Microbial Enhanced Oil Recovery at High Salinities using Biosurfactant at lower concentrations

Abstract

This study investigates the ability of lipopeptide biosurfactant produced from Bacillus subtillis W19 isolated from oil contaminated Omani oil field soil samples to recover the residual oil at reduced concentration. The biosurfactant reduced the interfacial tension to 1.8 mN/m and also altered the wettability to more neutral wettability. The biosurfactant is stable over wide range of pH and temperatures. The minimum biosurfactant concentration required to make the process economically feasible was determined by performing core-flood experiments at various critical micelle dilutions using 200-300 mD Berea sandstone cores with porosity of 22%. The fluids used in the work are 32 o API crude oil, and brine with 7-9% salinity collected from the field of interest. All core-flood experiments were conducted at the reservoir temperature, 60 o C. It was found that even after 20 times dilution biosurfactant can maintain an extra recovery of 14% of residual oil after water flooding. These results revealed that the biosurfactant is still effective even at concentration as low as the CMC value (0.1 g/L). Furthermore, the performance of 20 times diluted biosurfactant was improved by mixing it with commercial chemical surfactant to the ratios of 50% biosurfactant: 50% chemical surfactant and 25% biosurfactant: 75% chemical surfactant, and, resulted in extra recovery of 28% and 27% of residual oil after water flooding respectively. Salinity studies show that this biosurfactant has high turbidity point, and maintained a relatively low interfacial tension values over wide range of salinities. When the salinity was increased to 20%, the biosurfactant was still successful in reducing the water flooding residual oil saturation by 12% even when diluted by 10 times. Economical evaluation showed that using this biosurfactant at low concentration would produce appreciable amount of trapped oil with minimum cost.

Physicochemical characterization and optimization of glycolipid biosurfactant production by a native strain ofPseudomonas aeruginosaHAK01 and its performance evaluation for the MEOR process

“…[9][10][11] Conventional enhanced oil recovery (EOR) technologies can only extract a maximum of 50% of trapped oils in the oil elds; therefore, most of the oil is le in the ground. 12,13 MEOR has been developed as an alternative technology for secondary and tertiary methods for extracting more oil from reservoirs. MEOR has its own limitations and difficulties.…”

Promising Biotechnology on Selective Plugging and Wettability Alteration for Enhanced Oil Recovery

“…It affects adsorbed oil on reservoir rock by changing the interfacial tension between oil and water. Several studies have been shown that oil recovery is improved by this mechanism [21][22][23][24][25][26][27][28][29][30][31][32][33].…”

“…Using these microbes, several types of bio-surfactants can be controlled to improve oil recovery with other chemicals as an ex-situ method [2]. Bio-surfactant produced by Bacillus subtilis has been injected and validated the potential in core flood experiments [21][22][23]. One of the studies investigated and compared three bio-surfactants from different strains for successful ex-situ MEOR application [24].…”