GEOTHERMAL ENERGY PRODUCTION FROM HETEROGENEOUS RESERVOIRS

With the globalisation of the world, energy conservation has become one of the essential topics to investigate; geothermal energy storage is one of the ways for energy conservation, which uses aquifers for low-grade thermal energy like solar heat and waste heat storage during the seasons in which we do not have much use of them, like in summers, storing heat and vice-versa during the summers (Meyer and Todd, 1973). Moreover, recognised as equitably carbon-free, geothermal energy ensures renewable potentiality, establishing its importance for an ethical and sustainable production model for the forthcoming future, resulting in the extinction of fossil fuels at an accelerated rate. Therefore, there is a need to develop solutions to cope with energy demands at a global rate. This work aims to discuss in-depth about advancing the results of the research achieved in the past and enhancing the recovery efficiencies of the geothermal systems, evaluating the opportunities and obstacles presented concerning the coupled system. While analysing the previous research works supporting the foundation of this thesis, highlighting the fact that the preliminary investigations either focus primarily on energy storage or geothermal energy production (e.g., doublet system), often overlooking or paying less attention to the result of combining the two practices mentioned above for further possibilities. The modelling was conducted using an advanced finite element framework for heat transfer and Darcy's law in 3D. Over the last decade, several heat transfer and flow models have come into existence. The above-stated models being used for advancing knowledge in geothermal energy extraction from subsurface aquifers (e.g., Willems & Nick, 2019; Babaei & Nick, 2019; Daniilidis et al., 2021) and underground heat storage (e.g., Zeghici et al., 2015), among others. To properly evaluate the opportunities and obstacles presented regarding the coupled system, two main scenarios are made to gauge the efficiency of the combined model compared with the two separate systems. For this evaluation, performance matrices, including project lifetime, energy production and coefficient of performance (CoP), are formed. These are used for comparing the two scenarios for various operational and geological conditions. The primary outcome of this research is expected to enhance knowledge of geothermal energy production and whether the proposed combined method will be proven helpful to improve geothermal production. In addition, this thesis will report the conditions under which the proposed methodology outperforms the conventional systems. It was concluded that the lifetime, CoP, and net energy of the project were enhanced for the coupled system in comparison to the 3D doublet system. When the effect of heterogeneity was taken into consideration, the lifetime of the project outperforms the homogeneous coupled system.