In Situ Biosurfactant Production by Bacillus Strains Injected into a Limestone Petroleum Reservoir

Abstract

Biosurfactant-mediated oil recovery may be an economic approach for recovery of significant amounts of oil entrapped in reservoirs, but evidence that biosurfactants can be produced in situ at concentrations needed to mobilize oil is lacking. We tested whether two Bacillus strains that produce lipopeptide biosurfactants can metabolize and produce their biosurfactants in an oil reservoir. Five wells that produce from the same Viola limestone formation were used. Two wells received an inoculum (a mixture of Bacillus strain RS-1 and Bacillus subtilis subsp. spizizenii NRRL B-23049) and nutrients (glucose, sodium nitrate, and trace metals), two wells received just nutrients, and one well received only formation water. Results showed in situ metabolism and biosurfactant production. The average concentration of lipopeptide biosurfactant in the produced fluids of the inoculated wells was about 90 mg/liter. This concentration is approximately nine times the minimum concentration required to mobilize entrapped oil from sandstone cores. Carbon dioxide, acetate, lactate, ethanol, and 2,3-butanediol were detected in the produced fluids of the inoculated wells. Only CO 2 and ethanol were detected in the produced fluids of the nutrient-only-treated wells. Microbiological and molecular data showed that the microorganisms injected into the formation were retrieved in the produced fluids of the inoculated wells. We provide essential data for modeling microbial oil recovery processes in situ, including growth rates (0.06 ؎ 0.01 h ؊1 ), carbon balances (107% ؎ 34%), biosurfactant production rates (0.02 ؎ 0.001 h ؊1 ), and biosurfactant yields (0.015 ؎ 0.001 mol biosurfactant/mol glucose). The data demonstrate the technical feasibility of microbial processes for oil recovery.

Development of an In Situ Biosurfactant Production Technology for Enhanced Oil Recovery

“…Spore forming bacteria or biosurfactant-producing bacteria of which Bacilli would be included were not detected. Finally, an oil spread assay was also performed and established that surface active compounds such as biosurfactants were not present in the production water from each well [154,155].…”

“…spizizenii strain NRRL B-23049 were grown in Medium E [154,155] at 37 o C for 48 hours with dispersion tubes for agitation and aeration. After concentration of the cultures by tangential flow filtration, the cells were stored at 4 o C in sterile, 2-liter bottles.…”

“…Each frac tank was equipped with a 5-hp gasoline powered pump for recirculation of its contents. With the recirculation pump running, 79.5 kg of glucose, 7.9 kg of sodium nitrate, 19.9 g of magnesium sulfate, 2 g of manganese sulfate, 2 g of zinc sulfate, 2 g of iron sulfate, 0.2 g of copper sulfate, 0.2 g of aluminum potassium sulfate, 0.2 g of boric acid, 0.2 g of sodium molybdate, 0.1 g of sodium selenate and 0.6 g of nickel chloride were added to each frac tank [155]. Next, each frac tank received 3.5 liters of concentrated B. licheniformis RS-1 and 3 liters of B. subtilis subsp.…”

“…The sugar concentration was determined by using a modified orcinol/H 2 SO 4 method with glucose as the standard [157]. Acetate, succinate, formate, ethanol and 2, 3-butanediol were quantified by using gas chromatography (GC) [155,158,159]. Lactate was quantified by HPLC [155].…”

Characterization and emulsifying property of a novel bioemulsifier by Aeribacillus pallidus YM-1

“…These properties enable their wide application in areas such as the bioremediation (Banat et al 2002) and microbial enhanced oil recovery (MEOR) (Youssef et al 2007).…”