Hydrogeochemical and Isotopic Analyses of Deep Geothermal Fluids in the Wumishan Formation in Xiong’an New Area, China

Abstract

Medium-low temperature geothermal resources in the Wumishan Formation, which is the geothermal reservoir, are local enrichment resources in Xiong’an New Area, North China. In this study, 35 water samples were collected from the bedrock of Taihang Mountains and Wumishan Formation in Xiong’an New Area and display the chemical compositions of water samples as well as the stable isotope compositions for hydrogen, oxygen, carbon, sulfur, and strontium. Hydrogeochemical characteristics and isotope compositions of water samples are analyzed to understand the origin and circulation processes of these geothermal fluids. Our results of cold groundwaters in the bedrock of Taihang Mountain indicate a more open oxidation environment, and the HCO3-Ca·Mg-type groundwater also indicates a prevailing carbonate dissolution condition. The deep geothermal fluids in the Wumishan Formation beneath Xiong’an New Area indicate a closed reduction condition, and their hydrochemical types are mainly Cl·HCO3-Na type. The diagram of hydrogen vs. oxygen isotope indicates that the recharge for the deep geothermal fluids in the Wumishan Formation of Xiong’an New Area is mainly from atmospheric precipitation. The high δ13C values (-3.4‰−-4.9‰) are notably controlled by the eluviation of the carbonate rock layers. The δ34S values vary from 18.02‰ to 27.01‰; the relatively high values indicate the eluviation of sedimentary rock layers. The high 87Sr/86Sr ratios (0.70806−0.71270) and the high Sr2+ concentrations (0.69−2.92 mg/L) suggest that the Sr in the deep geothermal fluids originates from the eluviation of both silicates and carbonates. According to the multimineral equilibrium diagram, chalcedony is saturated at the measured temperature of geothermal wells; therefore, we chose chalcedony as a geothermal thermometer for the calculation of the reservoir temperature of the Wumishan Formation, and the results vary from 68.63 to 89.10°C. Our study identifies the geothermal type of the deep medium-low temperature hydrothermal systems and also recognizes their water-rock interaction processes. We get a comprehensive understanding that the geothermal resources in the Wumishan Formation beneath Xiong’an New Area is convection-conduction type, for which potential of geothermal development and utilization is enormous.

Influence of underground space development mode on the groundwater flow field in Xiong’an new area

“…There is a close hydraulic connection between the first and the second aquifer groups and they can be considered a unified water-bearing body which is the main exploitation target of the area. It has a significant influence on the development of underground space in the study area (Chi et al 2021;Zhu et al 2022;Qin et al 2013).…”

Characteristics, Formation Periods, and Controlling Factors of Tectonic Fractures in Carbonate Geothermal Reservoirs: A Case Study of the Jixianian System in the Xiong'an New Area, China

“…1), which is a Mesozoic-Cenozoic faulted depression developed in the western part of the North China Craton (NCC) (Li et al, 2017;Liu et al, 2018;Zhang et al, 2018;Wang et al, 2021a;Wang et al, 2022) and is a secondary negative tectonic unit within the Bohai Bay Basin (BBB). Starting from the Cangxian uplift to the east, the Xiong'an New Area is bounded by the eastern margin fault on the Taihang Mountains in the west, is adjacent to the Yanshan fold-thrust belt in the north, and extends to the Xingheng uplift to the south (Guo et al, 2020;Wang et al, 2021b;Zhu et al, 2022).…”

Geochemical Characteristics of Geothermal Fluids of a Deep Ancient Buried Hill in the Xiong’an New Area of China

“…The Rongcheng fault is a growth fault controlling the development of the Neoproterozoic strata and serves as the dividing line between the Niutuozhen uplift and the Rongcheng uplift. As a deep major fault active in a long term, the Xushui fault to the south was encountered by boreholes XR05 (D16) and XR21 (D19) and extends into the crystalline basement, acting as the dividing line between the Rongcheng uplift and the Baoding depression [21]. The Niudong fault, which is a syngenetic extensional fault, is the boundary between the Wuqing-Bazhou depression and the Niutuozhen uplift.…”

“…Therefore, the China Geological Survey has increased the exploration activities in the Rongcheng geothermal field since 2017, aiming to promote its development process. Previous studies on the geochemical characteristics of geothermal fluids in deep thermal storage in this area essentially focused on the geothermal reservoirs of the Jixianian Wumishan Formation [20,21]. By contrast, limited studies have been conducted on the geothermal reservoirs of the Gaoyuzhuang Formation-another main Jixianian thermal reservoir discovered in recent years-due to the karst characteristics of the reservoirs [22], leading to insufficient understanding of the occurrence environment and the migration and evolution patterns of the geothermal fluids in ancient buried-hill geothermal reservoirs.…”

“…Note: "*" indicates data collected from[21]. Ng denotes Neogene Guantao Formation; Jxw denotes Jixianian Wumishan Formation; Jxg denotes Jixianian Gaoyuzhuang Formation.…”