Aerobic bacteria from the oilwells of the supergiant romashkinskoye oilfield

Many oilfields such as supergiant Romaschkinskoye oilfield in Russia contain heavy oils that are complicated to recover. In order to increase the proportion of obtained oil, methods of enhanced oil recovery are implemented, and microbial methods (MEOR) are considered as safe and efficient once. In-situ MEOR are based on stimulation of oilwell microflora that partly decomposes hydrocarbon molecules or alters oil-water interface tension. Despite oilwells are an environments with anaerobic conditions, many allochtonous microbes there are able to use aerobic pathways. Moreover, stimulation of those aerobic microbes by addition of nutrients and oxygen (that is contained in the production water) results in significant oil recovery increase since aerobes produce metabolites that activate the microflora of the lower anaerobic zone. However, aerobic microbial communities of many oilwells remain unstudied and their role for oil recovery is underestimated. The purpose of the present study was to reveal the biodiversity and oil-emulsifying ability of the aerobic microorganisms inhabiting heavy oils from the supergiant Romaschkinskoye oilfield. For this purpose, oil was sampled from 5 oil reservoirs belonging to the Romaschkinskoye oilfield. For each reservoir, oil was obtained from 3 different wells recovering oil from different depths. After cultivation under aerobic conditions, 16 isolates belonging to Bacillus and Enterococcus genera were obtained from the samples. The emulsification index (E24) revealed for cultural media of those isolates ranged between 15 and 70%. For six isolates, it exceeded 60% which can be promising for using MEOR. Further investigation of the ability of those isolates to stimulate the oil anaerobic microflora is required.