Polymer/surfactant Flooding For Enhanced Common Heavy Oil Recovery

In this paper, the polymer/surfactant flooding was studied under the geological conditions of the heavy oil reservoir in Henan Oilfield. The heavy oil reservoir in Henan Oilfield is characterized by thin oil reservoir, high viscosity of crude oil and serious heterogeneity, but good reservoir physical property and high permeability.Firstly, the polymer and surfactant used for binarycompound flooding were screened, optimized, and evaluated. The result shows that: the compound systerm composed of lauryl polyoxyethylene ether betaine, TX-100, and polyacrylamide polymer A50 has good compatibility and the interfacial tension(IFT) between composite surfactant solution and crude oil can achieve ultra-low value. The optimal concentrations of each surfactant are both 0.1% and A50 is 1500 mg?L-1.The optimal slug size of polymer/surfactant binary system is 0.5 PV. The viscosity of the optimized polymer/surfactant binary system is 50.24 mPa?s, and the IFT between composite surfactant solution and crude oil can achieve 10-3 mN?m-1. Meanwhile, the optimized polymer/surfactant binary system has good aging stability and good temperature resistance.Effects of injection schemes and parameters in polymer/surfactant flooding on enhanced heavy-oil recovery were studied by conducting laboratory experiments. Different injection S/P flooding schemes were tested by using the same amount of chemical agent. The experimental results showed that in homogeneous sandpacks, injection of a polymer slug or a S/P slug with high viscosity could recover 3.6% ~ 4.6% IOIP more than the recovery by a single S/P slug injection. In heterogeneous sandpacks, high viscosity and large-scale slug are required for effectively improve heavy oil recovery. In both cases(i.e., for both homogeneous and heterogeneous conditions), injection of a polymer slug of high viscosity followed by a surfactant slug was also an effective method of enhancing heavy oil recovery. For investigating the effects of injection parameters, viscosity, interfacial tension and displacement velocity were tested as three factors at three levels by applying the orthogonal test design. The optimized result for water phase viscosity is 100 mPa?s, interfacial tension range is 10-2~10-3 mN?m-1 and displacement velocity is 1.5 m L?min-1. In the order of importance to oil recovery efficiency, viscosity of water phase is the most important one, followed by interfacial tension and displacement velocity.