| Abstract |
With the increasing demand for energy and the increasingly prominent greenhouse effect in recent years, more and more attention has been paid to the development and utilization of new renewable energy sources. Enhanced geothermal systems (EGS) (also known as engineered geothermal systems) are created by fracturing technologies to extract economic quantities of heat from low-permeability and/or low-porosity geothermal resources. The assumption of local thermal equilibrium is often used in the field scale numerical simulations of enhanced geothermal system. There is a few research on the local thermal non-equilibrium effect of heat recovery from fractured reservoir, and moreover the system including injection-production wells, reservoir and power generation cycle. Therefore, based on the correlation of convection heat transfer coefficient in a rock fracture, a local thermal non-equilibrium model of heat extraction process of hot dry rock reservoir is established to accurately describe the heat exchange between fluid and rock. Secondly, the coupling method of reservoir-wellbore flow heat transfer and ground power generation system is proposed, which realizes the integrated optimization design of heat exchange in reservoir and ground heat transfer process. The thermal reservoir of hot dry rock target stratum in Gonghe Basin, Qinghai Province, China is used as the research object. The prediction of water production temperature and system power generation under different circulating flow rates conditions are carried out. The local thermal non-equilibrium effect in the reservoir is analyzed in this paper. Considering the power generation capacity, power generation stability and system resistance, the optimal design of circulating water flow rates is completed under the target reservoir with fractured volume and permeability, and well group model built in this paper. The integrated model of enhanced geothermal system established in this paper can be used for the coulping analysis of heat exchange in reservoir and ground heat conversion in power generation cycle. It realizes the prediction of operation characteristics of enhanced geothermal system and strongly support the optimization of development and utilization scheme. |