Some characteristics of the microbial community of reservoir fluids of the Romashkinskoe field

Abstract

The condition of oil wells is reflected by the abundance and species composition of microorganisms in their reservoir fluids. However, such microorganisms are often present in small numbers, which hampers their analysis. The culture enrichment method is a good strategy to overcome this problem. Here we discuss the results of a molecular biology-based comparative analysis of some characteristics of the microbial communities from the following two samples: the initial reservoir fluid sample (2313A) and the enriched sample (2313B). The metagenomic analysis showed that sample 2313A was dominated by aerobic bacteria belonging to the genera Pseudomonas (order Pseudomonales) (47.5%) and Rhodococcus (order Actinomycetales) (45%). The community also comprised representatives of the anaerobic orders Halanaerobiales (1.4%) and Desulfovibrionales (0.03%). In sample 2313B, bacteria from the phylum Actinobacteria prevailed (99.9%) with Rhodococcus fascians (order Actinomycetales) identified as the dominant OTU. The quantitative real-time PCR analysis revealed that the enrichment process led to a 1063 and 244 times decrease in the relative abundance of copies of the rhlB and rhlAB genes encoding enzymes for the production of biosurfactants. The cultivation had a lesser effect on the abundance of copies of the dsrA and apsA genes, both involved in the sulfate reduction. When summarized, the obtained results indicate that the culture enrichment method enables the formation of a community differing substantially from the initial microbial communities of reservoir fluids of the oil wells.

Keywords

• reservoir fluid
• bacterial community
• sulfate reduction
• biosurfactants