Experimental study on improving oil recovery in fluvial reservoir with polymer solutions

To study the displacement law of polymer flooding in fluvial reservoirs, physical simulation cores are designed according to the characteristics of strong planar heterogeneity in such reservoir systems. Three different polymer solutions, namely, partially hydrolyzed polyacrylamide (HPAM), hydrophobically associating water-soluble polymer (AP-P4), and long-term shear retardant polymer (LSRP), are analyzed through oil displacement experiments. The results show that, in the simulated fluvial reservoir core model, the sweep efficiency of water flooding is about 80%, but the recovery is only about 20%, with poor oil displacement efficiency. The effects of HPAM and AP-P4 on improving sweep efficiency are poor, as they cannot effectively sweep the low- and medium-permeability areas on either side of the central core. The polymer LSRP, which has higher viscosity and better viscoelasticity, can effectively expand the sweep volume, with the sweep efficiency reaching 97.8%, but there is still the potential to greatly improve the oil displacement efficiency. The results indicate that, in fluvial reservoirs under the experimental conditions, expanding the sweep volume requires high-performance polymer solutions. The enhanced oil recovery method is required to obtain a greater oil displacement effect. The results provide a reference for the selection of displacement agents for the development of fluvial reservoirs.