深井换热技术是目前公认最环保的地热能开发利用技术,以同轴套管换热井最常见,取热能力和影响半径是这一技术推广过程中存在争议且急需解决的问题.以西安草滩2 500 m深同轴套管换热井为研究对象,基于实测地层温度和围岩热物性参数,通过原位测试及数值模拟技术,分析换热井的取热能力,探讨换热过程中围岩地层温度变化特征及范围.结果表明:目标换热井30年可持续取热功率可达350 kW,平均延米140 W/m;围岩地温衰减程度和范围随着取热功率增大而增大;换热井不同深度热影响半径不同,深部地层整体大于浅部,350 kW取热功率下取热30年最大热影响半径可达110 m.
Heat Extraction Capacity and Heat-affected Radius of Deep Coaxial Borehole Exchanger in Xi'an
Deep-borehole heat exchangers(DBHE)is currently recognized as the most environmentally friendly way to exploit geo-thermal energy.The deep coaxial borehole heat exchanger is the most common type of DBHE.Heat extraction capacity and influence radius are the controversial problems in the process of popularizing this technology.Based on the measured parameters of ground tem-perature and thermophysical properties,the heat extraction capacity and influence radius of the 2 500 m deep coaxial borehole heat ex-changer were analyzed by the way of in-situ test and numerical simulation in Caotan area of Xi'an.The results show that the sustainable heat extraction power of the heat exchange well in 30 years can reach 350 kW,with an average linear meter of 140 W.The attenuation degree and range of wall rock temperature increase with the increase of heat extraction power.The influence radius of the deep coaxial borehole heat exchanger are different at different depths,and the deep stratum is larger than the shallow stratum as a whole.The influence radius of the 2 500 m deep coaxial borehole heat exchanger with the heat extraction rates of 140 W/m can reach 110 m after work for 30 years.
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