Study on the complexity of hydraulic fractures in shale reservoirs of a continental rift basin in Eastern China

To address the unclear effects of varying vertical stress differentials, fracturing fluid viscosity, and pump rates on fracture propagation morphology and complexity in lamellar shale reservoirs in a continental rift basin in eastern China, this study utilizes the core samples from the Shahejie Formation, designing sample preparation based on the development characteristics of lamination. A series of small-scale true triaxial hydraulic fracturing experiments were conducted, along with staged flow rate tests on post-fracturing samples. By fitting the relationship between pump rates and pressure during various testing stages, a method for quantifying fracture complexity was established. Results indicate that higher vertical stress differentials and treatment scales promote the vertical propagation of fractures across the laminated layers, but may lead to the formation of a single longitudinal fracture. In contrast, higher lamination densities near the initial fracturing point of rock samples facilitate fracture deflection and branching, making it a primary factor influencing fracture complexity. This research offers new guidance for optimizing layer selection and treatment parameters in hydraulic fracturing of organic-rich laminated shale reservoirs.