页岩油储层可压性分析及指数预测

The fracability analysis and index prediction of shale oil reservoir

吕照,刘叶轩,陈希,贾海正,李嘉成,梁利喜,丁乙

中国石油新疆油田分公司工程技术研究院，新疆 克拉玛依 834000 西南石油大学油气藏地质及开发工程国家重点实验室，四川 成都 610500

Engineering Technology Research Institute, Xinjiang Oilfield Company, PetroChina, Karamay 834000, China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China

中国页岩油资源丰富，实现页岩油高效开采的关键技术之一是水平井体积压裂。页岩油储层可压性的精准评价是避免盲目压裂、保证高效压裂效果的基础。页岩油储层具有明显的隔层特征，压裂缝的扩展过程受到隔层效应的影响，而现有可压性研究未考虑隔层效应的影响，因此对页岩油储层的适用性有限。为此，文中结合室内实验、数值模拟、图像处理及数理分析等手段，分析了隔层效应对储层可压性的影响，建立了页岩油储层可压性评价方法。研究结果显示：隔层效应不改变储层可压性的影响机制，高脆性、低抗张强度储层具有更好的可压性；隔层的存在对储层可压性具有抑制效应，随着隔层的强度增大、弹性增强、层间应力差变大，隔层的抑制效应更显著。此外，在高地应力、高地应力差条件下，储层可压性降低。综合储、隔层的地质力学特征，构建了页岩油储层可压性指数，并验证了该指数的适用性。研究成果可为水平井压裂分段分簇设计提供理论支撑。

Shale oil is rich in China. One of the important technology of exploiting shale oil is horizontal well volume fracturing. In particular, precise evaluation of fracability of shale oil reservoir is the foundation of avoiding aimless fracturing and ensuring effective fracturing operation. Shale oil reservoir has clear barrier characteristics, in which the expansion of fracture is affected by barrier effect. The researches about fracability ignore the influence of barrier, thus having limited applicability to shale oil reservoir. Therefore, combined with experimental test, numerical simulation, imaging processing and mathematical analysis, the influence of barrier effect on fracability was analyzed. The evaluation method of fracability of shale oil reservoir was established. The results show that barrier effect has no impact on mechanism of reservoir fracability. The reservoir with higher brittleness and smaller tensile strength has better fracability. The barrier has inhibiting effect on reservoir fracability. With increasing barrier strength, elasticity and stronger stress difference between layers, inhibiting effect of barrier is becoming larger. Meanwhile, under high in situ stress and large in situ stress difference, fracability of reservoir is decreasing. Based on geodynamics characters of reservoir and barrier, the fracability index was established and applicability of the index on shale oil was verified. The conclusion can provide theoretical support for design of staged and cluster fracturing in horizontal well.

10.6056/dkyqt202106004