Molecular Characterization of Organic Indicators of Petroleum Biosouring

The production of sulfide in a petroleum reservoir by anaerobic sulfate reducing microorganisms (SRM) is environmentally, industrially, and epidemiologically hazardous. More knowledge is needed about the anaerobic respiration pathway of SRM in petroleum, and whether the activity of SRM could be effectively inhibited using nitrate or perchlorate treatments. In order to understand the molecular transformations and metabolic fingerprints of SRM in petroleum reservoirs, and how they are altered by nitrate or perchlorate treatments, the Coates and Goldstein Laboratories at UC-Berkeley have run controlled column incubation studies of petroleum from an oil reservoir. By using two dimensional gas chromatography (GCxGC) with high resolution time-of-flight mass spectrometry coupled to vacuum ultraviolet radiation at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory (LBNL), detailed chemical characterizations of hydrocarbons from approximately C9-C30 have been completed, separating the complete oil sample by number of carbon atoms and chemical classes (including normal alkanes, branched alkanes, number of alkyl rings, and number of aromatic rings) corresponding to petroleum transformations in sulfate, nitrate, and perchlorate reducing environments. Results demonstrate that the anaerobic pathway of SRM preferentially involves the transformation of heavier polycyclic aromatic hydrocarbons (PAHs), and that a large number of products are created that contain either two or four oxygen atoms, suggesting fumarate additions initialize the anaerobic process.