Fate(s) of injected CO2 in a coal-bearing formation, Louisiana, Gulf Coast Basin: Chemical and isotopic tracers of microbial-brine-rock-CO 2 interactions

This study utilized isotopic and geochemical tracers from co-produced natural gas, oil and brine to determine the fate of EOR-CO2, examining the storage possibilities of CO2 migration, dissolution, mineral trapping, gas-phase trapping, and sorption to coal beds, while also testing a previous hypothesis that EOR-CO2 may have been converted by microbes into methane. Major storage mechanisms were shown to be gas-phase trapping and dissolution into formation waters, while the minor storage mechanisms were shown to be migration and some conversion to microbial methane. Samples were examined from 8 adjacent oil fields to determine the cause of the increased methanogenesis. Microbial methane was found in all oil fields sampled, but indicators of methanogenesis were the greatest in the Olla Field, and the environmental conditions were most ideal for microbial CO2 reduction in the Olla field, compared to adjacent fields.