Feasibility Study On Major Reservoirs At Sazhong Area By Surfactant/polymer Flooding After Polymer Flooding

At present, enhanced oil recovery mainly depend on chemical flooding in China, one of the higher proportion is polymer flooding. However, there is still a great quantity of crude petroleum exists in the layer after polymer flooding, about 50% of the crude oil is remained underground. In recent years, the tendency to study of surfactant/polymer flooding is going up.In this paper, the initial formula of binary composite system is identified at the base of laboratory and field tests. According to the problems of main layer at Sazhong area during and after polymer flooding, researching and exploring the feasibility of P/S flooding (surfactant/polymer) after polymer flooding to further enhance oil recovery. By static experiments such as viscosity stability evaluation, and interfacial tension measurement, surfactant/polyment flooding system which suits to geological characteristics of main layer at Sazhong area have been optimised. Static and dynamic adsorption capacities of polymer-surfactant system are measured in laboratory. In the conditions of simulating reservoir conditions of main layer at Sazhong area of Daqing Oilfield, the displacement oil experiments were finished in natural and artificial core, oil-displacement effect of high-concentration polymer flooding and P/S flooding after water flooding and polymer flooding are comparative analyzed, quantitative analysis of the possibility to enhancing oil recovery of high-concentration polymer flooding and P/S flooding after polymer flooding.On the basis of the above researchment, displacement oil experiments of microscopic model were carried out to study features of residual oil distribution after water flooding and polymer flooding, the microscopic displacement mechanismes of different interfacial tension SP flooding and high-concentration polymer flooding after polymer flooding is acquired in the artificial homogeneous model, the probability of high-concentration polymer flooding and P/S flooding after polymer flooding to enhance oil recovery is further verified. At last, distribute regulation of remaining oil and porous characteristics of core before and after polymer flooding were researched by the technologies of nuclear magnetic resonance imaging and rate-controlled mercury penetration.Laboratory experimental results showed that the optimal concentration of the system is CP=1500mg/L, CS=0.3%. The results also indicated that stability of viscosity and interfacial tension of surfactant/polyment flooding system is better. High-concentration polymer flooding and SP flooding can further enhanced oil recovery after polymer flooding, but the effect of enhancing oil recovery is more obviously by P/S flooding after polymer flooding.