Biomonitoring studies and supervisory research for the purposes of underground gas storage and currently exploited natural gas deposits

This paper refers to several aspects of research studies supporting the oil and gas industry – in particular underground gas storage (UGS) in depleted deposits and salt caverns – and focuses on questions related to the formation of hydrogen sulphide contamination in reservoir conditions as well as on methods for limiting unfavourable biogenic phenomena. The main problem found at gas storage facilities is the activity of sulphate reducing bacteria (SRB). The elimination or limitation of H2S generation in microbiologically contaminated environments have been the subject of many extensive studies. Biocides, biocorrosion inhibitors and H2S scavengers are widely applied to protect reservoir structure, gas storage infrastructure as well as water-based drilling fluids from the negative effects of bacterial activity. One of the most popular biocidal products, recommended for oil and gas industry are triazine derivatives, laboratory tested in the presented biomonitoring studies. Triazine products prove very effective in biomass reduction and elimination of anaerobic bacteria, especially SRB. Before any industrial operation (based on technology of using biocides), it was necessary to analyse the sulphur compounds in the stored natural gas in different exploitation gas wells of UGS. It was also necessary to investigate the selection of a specific biocidal product and its proper concentration. A concentration that is too low may even stimulate the microbial growth; since the substance is not toxic for microorganisms, they may start to metabolise it. Moreover, the wrong choice of biocides may even generate an economic loss or environmental hazard. Generally, the application of biocides, H2S scavengers and nitrate-based treatment are one of the most effective world strategies to decrease microbiological contamination, which affects various areas of the oil and gas industry. These products have also been successfully applied to control bacterial growth in Polish natural gas wells. The issue of the influence of microorganisms and biomass on the permeability of reservoir rocks was also presented. In addition, the paper refers to biodegradation processes, that take place in the environment of drilling fluids. Also, the issue of choice of biocide/H2S scavenger preparations for industrial applications is presented. The choice of chemicals includes efficiency tests of nanoparticles in contaminated media.