Microbiological Characteristics of Sapropel and the Possibility of Its Application for Enhanced Oil Recovery from Carbonate Reservoirs

Oil reservoirs with carbonate oil-bearing collectors are characterized by high fracturing. To improve the coverage of a reservoir by flooding, clogging agents should be introduced into the formation. In the patent literature, using sapropel as a plugging agent has been proposed. In the present work, application of cultural methods revealed that sapropel can be not only a dispersant, but also a source of aerobic hydrocarbon-oxidizing and anaerobic fermenting bacteria. Taxonomic analysis of the sapropel microbial community using high-throughput sequencing of the 16S rRNA gene V3–V4 region showed predominance of bacteria of the genus Streptomyces (40.7%) of the phylum Actinomycetota (55% of the total number of sequences). The possibility of using starch, sucrose, and other sugars by the microorganisms of sapropel and reservoir water predicted using the iVikodak program was also confirmed experimentally. Formation microbiota and sapropel bacteria fermented starch and sucrose (a molasses component) with formation of alcohols and lower fatty acids, which may contribute in decreasing the viscosity of oil, dissolve rock carbonates and lead to enhanced oil recovery.