Abstract:[Objective] The Liuzhong area of Xinjiang Oilfield is a typical ordinary heavy oil reservoir with poor water flooding effect and rich indigenous microorganisms. We studied the application potential of indigenous microbial flooding in this reservoir by analyzing the impact of indigenous microbial flooding on the microbial activities in the reservoir. [Methods] During the implementation of indigenous microbial flooding, we employed high-throughput sequencing and the techniques of analytical chemistry to systematically determine the microbial community structure, total bacterial count, number of functional microorganisms, and properties of the produced fluid. [Results] The injection of the activator and air into the reservoir in the field test significantly activated the indigenous microorganisms, changed the bacterial community structure, and increased the number of total bacteria and functional bacteria by 2-3 orders of magnitude. Moreover, it significantly enhanced the metabolic activities of indigenous microorganisms. After interaction with formation fluid, the crude oil was obviously emulsified, and the oil recovery was finally improved by 5.2%. [Conclusion] Indigenous microbial flooding significantly affects the microbial activities in the water drive ordinary heavy oil reservoirs with abundant indigenous microorganisms, demonstrating significant technical advantages and great application potential. The microbial community structure, number of functional microorganisms, and concentrations of related metabolites can be used as indicators to evaluate the on-site activation effect of indigenous microbial flooding. The findings of this study provide technical reference for other on-site experiments of indigenous microbial flooding.
