ABSTRACT
Nitrate injection into oil reservoirs to prevent souring stimulates the growth of heterotrophic nitrate reducing bacteria (hNRB) which couple reduction of nitrate to oxidation of oil organics. The microbial populations of hNRB in oil reservoirs are highly diverse. hNRB that belongs to the class Proteobacteria, prefer to use alkylbenzenezes for reduction of nitrate to nitrite and di-nitrogen (N2). However, in heavy oils these are present at low concentrations. But it can be increased by injection of water-dissolved alkylbenzenes that can bind to oil along the water injection channels. Hydrocarbon- and nitrate-mediated microbially enhanced oil recovery (HN-MEOR) is based on enhancing the hNRB growth by providing high concentrations of alkylbenzenes and nitrate. The oil production was increased up to 20% of residual oil contained in the model sand pack columns using this strategy. The formation of hNRB biomass, gases (N2 and CO2) and other microbial products most likely contributed to oil production.
