(1. Key Laboratory of Shale Gas and Geoengineering，Institute of Geology and Geophysics，Chinese Academy of Sciences，Beijing 100029，China；2. College of Earth Sciences，University of Chinese Academy of Sciences，Beijing 100049，China)
Abstract：In order to reveal the influence of cyclic progressive pressure on the fracturing effect of shale，the true triaxial hydraulic fracturing test of shale samples was carried out，and the rupture effects of one-time fracturing and progressive pressure fracturing were compared and analyzed. The experimental results show that：(1) Based on the comparison of fracturing pressure curve，and AE energy curve，one-time fracturing method is prone to produce a single main fracture and generate relative sample hydraulic fracture networks. Progressive fracturing method tends to create multiple fractures and complex networks. (2) Based on the analysis of the AE positioning，the one-time fracturing AE location shows a liner distribution with respect to a single fracture，and cyclic fracturing AE location presents a dense distribution which filled a larger volume of test samples. (3) Based on the comparative analysis of the morphological，quantitative and fractal dimensions of macroscopic cracks，the cyclic progressive method can significantly improve the seam network density and the permeability of test samples，hence optimizes field hydraulic fracturing methods. (4) Based on the extended finite element numerical simulation，the cyclic progressive fracturing method can produce long and devious main fractures and tend to generate more secondary fractures along the main fracture，which can increase the density of fractured seams networks and enhance the effect of volumetric fracturing.
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2019, Vol. 38 
