北京城区地热田西北部地热地质特征

自2001年在北京大学成功打成地下热水井后,北京西部隆起区的地热勘探开发受到重视。通过对区域地质背景条件的介绍,根据地热井钻探揭露的地热地质成果,对研究区的热储构造条件、地热地质特征及地下热水地球化学特征进行了分析研究。结果表明,八宝山断裂的性质具有先逆断层后正断层的多期活动性特征;研究区蓟县系雾迷山组白云岩为鼻状背斜凸起型热储构造;深部热流主要沿着黄庄—高丽营断裂的上盘向上传导聚集;浅部古生界碳酸盐岩地层富集强径流冷地下水的作用使青白口系的地温梯度高于北京平原区,纵向地温场坡度较北京平原区大;临近深大断裂构造带导致地下热水具有放射性镭含量高的特征;地下热水的14C年龄特征反映城区地热田接受西部隆起区地下水的补给很少;地热井水头分布趋势反映雾迷山组白云岩热储地下热水受黄庄—高丽营断裂阻隔后由南向北方向径流。

Characteristics of Geothermal Geology in the Northwestern Part of the Urban Beijing Geothermal Field

More attention has been paid to the investigation and development of geothermal resources in the northern uplift of the urban Beijing geothermal field since the geothermal well in Peking University was successfully drilled in 2001.Regional geological conditions of the study area are described in this paper.Based on geological survey of several geothermal wells,the structure of geothermal reservoirs,geothermal geological characteristics and hydrochemistry of thermal groundwater are also examined.The results show that the Babaoshan fault is characterized by multi-activity from a reverse fault to a normal fault and the geothermal reservoir consisting of dolomite of the Wumishan Group of the Jixian System is a nose-type-anticline uplift.Conductive heat flow from beneath mainly flows along the hanging wall of the Huangzhuang-Gaoliying fault.The cold groundwater in the shallow carbonate of Palaeozoic age causes the geothermal gradient of the Qingbaikou reservoir higher than that in the Beijing plain.Thermal groundwater near the deep and huge faults has high Ra contents.14C age of the hot water indicates that little recharge occurred in the western uplifted mountain area.Hydraulic heads at the geothermal wells reflect a flow trend from south to north of thermal groundwater in the Wumishan Group due to the obstructing of the Huangzhuang-Gaoliying fault.