S78: The biodegradation of hydrocarbons and biocorrosion of metal surfaces from a microbial ecology perspective

The degradation of hydrocarbons and corrosion of metal surfaces are complex activities that can only be carried out through the collective metabolic capabilities of a mixed assemblage of microorganisms.  The ecological forces influencing the composition of these assemblages therefore, should be linked to the extent of hydrocarbon degradation and the risk of biocorrosion.  Our approach to studying the microbial ecology of oil and gas production facilities has focused on testing correlations between the composition of assemblages and their collective activities.  The microbial assemblages, profiles of potential hydrocarbon metabolites and corrosion histories were compared between two oil production facilities on the North Slope of Alaska under different management practices.  Field A is younger, producing relatively high oil/water ratios.  Seawater is added to the formation to maintain proper operating pressures.  Field B, in contrast, is an older facility with lower oil/water ratios.  As a result, the water produced from the formation is re-circulated throughout the formation to maintain pressures instead of seawater, leading to higher temperatures and lower concentrations of electron acceptors such as sulfate and thiosulfate.  Field A was dominated by members of the Proteobacteria, and metabolites of mostly “lighter” hydrocarbons.  Field B contained thermophilic members of the Firmicutes and Synergistes and had a greater diversity of hydrocarbon metabolites.  These results highlight the link between microbial assemblages and their metabolic activities, as well as how the properties of the oil reservoirs and oil production practices can be considered ecological forces driving the microbial community structures and functions.