A Mineral-Composition Dependent Fracture Numerical Model of Thermally Treated Shale Gas Reservoirs

Thermal treatment of shale gas reservoirs can vaporize water, accelerate gas desorption, and induce micro-fractures in shale matrix, which is a potential method to enhance shale gas productivity. However, few studies are focused on the thermal micro-cracking behavior of shale, especially at the mineral-scale. Furthermore, the effect of mineral composition on micro-fracture generation and shale permeability alternations are not fully understood in the current research results. In this work, a mineral-dependent fracture numerical model of thermally treated shale gas reservoirs is proposed. This model couples thermally induced stress in minerals, permeability enhancement, fluids flow and energy conservations in shale. A novel constitutive model based on volumetric constraint to relate stress and strain of minerals in shale is applied in the numerical simulation process. Comparison to experimental results demonstrates the reliability and robustness of the presented computation model. The proposed simulation method in this work is a powerful tool to link the macro-scale characteristics and thermally induced micro-fracture of shale.