Classification of Flow Pathways for Waterflooding Operations in a Hydrocarbon Reservoir in Terms of Displacement Constraints and Incremental Oil Recovery

A robust and pragmatical technique was developed to classify flow pathways during long-term waterflooding operations in a hydrocarbon reservoir. More specifically, pore structure analysis, wettability tests, relative permeability tests, and long-term waterflooding experiments were conducted and integrated. Then, effects of pore-throat structures, displacement rates, crude oil viscosities, and wettability on the oil displacement efficiency across different flow pathways were systematically investigated, allowing us to classify flow pathways into the primary and secondary ones. For the former, pore-throat structure significantly affects the efficiency of displacement: for mouth-bar microfacies, cores with larger pore-throat radii and lower fractal dimensions exhibit superior displacement performance, whereas, for point-bar microfacies, it exhibits greater sensitivity to variations in injection parameters. Increasing the injection rate from 0.2 mL/min to 0.5 mL/min can lead to a 7.31% improvement in oil recovery. Also, high-viscosity crude oil leads to an overall decline in displacement efficiency, with a more pronounced reduction observed in the point-bar microfacies, suggesting that complex pore-throat structures are more sensitive to viscous resistance. For the latter, wettability shows its dominant impact with an increase in oil recovery to 7.12% if the wettability index is increased from 0.17 to 0.21 in the point-bar microfacies.