A global review of deep geothermal energy exploration: from a view of rock mechanics and engineering

Abstract

Deep geothermal energy exploitation has gained a lot of attentions in energy field due to its large reserve. Enhanced geothermal system (EGS) is the only one mode to explore hot dry rock (HDR) with real engineering practice throughout the world. To date, it is also a topic facing several key issues among sustainable and renewable energies because no commercialized mode has been made. Rock plays an important role in deep geothermal energy exploitation because it is not only a carrier of heat energy but also provides artificial paths for heat exchange after stimulation. There are some practices and researches about rock drilling, stimulation and stability of fractures in deep geothermal engineering. This paper collected the results of the previous deep geothermal exploitation researches that relate to rock mechanics and engineering and summarized the experiences and lessons of deep geothermal energy exploitation from literatures. Some new thoughts like the mode based on EGS and pipe were also collected. Finally, the knowledge about deep geothermal energy exploitation has been derived. Despite of many works on HDR, some key issues still face challenges and need breakthrough. Therefore, deficiencies and prospection in future research were pointed out. The review results showed that the evolution and mechanism of HDR such as weathering, damage, cracking, failure and stability under multi-field coupling with the interaction of fluid is an important issue to be further studied and addressed.