Hydraulic fracturing techniques for developing deeply buried coal reservoirs face routine problems related to high initial pressures and limited control over the fracture propagation direction. A novel method of directional hydraulic fracturing (DHF) based on hydraulic slotting in a nonuniform pore pressure field is proposed. A mechanical model is used to address crack initiation and propagation in a nonuniform pore pressure field, where cracks tend to rupture and propagate towards zones of high pore pressure for reducing the effective rock stress more. The crack initiation pressure and propagation morphology are analyzed by rock failure process analysis software. The numerical results show that the directional propagation of hydraulic fracturing cracks is possible when the horizontal stress difference coefficient is less than or equal to 0.5 or the slotting deviation angle is less than or equal to 30°. These findings are in good agreement with experimental results, which support the accuracy and reliability of the proposed method and theory.

中文翻译：

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基于非均匀孔隙压力场的定向水力压裂裂缝扩展控制研究

用于开发深埋煤层的水力压裂技术面临与高初始压力和对裂缝扩展方向的有限控制相关的常规问题。提出了一种在非均匀孔隙压力场中基于水力开槽的定向水力压裂（DHF）新方法。力学模型用于解决非均匀孔隙压力场中的裂纹萌生和扩展问题，其中裂纹倾向于破裂并向高孔隙压力区域扩展，以进一步降低有效岩石应力。通过岩石破坏过程分析软件对裂纹起裂压力和扩展形态进行分析。数值结果表明，当水平应力差系数小于等于0时，水力压裂裂缝有可能定向扩展。5或开槽偏差角≤30°。这些发现与实验结果非常吻合，支持了所提出方法和理论的准确性和可靠性。