Properties Evaluation Of Polymer-surfactant Flooding System In Sub-layers

Polymer/surfactant flooding has been applied to the main reservoir in Daqing oil field, and has achieved good economic results. But as the years of oil exploitation increased, most of the main reservoir has entered the high water cut stage. With water cut increasing in oil wells, economy benefit of oil exploitation is getting worse. This brings an insistent demand to find a new effective way to enhance the exploitation efforts of sub-layers at the same time. Compared to the main reservoirs, the sub-layers generally have properties of low permeability, thin in depth and poor connectivity, therefore, the traditional flooding method are not fully applicable in the sub-layers. People need to further study enhanced oil recovery methods under the conditions of sub-layers for the goal of 40 million tons production in Daqing oilfield.In this paper, based on a comprehensive survey of the mechanism of chemical flooding, the interfacial tension and viscosity of the binary system which consisted of polymer and surfactant produced by No. 2 Oil Production of Daqing were evaluated. Through experiments, it was seen that the binary system has good salt-resistant, anti-shear performance and stability, and has ultra-low interfacial tension. At the same time, through experiments, the static adsorption capacity and dynamic retention volume of surfactant were measured, and the average retention volume is 0.251mg/g which can meet the actual production requirements. According to simulation experiments, the binary system flooding effect of different surfactant concentrations, different polymer viscosity, the different sizes of main slug, different sizes of pre-slug, different sizes of protect slug were compared so that the law of various factors influence on displacement effect was sumed up to achieve the best surfactant/polymer flooding formula in sub-layers of Daqing oilfield: 0.03PV polymer slug+0.3PV surfactant/polymer slug (S:0.3%+HPAM:1610mg/L, Viscosity is 40.3mPa·s)+0.3PV polymer protect slug+ water flooding. Finally, the experiments were carried out with the binary system in natural cores and heterogeneous cores. At the same time, a single polymer flooding at the same economic conditions and the polymer flooding and ASP flooding with the same size of slug were compared with the flooding effect of binary system so as to establish the best surfactant/polymer flooding fomular for sub-layers in Daqing. Physical simulation experiment results show that the polymer-surfactant system can enhance oil recovery over 17%.