Formulation of Oil Displacement and Viscosity Reduction System for Tight Oil Reservoir

Tight oil reservoir in Daqing oilfield has low permeability, small pore throat radius, high gelatinous and waxy content of crude oil in the reservoir, and low fluidity of crude oil. Conventional guanidine gum fracturing fluid used in hydraulic fracturing has some problems, such as poor reservoir adaptability, low utilization degree and fast production decline. In this paper, through the research of oil displacement viscosity reduction fracturing system, micro and nano oil displacement agent and viscosity reduction agent are organically combined to reduce the interfacial tension, so as to achieve the wettability effect of tight oil reservoir, and obtain the oil displacement viscosity reduction system XYJ01 with good oil displacement and viscosity reduction effect. Performance evaluation experiments were carried out on the amount of displacement viscosity reduction system, core permeability and the influence of different fluids on the efficiency of self-imbibition and oil washing, and the compatibility of fracturing fluid, reservoir rock and reservoir fluid was comprehensively analyzed. The experimental results show that when the oil displacement viscosity reduction system is 0.20%, the self-imbibition efficiency reaches 17.62%. With the increase of water content, the viscosity reduction effect becomes more obvious. When the oil-water ratio is 7:3, the emulsification viscosity reduction rate can reach 36.23%. The displacement viscosity reducing system has no effect on the rheological property of fracturing fluid and the performance of suspended sand. The oil displacement viscous-reducing system has good compatibility with reservoir rocks. After the addition of oil displacement viscous-reducing system, the damage of fracturing fluid to reservoir core is reduced to a certain extent. It is proved that the hydraulic fracturing fluid system with oil displacement and viscosity reduction has obvious effect on the fracturing reconstruction of tight oil reservoir, which is conducive to improving the oil and gas recovery efficiency of tight oil reservoir and realizing the efficient exploitation of tight oil.