关中盆地西安凹陷深层地热U型对接井地温特征  

Geothermal Features of Two Deep U-Shape Downhole Heat Exchangers in the Xi’an Depression,Guanzhong Basin

作　　者：张育平[1,2,3] 黄少鹏 杨甫[1,3] 王兴[1,3] 余如洋 李毅[2] 荀迎九 周聪 Zhang Yuping;Huang Shaopeng;Yang Fu;Wang Xing;Yu Ruyang;Li Yi;Xun Yingjiu;Zhou Cong(Key Laboratory of Coal Resources Exploration and Comprehensive Utilization, Ministry of Land and Resources, Xi'an, Shaanxi 710021;Xi'an Jiaotong University, Xi'an, Shaanxi 710048;Shaanxi Coal Geology Group Co. Ltd., Xi'an, Shaanxi 710021;Shaanxi Zhongmei New Energy Co.,Ltd., Xi'an, Shaanxi 710054)

机构地区：[1]国土资源部煤炭资源勘查与综合利用重点实验室,西安710021 [2]西安交通大学,西安710048 [3]陕西省煤田地质集团有限公司,西安710021 [4]陕西中煤新能源有限公司,西安710054

出　　处：《中国煤炭地质》2019年第6期54-61,共8页Coal Geology of China

基　　金：陕西省科技厅工业科技重点攻关项目(2017ZDXM-GY-075);国土资源部煤炭资源勘查与综合利用重点实验室重点项目(SMDZ-ZD2016-2)

摘　　要：关中盆地中深层地热资源丰富,为关中地区冬季供暖提供了保障。作为深层能地热开发利用的示范项目,首次在西安凹陷中施工了2000m以深的两对U型对接井,对接井水平段长200m,形成了闭式地埋管换热器,且静置时间超过2年,能够反映初始地温。地层初始地温是深层地热井换热能力计算关键参数,高精度的测量可保证数据的可靠性。利用进口直读式热电偶测温探头,对上述2组对接井(4口)初始地层温度进行了测量,并利用线性回归的方法计算了地温梯度。结果显示,在垂向上和平面上,4口井地温都表现出高度的重合性,显示区内对接井地温和地下流场稳定,地热能开采潜力大;4口地热井单井地温梯度变化范围为3.45~3.47℃/hm,平均3.46±0.01℃/hm,地温梯度异常是由于关中盆地地壳厚度较薄,以及相对高的地幔热流的热传导和深大断裂沟通的水体热对流相互叠加造成的;蓝田-灞河组分布稳定、富水性好、渗透率高和导热性强,为区域稳定的热储层,根据地温和地温梯度的变化规律,建议区内对接井对接层段为1866m以深的蓝田-灞河组,以保证最大的换热效率和持续稳定的热源;通过测井资料验证,对接井在1500~1600m存在地温异常,与地层地下水活动和地层含砂量高相关。Deep geothermal resources are abundant in the GuanzhongBasin, which provides great potential for winter district heating in Guanzhong area. As a demonstration project fordeep geothermal exploitation and utilization, four boreholes of over 2 000m depths were connectedat the bottom with directional drilling to form two U-shape heat exchangers (DHEs) in the Xi'an Depression of the Guanzhong Basin. Each U-shape DHE comprises a 200m horizontal section. Here we report the result of the equilibrium borehole temperature measurements of these two DHEs 2 years after the systems were completed. The initial formation temperature is the keyparameter to compute deep geothermal borehole heat transfer capacity;high accuracy measurement can ensure data reliability. This studyhas used imported direct-reading thermocouple temperature probe, carried out measurement for initial temperature of two U-shape DHEs, and computed geothermal gradient through linear regression method. The results have shown: on the plane and vertically,4 borehole geo-temperatures presented high coincidence;geo-temperature and underground flowfield of DHEs in the area are stable with great geothermal energy exploitation potential. Single borehole geothermal gradientvariation range of 4 boreholes is 3.45~3.47℃/hm with anaverageof 3.46±0.01℃/hm. The geothermal gradient anomaly is causedby rather thin crust thickness in Guanzhong Basin, and mutualsuperposition of relatively high heat conduction of mantle heat flowand discordogenic fault linked-up waters thermal convection. The Lantian and BaheFormations have the features of stable distribution, good wateryield property, high permeability and strong thermal conductivity, and formed a regionally stable heat reservoir. According togeo-temperature and geothermal gradient changing principle, it hassuggested that the horizontal section in this area should be in Lantianand BaheFormations under 1,866m to ensure maximum heat exchange efficiencyand to be a sustained and stable heat source. Through borehole loggingdata

关 键 词：深层地热对接井 地温测量 地温梯度 地温异常 关中盆地 

分 类 号：P314.3[天文地球—固体地球物理学]