Research and Application of CO₂ Huff and Puff Differentiation Technology in Edge and Bottom Water Heavy Oil Reservoir

A fault block in Gaoshangpu of Jidong Oilfield is a heavy oil reservoir with edge and bottom water. The water body has sufficient energy, and the whole is in the stage of ultra-high water cut development. After several rounds of CO2 huff and puff, the remaining oil is highly dispersed, and it is difficult to tap the potential by conventional technical means. By analyzing the implementation effect of CO2 huff and puff in the fault block, it is clear that the injection volume of CO2 huff and puff and the average remaining oil saturation in the production well control well area are the main controlling factors affecting the huff and puff effect, and the CO2 differential huff and puff technology under different remaining oil saturation conditions in heavy oil reservoirs is proposed. Through laboratory experiments, this technology clarifies the four mechanisms of viscosity reduction, expansion, dissolved gas flooding and extraction of CO2 injection to improve heavy oil recovery. Through the numerical simulation method, four differential design charts of throughput injection volume, round-by-round increase ratio of gas injection volume, throughput rounds and liquid production speed under different saturation conditions were optimized. During the implementation of the field, through the analysis of oil well production characteristics and numerical simulation calculation, the remaining oil saturation of different well areas in the reservoir is clarified. Using the differential design chart, the injection and production parameters of huff and puff wells under different remaining oil saturation conditions are calculated. The design of 88 wells of CO2 differential huff and puff in the heavy oil reservoir of the fault block is guided. The average daily oil production of single well is 6.0 tons, and the cumulative oil production is 45,000 tons, which effectively guides the same type of reservoir to further improve the huff and puff effect.