Present challenge and prospects of drilling and hydraulic fracturing technology for hot dry rock geothermal reservoir

Abstract

The hot dry rock geothermal energy is one kind of the clean energies which are contained in the China National Energy Strategy. This strategy is to encourage the development of the green and clean energy instead of the fossil energy. In the development of hot dry rock (HDR), the artificial geothermal reservoir is built through drilling and hydraulic fracturing. Two wells are drilled and connected by hydraulic fractures. Then, the geothermal energy can be extracted by the water circulation. The cold water is injected into one of the two wells and flowed along with the hydraulic fractures. The water becomes gas when it contacts the formation rock because of the high temperature. The phase change since the temperature and pressure are reduced at the wellhead of the another well can provide power to generate electricity. Therefore, the key technology to build artificial geothermal reservoir is drilling and hydraulic fracturing. However, there is few experiences in drilling and hydraulic fracturing in the HDR in China. This paper summarized and analyzed the research and field cases around the world to investigate the challenges and key points during drilling and hydraulic fracturing in the HDR. The investigation was based on geology condition, rock physics and chemistry, and field operation during the HDR development. The summary provided the common problems and experience of the drilling and hydraulic fracturing. In addition, the further research directions of related technologies were expounded. Finally, this paper could be referenced for the drilling and hydraulic fracturing in the development of HDR in China for effective utilization.