Hydro-electric effect based experimental study on shale cracking caused by high-strength electric detonation
In order to study the formation of shale due to high-strength electric detonation and the feasibility of reconstructing a shale gas reservoir,the black shale found in the Changning area,Sichuan Basin,China,was selected as the test sample.The test was conducted on a multi-topographic movable high-strength electric detonation test system locally developed for fracturing rock mass.As discharge parameters,voltage of 10 kV to 14 kV and capacitance of 500 μF were preset by oscilloscope system,strain testing system and Keynes VHX-6000 digital microscope system.The shale samples were analyzed under different settings of voltage,cur-rent and strain of the high-strength electric detonation.The morphologies of surface cracks and cross sections were expounded before and after the electric detonation under different settings of discharge parameters.And the mechanism of inducing shale by electric detonation was pre-liminarily revealed.The obtained experimental results show that the shale could obviously be cracked by high-strength electric detonation.The peak current,maximum peak of compressive-tensile strain,and the first and second peaks of strain are positively correlated with the dis-charge voltage.The surface cracks after the high-strength electric detonation mainly include penetrating cracks,radial cracks and orthogonal cracks.The communication between different cracks occurred at 14 kV.And the surface cracks showed good fractal characteristics.After the high-strength electric detonation,the roughness of the cross-section was large.There were more rock debris on the surface,and the shale samples were cracked mainly due to flake,wave,step and other tensile failure.This experimental study could demonstrate the applicabili-ty of the high-strength electric detonation technology in reconstructing a shale gas reservoir based on hydro-electric effect.
shale crackinghydroelectric effecthigh strength electric detonationsurface crackvoltage and currentsurface strain
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