A simplified coupled hydro-thermal model for enhanced geothermal systems

The modelling of fluid flow and heat transfer under coupled conditions remains a challenging issue particularly for industrial-scale enhanced geothermal systems. This paper proposes a simplified approach to model the coupled hydro-thermal system for hot dry rock geothermal applications. The simplified heat exchange model is based on the first principle of heat exchange between two media (fluid and rock) and Newton's law of cooling so that it simplifies significantly the modelling process that otherwise requires the solution of a complex coupled system. The proposed approach has been implemented in an in-house geothermal simulation system that is based on an equivalent pipe network model. The approach is validated against detailed prediction of fluid flow and heat transfer in a public domain fracture network using finite volume based ANSYS/CFX results. It is then applied to modelling heat extraction from the Geodynamics Habanero reservoir in the Cooper Basin, South Australia. The application demonstrates that the proposed approach is an efficient and effective means of modelling heat transfer in industrial-scale EGS reservoirs.