Ra and Rn isotopic tracing of faulting and water-rock interaction in carbonate geothermal reservoirs

Tianxue Lyu, Chuanxia Ruan, Tingting Zhang, Lixin Yi and Long Li

Energy, 2025, vol. 326, issue C

Abstract: Groundwater discharge regime, flow pathway, and fault characteristics are crucial parameters for sustainable management of geothermal resources, but have been difficult to constrain. Radionuclide disequilibria in groundwater due to water-rock interaction can potentially provide site-specific information for the assessment of above-mentioned parameters of geothermal systems, but has been poorly understood. Here, a multidisciplinary investigation integrating aqueous geochemistry, radioactive isotopes (223Ra, 224Ra, 228Ra, 226Ra, 222Rn and 228Th) and hydrological analysis was applied to a carbonate geothermal field in the North China Plain to examine water-rock interaction, and explore the application of Ra-Rn isotopes to constraining discharge regimes of geothermal groundwater. Our results show that Ra isotopes in the aquifer are at disequilibrium. Modeling of the isotopic data indicates that Ra is highly mobile and thus can serve as an effective tracer for geothermal fluid mobility. In addition, 222Rn recoil efficiency can be used to quantify fracture apertures and guide geothermal exploitation of high-permeability zones. Our results also show that radionuclide disequilibrium patterns can not only delineate fault structure, but also reveal recharge site and preferential flow pathway in groundwater systems. These findings suggest that radionuclides can be a robust tool to provide scientific support for effective management and sustainable development of geothermal resources.

Keywords: Carbonate geothermal system; Water-rock interactions; Recharge site; Flow pathways; Fault identification (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:326:y:2025:i:c:s0360544225019310

DOI: 10.1016/j.energy.2025.136289

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