With the gradual depletion of hydrocarbons (oil and natural gas) in shallow reservoirs, the exploration and exploitation of deep underground reservoirs has become a necessity to ensure an adequate energy supply for the society. The deep reservoirs are characterized by high in situ stress and relatively high temperature. In this work, we propose a thermo-hydro-mechanical (THM) coupled phase-field model and verify its accuracy with benchmarks. The effects of in situ stress and temperature are taken into consideration. A staggered scheme and a fixed stress-split method are employed to solve the coupled THM equations. Simulations of hydraulic fracturing on single injection well models, and then multi-well models are implemented in the open-source FEM package OpenGeoSys. On single injection well models, the hydraulic crack grows longer when a higher in situ stress difference (difference between the maximum horizontal stress and the minimum horizontal stress) is applied. The effect of temperature is mainly reflected on the hydraulic crack characters such as length and width. Numerical results from multi-perforation models show that the heterogeneous pressure induced by depleted production wells can affect the hydraulic crack growth path, causing limited hydraulic crack length. Meanwhile, the simultaneous fracturing of multiple perforations results in competition and suppression of crack propagation between adjacent perforations.