The shift of microbial population composition accompanying the injected water flowing in the water-flooding petroleum reservoirs

Abstract

Abstract. In water-flooding petroleum reservoir, microbial populations in injected water are expected to migrate into oil-bearing strata and reach production wells. To demonstrate this, we firstly investigated microbial compositions in a homogeneous sandstone reservoir. The results indicated that the injected water harbored more microbial cells than produced water, and the shared populations and their abundance accounted for a minor fraction in injected water, while dominated in produced water, suggesting that most populations in injected water did hardly reach production wells in this reservoir. We further investigated microbial communities in water samples collected from wellhead and downhole of injection wells and production wells in a heterogeneous conglomerate reservoir. The results indicated that, except for the community reconstruction mainly resulted from dissolved oxygen, most populations were simultaneously detected in the wellhead and downhole of injection wells and production wells, suggesting that most microbial populations in injected water reached the production wells. This study suggest that microbial populations in injected water can pass through reservoir strata and reach production wells, but the reservoir heterogeneity, interwell spacing, sieve effect of strata and dissolved oxygen exert significant influence on microbial migration and distribution in reservoirs.