【摘要】 为了研究不同参数对水力压裂中地层破裂压力和水力裂缝起裂角的影响规律,利用井筒-射孔模型,将射孔简化为裂缝,采用保角映射的方法求得射孔端部的应力强度因子;根据最大拉应力准则求得射孔端部水力裂缝的起裂角和地层破裂压力的理论公式。为了验证该方法的有效性,将理论值与文献中的实验结果和工程实际值进行对比。研究结果表明:理论值与实验结果和工程实际值均吻合较好。水力裂缝的起裂角随主应力差、射孔长度和射孔角度的增大而增大;最优射孔方位角应在0°～15°范围内;最优射孔长度应为井筒直径的2～3倍。更多还原

【Abstract】 In order to study the influences of perforation parameters on break down pressures and hydraulic crack initiation angles, a 2 D model containing perforations and wellbore was established to simplify the perforations as a crack.By conformal mapping techniques, the stress intensity factors at perforation tips were obtained. The theoretical method to calculate break down pressure and initiation angle was acquired according to the maximum tensile failure criterion. For validating the theoretical solutions, the experimental results and the in-situ test results were compared with the calculated results. The results show that they are in good agreement. The hydraulic crack initiation angles increase with the increase of two principal stresses, the perforation lengths and the perforation azimuths. The optimal perforation azimuth is between 0° to 15° with the major principal stress. The optimal perforation length is between 2 and 3 times wellbore diameter.更多还原