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

摘要： 针对页岩油储层水力压裂后立体动用效果评价较为欠缺的问题,提出了一套考虑压裂液渗吸换油和排驱泄油协同作用的压后储层动用体积计算方法,区分了岩石弹性能、原油弹性能和压裂液渗吸置换作用对原油产出的贡献特征,分析了储层原油动用体积(DRV)、动用程度的变化规律以及与压裂改造体积(SRV)的关系。研究结果表明:渗吸换油作用是页岩油储层压后初产油量(3个月内)的主要动力,3个月后产油贡献主要依靠弹性能的排驱泄油作用;生产过程中DRV逐渐扩大至整个SRV,原油的动用速度呈现"先快、后慢"的变化特征;动用程度沿裂缝壁面到基质方向逐渐变弱,呈现出高度非均匀的变化特征。以新疆吉木萨尔页岩油储层为例:生产1年时DRV动用到SRV的57.8%,剩下42.2%的SRV则需要额外约2年才能动用;前一年50%的DRV贡献了80%的原油产量;在相同井距和压裂施工条件下,亲水且高应力敏感储层动用程度更不均匀,渗吸换油作用更显著;亲油且低应力敏感储层动用程度相对均匀,排驱泄油作用更显著。选取新疆吉木萨尔凹陷上、下甜点6口典型页岩油水平井开展实例分析,计算出压裂液渗吸换油体积、基质排驱泄油体积、原油动用体积和动用均匀程度,为页岩油水平井压后储层立体动用效果评价、后续立体改造方案优化提供了设计依据。

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