## 4 Discussion  
This study compared the microbial communities of production wells in ASP and WF, and investigated the structure and characteristics of the microbial community compositions in oil reservoirs of different development blocks. In terms of the microbial community composition, most of these bacteria had the function of denitrification and hydrocarbon degradation [25,26], as well as the ability to reduce hydrocarbon viscosity. Among them, _Pseudomonas_ sp. is a commonly used bacterium for oil recovery, and most species in this genus have the ability to produce biosurfactants such as lipopeptide and glycolipid biosurfactants. In addition, the rhamnpid produced by _Pseudomonas_ sp. could reduce  
Figure 6: (**a**) A spatially constrained, distance-based redundancy analysis (RDA) was performed to assess the quantitative composition of bacterial communities in plot-based samples. The dominant genus is highlighted in a different colour. Arrows indicate the direction of maximum change in variables. (**b**) Heatmap was performed to assess the positive and negative correlation between environmental factors and dominant genus in two blocks. “** indicates significant correlation at 0.01 level and “** indicates significant correlation at 0.05 level; otherwise, there is no significant difference. the interfacial tension of the oil-water phase for EOR [25; 27]. _Thuera_ sp. is capable of denitrification using a variety of carbon sources, including aromatic compounds [28]. _Acinetobacter_ sp. has the ability to degrade saturated and aromatic hydrocarbons [29]. From the above results, it can also be seen that, when comparing the significant indicators observed in the microbial communities, the Shannon index and Chaol1 index of the ASP block were both lower than those of the WF block. These results indicate that the microbial diversity of the ASP block of produced wells was relatively low. This is consistent with the previous literature on microbial communities in different reservoirs: the diversity of bacteria and archaea is significantly influenced by extreme reservoir environments such as steam soaking, high temperatures, high pressures, and a high salinity [30]. A highly alkaline environment exceeds the survival limits of most microbial populations. Alkali-tolerant populations of _Halomonas_ sp. dominated the ASP block, but not the bacterial communities of the WF block. These phenomena indicated that some microbial populations inhabiting the WF block disappeared in the ASP block due to the harsh selection pressure of the extreme environment, and fewer microbial populations that were well adapted or tolerant to the extreme environment survived. During the WF block, there was a lack of external selective pressure. It seemed that the WF block was more suitable for the subsequent implementation of microbial flooding. Most previous studies on microbial community biodiversity have focused on species numbers and abundances rather than on species interactions. However, the impact of species interactions on ecosystem function may be more important than species richness and abundance, especially in complex ecosystems [31]. Recent analyses have shown that the ecological network of ecosystems is highly structured [32], yet the interactions between the network structure and its components are ignored, hindering further assessment of biodiversity and its dynamics. In this study, we applied a correlation-based network analysis to investigate the co-occurrence models of the bacterial communities in the WF and ASP blocks. Previous studies have shown that microbial interactions can maintain ecosystem function and stability [33; 34]. Our results indicated that, compared to the WF blocks, fewer connections, lower clustering coefficients, and network density were observed in the co-occurrence network of the ASP blocks. This means that the network complexity of the WF blocks was higher than that of the ASP blocks. This led to a higher diversity of the microbial community structure in the WF block.