Experimental Investigations on Enhanced Oil Recovery by Electrical Heating Synergistic Expanding Solvent-Steam-Assisted Gravity Drainage in Ultraheavy Oil Reservoirs

Summary Steam-assisted gravity drainage (SAGD) is one of the most classic and effective developing techniques in heavy oil reservoirs. However, thermal losses along the flow path reduce the thermal upgrading effect of steam as viscosity and reservoir depth increase. Due to the heterogeneity of reservoirs, the effectiveness of solvent assistance alone in enhancing oil recovery is limited. To address this issue, electrical heating-SAGD (EH-SAGD) and electrical heating synergistic expanding solvent-SAGD (EHES-SAGD) are proposed based on conventional SAGD in this paper. To elucidate the mechanisms of mass and heat transfer improvements facilitated by electrical heating and electrical heating synergistic solvent, three sets of 3D physical simulation experiments were designed and conducted based on field sampling from the FC Block in Xinjiang oil field, China. The results demonstrate that EHES-SAGD substantially outperforms conventional SAGD and EH-SAGD in production metrics. The method achieves higher ultimate oil recovery, with 9.4% and 15.7% improvements over SAGD and EH-SAGD, respectively, while it enhances the oil production rate (OPR) and reduces the equivalent steam/energy-oil ratio by effectively decreasing oil viscosity and improving thermal efficiency within the reservoir. Furthermore, electrical heating enhances heat distribution near the wellbore and improves the steam absorption profile of the horizontal well. The integration of solvent with electrical heating further accelerates the development of steam chambers, and it promotes the emulsification of crude oil and enhances the foamy oil effect, thereby greatly reducing seepage resistance and enhancing the affected area of EHES-SAGD. Additionally, EHES-SAGD demonstrates lower energy requirements during the production stage, highlighting the energy efficiency and economic viability of the electrical heating. These findings articulate the efficacy of the synergism of electrical heating and solvent injection presenting the excellent potential of EHES-SAGD for economically viable and environmentally sustainable development of ultraheavy oil reservoirs. Keywords Ultra-heavy oil reservoirs, Electrical heating, synergistic expanding solvent, Steam-assisted gravity drainage (SAGD), Enhancing oil recovery (EOR)