Microbial response to low concentrations of oxygen in a carbon dioxide storage environment

The storage of carbon dioxide in deep saline aquifers is designed to reduce carbon emissions. Current specifications on oxygen within stored carbon dioxide do not appear to take into consideration storage site microbiology. The oxygen impurities within the carbon dioxide could alter microbial activity within the storage site and lead to operational issues, including injection well blockage and well pump corrosion, caused by the production of hydrogen sulphide by sulphate reducing bacteria. This thesis investigates the microbial response to 10 ppm oxygen and 100 ppm oxygen in experiments representing deep saline aquifer conditions. All experiments were conducted using sandstone, artificial groundwater and a microbial community designed to represent conditions found within deep saline aquifers. A microbial community, containing sulphate reducing bacteria, was isolated and identified from sandstone samples and then used in the experiments. The experiments were batch microcosms, a high pressure bioreactor and column flow experiments. Analyses of these experiments were conducted through gas analysis, water chemistry and DNA analysis from microbial communities. The results from the experiments show that the presence of 100 ppm oxygen within carbon dioxide leads to increased production of hydrogen sulphide and methane, and increased microbial diversity, compared to 10 ppm oxygen. Hydrogen sulphide can lead to the blockage of injection well from iron sulphide formation and the corrosion well pumps. Methane production from microbes can reduce the capacity of storage sites and contribute to corrosion. This suggests that having 10 ppm oxygen, instead of 100 ppm oxygen, within stored carbon dioxide would reduce microbially associated problems, such as well corrosion and blockages