Abstract In this study, hydromechanical hybrid finite-discrete element method (FDEM) models were employed to investigate hydraulic fracturing from oriented perforations at the microscale. Numerical calibrations were first used to obtain the microproperties that can represent the realistic behavior of sandstone. The fracture morphology and breakdown pressure obtained from the numerical hydraulic fracturing show reasonable agreements with the experimental results, indicating that the numerical results are convincing. Then, this method was applied to investigate the effects of the differential stress, perforation angle, perforation length, and injection rate on both the geometry nature of the hydraulic fractures (HFs) and the breakdown pressure. The perforation orientation, differential stress, and injection rate are found to strongly affect the breakdown pressure and HF geometry. However, the perforation length shows a weaker effect, especially when the perforation length is larger than the wellbore diameter. Furthermore, small-scale simulations were performed to investigate the formation of connected fractures developed from multiple perforated wellbores under the concept of directional hydraulic fracturing (DHF). The different fracture propagations and geometries in the DHF model indicate that conclusions from studying hydraulic fracturing from a single perforated wellbore may provide a limited reference for hydraulic fracturing from multiple perforated wellbores. The stress shadow effects during HF interactions were identified as the primary factor that contributed to these differences. Numerical results also provide new information on the roles of several factors (differential stress, injection rate, perforation orientation, and injection sequence) in DHF. DHF could take advantage of stress shadow effects by optimizing related factors. Based on the numerical results, some implications on the design of DHF, from small-scale simulations to field-scale applications, are discussed.

中文翻译：

---

定向射孔水力压裂扩展的几何性质及对定向水力压裂的影响

摘要 在这项研究中，流体力学混合有限离散元法 (FDEM) 模型被用来研究微观尺度下定向射孔的水力压裂。数值校准首先用于获得能够代表砂岩真实行为的微观特性。数值水力压裂得到的裂缝形貌和破裂压力与实验结果具有合理的一致性，表明数值结果令人信服。然后，该方法用于研究不同应力、射孔角度、射孔长度和注入速率对水力压裂 (HF) 几何性质和击穿压力的影响。射孔方向、差应力、发现注入速率和注入速率强烈影响击穿压力和 HF 几何形状。然而，射孔长度的影响较弱，尤其是当射孔长度大于井筒直径时。此外，还进行了小规模模拟，以研究在定向水力压裂 (DHF) 概念下由多个射孔井筒形成的连接裂缝。DHF 模型中不同的裂缝扩展和几何结构表明，研究单个射孔井眼水力压裂的结论可能为多个射孔井眼水力压裂提供有限的参考。HF 相互作用期间的应力阴影效应被确定为导致这些差异的主要因素。数值结果还提供了有关 DHF 中几个因素（应力差、注入速率、射孔方向和注入顺序）的作用的新信息。DHF可以通过优化相关因素来利用应力阴影效应。基于数值结果，讨论了对 DHF 设计的一些影响，从小规模模拟到现场规模应用。