Microbiomes in Zhansan area, Shengli Oilfield, Shandong Province, China

Abstract

The purpose of this study was to characterize bacterial and archaeal communities in a high temperature oil reservoir and their relationships with environmental factors. Production liquid (further separated to oil and water samples) and injection water samples were collected in the Zhansan area of the Shengli Oilfield, Shandong Province and subjected to 16S rRNA gene analysis by high-throughput sequencing. The physicochemical properties of the water samples were also analyzed. The bacterial communities in the Zhansan area showed a relatively high diversity compared with those in other oil reservoirs previously reported. High diversity may be due to nutrients introduced in the injection water during microbial enhanced oil recovery in this area. The highest diversity of bacterial communities was observed in the injection water samples and the lowest in oil samples of the production liquid. Bacterial compositions showed a clustering pattern according to the sample types. Specifically, the dominant bacterial groups in the oil and water samples of the production liquid were γ-Proteobacteria, ε-Proteobacteria, α-Proteobacteria, Actinomycetes and Clostridium. At the genus level, Pseudomonas was dominant in both oil and water samples of the production liquid, whereas the bacterial community in injection water was dominated by Sulfurimonas. In general, Pseudomonas spp. are mesophilic facultative anaerobes and many species of this genus can degrade petroleum fractions. The presence of this genus in the high temperature oil reservoir suggests that they were associated with low-to moderate temperature zones in contact with various hydrocarbons. As for the archaeal biomes, the diversity was low in all samples. The major archaeal groups in the production liquid were Methanomicrobia, Halobacteria, Thermoplasmata, Thermoprotei, and Thermococci, dominated by Methanosaeta and Methanobacteriaceae especially. They also showed a clustering pattern according to sample types. Redundancy analysis (RDA) of microbiomes and environmental parameters indicated that the sulfate concentration significantly constructed the bacterial and archaeal communities in the injection water, which was one order of magnitude higher than that in the water samples of the production liquid. In contrast, the bacterial communities in the water samples of the production liquid were impacted by Ca2+ and pH. The archaeal communities had significant correlations with Cl-, Mg2+ and HCO3-. These results revealed the ecological distribution of microbiomes in different phases of production liquid, which are useful to our understanding about microbiomes in high temperature oil reservoirs and provide clues on possible manipulation and control of microbiomes in microbial enhanced oil recovery.