Impact of cold fluid injection on thermally hydraulic fracture propagation in a heterogeneous rock formation

Hydraulic fracturing is extensively used to stimulate oil, gas, and geothermal reservoirs. Traditional analytical and numerical models neglect the thermal effects within the porous medium and consider fracture propagation in homogeneous formations. This work proposes a numerical methodology to investigate the impact of cold fluid injection on thermally induced hydraulic fracture propagation in a heterogenous reservoir. The heterogeneity is idealized as a rock formation with multiple layers, adopting vertical variability. A fully coupled thermo-hydro-mechanical (THM) finite element model was employed. The model incorporates poroelasticity, fluid flow, diffusion/convection heat transfer within the porous rock formation, and thermally fluid-driven fractures under single-phase fluid flow conditions. The model is verified against relevant analytical solutions. The numerical findings highlight the substantial influence of the initial rock temperature, confining stresses, rock permeability, and injection rate on the evolution of pore pressure and fracture geometry growth. The numerical results indicate that increased rock permeability combined with confining stresses accelerate the cooling of rock formations, leading to pore pressure reduction and facilitating fracture development into the barrier layers, which differs from isothermal scenarios. Finally, this study provides valuable insights into the complex hydraulic fracturing process in a heterogeneous formation considering the coupled thermal, hydraulic, and mechanical behaviors.