Noble gas and carbon isotopic evidence for CO2-driven silicate dissolution in a recent natural CO2 field
Noble gas and carbon isotopic evidence for CO2-driven silicate dissolution in a recent natural CO2 field
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DOI：
10.1016/j.epsl.2012.05.040
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发表时间：
2012-08
影响因子：
5.3
通讯作者：
B. Dubacq;M. Bickle;Max Wigley;N. Kampman;C. Ballentine;B. S. Lollar
中科院分区：
文献类型：
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作者：
B. Dubacq;M. Bickle;Max Wigley;N. Kampman;C. Ballentine;B. S. Lollar
在地质储层中安全储存人为二氧化碳 (CO2) 需要预测千年时间尺度内的气-水-岩石相互作用。稀有气体和碳同位素测量可用于揭示不同时间尺度上竞争性溶解沉淀过程的本质，从地下水中气态二氧化碳的快速溶解到涉及储层中新形成矿物的溶解和沉淀的更缓慢的反应。在这里，我们研究了气体分析汇编，包括来自九个不同天然 CO2 储层的稀有气体和 CO2 的 δ13C。在这些储层中，Bravo Dome CO2field（美国新墨西哥州）显示出明显的地球化学趋势，这可以通过地下水中稀有气体的脱气改变气相的组成来解释。这种地下水脱气与地下水中二氧化碳的溶解同步。需要通过 CO2 促进矿物溶解逐渐产生碱度来解释观察到的 CO2/3He 和气相 δ13C 之间的正相关性，这是 Bravo Dome 的独特特征。 Bravo Dome 与其他天然 CO2 储层之间的差异可能是由于 Bravo Dome 最近的填充所致，反映了 CO2-水-岩石数千年的相互作用，而不是较老的储层中数百万年的相互作用。
Secure storage of anthropogenic carbon dioxide (CO2) in geological reservoirs requires predicting gas–water–rock interactions over millennial timescales. Noble gases and carbon isotope measurements can be used to shed light on the nature of competing dissolution—precipitation processes over different timescales, from the fast dissolution of gaseous CO2in groundwater to more sluggish reactions involving dissolution and precipitation of newly formed minerals in the reservoir. Here we study a compilation of gas analyses including noble gases and δ13C of CO2from nine different natural CO2reservoirs. Amongst these reservoirs, the Bravo Dome CO2field (New Mexico, USA) shows distinct geochemical trends which are explained by degassing of noble gases from groundwater altering the composition of the gas phase. This groundwater degassing is synchronous with the dissolution of CO2in groundwater. Progressive creation of alkalinity via CO2-promoted mineral dissolution is required to explain the observed positive correlation between CO2/3He and δ13C of the gas phase, a unique feature of Bravo Dome. The differences between Bravo Dome and other natural CO2reservoirs are likely explained by the more recent filling of Bravo Dome, reflecting CO2–water–rock interactions over thousands of years rather than over millions of years in older reservoirs.