Ökologische Prinzipien von mikrobiellem Abbau in Ölreservoiren
Mineralogie, Petrologie und Geochemie
Zusammenfassung der Projektergebnisse
Heavy oil and bitumen dominate the world’s oil reservoirs due to the degradation by anaerobic microorganisms over geological time scales. However, the specifics of metabolic processes and biodegradation rates in deep oil reservoirs remain unclear due to insufficient samples and extensive timescales. Earlier studies showed that microbial activity and biodegradation rates most prominent at the oil-water transition zone (OWTZ), the interface between the oil-bearing and water-bearing layers. Biodegradation is believed to decrease with distance from this zone due to a lack of water, electron acceptors, and nutrients, suggesting no degradation occurs within the oil leg itself. Yet, signs of microbial life are found in almost all oil and water samples from reservoirs with temperatures up to 82°C. Here we show that microbes are present and active in a newly drilled oil well located in Daqing, China which was sampled over 11 months. Since the well steadily produced oil, the time series of samples reflected oil more and more distant from the well. Providing that all microorganisms in the oil samples originated from the reservoir, the samples contained information about the spatial heterogeneity of microbial communities within the reservoir which we analyzed with 16S rRNA gene amplicon sequencing and reverse stable isotope labelling to assess the potential microbial activity. Our study demonstrates that microorganisms are present and metabolically active in various zones of this oil reservoir suggesting this may be a common trait of most oil reservoirs. To accurately process the incoming samples from China, our methods were first established for reverse stable isotope labeling and 16S rRNA gene amplicon sequencing with light oil. During this work, we also observed a potential presence of biosurfactant-producing bacteria in our incubations. Although this work did not promising results for anaerobic biosurfactant production, we could interestingly detect methane production in incubations with sulfate as an electron acceptor. Based on this unexpected finding we investigated methane production in a highly adapted sulfate-reducing community and found that despite the known thermodynamic constraints methanogenesis can occur in the presence of sulfate.
Projektbezogene Publikationen (Auswahl)
-
Assessing anaerobic microbial degradation rates of crude light oil with reverse stable isotope labelling and community analysis. Frontiers in Microbiomes, 3.
Beilig, Sebastian; Pannekens, Mark; Voskuhl, Lisa & Meckenstock, Rainer U.
