A fully coupled thermo-hydro-mechanical, three-dimensional model for hydraulic stimulation treatments

Abstract In this study, we developed a fully coupled thermo-hydro-mechanical (THM), three-dimensional model to simulate hydraulic fracturing (HF) treatments. Using the pseudo-continuum approach, we extended the classical THM constitutive equation into an anisotropic formulation for the purpose of capturing the effects of fracture sets. Consequently, the dynamic process of fracturing propagation can be modeled for both tensile and shear failures. The fluid flow terms with tensor permeability, or heat transfer terms with tensor conductivity, are calculated using the Multi Point Flux Approximation (MPFA) L-method. The model is capable of predicting the detailed permeability distribution within the stimulated reservoir volume (SRV), while also considering the fluid leak-off and thermal stresses. To verify the developed THM code, we compared its numerical solutions with some other reliable solutions in several benchmark cases. Specifically, the dynamic fracturing propagation modeling is verified by the KGD model. Finally, the code is used to investigate the complicated multi-physical HF processes. The results show that the geometry of hydraulic fractures is affected by the following factors: in-situ stress, anisotropic permeability, heterogeneity, thermal stress, shear failure, and the stress shadow effect, not all of which can be considered with the conventional HF models due to the over-simplification employed.