Potential of viscosity reducing thermophillic anaerobic bacterial consortium TERIB#90 in upgrading heavy oil

• An anaerobic viscosity reducing consortium (TERIB#90) enriched from oil reservoir.
• TERIB#90 has potential to reduce viscosity (665 to 10 cP) at 70 °C.
• TERIB#90 produces H2 (65%), CO2 (27%) and volatile fatty acids (2500 mg/L).
• Belong to genus Moorella sp. and also reduces surface tension (64–27 mN/m).
• TEPIB#90 enhanced heavy oil recovery (27%) at 70 °C in core flood studies.

An anaerobic, thermophilic microbial viscosity reducing consortium TERIB#90 was isolated from formation fluid of an oil reservoir located in India. It was able to reduce 98% viscosity of crude oil (665 to 10 cP) at 70 °C on the 30th day of incubation. Sequence analysis of the clones obtained from 16S rDNA clonal library showed affiliations with the genus Moorella sp. CF4 ranging from 94% to 97% identity. Gas chromatography results indicated degradation of aromatics (56%). The metabolic capabilities of this consortium to survive and grow under selected heavy oil reservoir conditions such as high temperature, salinity and presence of oil were also evaluated. A higher percentage of viscosity reduction (75–98%) was observed at 60–70 °C as compared to 80 °C (14%). It could grow up to 2% NaCl concentration and effectively reduce viscosity up to 80% but it showed maximum viscosity reduction when no NaCl was added. Metabolites in the form of hydrogen (65%), carbon dioxide (27%), volatile fatty acids (2500 mg/L) and biosurfactant as indicated by a reduced surface tension (27 from 64 mN/m) were observed. A core flooding test was designed to explore the potential of TERIB#90 as an agent for viscosity reduction of heavy oil. The results showed that the viscosity reduction of heavy oil by the microbial metabolites and degradation of heavy fractions are the dominant mechanisms for oil recovery efficiency. The microbial processes elucidated by this consortium both in terms of targeted heavy crude oil degradation and byproduct formation ascertain its value as an economical and environmentally attractive option.