Viral Abundance and Diversity of Production Fluids in Oil Reservoirs

Abstract

Viruses are widely distributed in various ecosystems and have important impacts on microbial evolution, community structure and function and nutrient cycling in the environment. Viral abundance, diversity and distribution are important for a better understanding of ecosystem functioning and have often been investigated in marine, soil, and other environments. Though microbes have proven useful in oil recovery under extreme conditions, little is known about virus community dynamics in such systems. In this study, injection water and production fluids were sampled in two blocks of the Daqing oilfield limited company where water flooding and microbial flooding were continuously used to improve oil recovery. Virus-like particles (VLPs) and bacteria in these samples were extracted and enumerated with epifluorescence microscopy, and viromes of these samples were also sequenced with Illumina Hiseq PE150. The results showed that a large number of viruses existed in the oil reservoir, and VLPs abundance of production wells was 3.9 ± 0.7 × 108 mL−1 and virus to bacteria ratio (VBR) was 6.6 ± 1.1 during water flooding. Compared with water flooding, the production wells of microbial flooding had relative lower VLPs abundance (3.3 ± 0.3 × 108 mL−1) but higher VBR (7.9 ± 2.2). Assembled viral contigs were mapped to an in-house virus reference data separate from the GenBank non-redundant nucleotide (NT) database, and the sequences annotated as virus accounted for 35.34 and 55.04% of total sequences in samples of water flooding and microbial flooding, respectively. In water flooding, 7 and 6 viral families were identified in the injection and production wells, respectively. In microbial flooding, 6 viral families were identified in the injection and production wells. The total number of identified viral species in the injection well was higher than that in the production wells for both water flooding and microbial flooding. The Shannon diversity index was higher in the production well of water flooding than in the production well of microbial flooding. These results show that viruses are very abundant and diverse in the oil reservoir’s ecosystem, and future efforts are needed to reveal the potential function of viral communities in this extreme environment.

Diversity and ecological functions of viruses inhabiting the oil reservoirs

“…A meta-analysis of eight production wells indicated that the abundance of viruses is approximately 3 × 10 8 mL −1 . Viral abundance of production wells during water flooding is higher than that in production wells during microbial flooding 31 . In addition, previous study uncovered that viruses are widespread in hydraulically fractured wells, rivalling the viral abundance observed in peatland soil ecosystems 33 .…”

“…Furthermore, viruses actively regulate and rebuild host metabolism by deploying auxiliary metabolic genes (AMGs) during infection. Recent studies have uncovered the presence of a substantial number of viruses within the oil reservoir environment 31,32 . A meta-analysis of eight production wells indicated that the abundance of viruses is approximately 3 × 10 8 mL −1 .…”

Viruses in astrobiology

“…They can thrive at temperature ranges between −12 and 96°C ( Munson-Mcgee et al, 2018 ), pH values from 1 to 11 (at the least), saturated salinity ( Pietilä et al, 2013 ), and extreme dryness ( Gil et al, 2021 ). According to this, viruses have been found in hydrothermal vents ( Russell and Hall, 1997 ), including those located at great depths in the oceans ( Thomas et al, 2021 ), in oil fields ( Zheng et al, 2020 ), in the soils of hyper-arid deserts ( Zablocki et al, 2015 ), at hundreds of meters in the subsurface ( Daly et al, 2019 ), or in places with salt concentrations far above the optimal for most living beings ( Santos et al, 2012 ). Many of these locations share environmental characteristics that also occur in extraterrestrial environments.…”

Virioplankton as an important component of plankton in the Volga Reservoirs

“…Research over the past three decades has firmly established that viruses are the most abundant and diverse biological entities (Bratbak & Heldal, 2000;Wommack & Colwell, 2000;Weinbauer, 2004), thereby forming an integral component of microbial food web (viruses, bacteria, picophytoplankton, protozoa) in a great variety of aquatic environments (Bratbak et al, 1994;Clasen et al, 2008;Wilhelm & Matteson, 2008). Viral lysis plays fundamental roles in cycling nutrients and organic matter (Middelboe et al, 2008;Staniewsski & Short, 2014), structuring the microbial food web dynamics and regulating carbon flow (Fuhrman, 1999;Bouvy et al, 2011;Breitbart, 2012), governing microbial diversity (Weinbauer & Rassoulzadegan, 2004;Keshri et al, 2017;Zheng et al, 2020). Bacteriophages prevail in virioplankton in many aquatic ecosystems, including reservoirs (Peduzzi & Schiemer, 2004;Ram et al, 2005;Sime-Ngando, 2014;Hanson et al, 2017).…”