The Community Structure And Biodiversity Of Microorganism In The CO₂-Brine-Sandstone Interaction Process

In recent years, greenhouse effects caused by burning of fossil fuel due to the industrial production and the fast-developing economics have attracted widespread concerns in the world. CCS（Carbon dioxide Capture and Storage） is one of the best effective methods in limiting greenhouse gas emission and addressing climate change in the world. In CO₂ geological storage process, Microbial communities play an important role in the underground environment, and they have rich variety and huge quantity. The participation of microbial is one of the most important part during the evolution process of CO₂-water-stone interactions, especially the dynamic process. First it functions as a catalyst to increase the reaction rate, on the other hand, it can change the rate of dissolution and precipitation of minerals as a reactant. As a result, the structure, functionality and biodiversity of indigenous microorganism will respond to dynamic changes in the process of dissolution and precipitation of minerals during the CO₂-brine-sandstone interaction process. However, people pay little attention to the dynamic variation of the structure, functionality and biodiversity of indigenous microorganism during the CO₂-brine-sandstone interaction process. And there was no similarly report in domestic at present.By enriching microbial from water sample, we pay close attention to different kinds of microorganisms on CO₂-brine-sandstone interaction process. The main research results are as follows:（1） It made the environment less favorable for the indigenous microorganism after CO₂’s injection. But this research showed that some kinds of indigenous microorganism such as bacteria of the genera Brevundimonas, Pseudomonas and Bacillus could grow well under the extreme condition induced by CO₂’s injection, leading to the variation of the structure, functionality and biodiversity of indigenous microorganism and potential consequences for the process of CO₂’s capture.（2） After CO₂’s injection, the relative abundance of indigenous microorganism tended to be single, after 6 months, the relative abundance of Proteobacteria reached up to 99.77%. The dominant species were varied as follows: Pseudomonas sp., Citrobacter sp. and Brevundimonas sp.. Meanwhile, some special genus such as Bacillus sp., Hydrogenophaga sp. and Rhizobium sp. with functionality of iron-reducing and denitrification was found in this study, which may had a potential effect on CO₂’s capture and storage. In addition, the shannon index was decreased and Simpson index was increased along with the CO₂’s injection, suggesting that the biodiversity reduced significantly.（3） Results 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, they also 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 p H and the chemical composition of brine water（anion and cation）, etc.