Numerical Investigation of Thermally Induced Fracturing via Endothermic Thermal Shock in Ultratight High-Temperature...

Hydraulic fracturing operation in ultratight gas reservoirs under high temperature has often proved inadequate due to large fluid requirements, limited fracture propagation, and rapid production decline. This study proposes and evaluates a novel cooling-driven stimulation technique in which an externally heated rock is subjected to rapid thermal shock through the injection of endothermic chemicals. Unlike conventional thermochemical fracturing methods that rely on heat generation and pressure buildup, the proposed approach utilizes rapid heat extraction to induce tensile stresses, fracture initiation, and enhanced reservoir connectivity. Laboratory-scale experiments were conducted on tight sandstone and shale samples, confirming the mechanical degradation and microcrack development due to thermally induced tensile stresses. These findings were integrated into a finite element model using the concrete damage plasticity (CDP) in ABAQUS to simulate fracture development. The resulting fracture morphologies were subsequently incorporated into a field-scale compositional reservoir model in CMG-GEM to evaluate long-term production performance. The simulation study investigates the impact of the thermal shock treatment on production performance across five different scenarios: (i) unstimulated, (ii) single-stage hydraulically fractured, (iii) multistage hydraulic fractures, (iv) thermochemical fractures with limited complexity, and (v) thermochemically fractured with high complexity. The results demonstrate that thermochemical stimulation significantly enhances fracture complexity, stimulated reservoir volume, and gas recovery. The cumulative gas production and the recovery factor were found to be enhanced by approximately 1.6 times with thermochemical stimulation as compared to the multistage hydraulic fracture case. The high-complexity thermochemical case achieved the highest production rate and recovery factor, outperforming conventional methods throughout the simulation period. These findings demonstrate the viability of thermally induced fracturing via endothermic reactions as a promising and efficient stimulation method for enhancing gas recovery in ultratight formations.