Fluid flow-induced deformation dynamics under biaxial loading in anisotropic (layered) analogues of unconventional reservoirs: insights from physical model experiments and numerical simulations.

Understanding fluid-driven fracture propagation in anisotropic, layered geological formations is critical for optimizing resource recovery in unconventional reservoirs. In this study, we present a novel experimental and numerical investigation into fluid flow-induced deformation dynamics under biaxial loading using analogue models of shale and reservoir rock. A custom-designed low-pressure biaxial compression system is developed to simulate realistic subsurface conditions while allowing real-time, high-resolution visualization of fracture evolution in low-modulus elastic and viscoelastic materials. Gelatin-based analogues, representing both isotropic and anisotropic formations, are employed to mimic geological heterogeneity and elasticity. Fracturing experiments are conducted using water, SAE 140 oil, and oil-toluene mixtures injected at a constant rate of 1 ml/min under controlled loading conditions (confining load: 1.23 bar; top load: 0.52 bar). The evolving fracture geometries are analysed using ImageJ, focusing on metrics such as aspect ratio and fracture length. Numerical simulations based on a phase field damage model are performed to predict fracture initiation and propagation, showing strong agreement with experimental results and qualitative consistency with the analytical Khristianovic-Geertsma-de Klerk (KGD) model. Our integrated approach provides critical insights into the role of fluid viscosity, heterogeneity and loading conditions on fracture dynamics. The experimental setup also supports studies relevant to CO₂ sequestration and gas hydrate dissociation. This work advances the mechanistic understanding of fracture processes in layered formations, offering insights for field-scale hydraulic fracturing and sustainable subsurface resource management.