ABSTRACT:

Geothermal energy has received significant attention because of its potential as the long-term sustainable energy resource. However, enhanced or engineered geothermal system (EGS) cannot currently compete with other commonly used forms of energy economically, such as oil and gas, despite the substantial progress made in laboratory, modeling and field tests. There is a great need for further research before EGS becomes viable as a primary energy resource. It is a must to better understand the thermal-hydraulic- mechanical (THM) processes where complex heat transfer, multiphase flow, and rock deformation interactions are involved. A simulator of coupling thermal-hydraulic-mechanical process is needed for geothermal reservoirs so that the engineering project can be designed and optimized. In this paper, a methodology of coupling thermal, hydrological, and mechanical processes will be presented. A conventional approach of geomechanics modeling is the finite element method, which gives a continuous displacement field. In this paper, an approach based on discretizing thermo-poro-elastic Navier equation using an integral finite difference method is discussed. This method reduces the computational intensity of modifying the fluid/heat flow simulator and provides a fully coupled methodology for the three strongly interacted processes. Several programs based on this methodology are applied to the simulation cases of geothermal reservoirs, including fracture aperture enhancement, thermal stress impact, and tracer transport in field-scale reservoir. Results are displayed to demonstrate the geomechanics impact on fluid and heat flow in geothermal reservoirs.

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