The rational choice of perforation arrangement and injection angle is of great significance to improve the efficiency of synchronous fracturing and to achieve the stimulation of the shale reservoir. In this paper, the influence of perforation angle and perforation arrangement on the crack propagation mechanism and rock failure mode of synchronous fracturing is studied based on the particle discrete element software PFC. Results show that due to the influence of the stress shadow effect, elliptical cutting cracks are produced between perforations during the synchronous fracturing. When the perforations are arranged in alignment, the fracture mode of rock mass between the perforations is single crack cutting failure under low injection angle, and double-crack cutting failure under high injection angle. Meanwhile, when the injection angle tends to the direction of maximum principal stress (\(\uptheta\) ≥ 60°), the fracturing effect can be greatly improved. In addition, the small perforation spacing under the high principal stress difference is more conducive to the fracturing of the central rock mass. When the perforation is staggered arrangement and the horizontal distance between the perforation centers is the perforation length, it is easy to form the intersection phenomenon of wing cracks under the high principal stress difference, which is more conducive to the realization of fracturing in the central rock mass. In addition, high injection angle is more conducive to the formation of penetrating cracks, but not easy to achieve the central rock mass fracturing. The findings of this study can help for a better understanding of crack propagation law and rock failure mode under different perforation arrangements, which can provide some theoretical guidance for the field synchronous fracturing construction.

中文翻译：

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双裂隙岩体中同步压裂裂缝扩展的DEM数值模拟研究

合理选择射孔排列方式和注入角度对提高同步压裂效率，实现页岩储层增产具有重要意义。本文基于粒子离散元软件PFC，研究了射孔角度和射孔排列对同步压裂裂纹扩展机理和岩石破坏模式的影响。结果表明，由于应力阴影效应的影响，在同步压裂过程中，射孔之间会产生椭圆形的切割裂纹。当孔眼排成一直线时，孔眼之间的岩体破裂模式为低注入角下的单裂纹切割破坏和高注入角下的双裂纹切割破坏。与此同时，\（\ uptheta \） ≥60°），可以大大提高压裂效果。另外，高主应力差下的小射孔间距更有利于中心岩体的破裂。当射孔错开排列时，射孔中心之间的水平距离为射孔长度，在高主应力差下很容易形成机翼裂纹的相交现象，更有利于中心岩石的压裂实现。质量 另外，大的注入角更有利于形成穿透性裂缝，但不易实现中心岩体的压裂。这项研究的结果有助于更好地了解不同射孔排列下的裂纹扩展规律和岩石破坏模式，