U型井开发干热岩井筒温度场研究

干热岩开发主要采用水力压裂的方式，而以U型井方法取代固有开发模式，具有减少水损、提高能量衰减周期，避免诱发地震等显著优势。因此，建立了U型井井筒和干热岩储层非稳态流动传热耦合模型，采用有限体积法结合Crank-Nicolson全隐式格式进行离散求解，并通过地热井数据验证了模型的可靠性。研究了干热岩开采过程中井筒及地层的温度变化特征，定量分析不同的敏感性因素对出口温度的影响，利用正交试验法明确影响取热量大小的因素排列。结果表明：各个因素的大小对出口温度影响明显，而影响取热量的因素由主到次为注入流量、水损率、岩石导热系数、水平段长度、入口温度、井筒直径。研究成果进一步完善了干热岩高效热提取理论，可为我国干热岩地热能的开发利用提供借鉴作用。

Study on temperature field of U-shaped well for developing dry hot rock

At present, the development of dry hot rock mainly adopts hydraulic fracturing, and the U-shaped well method replaces the inherent development mode, which has the obvious advantages of reducing water loss, improving energy attenuation period and avoiding induced earthquakes. Therefore, a coupling model of unsteady flow and heat transfer between u-shaped wellbore and dry hot rock reservoir was established. Finite volume method and Crank-Nicolson fully implicit scheme were used for discrete solution, and the reliability of the model was verified by geothermal well data. The temperature variation characteristics of wellbore and stratum in the process of dry hot rock mining are studied, the influence of different sensitivity factors on outlet temperature is quantitatively analyzed, and the factors that affect the amount of heat taken are determined by orthogonal test method. The results show that the size of each factor has a significant effect on outlet temperature, and the factors affecting heat extraction from primary to secondary order are: injection flow rate, water loss rate, rock thermal conductivity, horizontal section length, inlet temperature, wellbore diameter. The research results further improve the efficient thermal extraction theory of hot dry rock, which can provide reference for the development and utilization of geothermal energy from hot dry rock in China.