文章基本信息

标题：Experimental investigation of geochemical and mineralogical effects of CO2 sequestration on flow characteristics of reservoir rock in deep saline aquifers
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作者：T. D. Rathnaweera ; P. G. Ranjith ; M. S. A. Perera 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2016
卷号：6
期号：1
DOI：10.1038/srep19362
语种：English
出版社：Springer Nature
摘要：Interactions between injected CO₂, brine, and rock during CO₂ sequestration in deep saline aquifers alter their natural hydro-mechanical properties, affecting the safety, and efficiency of the sequestration process. This study aims to identify such interaction-induced mineralogical changes in aquifers, and in particular their impact on the reservoir rock’s flow characteristics. Sandstone samples were first exposed for 1.5 years to a mixture of brine and super-critical CO₂ (scCO₂), then tested to determine their altered geochemical and mineralogical properties. Changes caused uniquely by CO₂ were identified by comparison with samples exposed over a similar period to either plain brine or brine saturated with N₂. The results show that long-term reaction with CO₂ causes a significant pH drop in the saline pore fluid, clearly due to carbonic acid (as dissolved CO₂) in the brine. Free H ⁺ ions released into the pore fluid alter the mineralogical structure of the rock formation, through the dissolution of minerals such as calcite, siderite, barite, and quartz. Long-term CO₂ injection also creates a significant CO₂ drying-out effect and crystals of salt ( NaCl ) precipitate in the system, further changing the pore structure. Such mineralogical alterations significantly affect the saline aquifer’s permeability, with important practical consequences for the sequestration process.