Microbial distribution and variation in produced water from separators to storage tanks of shale gas wells in Sichuan Basin, China

Abstract

Microorganisms present in production facilities of shale gas can cause substantial increases in production costs and complicate water management. Here, an uncommon microbial distribution was observed at six gas-gathering stations of deep shale wells (average depth: 4162 m) in the Sichuan Basin, China. Employing Illumina MiSeq 16S rRNA gene sequencing and quantitative polymerase chain reaction (qPCR), the majority of bacterial communities in gas–water separators and water storage tanks sampled belonged to the genus Shewanella (accounting for 60.67% of total bacterial sequences detected) as well as Marinobacter, Marinobacterium, Arcobacter, Acetobacterium, and Alkalibacter that were encountered in previously reported shale produced water. Archaea were mainly methylotrophic and halotolerant methanogenic genera, including Methanolobus, Methanohalophilus, and Methanocalculus. For the first time, fungi (primarily Ascomycota and Basidiomycota) were detected in the produced water from production facilities, and some genera, such as Cladosporium, may be associated with corrosion. Apart from Shewanella, other sulfidogenic taxa mainly belonging to Dethiosulfovibrio and Dethiosulfatibacter and acid producers belonging to Acetobacterium were also encountered. Microbial communities in storage tanks were more abundant and diverse than those in separators. Notably, detection of biocorrosive sulfate-reducing bacteria (SRB) increased from separators (0.39%) to storage tanks (2.37%). This study expands our knowledge about microbial diversity in production facilities of shale gas and the findings may have implications in guiding wastewater management during shale gas production.