Activation of the geochemical activity of stratal microflora as the basis of a biotechnology for enhancement of oil recovery

A biotechnology for the enhancement of oil recovery, based on the activatio n of the geochemical activity of stratal microflora, was subjected to a pil ot trial at the Romashkinskoe oil field. In the main technological variant, activation of microbial activity was achieved by cyclic introduction of ae rated water supplemented with mineral salts of nitrogen and phosphorus thro ugh injection wells. In an additional variant, crude oil was also introduce d through the injection well. The use of this biotechnology led to the acti vation of microbial processes, first in the near-bottom zones of injection wells and then along the stratum in accordance with hydrodynamic conditions . At the first stage, the activity of aerobic oil-oxidizing microorganisms increased, resulting in an increase in the bicarbonate and acetate content of the stratal water. The second stage was characterized by an enhancement of microbial methanogenesis in the anoxic zone of the stratum and by a cons equent increase in the portion of biogenic isotopically light methane in th e total methane pool in stratal fluids. The dynamics of microbial metabolit es in stratal waters correlated with an increase in the production of the p roducing wells. The pilot trials of the MEOR biotechnology at four sites of the Romashkinskoe oil field yielded 41560 tons of additionally recovered o il (29% of the oil extracted at these sites during the trials).