Study on Viscosity Reducing and Oil Displacement Agent for Water-Flooding Heavy Oil Reservoir

In the process of water-flooding development of heavy oil reservoir, due to the high viscosity and oil-water mobility ratio of heavy oil, there are some problems such as poor fluidity, high residual oil saturation and low recovery efficiency, which seriously restrict the efficient development of heavy oil. The molecular structure characteristics of asphaltenes and resins in heavy oil were analyzed. Based on the three most concerned properties of chemical agents, including the emulsification performance, the interface performance and the oil washing performance, three chemical oil displacement agents for heavy oil reservoirs were developed, and the structure of the chemical agents were characterized by high resolution mass spectrometry. The performance evaluation of chemical agents and core displacement experiments show that there is no obvious correlation between the properties of chemical agents, including interfacial tension, emulsifying ability and oil washing ability. For heavy oil reservoirs, the emulsification and viscosity reduction performance of chemical agents was more important than the oil washing capacity, and the oil washing capacity was more important than the interface performance. Viscosity reduction performance was the key parameter of oil displacement agent suitable for heavy oil reservoir. The composite binary system consisting of the viscosity reducer and the polymer had better oil recovery than using viscosity reducer alone.