Experimental Measurements of Shale Fracture Conductivity Under Cyclic Loading
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Existing research on shale fracture conductivity is rather sparse and has not taken the effect of loading history into consideration. A splitting device was used to split the shale specimens along bedding, and a 3D scanner was used to characterize the fracture surface. Using a constant 0.3 MPa gas pressure, three shale specimens split by single fractures of different roughness were tested for gas flow during four loading–unloading cycles of 0–10 MPa. Test results show that fracture conductivity exhibited hysteresis similar to that observed in rock mechanics experiments. In addition, it is clear that fracture conductivity is smaller for fractures with rougher surfaces. Building on the cubic law and soil mechanics consolidation theory, a hydraulic aperture model for cyclic loading was developed that helps explain the influence of plastic deformation during loading and unloading on fracture conductivity. This model exhibited trends get the agreement with the data for the range of confining stresses used in the experiments.
KeywordsShale fracture conductivity Cyclic loading Surface roughness Hydraulic aperture model
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