Research on Cold Production Technology at the End of Huff and Puff in Shallow and Thin Extra-Heavy Oil Reservoirs in Xinjiang

Aiming at the problems of rapid production decline, rapid water cut increase and poor economy in the late stage of thermal recovery of shallow and thin heavy oil reservoirs in Xinjiang, the distribution law of pressure field, temperature field and oil saturation field in heavy oil reservoirs at the end of steam stimulation was clarified by numerical simulation. A variety of viscosity reducers including nano-viscosity reducers and microbial composite viscosity reducers were screened out, and the viscosity reduction rate of 0.4% mass concentration could reach more than 98%. The synergistic mechanism of viscosity reducer with polymer and alkali was clarified, which had the characteristics of wide temperature adaptation range, high viscosity reduction rate, low interfacial tension, strong emulsification and anti-agglomeration. The hot water injection process can achieve 19.5% indoor enhanced oil recovery under 0.5 PV, and the internal rate of return of the test area under the oil price of USD 60 is more than 15%, and the carbon emission per ton of oil is reduced by more than 50%. The research results of this paper have solved the problems of how to effectively use the remaining oil in the ‘double high stage’ scattered distribution of heavy oil, the combination of low-cost and high-efficiency cold recovery system, and the optimization and adjustment of typical well group parameters in the oilfield. It is helpful to promote the development of cold production after steam injection in shallow extra-heavy oil reservoirs and realize green and low-carbon transformation.