关键词: 页岩油, 渗吸换油, 排驱泄油, 原油动用体积, 压裂改造体积, 动用均匀程度

Abstract: There is currently a lack of evaluation methods for three-dimensional production performance of shale oil reservoirs after hydraulic fracturing. To address this, this paper proposes a post-fracturing drained rock volume calculation method that considers the synergistic interactions between fracturing fluid imbibition and drainage displacement, clarifies the contributions of rock elastic energy, crude oil elastic energy, and fracturing fluid imbibition displacement to crude oil production, and analyzes the change laws of drainage drivement (DRV), hydrocarbon production efficiency and their correlations with stimulated reservoir volume (SRV). The results show that imbibition displacement serves as the main driving force for the initial oil production of hydraulic fractured shale oil reservoirs (within the first three months); after 3 months, drained rock volume palys a dominant role, which mainly depends on rock elastic energy. During the production process, the DRV gradually expands to encompass the entire SRV, and the drain rate of oil in formation exhibits the highly heterogenous variation pattern of increasing fast first and then slow. The drain efficiency exhibits a progressive attenuation from the fracture walls to the matrix. Using the Jimsar shale oil reservoirs in Xinjiang as a case study, it is revealed that:(1)After 1 year of production, the DRV accounts for 57.8% of the SRV, while the remaining 42.2% SRV requires more about 2 years for full account; (2)During the first year, 50% of the DRV contributes to 80% of the crude oil production; (3)Under the same well spacing and fracturing conditions, the hydrophilic and highly stress-sensitive reservoirs demonstrate more heterogeneous production efficiency, as well as more significant imbibition displacement effects. Through a case study of 6 typical horizontal wells in shale oil reservoirs in Jimsar sag, Xinjiang, the imbibition oil displacement volume, matrix drainage drivement volume, drained rock volume and production heterogeneity index were calculated, providing a theoretical basis for evaluating the three-dimensional production performance of shale oil reservoirs in post-fracturing horizontal wells, and optimizing the subsequent three-dimensional stimulation strategies.

Key words: shale oil, imbibition replacement, oil drainage, drained rock volume, stimulated reservoir volume, drain effect uniformity