长沙某地区同轴套管式中深层地热试验井换热及恢复性能研究

Research on heat transfer and recovery performance of a coaxial casing-type medium-depth geothermal test well in Changsha

在能源结构亟待转型背景下,中深层地热资源展现出了极大优势和开发潜力,但地热资源受地域差异性影响较大,实测研究相对匮乏,给产业规模化应用带来了阻力。本文针对中南地区中深层地热实测研究空缺现实情况,首次基于长沙地区中深层地热试验井,通过分布式光纤实时监测和换热试验测试,探索该区中深层地热资源情况、换热性能和地温恢复能力。试验结果表明:该区中深层地热资源具有良好开发潜力,井底2611m温度达82.8℃,全井平均地温梯度为2.47℃/100m,试验期稳定换热功率达到534.7kW;循环流量与地埋管换热功率呈正相关,与工质温升呈负相关;井温恢复呈现初期快后期慢特点,前24h完成50%的温度恢复量,纵向深度呈现深处快浅处慢的情形,井底温度完全恢复时,300m深处温度仅恢复至初始工况74.6%;与北方高异常区资源禀赋对比,长沙地区中深层地热条件仍处于劣势。

In the context of urgent transformation of energy structure,the medium and deep geothermal resources have shown great advantages and development potential,but the geothermal resources are greatly affected by regional differences,and the measured research is relatively scarce,which brings resistance to industrial scale application.In this paper,based on the actual situation of middle-deep geothermal field research in central and southern China,for the first time,based on the middle-deep geothermal test well in Changsha area,through distributed optical fiber real-time monitoring and heat transfer test,to explore the middle-deep geothermal resources,heat transfer performance and geothermal recovery ability in this area.The test results show that the middle and deep geothermal in this area has good development potential;the temperature at the bottom of the well is 82.8℃at 2611m in depth,the average geothermal gradient of the whole well is 2.47℃/100m,and the stable heat transfer power during the test period is 534.7kW;the circulating flow is positively correlated with the heat transfer power of the buried pipe,and negatively correlated with the temperature rise of the working medium;in the first 24 hours,50%of the temperature recovery is completed,and the longitudinal depth is fast in the deep and slow in the shallow;when the bottom hole temperature is fully recovered,the temperature at 300m depth only recovers to 74.6%of the initial operating condition;compared with the resource endowment in the northern high anomaly area,the medium and deep geothermal conditions in Changsha area are still at a disadvantage.