CO2BioPerm—Influence of Bio-geochemical CO2-Transformation Processes on the Long-Term Permeability

The RECOBIO projects (Hoth et al. in Recycling of sequestrated CO2 by microbial—biogeochemical transformation in the deep subsurface—RECOBIO 2009a; Geotechnol Sci Rep 14:58–65, 2009b; Untersuchung der biogeochemischen transformation von im tiefen Untergrund gespeichertem CO2—RECOBIO 2 2011) have shown the relevance of biogeochemical processes, related to CO2 injection. These processes represent an additional pathway for biogeochemical CO2 storage. The main result was the microbial transformation (binding) of injected CO2 (formation of organic compounds). This can also influence the pressure behaviour of the system. Furthermore the organic layers can act as nucleation sites and so catalyse the carbonate solid formation. So the main focus of the CO2BIOPERM project was now to investigate the influence of these processes on the permeability behaviour of the system. Furthermore other aquifer structures, not related to natural gas fields, were characterised by microbiological, molecular genetic investigations. The biocenosis is also often dominated, like in natural gas fields, by sulphate reducers and fermenting bacteria. The study of CO2 effects to the cultivation of microorganisms showed for deep aquifer microorganisms a strategy to survive the CO2 stress by spore forming. The proteomic analysis gave a first view how many and which proteins were down and up regulated under CO2 stress. A part of the flow experiments, which were operated in discontinuously flowed batch mode, are presented in detail. There is no strong influence of the processes on the permeability behaviour for high permeable reservoir sandstones. Nevertheless the sequential extractions on the solid materials, after the tests, underline the ongoing biogeochemical reactions.