MICROBIOLOGICAL AND GEOCHEMICAL CHARACTERIZATION OF CARBONATE OIL COLLECTORS OF TATARSTAN

Regularities in the distribution of microorganisms were studied in the carbonate oil collectors of the Romashkinskoe and Bavlinskoe oil fiel ds differing in hydrochemical conditions. In the Turneiskii stratum of the Bavlinskoe oil field flooded with fresh river water, the greatest diversity and activity of microflora were observed in the near-bottom zone of injection wells. In this zone, anaerobic microflora was repre sented by fermentative (10(4) cells/ml), sulfate-reducing (10(4) to 10 (5) cells/ml), and methanogenic (10(2) to 10(4) cells/ml) bacteria; th e number of aerobic bacteria was low. The sulfate reduction rate reach ed 237.5 mu g H2S/(1 day). Analysis of samples of oil-water emulsion f rom producing wells showed a scarce microbial population in the Turnei skii stratum. In the Serpukhovskoi stratum (bed 303) of the Romashkins koe oil field, which has been exploited without flooding, the reduced environment prevented the development of aerobic microorganisms: sapro trophs growing on nutrient agar were detected only in two out of nine samples; hydrocarbon oxidizers were absent. Among anaerobes, most nume rous were fermentative (10-10(4) cells/ml) and sulfate-reducing (10(2) -10(4) cells/ml) bacteria. In bed 303, we recorded contemporary proces ses of sulfate reduction and methanogenesis. The sulfate reduction rat e did not exceed 17.1 mu g S2-/(1 day). Methane was produced mainly fr om bicarbonate (0.009-0.199 mu g CH4/(1 day). Methanogenesis from acet ate was detected in only two water samples, where its rate was 0.004 a nd 0.023 mu g CH4/(1 day). Thus, the carbonate collectors studied cont ained fermentative microflora, and this is a factor calling for the em ployment of microbiological methods for the enhancement of oil recover y.