Investigation of Enhanced Oil Recovery by Surfactin Flooding in a Micromodel and Core

The surfactants produced by bacteria are known as biosurfactants. Low toxicity and high biodegradability are among the main characteristics of these surface active materials. These features make biosurfactants potential alternatives for chemically synthesized surfactants in a variety of applications such as microbial enhanced oil recovery. One of the best known biosurfactants, i.e. surfactin, is a cyclic lipopeptide produced by various strains of Bacillus subtilis. In this work, the production of surfactin by Bacillus subtilis NLIM 0110 isolated from an Iranian agricultural area was studied. The produced surfactin showed a good surface activity and was able to reduce the surface tension of water from 69 mN/m to 26 mN/m and the interfacial tension from 38 mN/m to 2 mN/m at 50 mg/l (CMC concentration). The oil spreading technique showed that the diameter of appeared clear zone on the oil layer increased immediately as the produced biosurfactant was added at CMC concentration. Also, in visual experiments, the effect of produced surfactin on enhanced oil recovery was studied using a micromodel. Oil displacement experiments in the micromodel with crude oil showed a recovery of residual oil around 10.1% after water flooding when the biosurfactant of Bacillus subtilis NLIM 0110 was added. Moreover, 4.9% of the original oil in place was recovered using this biosurfactant after water flooding in the core. These results suggest that the produced biosurfactant is an appropriate candidate for enhanced oil recovery.