Sub-project II: Influence of inhibitors on microorganisms with special focus on microorganisms involved in scaling and corrosion processes
Chemical inhibitors are used to prevent scale formation and corrosion that adversely affect the reliability and economic efficiency of geothermal plants. However, knowledge about inhibitor efficiency with respect to chemical fluid composition, temperature and fluid abundant microorganisms is required. On the one hand inhibitors have to be stable in the geothermal plant and the near wellbore area to be sufficiently effective, on the other also degradable to allow for a sustainable exploitation and development of the reservoir and to protect the ecological function of the subsurface. Since microorganisms, such as sulfate reducing bacteria (SRB), are involved in scaling and corrosion processes, the influence of the inhibitor on the microbial community composition and the subsequent effects will be investigated. Thus, lab-scale experiments with fluid samples from different geothermal plants in Germany are performed. As fluids from the North German Basin, the Upper Rhine Graben and the Molasse Basin have a significantly different chemical fluid composition that leads to a region-specific formation of scales, different inhibitors are tested. In order to investigate the interactions between microbes and reservoir rock material, fluids are incubated with rock material from outcrop analogues. Thereby, influence of different parameters such as pH values, ionic strength, temperature, salinity and microbial biocenosis on the inhibitors stability is examined. In addition, short- and long-term tests at different geothermal plants will be used to monitor changes of microbial communities due to the inhibitor addition.