Microbial communities and their roles in the Cenozoic sulfurous oil reservoirs in the Southwestern Qaidam Basin, Western China

Abstract

The latest discovery of sulfurous natural gas marked a breakthrough in the Cenozoic natural gas exploration in the southwestern margin of Qaidam Basin. The 16S rRNA analyses were performed on the crude oil samples from H2S-rich reservoirs in the Yuejin, Shizigou and Huatugou profiles, to understand the sulfurous gas origin, which was also integrated with carbon and hydrogen isotopes of alkane and sulfur isotopes of H2S collected from the Yingxiongling Area. Results show that the microorganisms in samples can survive in the hypersaline reservoirs, and can be classified into multiple phyla, including Proteobacteria, Planctomycetes, Firmicutes, Bacteroidetes, and Haloanaerobiaeota. Methanogens are abundant in all of the three profiles, while sulfate-reducing bacteria are abundant in Yuejin and Huatugou profiles, contributing to the methane and H2S components in the natural gas. The carbon, hydrogen and sulfur isotopes of sulfurous natural gas in the Yingxiongling Area show that the natural gas is a mixture of coal-type gas and oil-type gas, which was primarily derived from thermal degradation, and natural gas from the Yuejin and Huatugou profiles also originated from biodegradation. The isotopic analysis agrees well with the 16S rRNA results, i.e., H2S-rich natural gas from the Cenozoic reservoirs in the southwest margin of the Qaidam Basin was primarily of thermal genesis, with microbial genesis of secondary importance.

Microbial Diversity of the Produced Waters from the Oilfields in the Republic of Tatarstan (Russian Federation): Participation in Biocorrosion

“…Researchers conclude that fermentation, methanogenesis, and sulfate reduction are common to oil reservoirs; however, other microbial groups such as iron-, manganese-, or nitratereducing bacteria were also detected in various oil reservoirs [8,9,12,17]. Understanding the microbial nature and processes in oil reservoirs is important for the oil industry, for example, for the development of technologies such as MEOR, mitigation of MIC, and bioremediation of oil-polluted sites [43,44]. It should be noted that many species cannot be cultivated, so methods of molecular biology must be used in such studies.…”

Metagenomic and Culture-Based Analyses of Microbial Communities from Petroleum Reservoirs with High-Salinity Formation Water, and Their Biotechnological Potential

“…Abundant information has been obtained on microbial diversity and geochemical activity in oil fields with low-saline formation water, characterized by a wide temperature range, using culture-based, radiotracer, and 16S rRNA-based approaches [4][5][6][7]. Metagenome analysis of microbial communities has been carried out for various hydrocarbon resource environments and petroleum reservoirs in Canada [8], China [9][10][11][12][13], USA [14], the North Sea [15], and Brazil [16,17], while metagenomic studies of the microorganisms inhabiting oil reservoirs with high-salinity formation water are scarce [18][19][20][21][22].…”

“…The composition of microbial communities depends on such physicochemical conditions of the oil field as temperature, salinity, and the pH of injected and formation water, as well as on sulfate and sulfide concentrations [7,13,[23][24][25][26]. The major physiological groups of oil field microorganisms usually comprise fermentative, syntrophic, iron-reducing, sulfatereducing, and methanogenic prokaryotes [4,[27][28][29].…”