Assessment of bacterial communities and activities of thermotolerant enzymes produced by bacteria indigenous to oil-bearing sandstone cores for potential application in Enhanced Oil Recovery

Enhanced Oil Recovery (EOR) is a potential approach to improve oil yield in petroleum production. In this research, indigenous bacterial communities residing in oil-bearing sandstone cores, taken from oil wells in Fang oil field in Northern Thailand, were investigated using the Ion Torrent PGM sequencing method. Based on 16rRNA gene sequences, Proteobacteria and Firmicutes were found to be the predominant phyla, and Bacillus, Sinomonas, Paenibacillus and Hydrogenophaga were the major genera. Thermotolerant lipase-esterase and urease producing bacteria were also isolated from the oil-bearing sandstone core samples. One lipase-esterase producing isolate, Bacillus licheniformis L3-2, produced the enzyme with highest activity at 80 °C. The enzyme retained up to 50% of its activity after incubation at 60 °C for 4 h. The results suggest the possibility of applying an in situ EOR approach using a combination of Enzyme Enhanced Oil Recovery (EEOR) and Microbial Enhanced Oil Recovery (MEOR) methods, with this lipase-esterase producing Bacillus licheniformis isolate, which is indigenous to one of the wells in this oil field.