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In response to the development of multiple sets of shell interlayers in the longitudinal direction of the Fuxing continental shale oil reservoir, as well as the development of high stress interlayer in the longitudinal direction, which is not conducive to the expansion of fracture height and the passage of proppant, and is not easy to form complex fractures, a study was conducted on the law of vertical perforation fracture height expansion and plane stress and fracture interference in the reservoir. A perforation expansion high reverse mixed volume fracturing technology was developed based on the concept of high viscosity liquid pre-loading, large displacement and fast fracturing. The reverse mixing pump injection process mode of using high viscosity liquid to break rock and expand joints, high slippery water to create complex joints, moderate amount of glue in the middle, medium high viscosity slippery water to add sand, with a pre-liquid volume greater than 130 m3, viscosity greater than 50 mPas, displacement greater than 15 m3/min, high quality of joint formation, and more stable fractures. The longitudinal lithology of FY10HF well contains multiple decimeter and meter scale crust limestone, and the stress profile shows strong heterogeneity. After compression, microseismic monitoring shows that the height of crack propagation is 51 meters, and the volume of single section reconstruction is 44.3 meters×104 m3, with a total well renovation volume of 1594.6×104 m3, daily oil production of 15t, daily gas production of 5.57 ×104 m3。

As for the problem of shale oil reservoirs having high clay mineral content and a high proportion of expansive and sensitive minerals in terms of mineral composition, an efficient anti swelling agent with good compatibility with reservoirs and resistance reducing agents has been developed, effectively reducing the damage caused by water-based fracturing fluids to the reservoir; A nano oil displacement agent has been developed, which has the characteristics of small volume and low interfacial tension between oil and water. It can effectively increase the liquid coverage range, significantly reduce the driving pressure difference, and improve oil recovery. The developed high-efficiency anti expansion agent and nano oil displacement agent are combined with an integrated drag reducing agent to form an integrated anti expansion and oil displacement variable viscosity fracturing fluid system suitable for shale oil reservoirs. This system adopts 100% backflow drainage online liquid preparation, which can achieve real-time adjustment of online viscosity (1-150) mPas, meeting the needs of on-site large-scale volume fracturing and real-time adjustment of construction technology. Successfully applied in the fracturing of QY1HF well, with low viscosity slick water (1-3) mPas, high viscosity slick water (12-15) mPas, and glue viscosity (50-75) mPa s, helping QY1HF well achieve a high industrial oil flow rate of 62.6 t/d for testing oil production.