Dynamic tensile strength and fracture evolution of characteristic shale with bedding and hole using linear regression theory

Abstract

In methane in situ explosion fracturing technology, it is critical to investigate the effects of bedding characteristics and perforation holes on the dynamic mechanical properties and fracture behavior of shale reservoirs. Dynamic Brazilian splitting experiments were conducted to investigate the effects of the bedding angle and the central aperture on the dynamic mechanical properties and fracture behavior of shale disc samples with a central hole using a modified split Hopkinson pressure bar device, a three-dimensional digital image correlation system, and high-speed photography. Multiple regression analysis was used to evaluate the influence on the dynamic tensile strength, while fracture evolution characteristics, including area and morphology, were selected to quantify fracture complexity. The results showed that the bedding angle exerted a more pronounced effect on the tensile strength compared to the central aperture, and increasing impact pressure amplified both effects. Tensile fractures predominated across varying bedding angles, while larger central apertures promoted shear fracture formation. The bedding plane facilitated the expansion of shear fractures in its direction, while the central hole primarily guided fracture propagation along the bedding plane. Fracture initiation occurred at the central hole's edge, with subsequent propagation influenced by both the bedding angle and the central aperture. Higher impact pressures resulted in a significant increase in the fracture area, with 90° bedding and larger apertures (8 and 10 mm) resulting in larger areas. These findings provide essential theoretical guidance for constructing efficient shale reservoir fracture networks in methane in situ explosion fracturing, particularly for applications in deep shale formations.

Keywords

3D-DIC / dynamic tensile strength / fracture evolution characteristics / m-SHPB / multiple regression analysis method

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