Hydrogeochemistry of surface and spring waters in the surroundings of the CO₂ injection site at Hontom¡§an-Huermeces (Burgos, Spain)

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• 作者：Barbara Nisi^a ; ^{b.nisi@igg.cnr.it} ; ^{barbara.nisi@unifi.it} ; Orlando Vaselli^b ; ^c ; Franco Tassi^b ; ^c ; Javier de Elio^d ; ^e ; Antó ; nio Delgado Huertas^f ; Luis Felipe Mazadiego^d ; Marcelo F. Ortega^d
• 关键词：Hontomí ; n&ndash ; Huermeces ; CO2 injection ; Geochemical monitoring ; Dissolved gases ; Trace elements ; Carbon isotopes
• 刊名：International Journal of Greenhouse Gas Control
• 出版年：2013
• 出版时间：May, 2013
• 年：2013
• 卷：14
• 期：Complete
• 页码：151-168
• 全文大小：2347 K

文摘

In this paper the very first geochemical and isotopic data related to surface and spring waters and dissolved gases in the area of Hontom¡§an-Huermeces (Burgos, Spain) are presented and discussed. Hontom¡§an-Huermeces has been selected as a pilot site for the injection of pure (>99 % ) CO₂. Injection and monitoring wells are planned to be drilled close to 6 oil wells completed in the 1980s for which detailed stratigraphical logs are available, indicating the presence of a confined saline aquifer at the depth of about 1500 m into which less than 100,000 tons of liquid CO₂ will be injected, possibly starting in 2013.

The chemical and features of the spring waters suggest that they are related to a shallow hydrogeological system as the concentration of the Total Dissolved Solids approaches 800 mg/L with a Ca²⁺(Mg²⁺)-HCO₃^? composition, similar to that of the surface waters. This is also supported by the oxygen and hydrogen isotopic ratios that have values lying between those of the Global and the Mediterranean Meteoric Water Lines. Some spring waters close to the oil wells are characterized by relatively high concentrations of NO₃^? (up to 123 mg/L), unequivocally suggesting an anthropogenic source that adds to the main water-rock interaction processes. The latter can be referred to Ca-Mg-carbonate and, at a minor extent, Al-silicate dissolution, being the outcropping sedimentary rocks characterized by Palaeozoic to Quaternary rocks. Anomalous concentrations of Cl^?, SO₄^2?, As, B and Ba were measured in two springs discharging a few hundred meters from the oil wells and in the Rio Ubierna. These contents are significantly higher than those of the whole set of the studied waters and are possibly indicative of mixing processes, although at very low extent, between deep and shallow aquifers. No evidence of deep-seated gases interacting with the Hontom¡§an-Huermeces waters was recognized in the chemistry of the dissolved gases. This is likely due to the fact that they are mainly characterized by an atmospheric source as highlighted by the high contents of N₂, O₂ and Ar and by N₂/Ar ratios that approach that of ASW (Air Saturated Water) and possibly masking any contribution related to a deep source. Nevertheless, significant concentrations (up to 63 % by vol.) of isotopically negative CO₂ (<?17.7?íq-PDB) were found in some water samples, likely related to a biogenic source.

The geochemical and isotopic data of this work are of particular importance when a monitoring program will be established to verify whether CO₂ leakages, induced by the injection of this greenhouse gas, may be affecting the quality of the waters in the shallow hydrological circuits at Hontom¡§an-Huermeces. In this respect, carbonate chemistry, the isotopic carbon of dissolved CO₂ and TDIC (Total Dissolved Inorganic Carbon) and selected trace elements can be considered as useful parameters to trace the migration of the injected CO₂ into near-surface environments.