To efficiently develop hot dry rock and other geothermal energy, a multilateral butted closed loop geothermal system (MBCLGS) is presented in this paper to replace the U-shaped closed-loop geothermal system (UCLGS). Besides, a casing-cement-formation transient heat transfer model is established to investigate the influences of key factors on the heat production of MBCLGS. After thermal-fluid-structural coupling analysis, we can find that higher injected rate and lower fluid temperature can improve heat power but reduce output temperature. In addition, the output temperature and heat power do not increase continuously with the increasing of branch well number. There is an optimal value of branch well number. Longer well pair distance can improve both output temperature and heat power. Considering the drilling technology level and design purpose, the recommended injected flow rate of MBCLGS is 90 m3/h, the injected fluid temperature is 42.5 °C, the number of branch wells is 10 and the well pair distance is 200m. Finally, by comparing MBCLGS and UCLGS, it is found that MBCLGS has a lower temperature decline rate and higher output temperature than UCLGS under the same conditions. It works more stable and has better economy. Overall, the proposal of MBCLGS is expected to promote the efficient development of deep geothermal resources.

中文翻译：

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设计参数对多边对接闭环地热系统产热量的影响


为了有效开发干热岩和其他地热能，本文提出了多边对接闭环地热系统（MBCLGS）来替代U形闭环地热系统（UCLGS）。此外，还建立了套管-水泥-地层瞬态传热模型，研究关键因素对MBCLGS产热的影响。经过热-流-固耦合分析，我们可以发现较高的注入量和较低的流体温度可以提高热功率但降低输出温度。另外，输出温度和热功率并不随着分支井数量的增加而持续增加。分支井数存在一个最优值。较长的井对距离可以提高输出温度和热功率。考虑到钻井技术水平和设计目的，MBCLGS推荐注入流量为90 m3/h，注入液温度为42.5 ℃，分支井数量为10口，井对距离为200 m。最后通过对比MBCLGS和UCLGS发现，同等条件下MBCLGS比UCLGS具有更低的温降率和更高的输出温度。工作更稳定，经济性更好。总体而言，MBCLGS的提出有望促进深层地热资源的高效开发。