Abstract: Temporary plugging and diverting fracturing technique is an essential way to improve the refracturing fracture network of shale reservoirs. However, there are still some uncertainty factors for this fracturing technique over the influence on fracture propagation of shale hydraulic fracturing. Therefore,based on the indoor true tri⁃axial hydraulic fracturing physical experiment, this paper studied and analyzed the fracture initiation and diversion mechanism under the condition of differential stress and pumping rate. The index of fracture stimulation area (SRA) was utilized to represent the hydraulic fracturing effect quantificationally. The results show that: the temporary plugging agent, practically, could plug the pre⁃fractured fracture till the pressure to a certain value, so as to induce the diverting of hydraulic fracture in the channel from pre⁃fractured fracture or simulate the primary natural fracture network, which improve the complexity of the fracture morphology. Ultimately, there are four patterns of hydraulic fracture including sidestep⁃shaped fracture, transvers fracture with stimulated⁃natural weak discontinuities, simple multi⁃fracture and complicated multi⁃fracture network. The temporary plugging agent would block pre⁃opened natural fractures and stimulate the skewed new fracture when the horizontal differential stress is less than 12 MPa. As the differential stress is higher than 15 MPa, it is hard to simulate the natural fractures and the temporary plugging would block the pre⁃fractured transversal fracture, parallel to which a new fracture formed. Enhancing the fluid pumping rate could improve the activation probability of discontinuities, simultaneously, increase the fracture network complexity.

Key words: Temporary plugging and diverting, Shale fracturing, Fracture morphology, Diverting mechanism

摘要： 暂堵转向压裂是提高页岩储层重复压裂缝网改造效果的重要手段，然而该压裂工艺对页岩水力裂缝扩展规律的影响机理尚不明确。因此，基于室内真三轴压裂物模试验，研究页岩暂堵转向压裂裂缝起裂与扩展规律，分析地应力及注入速率等因素对水力裂缝延伸行为的影响，并通过油藏改造面积(SRA)定量表征暂堵转向压裂缝网改造效果。结果表明，暂堵剂可有效封堵初始裂缝，憋压促使水力裂缝发生缝内转向或激活原生天然裂缝系统，提高页岩缝网复杂程度；根据最终水力裂缝形态展，可划分为4种基本类型，包括台阶状缝、激活天然弱面的横切缝、简单多裂缝以及复杂多裂缝网络；不同地应力差异条件下暂堵机理及裂缝延伸规律不同，当水平应力差小于12 MPa时，暂堵剂通过封堵近井筒初始张开的原生层理或天然裂缝，诱导产生与天然裂缝斜交的二次裂缝，当应力差高于15 MPa时，近井筒天然弱面难以激活，暂堵剂通过封堵垂直井筒的初始横切裂缝，诱发形成平行多横切裂缝；增大注液排量可以提高多裂缝形成几率及裂缝沟通面积。

关键词: 暂堵转向, 页岩压裂, 裂缝扩展, 转向机理