Abstract: Considering the challenges associated with effectively producing scattered residual oil in reservoirs with edge and bottom water during the “dual high-stage of high degree of reserve recovery and high water cut”, as well as developing a cost-effective and efficient microbial oil displacement system, evaluating the effectiveness of microbial flooding, and identifying key supporting technologies, this study establishes a screening chart for microbial flooding and evaluates its adaptability.The microbial community structure of the reservoir was comprehensively analyzed using microbial molecular ecology technology, and strain H3 with excellent emulsifying effect for oil recovery was screened.Through screening of key nutrients including carbon source, nitrogen source, and phosphorus source, single-factor experiments and orthogonal experiments were conducted to determine a composite powder activation system capable of achieving emulsification dispersion of crude oil while inhibiting the growth of sulfate reducing bacteria.The enrichment characteristics of residual oil of "ship bottom type" in bottom water reservoir were investigated, and a microbial emulsification + air efficiency improvement + thickener plugging EOR mode was developed. It was found that the enhanced oil recovery had a positive correlation with both the injection concentration of bacteria and the injection volume multiple.The research findings were applied to the thin sandstone reservoir with edge and bottom water of Luliang Oilfield in Junggar Basin. A pilot test was conducted to enhance recovery through "4 injectors and 20 producers" microbial flooding pattern. The microbial activator was injected at a rate of 0.13 times the pore volume. From 2017 to 2023, there was an increase in oil production by 5.6×10⁴ t, resulting in a rise of the recovery rate by 4.0 percentage points. It is evident that wells with significant improvement of oil production are primarily located in areas characterized by with high total bacterial concentration, large geological reserves, high structural parts, large reservoir thickness, thin bottom water and high degree of reserve recovery.The research findings can serve as a valuable reference for enhancing the sequencing of microbial flooding in order to optimize recovery efficiency.

Key words: endogenous microbial drive, edge-bottom water reservoir, residual oil, activating system, recovery factor, Junggar Basin, Luliang Oilfield