Experimental study of hydraulic fracturing in interlayered lacustrine shales using physical models

The mechanical property distribution and hydraulic fracturing behavior of Jurassic lacustrine shales in the Sichuan Basin remain poorly understood, and systematic experimental research is still lacking. This study integrates high-resolution continuous scratch and impulse hammer tests to characterize the spatial variations in key mechanical properties (uniaxial compressive strength and Young’s modulus) between the shale matrix and three representative interlayer types (shell, sandy, and argillaceous interlayers). Based on the experimental data, we developed mechanically similar physical-model materials and established reliable similarity relationships between the prototype shale and model materials, enabling the development of layered physical models that reproduce both interlayer architecture and mechanical response. The physical simulation experiments of true triaxial hydraulic fracturing were subsequently conducted, revealing clear differences in fracture distribution and propagation patterns depending on the interlayer type. Furthermore, based on Mohr circle and tensile strength parameters obtained from variable confining pressure triaxial compression tests, the study elucidates the mechanism by which interlayers control hydraulic fracture propagation and its complexity. The results provide an experimental basis for improving fracture network control and enhancing hydraulic fracturing efficiency in lacustrine shale reservoirs.