Simulation of Segmented Subdivision Cutting Fracturing in Horizontal Wells in Shale Oil Reservoirs Based on Boundary Element Method

Abstract

Abstract For the segmented subdivision cutting fracturing in horizontal wells in shale oil reservoirs, using the boundary element method, a horizontal wellbore fracturing model is established considering the stress interference of the horizontal well section and the flow distribution at the opening of multiple hydraulic fractures (HF). The simulation of subdivision cutting fracturing of horizontal wells in shale oil reservoirs was carried out. Combined with the orthogonal test method, the influencing factors of the fluid pressure of HFs, the effective volume of HFs, and the fracturing fluid efficiency were analyzed. The results show that when the spacing between the sections and perforation clusters in horizontal wells is small, HFs in the middle are “squeezed” by the stress induced by the outer HFs, resulting in a much smaller length than the outer HFs. During the segmented subdivision cutting fracturing in horizontal wells, the spacing of each section has the most significant impact on the effective volume of HFs and fracturing fluid efficiency, followed by the number of HFs within a section. The spacing of each perforation cluster has the most negligible effect. Introduction Shale oil is an unconventional oil and gas resource, which is a vital alternative resource to conventional oil and gas (Qian, 2015). According to the EIA assessment, the technically recoverable shale oil resources in the world are 473 × 108 t (Qianru et al., 2020). Horizontal well volume fracturing technology is an effective means of achieving efficient development of shale oil and gas. Currently, the staged fracturing of horizontal wells in shale oil reservoirs is no longer aimed at increasing the length of the hydraulic fracture (HF) but at maximizing the comprehensive stimulation of the near well zone (Minsheng et al., 2019). Sinopec has proved the feasibility of using horizontal well subdivision cutting and volume fracturing technology for continental medium and high-maturity shale oil in several development areas (Tingxue and Haitao, 2021). In 2020, after the Jimsar shale oil reservoir was stimulated with subdivision cutting volume fracturing technology, the average daily oil production in the first year reached 36 t (Chengmei et al., 2021). Continental shale oil reservoirs have significant heterogeneity, and the effect of fracturing operations is poor. The relationship between the cost of fracturing operations and the expected development benefits must be comprehensively considered (Chengmei et al., 2021, Shanshan et al., 2021, Daohan et al., 2022, Xiaodong et al., 2022).