大尺寸真三轴页岩水平井水力压裂物理模拟试验与裂缝延伸规律分析

采用真三轴物理模型试验机、水力压裂伺服系统、声发射定位系统以及压裂液中添加示踪剂等方式，在真三轴条件下对大尺寸页岩水平井进行了水力压裂物理模拟试验，通过裂缝的动态监测和压裂后剖切等分析了裂缝的扩展规律，并对页岩压裂缝网的形成机制进行了初步探讨。结果表明：（1）水力裂缝自割缝处起裂并扩展、压开或贯穿层理面，形成相对较复杂的裂缝形态；（2）裂缝中既有垂直于层理面的新生水力主裂缝，又有沿弱层理面扩展延伸的次级裂缝，形成了纵向和横向裂缝并存的裂缝网络；（3）水力裂缝在延伸过程中会发生转向而逐渐垂直最小主应力；（4）水力裂缝在扩展过程中遇到弱层理面时的止裂、分叉、穿过和转向现象是形成页岩储层复杂裂缝网络的主要原因，而弱结构面的大量存在是形成复杂裂缝的基础。其研究结果可为页岩气藏水平井分段压裂开采等提供有力技术支持。

Hydraulic fracture propagation of shale horizontal well by large-scale true triaxial physical simulation test

Based on true triaxial simulation experimental system, servo control system of hydraulic fracturing equipment and tracer technique, a large-scale true triaxial physical simulation test on hydraulic fracturing of shale horizontal well is conducted. The extension of the hydraulic fractures is analyzed by dynamically monitoring of fractures and sectioning the fractured specimen. The formation mechanism of fracture network is discussed. The results indicate that: (1) A relatively complex fracture morphology is formed due to the hydraulic fractures extending along and perpendicular to the bedding planes after initiation. (2) The fracture network which contains longitudinal and transverse fractures is formed in hydraulic fracturing of shale specimens. Main hydraulic fractures perpendicular to the bedding plane and secondary fractures extending along the week bedding plane all exist in the fracture network. (3) Hydraulic fractures will gradually turn to the direction perpendicular to the minimum principal stress in extension. (4) Arresting, branching, penetrating and re-orientation of hydraulic fractures in bedding planes are the main reason for the formation of complex fracture network of shale gas reservoir. The existance of the weak structural planes is the foundation of the forming of complex fracture morphology. The results can provide technical supports for staged exploitation of horizontal well of shale gas reservoir.