Pore Network Modeling of Quasi-static Two-Phase Flow Considering Modification of Pore-Scale Remaining Oil Saturation During High-Flux Water Flooding

Summary Long-term high-flux waterflooding is a crucial technology for achieving the economic, environmental, and sustainable development of mature oilfields during the ultrahigh water cut period by further reducing microremaining oil saturation (Sor) in the swept area. However, traditional quasi-static two-phase flow simulations based on pore network models (PNMs) do not account for the impact of cumulative pore volumes (PVs) through water on pore-scale remaining oil saturation, resulting in the inability to obtain the oil saturation distribution and relative permeability curves of high-flux waterflooding. In this study, we designed a novel high-flux core displacement experiment monitored by online NMR to establish the relationship between Sor and PV in pore-throats of varying diameters (d). Subsequently, we integrated the function of Sor into the governing equations of quasi-static two-phase flow in PNMs to modify the calculation of saturation and conductance during the secondary imbibition (SI) process. The results show that with increasing PV, the overall Sor in the PNM decreases, the two-phase coflow intervals increase, and the iso-permeability point on the relative permeability curves shifts progressively downward and to the right during the SI process. This research advances the characterization of pore-scale Sor affected by PV, addressing a critical gap in pore-scale simulation research.