A discrete element approach for simulating progressive fracturing in geothermal reservoirs via a new cohesive crack model

In fractured geothermal energy storage systems, repeated heating and cooling cycles and fluid interactions cause non-linear and non-monotonic fracture deformations, requiring sophisticated modeling of complex thermo-hydro-mechanical (THM) behaviors. This paper proposes a new cohesive crack model for the discrete element method (DEM), aiming to enhance the characterization of the entire fracturing process in rocks during loading–unloading-reloading while considering thermo-hydraulic conditions. Specifically, the model proposed allows for flexible adjustment of post-peak tension behavior and is able to capture the progressive evolution of fracture opening and closing under cyclic THM loadings. Validation of the new model was performed under a range of thermo-hydraulic conditions, confirming its ability to replicate diverse fracture behaviors, and offering a comprehensive solution to modeling the complex interplay of thermal, hydraulic, and mechanical factors influencing rock fractures in the context of geothermal energy storage and extraction systems.