苏北盆地典型地区中低温地热流体地球化学特征研究

苏北盆地作为江苏省地热地质条件最优的地区,发育丰富的中低温地热资源.文章选择存在已探明的中温地热井及干热岩验证孔所在的盆地区作为研究区,利用地热流体携带的地球化学信息,了解深部地热储层基本特征及不同深度地热资源的成生关系.结果表明:研究区地热流体中优势阳离子为Na+,阴离子呈复合离子型,以Cl-为主,Na+、TDS与C...

Study on Geochemical Characteristics of Mid-Low Temperature Geothermal Fluid in Representative Area of Subei Basin

The Subei Basin was enriched with medium-low temperature geothermal resources. This paper selected one representative area of the Subei Basin where one proven middle-temperature geothermal well and a hot-dry-rock verification hole were found as the study area. We employed the geochemical information carried by the geothermal fluid to have knowledge of the basic characteristics of deep geothermal reservoirs and the formation of geothermal resources at different depths. Results showed that the dominant cation in the geothermal fluid in the study area was Na+, however, the anion was of composite ion type, mainly Cl-. There was a good positive correlation beween Na+, TDS and Cl-. The calculation results of geothermal reservoir temperature were 73.8-145.1℃ estimated by the cations and silica geothermometer. In addition, the deep circulation depth of geothermal fluids in the Huangdang geothermal field was estimated to be 2.1 km. Through quantitative calculation, the elevation of recharge area for the geothermal fluids has been estimated from 203.5 m to 418.5 m. The 14C age of the geothermal fluid corrected by Bayesian algorithm showed an increasing trend from west to east, which was related to the direction of runoff of the geothermal fluid. The recharge area might be located in Zhangbaling Hilly area along the Xuyi Laozi Mountain, Mingguang city as well as Chuzhou city on the southwest side of the study area. The hydrogen and oxygen isotopic composition of the atmospheric precipitation in the recharge area was relatively consistent with that of the geothermal fluids, which further demonstrated the rationality of the inference of recharge elevation. According to the circulation depth of geothermal fluids, circulation period（or revised age of the Huangdang geothermal field）, recharge elevation, geothermal reservior temperature, and logging results, the mineralization model of the Huangdang geothermal field in Baoying county was established for the first time.