Simulating three dimensional thermal cracking with TOUGH-FEMM

Temperature change often generates thermal stress, which leads to crack propagation in rocks. In this paper, the TOUGH-FEMM simulator, which links the TOUGH2 thermal-hydraulic simulator and a mechanical simulator based on hybrid the finite-element meshfree method (FEMM), is developed to model three-dimensional cracking induced by thermal stress. The temperature distribution is solved using TOUGH2, which is an established software for modeling fluid flow and heat transfer in porous and fractured media. The thermal stress, mechanical deformation and cracking simulated with FEMM does not require any remeshing during cracking simulation, which greatly reduces the complexity and computational cost. Three benchmark examples are carried out to verify and validate the performance of the TOUGH-FEMM simulator, including thermal-mechanical stress under steady-state heat transfer, transient heat transfer and single crack propagation influenced by a heat source. Finally, the TOUGH-FEMM simulator is applied to model propagation of multiple cracks during cryogenic (low temperature) fracturing, in which the numerical results provide an effective prediction of fracture distribution after thermal cooling shock.