Investigation of the Synergistic Effect Between Viscosity Reducer, Polymer and Branched Preformed Particle Gel in Enhanced Oil Recovery for Conventional Heavy-Oil Reservoir

In view of the limited applicability of traditional chemical flooding and binary composite flooding for heavy-oil reservoirs, branched-preformed particle gel (B-PPG) with excellent plugging performance was added to construct the B-PPG/SP (B-PPG/surfactant/polymer) composite system. Through sand pack flooding experiments, it has been proven that the synergistic effect between B-PPG and polymer can expand the swept area and increase the contact between the viscosity reducer and heavy oil, enabling the viscosity reducer to better exert emulsification and viscosity reduction effects. The synergistic effect between B-PPG, polymer and viscosity reducer can further expand the swept area and oil displacement efficiency, ultimately enhancing the heavy-oil recovery by 37.8%. Microscopic visualization flooding experiments proved that cluster remaining oil accounts for the largest proportion in the microscopic remaining oil in heavy oil. By adding B-PPG and polymers, cluster remaining oil can be effectively displaced, thereby significantly enhancing the heavy-oil recovery. And adding viscosity reducer to the composite system can effectively enhance the dispersed residual oil recovery within the swept area. The sand pack flooding experiments with different heavy-oil viscosity proved that the optimal oil viscosity of the B-PPG/SP composite system can reach 657.2 mPa·s, with an incremental oil recovery rate increase of 30.2%.