Abstract
Abstract. Microbial communities in injected water are expected to have significant influence on those of reservoir strata in long-term water flooding petroleum reservoirs. To investigate the similarities and differences in microbial communities in injected water and reservoir strata, high-throughput sequencing of microbial partial 16S rRNA of the water samples collected from the wellhead and downhole of injection wells, and from production wells in a homogeneous sandstone reservoir and a heterogeneous conglomerate reservoir were performed. The results indicate that a small number of microbial populations are shared between the water samples from the injection and production wells in the sandstone reservoir, whereas a large number of microbial populations are shared in the conglomerate reservoir. The bacterial and archaeal communities in the reservoir strata have high concentrations, which are similar to those in the injected water. However, microbial population abundance exhibited large differences between the water samples from the injection and production wells. The number of shared populations reflects the influence of microbial communities in injected water on those in reservoir strata to some extent, and show strong association with the unique variation of reservoir environments.
Highlights
Water flooding is an efficient and inexpensive oil recovery process that is employed worldwide
If microbial populations in injected water can flow into reservoir strata and reach production wells, is the microbial community in the injected water expected to have a similar community composition to those in the production wells? If there is a large difference in community composition, what is the difference and how many microbial populations are shared? To explore these issues, we investigated the microbial populations and their abundance in injection and production wells in a homogeneous sandstone petroleum reservoir with a permeability of 522 × 10−3 μm2 and inter-well spacing of 300–425 m using 16S rRNA pyrosequencing and realtime fluorescent quantitative PCR
The results of quantitative PCR (qPCR) indicated that the copy number of bacterial 16S rRNA in water samples of the injection well was 8.25 × 106 copies mL−1, while 1.5 × 106 to 2.75 × 106 copies mL−1 in the water samples of the production wells
Summary
Water flooding is an efficient and inexpensive oil recovery process that is employed worldwide. When injecting nutrients and air into reservoir strata, these microbial populations can be stimulated, and produce metabolites, such as polysaccharide, surfactants, acid, alcohol, and biogas. Because these metabolites can improve reservoir properties by blocking preferred water flow paths, by lowering interfacial tension between brine and the oil phase, and by decreasing oil viscosity (Youssef et al, 2009), microbial enhanced oil recovery (MEOR) has been applied to the petroleum industry and is currently being studied extensively (AbdelWaly, 1999; Zhang et al, 2012b; Bao et al, 2009; Gao et al, 2013; Li et al, 2014). To the best of our knowledge, detailed studies about the effects of the microbial
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