Changes of Microorganism and Corrosion Tendency During Fracturing of Flowback Fluid Recovery Wells of Shale Gas

The study is focused on understanding microbiological changes and the corrosion tendency in the fracturing wells with a flowback fluid reuse during the exploration and production process in the Changning shale gas field, Sichuan. High-throughput sequencing technology and electrochemical workstation were used to analyze the pre-fracturing fluid, the flowback and produced water (FPW) at each stage of the production process of a single shale gas well in Southern Sichuan. The fracturing fluid was prepared with the flowback fluid. The results showed that during exploration and production, the dominant bacteria is Roseovarius (32.69%), and the others include Arcobacter, Marinobacter, Marinobacterium, etc. The dominant archaea is Methanthermobacter (59.19%), and the others include Methannolobus, Thermococcus, etc. The enrichment of the halophilic and halotolerant microorganisms is due to the changes of the fluid salinity. Besides, the relative abundance of the sulfate reducing bacteria (SRB) which can be identified as the cause of the microbiologically influenced corrosion (MIC) during the exploration and production process first dropped sharply from 21% to below 1% and finally rose to 31%. It is worth noting that the corrosion tendency shown by the electrochemical results is basically consistent with the change in abundance of SRB. This study preliminarily reveals the changes of microorganisms in the exploration and production process of fracturing with the flowback fluid, and provides new ideas for the prevention and control of corrosive microorganisms, protection against pipe corrosion, and effective management of water resources.