A microbiological study of an underground gas storage in the process of gas extraction

The numbers of microorganisms belonging to ecologically significant groups and the rates of terminal microbial processes of sulfate reduction and methanogenesis were determined in the liquid phase of an underground gas storage (UGS) in the period of gas extraction. The total number of microorganisms in water samples from the operation and injection wells reached 2.1 × 106 cells/ml. Aerobic organotrophs (including hydrocarbon-and oil-oxidizing ones) and various anaerobic microorganisms (fermenting bacteria, methanogens, acetogens, sulfate-, nitrate-, and iron-reducing bacteria) were constituent parts of the community. The radioisotopic method showed that, in all the UGS units, the terminal stages of organic matter decomposition included sulfate reduction and methanogenesis, with the maximal rate of these processes recorded in the aqueous phase of above-ground technological equipment which the gas enters from the operation wells. A comparative analysis by these parameters of different anaerobic ecotopes, including natural hydrocarbon fields, allows us to assess the rate of these processes in the UGS as high throughout the annual cycle of its operation. The data obtained indicate the existence in the UGS of a bacterial community that is unique in its diversity and metabolic capacities and able to make a certain contribution to the geochemistry of organic and inorganic compounds in the natural and technogenic ecosystem of the UGS and thus influence the industrial gas composition.