北京平原区西北部大地热流与深部地温分布特征

Characteristics of heat flow and geothermal distribution in the northwest Beijing plain

北京平原区蕴藏着丰富的中-低温水热型地热资源,其西北部分布着小汤山地热田和京西北地热田,两大地热田以南口—孙河断裂带为界.地热田及其外围地区基础的地热地质研究工作较少.为给地热学研究和地热资源精细勘探提供科学依据,本文基于前人23眼钻孔的温度测量数据以及近期完成的548件热导率和100件放射性生热率实测数据,研究了区域大地热流和0~4km深部地温特征.结果表明:(1)研究区现今地温梯度为11.31~94.89℃·km^(-1),平均值为31.79℃·km^(-1);岩石热导率为0.895~5.111 W·(m·K)^(-1),放射性生热率为0.257~2.305μW·m^(-3),大地热流为48.1~99.1mW·m^(-2),平均值为68.3mW·m^(-2),热流的分布受基底形态和断裂构造控制.研究区东部南口—孙河断裂带两侧小汤山和郑各庄地区为高热流异常区,中部马池口地区也存在局部高热流异常区.(2)在南口—孙河断裂带的不同位置,不同深度地层温度差异明显,体现出区域现今地温场不只受控于该活动断裂,更是多期次构造事件复合叠加的结果.(3)南口—孙河断裂带南侧存在两处有意义的较高地温异常区,分别为郑各庄异常区和马池口异常区,其中马池口异常区是未来地热开发利用有一定潜力的地区.

The Beijing plain area is rich in medium-low temperature hydrothermal geothermal resources.There are two main geothermal fields located in the northwest of the plain:the Xiaotangshan geothermal field and Jingxibei geothermal field,which are bounded by the Nankou-Sunhe fault zone.However,so far there have been few studies on these two geothermal fields and peripheral areas.In order to provide scientific basis for geothermal research and precise exploration of geothermal resources,based on the data of temperature measurement from 23 wells available as well as recently completed measurements of thermal conductivity on 548 rock specimens and radioactive heat rate on 100 samples,this paper studies the regional terrestrial heat flow and geothermal features at 0~4 km depths.Results indicate that(1)The present geothermal gradient in the study areas is 11.31~94.89℃·km-1 with average 31.79℃·km-1.The rock thermal conductivity is 0.895~5.111 W·(m·K)-1.The radiogenic heat production rate is 0.257~2.305μW·m-3.The terrestrial heat flow is 48.1~99.1 mW·m-2 with average 68.3 mW·m-2.The distribution of heat flow is controlled by basement morphology and fault structure.In the east,the Xiaotangshan and Zhenggezhuang areas on either side of the Nankou-Sunhe fault zone,there exist high heat flow anomalies,so is in the central Machikou area.(2)Formation temperature is significantly different at different buried depths at different sites of the Nankou-Sunhe fault zone,reflecting present region geothermal field is not only controlled by this active fault but also the superposition consequence of multiple tectonic events.(3)The Zhenggezhuang and Machikou areas are two significant geothermal anomaly regions located on the south side of the Nankou-Sunhe fault zone,and Machikou is a potential area for geothermal exploitation and utilization in the future.