Anaerobic microbial communities and their potential for bioenergy production in heavily biodegraded petroleum reservoirs

Abstract

Most of the oil in low temperature, non-uplifted reservoirs is biodegraded due to millions of years of microbial activity, including via methanogenesis from crude oil. To evaluate stimulating additional methanogenesis in already heavily biodegraded oil reservoirs, oil sands samples were amended with nutrients and electron acceptors, but oil sands bitumen was the only organic substrate. Methane production was monitored for over 3000 days. Methanogenesis was observed in duplicate microcosms that were unamended, amended with sulfate or that were initially oxic, however methanogenesis was not observed in nitrate-amended controls. The highest rate of methane production was 0.15 μmol CH 4 g −1 oil d −1 , orders of magnitude lower than other reports of methanogenesis from lighter crude oils. Methanogenic Archaea and several potential syntrophic bacterial partners were detected following the incubations. GC-MS and FTICR-MS revealed no significant bitumen alteration for any specific compound or compound class, suggesting that the very slow methanogenesis observed was coupled to bitumen biodegradation in an unspecific manner. After 3000 days, methanogenic communities were amended with benzoate resulting in methanogenesis rates that were 110-fold greater. This suggests that oil-to-methane conversion is limited by the recalcitrant nature of oil sands bitumen, not the microbial communities resident in heavy oil reservoirs.

Metagenomic Investigation of a Low Diversity, High Salinity Offshore Oil Reservoir

“…A clean (unused) 0.2 µm polycarbonate membrane filter was used as a negative control for the extractions. DNA extracts were first used for 16S rRNA gene amplification (30 cycles) and sequencing on an Ion Personal Genome Machine (Ion Torrent, Life Technologies, Paisley, UK), using primers F515 and R926 [14] and procedures as described previously [15]. A fastq file was generated and further analyses were conducted with mothur [16] software, version 1.39.5.…”

Liposoluble quinone promotes the reduction of hydrophobic mineral and extracellular electron transfer of Shewanella oneidensis MR-1

“… 34 Microorganisms in anaerobic reservoir environments also exhibit extracellular respiration. Microbes existing in petroleum, oil sands 35 and asphalt lakes 36 can utilize these hydrophobic carbon sources. The methane-producing degradation of petroleum is considered to be the main degradation pathway in crude oil.…”

“…The methane-producing degradation of petroleum is considered to be the main degradation pathway in crude oil. 36 The above-mentioned substrates with a hydrophobic surface usually possess the characteristics of large molecular weight and low affinity with bacteria, making it difficult for them to reach the cell interior. Microorganisms with EET ability has a natural advantage to interact with heterogeneous substances.…”