Dominant Controlling Factors and Displacement Performance in Heavy Oil Recovery Processes

During immiscible displacement in heavy oil reservoirs, the multiphase flow of oil-water or oil-steam systems is governed by the combined effects of viscous forces, capillary forces, and gravity. Identifying the dominant forces and clarifying their competitive relationships are essential for improving the oil recovery. On the basis of core-scale physical simulation experiments, a unified dimensionless framework for analyzing force competition was established, enabling dimensionless characterization and recovery prediction for both conventional heavy oil-water flooding and super heavy oil-steam flooding. By systematically analyzing residual oil variation under different injection rates, temperatures, permeabilities, steam qualities, and injection inclination angles, we quantitatively characterized the competitive interactions among viscous, capillary, and gravitational forces. The results indicate that conventional heavy oil-water flooding is predominantly controlled by capillary forces, and oil recovery exhibits a significant linear negative correlation with the modified capillary number. In contrast, super-heavy oil-steam flooding is mainly governed by gravity-driven flow and thermal viscosity reduction. The composite model developed based on the thermogravimetry number (N _TG) demonstrates high predictive accuracy (R = 0.9692), providing a quantitative basis for parameter optimization in heavy oil reservoir development.