A realistic assessment of recoverable thermal energy from Australian geothermal reservoirs: a simulation study

Abstract

This paper presents an innovative distributed dislocation theory for estimation of change in fracture aperture due fluid induced pressure. The new approach is used to analyze the potential for thermal energy recovery from the Patchawarra geothermal reservoir in Australia. Results of this study show that the time required to stimulate a 500 m2 reservoir rock and sustain commercial flow rate (80 l/s) is much greater (two to three folds) than that previously studied. These results, however, agree well with the experience of existing EGS trials around the world. Thermal stresses induced during the circulation of cold water have a significant bearing on the long term production rate. As thermal drawdown of the rock matrix takes place, tensile thermal stresses are induced which allow residing fractures to dilate and enhance permeability. This gradually increases the fluid velocities between the injector and producer, yielding increasing production rates with time. It was also observed that the maximum thermal energy that can be recovered by use of our current know-how would be as much as 42%.