The Tianjin geothermal field (north-eastern China): Water chemistry and possible reservoir permeability reduction phenomena |
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Authors: | Angelo Minissale Daniele Borrini Giordano Montegrossi Andrea Orlando Franco Tassi Orlando Vaselli Antonio Delgado Huertas Jincheng Yang Wanquing Cheng Dario Tedesco Robert Poreda |
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Affiliation: | 1. Institute of Geosciences and Earth Resources, National Research Council of Italy (CNR), Via G. La Pira 4, 50121 Florence, Italy;2. Department of Earth Sciences, University of Florence, Via G. La Pira 4, 50121 Florence, Italy;3. Estación Experimental de Zaidín (CSIC), Prof. Albareda 1, 18008 Granada, Spain;4. Aode Renewable Energy Research Institute, 90 Weijin South Road, Nankai District, 300381 Tianjin, China;5. Department of Environmental Sciences, Second University of Naples, Via Vivaldi 43, Caserta 81100, Italy;6. Institute of Environmental Geology and Geo Engineering (CNR), Piazzale A. Moro 5, Roma 00100, Italy;g Department of Earth & Environmental Sciences, University of Rochester, 227 Hutchison Hall, Rochester, NY 14627, USA |
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Abstract: | Injection of spent (cooled) thermal fluids began in the Tianjin geothermal district, north-eastern China, at the end of the 1990s. Well injectivities declined after 3–4 years because of self-sealing processes that reduced reservoir permeability. The study focuses on the factors that may have caused the observed decrease in permeability, using chemical and isotopic data on fluids (water and gas) and mineral phases collected from production and injection wells. The results of data processing and interpretation indicate that (1) it is very unlikely that calcite and silica precipitation is taking place in the reservoir; (2) the Fe- and Zn-rich mineral phases (e.g. sulfides, hydroxides and silicates) show positive saturation indexes; (3) SEM and XRD analyses of filtered material reveal that the latter mineral phases are common; (4) visual observation of casings and surface installations, and of corrosion products, suggests that a poor quality steel was used in their manufacture; (5) significant quantities of solids (e.g. quartz and feldspar crystals) are carried by the geothermal fluid; (6) seasonal changes in fluid composition lead to a reduction in casing corrosion during the summer. |
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Keywords: | Water chemistry Stable isotopes Reservoir permeability reduction Self-sealing Tianjin China |
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