ABSTRACT
In this study, the dynamic variation of the structure, functionality and biodiversity of indigenous microorganism during the CO2-brine-sandstone interaction process was investigated using MiSeq sequencing techniques. The results indicated that some kinds of indigenous microorganisms could grow well under the extreme condition induced by CO2-injection. After injection of CO2, the species of indigenous microorganisms tended to be single and the relative abundance of Proteobacteria reached up to 99.77% after 6 months. The dominant species varied as follows:Pseudomonas sp., Citrobacter sp. and Brevundimonas sp.. Meanwhile, some special genera such as Bacillus sp., Hydrogenophaga sp. and Rhizobium sp. with functionality of iron-reducing and denitrification were found in this study, which may have a potential effect on the capture and storage of CO2. In addition, the Shannon index decreased from 5.3302 to 1.9465 after injection of CO2, suggesting that the biodiversity reduced significantly. Function and main metabolites analysis of bacteria in the CO2-brine-sandstone interaction process showed that bacteria like Bacillus sp., Citrobacter sp. and Pseudomonas sp. could enhance CO2 solubility-trapping process. Bacteria metabolisms could accelerate the dissolution of feldspar and chlorites, and facilitate the formation of transition-state calcite and siderite. Otherwise, the great variation was mainly attributed to the change of condition driven by CO2-brine-sandstone interactions, such as pH and the chemical composition of brine water(anion and cation), etc.
