Modern geoscience challenges motivate the development of advanced simulation methods for large-scale geothermal fields, where single- or multi-phase flow is coupled with heat transfer equation in heterogeneous fractured formations. The state-of-the-art multiscale formulation for fractured media (F-AMS; Tene et al., JCP, 2016) develops an efficient approach for flow equation only.

Here, for the first time, the F-AMS formulation is extended to coupled flow-heat equations arising from single-phase flow in fractured geothermal reservoirs. To this end, the multiscale operator is obtained based on elliptic basis functions for both pressure and temperature, to preserve the simplicity and efficiency of the method. ILU(0) 2nd stage smoother is then used to guarantee convergence to any desired accuracy. Numerical results are presented to systematically analyse our multiscale approximate solutions compared with the fine scale ones for many challenging cases, including the outcrop-based geological fractured field. These results show that the developed multiscale formulation casts a promising framework for the real-field enhanced geothermal formations.