Impact of bio-competitive exclusion on the degradation of polymers for oil displacement by endogenous microorganisms in Bohai J-oilfield

Abstract:

[Objective] This study aimed to reveal the composition of endogenous microbial community degrading the polymers for oil displacement in the reservoir and analyze the influence of bio-competitive exclusion on the microbial degradation of polymers. [Methods] Through indoor culture experiments, we observed the influence of bio-competitive exclusion on the viscosity of the polymers, and used high-throughput sequencing technology to analyze the microbial strains related to polymer degradation in Bohai J-oilfield. We then mined the genes (encoding amidase, oxygenase, hydrogen sulfide-generating enzyme) with high abundance and involved in polymer degradation in the samples. After that, we employed the real-time fluorescence PCR to compare the abundance of the above-mentioned functional genes between samples, and finally annotated the microbial taxa carrying the above-mentioned functional genes. [Results] Bio-competitive exclusion mitigated the viscosity loss of the polymers for oil displacement. Nine taxa of microorganisms related to the degradation of polymers were identified, including Acetomicrobium, Tepidiphilus, Thermoanaerobacter, Fervidobacterium, Ralstonia, Halomonas, Roseovarius,Deferribacteraceae, and Comamonadaceae. High-throughput sequencing revealed that bio-competitive exclusion significantly down-regulated the abundance of 7 genes involved in the polymer degradation in the samples. The measurement of abundance in samples showed that the abundance of the amidase gene ansB and the oxygenase gene ssuD was down-regulated by bio-competitive exclusion, which was consistent with the sequencing results. The community composition annotation indicated that bio-competitive exclusion significantly inhibited Delftia, a highly efficient bacterial taxa for polymer degradation in Bohai J-oilfield. [Conclusion] We revealed the endogenous microbial taxa related to the degradation of polymers for oil displacement in the oilfield and discovered the inhibitory effect of bio-competitive exclusion on the degradation, confirming that bio-competitive exclusion can help to stabilize the viscosity of polymers for oil displacement in offshore oilfield.