Analysis of stress change and permeability variations caused by rock failure is much interest in geothermal reservoir. Cold water injection into the reservoir can cause significant change of pore pressure, temperature, and the stress state in the hot reservoir which in turn impact rock permeability. Analysis of this process is useful in designing geothermal reservoirs. In view of the complexity of the process, numerical modeling is generally necessary. In this paper, we present a three-dimensional fully-coupled thermo-poro-mechanical finite element model with damage mechanics to simulate reservoir stimulation by hydraulic fracturing. The model considers stress-dependent permeability, and convective heat transport in the thermo-poroelastic formulation. Rock damage is reflected in the alteration of elastic modulus and permeability. A series of numerical experiments have been carried out to study the impact of cold water injection on the reservoir. Results show different patterns of damage localization around the wellbore and its propagation into the reservoir under different stress regime. In addition to the geometry of the stimulated zone, locations of potential induced-seismicity caused by injection are calculated, and show qualitative agreement observations in the field. The model provides a useful tool for the analysis of stress induced micro-seismicity and fracture propagations in geothermal and petroleum reservoirs.

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