Multi-performance synergistic effects of poly-surfactant solution and optimization of oil displacement

To address the issues of composite water cut as high as 98% and poor water flooding performance in Block X in Daqing Oilfield, the pilot test on poly-surfactant flooding was conducted. This study systematically investigated the key indicators such as thickening efficiency, emulsification properties, salt tolerance, injectivity and oil displacement efficiency of polymer-surfactant solutions through physical simulation experiments by using dehydrated crude oil, produced water and artificial cores as subjects from Y Oil Production Plant of Daqing Oilfield. The results showed that at 51 ℃, the polymer-surfactant exhibited a significant concentration-dependent thickening effect and good viscosity retention, while its viscoelasticity contributed to mobilizing and displacing crude oil. The emulsion formed by the polymer-surfactant solution with crude oil is more stable at high concentrations, thereby enhancing the displacement efficiency. Even in high-salinity environments, the solution maintained good thickening capacity and stability. Core flooding experiments showed that this solution propagated throughout the entire process of injection, migration and production, exhibiting observed adsorption and carrying effects. Based on this research, three oil displacement schemes were designed for Type A and B polymer-surfactant solutions. Among them, Scheme A demonstrated the best oil displacement performance, achieving overall recovery ratio as much as 65.98%. This research reveals the oil displacement mechanism of polymer-surfactant solution under multi-performance synergy and offers a theoretical guidance for chemical flooding in high-water-cut reservoirs.