关键词: 暂堵转向, 页岩压裂, 裂缝扩展, 转向机理

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