基于高导热材料填充漏失构造的深井换热器性能分析

地热供暖可有效缓解北方雾霾天气。干热岩虽然储量丰富，但增强型地热技术由于开发费用较高，裂隙控制以及避免诱发地震的技术尚不成熟，现阶段还不能商业化应用。水热型地热开发技术虽较成熟，但受资源条件的限制，开发规模较小。对于大多地区，受地质构造和资源禀赋的控制，单井产水量较低或者回灌难，开发经济效益较差。深井换热器（DBHE）技术是开采地热水低产区或回灌难地区热能的有效方式，但受制于岩石导热系数低，单井输出功率小，投资回收期长。为提高DBHE的输出功率，本文提出了增强型深井换热器（EDBHE），通过主动将高导热性能的复合填充剂流进漏失构造的方式提高岩石的导热性能，通过调节回压、密度和黏度来控制漏失量。研究结果表明，单井EDBHE十个采暖季的平均取热功率为1002. 34 kW，是DBHE(424. 45 kW)的2. 36倍。而双井EDBHE十个采暖季的平均取热功率更是达到了27501. 61 kW，且热输出稳定，每年的衰减率0. 95%。EDBHE技术有效利用了出水量低或回灌难的水热型热储，大幅提高了其出力，扩大了地热供暖的应用范围。

Performance analysis of deep borehole heat exchanger through filling leakage formation using high thermal conductivity material

Geothermal heating can effectively alleviate the haze weather in northern China. Hot dry rocks have abundant geothermal energy reserves but their commercial exploitation is limited due to high cost, inefficient technology of crack distribution and resulting induced seismicity. Due to the limitations of resource properties and environment, their scale of development is also small. In most areas, the water output of geothermal single well is low, or recharge is difficult owing to the constraint of geologic structure and resource endowment, resulting in an uneconomic exploitation. Deep borehole heat exchanger (DBHE) is an effective way to exploit geothermal energy with low water output or difficult injection. However, its performance is difficult to improve because of poor thermal conductivity of rocks, thus leading to a longer cost recovery time. To enhance heat output, enhanced deep borehole heat exchanger (EDBHE) is proposed in this study. It functions by actively controlling composite filler to flow into leakage formation by adjusting its density, viscosity and back pressure during the drilling process with the aim of improving the thermal conductivity of rocks. The research result shows that the extracted thermal output from the single EDBHE well is 1002. 34 kW, which is 2. 36 times that of the DBHE (424. 45 kW) well. The extracted thermal output for double EDBHE wells reaches a remarkable 27501. 61 kW with an annual attenuation rate of 0. 95%. EDBHE significantly improves the performance of geothermal well with low water output and effectively enhances the potential of geothermal heating.