实现页岩气经济效益开发的关键是采用水力压裂技术形成复杂的压裂缝，增大储层有效改造范围。深部页岩储层埋深大于3 500 m，针对深层页岩高应力下压缝裂成缝不明的技术难题，采用多相流压裂试验系统模拟高三向地应力特征进行水力压裂试验，获得了不同应力状态下压裂缝扩展特征，研究表明：深层高应力绝对值、垂向地应力差10 MPa以内，主水力裂缝扩展遇到层理弱面可以沟通及转向扩展；相同垂向地应力差10 MPa，两向水平地应力差在10 MPa以内，垂直井筒起裂的主水力裂缝亦可沟通垂直于水平最大主应力方向的天然弱面缝，形成较为复杂的裂缝特征；页岩内部天然裂缝或层理弱面发育是形成复杂压裂缝的物质基础，如无天然弱结构特征，压裂后形成的均为单一压裂缝面；高地应力条件下形成的主水力压裂缝粗糙度分形维数在2.422~2.484，各应力状态下差异不大，但天然弱面缝粗糙度低于主水力裂缝。试验研究成果对认识深部高应力环境下页岩压裂缝形成过程具有一定的指导意义。

The key to achieving the economic benefits of shale gas development is to use fracturing technology to form complex fractures and increase the effective range of reservoir transformation. The buried depth of deep shale reservoirs is greater than 3 500 m. In response to the technical challenges of shale fracturing under high stress, a multiphase flow fracturing test system was used to simulate the characteristics of high triaxial stress for hydraulic fracturing tests. The characteristics of fracturing propagation under different stress states were obtained. The research shows that the absolute value of high stress and the vertical stress difference are within 10 MPa, and the main hydraulic fractures can communicate and turn to expand when encountering weak bedding planes. The vertical stress difference is 10 MPa, and the horizontal stress difference is within 10 MPa. The main hydraulic fractures that initiate vertical wellbore fractures can also communicate with natural weak surface fractures perpendicular to the direction of the maximum horizontal principal stress, forming more complex fracture characteristics. The development of natural fractures or weak bedding planes within shale is the material basis for the formation of complex fracturing fractures. If there are no natural weak structural features, the fractures formed after fracturing are all single fracturing fracture surfaces. The fractal dimension of the roughness of the main fracturing fractures under high stress ranges from 2.422 to 2.484, with little difference among different stress states. However, the roughness of natural weak surface fractures is lower than that of the main fracturing fractures. The research results have certain guiding significance for understanding the formation process of shale fractures under high stress state.