Browsing by Author "Kryachko, Yuriy"

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    Microbially enhanced oil recovery through stimulation of indigenous oil field microflora with nitrate or introduction of rhamnolipid producers
    (2013-01-03) Kryachko, Yuriy; Voordouw, Gerrit
    Sandpack model columns filled with two kinds of heavy oil were used to study the influence of nitrate injections on oil production. Columns containing trapped oil and nitrate consistently produced more oil than columns without nitrate in anaerobic conditions under counter-diffusion-induced gas drive. The presence of nitrate likely led to an increase of biomass and amounts of produced biosurfactants, allowing a reduction of oil-water interfacial tension. Gas-driven recovery of oil rich in alkanes (EO) was enhanced to a greater extent through nitrate injection than recovery of oil rich in polyaromatic hydrocarbons (LO). A water flood following incubation of columns containing nitrate did not lead to trapped oil production indicating that microbial growth was not sufficient to plug high permeability zones. Nitrate reducers Azoarcus and Delftia, the former being from the field of origin of EO, were found to consume heptane as a sole source of carbon and energy. Bioinformatics analysis of pyrosequenced 16S rDNA of the microbial communities adhering to EO and associated with an aqueous phase of a produced water-EO mixture showed that the former community was less diverse than the latter. Many known hydrocarbon degraders, e.g. Thalassolituus, Rhodococcus and Sphingomonas, were found to adhere to EO. In contrast, all identified genera of the Deltaproteobacteria were found to reside predominantly in the aqueous phase, likely because their substrates were mostly water-soluble. Consistently with the fact that hydrogen is more soluble in oil than in water, hydrogenotrophs, e.g. Methanolobus, Methanobacterium and Acetobacterium, had higher representation in the microbial community adhering to EO than in the community associated with an aqueous phase. The application of a cell-containing supernatant from the culture of a native rhamnolipid producer led to a greater enhancement of water-flood-driven LO recovery than the application of chemical surfactants. The application of cell-containing supernatants from cultures of a recombinant strain carrying genes responsible for rhamnolipid production and a strain with repressed transcription of rhamnolipid production genes led to enhancement of counter-diffusion-induced-gas-driven EO recovery, suggesting that very low surfactant concentrations are required for MEOR under solution gas drive.