The Influence of Microbial Community on Oil Reservoirs: A Case Study on the Mesozoic Natural Gas in the Pengyang Area, Southwestern Ordos Basin, China

Abstract

The formation of Mesozoic natural gas in the Pengyang area of southwestern Ordos Basin is discussed, from the perspective of microbial community characteristics, in order to clarify the relationship between the origin of natural gas and its associated indigenous microbial community. The types and diversity of indigenous microbial communities associated with the oil reservoir were studied by means of collecting reservoir formation water samples from exploration wells. The indigenous microbial communities in the Chang 8 member of the Yanchang Formation were primarily distributed within Proteobacteria and Firmicutes, including the specific species and genera of Methylobacter, Pseudomonas, Haibacter, Toxobacillus, Acinetobacter and Adura actinomyces. The results of diversity analysis shows that the number of common genes was 5448, while the number of unique genes and information was less. This reflects the fact that the strata in the study area are relatively closed and not invaded by external water sources, which leads to the development of biological community diversity. In conjunction with the analysis of geochemical characteristics of oil and gas reservoirs in this area, this indicates that the study area possesses the necessary geological conditions for microbial degradation. It is the first time that the species and diversity of the indigenous microbial community in the Ordos Basin have been analyzed, showing that microbial degradation is the main cause of natural gas formation here, changes the characteristics of crude oil in this area and provides first-hand information on the impact of indigenous microorganisms on the reservoir.