3D Numerical Simulation Study of Brazilian Splitting in Calcite Vein-bearing Shale Based on CT Scans

Shale affects reservoir fracture sprouting and expansion during fracture modification. The aim of this study was to investigate the influence of calcite veins with distinct flaw inclinations on the stretch strength and destruction pattern of shale. In the text, we reconstructed 3D numerical models of shale with seven groups of different calcite vein inclinations using CT scanning of shale specimens from the Niutitang Formation in the Feng’gang No. 3 block in the northern part of Guizhou Province and performed Brazilian splitting simulation tests. Research shows the effect of the calcite vein angle on the ultimate tensile strength and damage mode of shale, and the damage modes mainly include tensile damage, tensile-shear damage, pressure-shear damage and compression damage. Calcite veins have a significant structural effect on the tensile strength of shale. Due to the change in calcite vein inclination, the stress decomposition on the specimen acts on the positive and shear stresses along the calcite vein direction changes significantly, which results in a large difference in the splitting stress between calcite veins and shale matrix when destabilization damage occurs. The research efforts have a key impact on the crack mechanism of shale hydraulic fracturing, fracture expansion law and the improvement of shale gas recovery rate.