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

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 similar to 4 km depths. Results indicate that (1) The present geothermal gradient in the study areas is 11.31 similar to 94. 89 degrees C . km(-1) with average 31. 79 degrees C . km(-1). The rock thermal conductivity is 0. 895 similar to 5.111 W . (m . K)(-1). The radiogenic heat production rate is 0. 257 similar to 2. 305 mu W . m(-3). The terrestrial heat flow is 48.1 similar to 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.