Isolation and screening of Bacillus subtilis MJ01 for MEOR application: biosurfactant characterization, production optimization and wetting effect on carbonate surfaces

Abstract

The bacterial strain MJ01 was isolated from stock tank water of one of the Iranian south oil field production facilities. The 16S rRNA gene of isolate, MJ01, showed 99% similarity to Bacillus subtilis. The results revealed that biosurfactant produced by this strain was lipopeptide-like surfactin based on FTIR analysis. Critical micelle concentration of produced surfactin in distilled water was 0.06 g/l. Wettability study showed that at zero salinity surfactin can change original oil-wet state to water-wet state, but in seawater salinity it cannot modify the wettability significantly. To utilize this biosurfactant in ex situ MEOR process, economical and reservoir engineering technical parameters were considered to introduce a new optimization strategy using the response surface methodology. Comparing the result of this optimization strategy with the previous optimization research works was shown that significant save in use of nutrients is possible by using this medium. Furthermore, using this method leads to less formation damage due to the incompatibility of injecting fluid and formation brine, and less formation damage due to the bioplugging.

Microorganisms’ effect on the wettability of carbonate oil-wet surfaces: implications for MEOR, smart water injection and reservoir souring mitigation strategies

“…Bacteria isolation from the reservoir oil sample The procedure of bacteria isolation from the reservoir oil sample has been described in detail in the work of (Veshareh et al 2019) under the section "Isolation of oil degrading bacteria," where in this work we did the enrichment by using two ml of the oil sample.…”

“…The identification procedure has been described in detail in the work of (Veshareh et al 2019), under the section "Identification of bacteria. "…”

“…In the end, the optical density of the culture at 600 nm was set to 1, using sterile SNB medium. For other strains, we used a seed culture medium that was prepared following the instructions in the work of Veshareh et al (2019) under the section "Seed culture preparation. "…”

“…Surfactin used in this work was separated from MJ01 strain as has been reported by Veshareh et al (2019) under the section "Purification and partial identification of biosurfactant using FTIR." Rhamnolipid was produced by MJ03 strain, using MSSO medium reported in the work of (Sarafzadeh et al 2014).…”

“…Detail information about contact angle tests including the procedure used to take rock slices, age samples and measure contact angle can be found in the work of Veshareh et al (2019) under the section "Wettability studies." An asphaltenic crude oil (acid number = 0.58 mg KOH/g oil) was used in contact angle measurements.…”