Near-wellbore rock fracture is a key subject in subsurface energy extraction. Casing perforation completion is perhaps the most used type of well design mainly in comparison to the open hole completion. However, the effects of the combined casing-cementing-rock structure on pressure transmission in fracturing the rock have not been sufficiently addressed, but is key to understanding some important phenomena in hydraulic fracturing, such as fracture tortuosity. Here we develop a combined analytical-numerical model to investigate the rock fracture mechanism near the wellbore with realistic consideration of the boundary condition imposed by the complete well system. Different well configurations can lead to variation in the pressure applied on the rock formation and hence affect the fracture propagation near the wellbore. Our results show, as the pressure transmission through the well structure is enhanced, the fracture propagates more closely to the perforation orientation with a smaller deflection angle and the breakdown pressure is increased. The near-well tortuosity of the crack can be reduced by decreasing the thickness of casing and cement sheath, reducing Young's modulus of casing and increasing Young's modulus of cement up to around 15 GPa, based on the realistic range of values of the well parameters. The effects of in-situ stress condition and perforation angle and length on the near-well cracking are also investigated. The developed model can be used to aid decision making in terms of improved understanding of hydraulic fracturing technology and well design optimization.

近井筒岩石断裂是地下能量提取的重点课题。与裸眼完井相比，套管射孔完井可能是最常用的井设计类型。然而，套管-固井-岩石组合结构对岩石压裂中压力传递的影响尚未得到充分解决，但对于理解水力压裂中的一些重要现象（如裂缝曲折）至关重要。在这里，我们开发了一个组合解析数值模型来研究井筒附近的岩石破裂机制实际考虑完整井系统施加的边界条件。不同的井配置会导致施加在岩层上的压力发生变化，从而影响井筒附近的裂缝扩展。我们的研究结果表明，随着通过井结构的压力传递增强，裂缝更接近于射孔方向，偏转角更小，破坏压力增加。减小套管和水泥环的厚度可以减少裂缝的近井曲折度，减少根据井参数的实际值范围，套管的杨氏模量和水泥的杨氏模量增加到 15 GPa 左右。还研究了地应力条件、射孔角度和长度对近井开裂的影响。开发的模型可用于辅助决策，以提高对水力压裂技术的理解和油井设计优化。