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Published July 2003 | public
Journal Article

Geochemical Influence on Diversity and Microbial Processes in High Temperature Oil Reservoirs

Abstract

The diversity of thermophilic microbial assemblages detected within two neighboring high temperature petroleum formations was shown to closely parallel the different geochemical regimes existing in each. A high percentage of archaeal 16S rRNA gene sequences, related to thermophilic aceticlastic and hydrogenotrophic methanogens, were detected in the natural gas producing Rincon Formation. In contrast, rRNA gene libraries from the highly sulfidogenic Monterey Formation contained primarily sulfur-utilizing and fermentative archaea and bacteria. In addition to the variations in microbial community structure, microbial activities measured in microcosm experiments using high temperature production fluids from oil-bearing formations also demonstrated fundamental differences in the terminal respiratory and redox processes. Provided with the same suite of basic energy substrates, production fluids from the South Elwood Rincon Formation actively generated methane, while thermophilic microflora within the Monterey production fluids were dominated by hydrogen sulfide producing microorganisms. In both cases, molecular hydrogen appeared to play a central role in the stimulation of carbon and sulfur cycling in these systems. In methanogenic production fluids, the addition of sulfur compounds induced a rapid shift in the terminal electron accepting process, stimulating hydrogen sulfide formation and illustrating the metabolic versatility of the subsurface thermophilic assemblage. The high similarity between microbial community structure and activity corresponding with the prevalent geochemical conditions observed in deep subsurface petroleum reservoirs suggests that the resident microflora have adapted to the subsurface physicochemical conditions and may actively influence the geochemical environment in situ.

Additional Information

© 2003 Taylor & Francis Inc. Received 20 February 2002; accepted 7 April 2003. We thank Peter Eichhubl and Steve Franks for generously sharing their unpublished work with us. We also are indebted to Prentice Patterson and the crew from Platform Holly (Mobil and Venoco Inc), Trent Taylor, Christa Schleper, and Chris Preston for assistance with sample collection and Jim Childress for technical advice and use of his analytical equipment. V. J. Orphan is currently supported by a National Research Council Fellowship at NASA Ames Research Center.

Additional details

Created:
August 22, 2023
Modified:
October 23, 2023