical model based on the WX medium-deep reservoir in Xinjiang Oil Field, China. The results indicate that MMEH-CS enhances crude oil recovery by 10.2%, 8.5%, 4.9%, 2.8%, and 1.6% while increasing CO2 storage multiple by 6.0 PV, 5.0 PV, 2.0 PV, 1.0 PV, and 0.8 PV, respectively, relative to CS, solvent-assisted CS (S-CS), electrical heating-assisted CS (EH-CS), solvent synergistic electrical heating-assisted CS (SEH-CS), and foam synergistic electrical heating-assisted CS (FEH-CS). In comparison with standalone methods, MMEH-CS exhibits superior energy efficiency, with cumulative injected CO2-produced oil ratio (cCOR), cumulative storage CO2-residual oil ratio (cSCROR), cumulative energy-produced oil ratio (cEOR), and cumulative energy-storage CO2 ratio (cESCR) of 152.4 mL/mL, 13.7 mL/mL, 3.94 kJ/mL, and 0.089 kJ/mL, respectively. Key mechanisms of MMEH-CS include thermodynamic enhancement (via electrical heating), dissolution enhancement (via solvent), and conformance improvement (via foam), which synergistically reduce oil viscosity, promote CO2 molecular diffusion, and mitigate CO2 cold damage. Additionally, temperature profiles reveal broader thermal propagation (effective radius exceeds 7.5 m in field scale) and stable foamy oil flow, ensuring sustainable reservoir performance. These findings indicate MMEH-CS has the characteristics of satisfactory viability and sustainability in efficient energy, enhanced oil recovery (EOR), and enhanced carbon storage (ECS). This study provides a robust reference for economically feasible and environmentally friendly development of CS in medium-deep heavy oil reservoirs.