Characterization of bacillus licheniformis strain Ta62bi as potential selective plugging agent for enchanced oil recovery

Abstract

Bacterial plugging agents for microbial enhanced oil recovery were peviously studied using non-hydrocarbon substrate. They lacked the ability to survive and form stable plug at high concentration of hydrocarbon compounds. As an alternative, hydrocarbon was used as substrate to determine the bacterial potential as plugging agent. In this study, Bacillus licheniformis Ta62bi was used to study the potential of the bacteria as plugging agent in polycyclic aromatic hydrocarbon (PAH)-rich condition. Three responses (growth, exopolysaccharides (EPS) and PAH consumption) were analyzed. The survivability pattern was observed at 72 hours. From the analysis, pyrene was the best PAH compared to naphthalene. It was based on increment of 214% (415 CFU/mL) in growth and 30% (0.759 g/L) in EPS production. However, the consumption of soluble PAH (0.002 to 0.015 mg/L) was low. The assimilation of hydrocarbon by potential bacterial plugging agent is the only means of survival. Otherwise, it would degrade to a great extent the oil components that would lead to the reduction of the oil quality. Next, a two-level factorial design was conducted to analyze the effects of different concentration of pyrene (0.1 to 10 g/L) and temperatures (27°C to 50°C) to the responses. The results showed that both factors significantly affect the responses (P < 0.05). Both factors inhibited growth of bacterium Ta62bi. As the PAH concentration was increased, the EPS production and PAH consumption was also found to increase at 27˚C. At 50°C, there was an increase in the EPS production but not in the PAH consumption. Therefore, EPS might be implied to having an important role in the tolerance of the TA62bi strain towards hydrocarbon. The findings will be further used in future research as a model to predict and control enhanced oil recovery plugging mechanism