Experimental Investigation Of CO₂-water-sandstone Interactions By Microbial-mediated Process

Greenhouse effects caused by burning of fossil fuel have attracted widespreadconcerns in the world. As one of the biggest countries for CO2emission, the mostimportant resource type in our country is fossil fuel. It is still difficult for us tobalance the relationship between economic development and energy demand in theshort term. Therefore, more and more researches focus on how to effectively carry outthe work to control carbon dioxide in the atmosphere.Recently, carbon capture and geological storage (CCS) is widely considered as apromising technology to reduce CO2emission to the atmosphere. We hoped that theunderground carbon dioxide could took part in geological reaction with the host rocks,eventually they could stay permanently in the deep underground in the form ofcarbonate mineral. Geological storage of CO2depends on complex physical,geochemical capture mechanisms. With a combination of physical and geochemicalapproach, and ultimately achieve the goal of mineral trapping. However, it may take athousand years or longer to undergo mineral trapping in the deep saline aquifers,which could lead to a series of environmental safety issues. Microbial communitieswere one of the most important part in the underground environment, studies haveshown that certain microorganisms have played a role to accelerate the formation ofcarbonate minerals, microbial metabolisms play an important part in geochemicalenvironment of underground carbon sequestration Therefore, this study enrichedmicroorganisms from the underground water sample, and study on the process ofmicrobial-mediated CO2-water-sandstone interactions.Through enrich microbial from water sample in Shihezi, our study focus on theresearches of different kinds of microorganisms on CO2-water-sandstone interactionprocess at atmosphere pressure, and at high temperature and high pressureenvironments such as the deep saline aquifer. The main research results are asfollows:(1)The study enriched three kinds of microorganisms (bacteria, fungi andactinomycetes) from the underground water sample. Then this study investigated the tolerance ability of them in the extreme environments such as the CO2injection site.Results showed that bacteria and actinomycetes could adapt the extreme pH,temperature and salinity environment. Fungi could not adapt the relatively low pH (≤4).(2)The experiments at50°C for7days in atmospheric pressure showed that,bacteria could promoted the formation of carbonates contained calcium, fungi couldpromoted the erosion of rocks, actinomycetes could promoted the formation ofcarbonates contained irons. It also showed that unknown alumni-silicate mineralsformed in the shake flask experiments in bacteria ones, which indicated that bacteriacould enhance CO2trapping in the CO2injected condition.(3)Bacteria were chosen as the typical one to investigate the microbial-mediatedCO2-water-sandstone interaction process at50°C for60days. In the experimentalscale (the amount of bacteria between0-11.7×107CFU/mL), the more amount ofbacteria in CO2-water-sandstone system, the more amount of CO2could dissolved insalt water.(4)Bacteria were chosen as the typical one to investigate the microbial-mediatedCO2-water-sandstone interaction process at50°C for60days. Results showed thatbacteria could enhance CO2solubility-trapping process. Bacteria metabolisms couldenhance the dissolution of feldspar and clay minerals (chlorites), and facilitate theformation of transition-state calcite and siderite.