CO2-SPICER - CO2 Storage Pilot In a CarbonatE Reservoir: R5.3 Report and dataset: Geochemical and microbiological evidence of archea-bacterial activity, methanogenesis and pore throats clogging gas reservoir

The report provides an overview of the current knowledge about microbial consortia living in oil and gas fields. Majority of the published papers deals with the perturbed oil fields following water injection to recover residual oil from the depleted reservoir and/or technology of microbial enhanced oil recovery (MEOR), when water with nutrients, such as nitrates, and sometimes thickening agents (polymers) are injected.

many papers reviewed striking differences in the MC compositions can be found. These could be to a great extent atributed to the nature of the environment in the deposits most importantdly the fact that some of the deposits were forced by water injection or even water with selected nutrients (nitrates in most cases). This introduced electron acceptors (oxygen and nitrates)  into previously stritctly anaerobic environment and lead to an alternation of MCs present.

In general, MCs in the intact deposits were still dominated by proteobacteria (with some presence of other taxons like firmicutes) but methanogens are found as an important part of MCs which in fact drive the whole methabolic process. On the contrary, in the floaded, nutrient ammended or even surface storage environments the MCs are totally dominated by Proteobacteria, Actinobacteria etc. and the methanogenic component is weak or even non detected.