No abstract

Microbial Enhanced Oil Recovery (MEOR) is a promising strategy to improve recovery of residual oil in reservoirs, which can be performed by promoting specific indigenous microorganisms. In this study, we performed preliminary evaluation of the possibility of conducting MEOR at Mae Soon reservoir, an onshore reservoir in Northern Thailand. The reservoir’s physicochemical characteristics, including the characteristics of the wells, the oil-bearing sandstone cores, and the reservoir’s produced water, were determined. The microbiological characteristics of the oil wells in the reservoir were also investigated by submerging the reservoir’s sandstone core samples, obtained from 6 oil wells, in the reservoir’s produced water and in the produced water added with inorganic nutrients (KNO3 and NaH2PO4). The uncultured bacteria in both treatments were determined, using tagged 16S rRNA gene amplicon with Ion Torrent Sequencing Analysis. The effects of inorganic nutrients and the reservoir’s parameters on the bacterial communities were analysed. A total number of 16,828 OTUs were taxonomically classified into 89 classes and 584 genera. In the controls (sandstone cores submerged in the produced water), the dominant bacterial populations were related to Deinococcus-Thermus, and Betaproteobacteria; while in the nutrient treated samples, there was a marked increase in the relative abundance of Gammaproteobacteria in three samples. Thermus, Acinetobacter, and Pseudomonas were the most abundant genera, and these are potential microorganisms for MEOR. Analysis of correlations between physiochemical properties of the reservoir and bacterial genera, using spearman’s correlation analysis, suggested that some of the reservoir’s properties, especially of the well and the rock, could influence some bacterial genera. To our knowledge, this is the first demonstration of the effect of inorganic nutrients on alteration of bacterial communities attached to reservoir’s rock, and how the bacterial, physical, and chemical properties of a reservoir were co-analysed to serve as a basis for designing a MEOR process.

Microbial Enhanced Oil Recovery (MEOR) is a promising strategy to improve recovery of residual oil in reservoirs, which can be performed by promoting specific indigenous microorganisms. In this study, bacterial communities and the effects of elemental nutrient treatment of oil-bearing sandstone cores originated from six oil wells of an onshore reservoir was determined by tagged 16S rRNA gene amplicon sequencing, using Ion Torrent Metagenomic Sequencing Analysis. A total number of sequences were taxonomically classified into 43 phyla, 320 families, and 584 genera, with the dominant bacterial populations being related to Deinococcus-Thermus, and Betaproteobacteria. The nutrient treatment resulted in markedly increase in the relative abundance of Gammaproteobacteria. Thermus, Acinetobacter, and Pseudomonas were the most abundant genera. To our knowledge, this is the first report on the effect of elemental nutrients on alteration of bacteria communities attached to the oil-bearing rock. It provides comprehensive data on bacterial, physical, and chemical structures within a reservoir and demonstrates how these parameters can be co-analyzed to serve as a basis for designing a MEOR process. It also provides a model of how a bacterial community in reservoirs’ strata can be altered by nutrient treatment to enhance the efficiency of MEOR applications.

Microbial Enhanced Oil Recovery (MEOR) is an effective alternative method for oil recovery in reservoirs using microorganisms or their secondary metabolites. This research aimed to evaluate the indigenous bacteria from Mae Soon reservoir by culture-dependent and culture-independent methods and to investigate the potential of biosurfactant-producing bacteria using a drop-collapsed assay. Indigenous bacteria were isolated from the oil sands of the reserved core of Mae Soon reservoir using fi ve different media (nutrient, Luria-Bertani, mineral salt, tryptic soy, and peptone yeast extract). Fifty-four facultative anaerobic bacterial isolates were obtained. Seven isolates showed their potential as biosurfactant producers in the drop-collapse assay. Based on 16S rRNA gene analysis, six of the biosurfactant-producing bacterial isolates belonged to the species Bacillus licheniformis and one belonged to the species B. subtilis. The biosurfactant producers and microbial community in the oil sands were determined using Denaturing Gradient Gel Electrophoresis (DGGE). Interestingly, DGGE bands corresponding to bacteria belonging to the genus Geobacillus sp. were detected. Overall, the results obtained from this work showed that indigenous bacteria in Mae Soon reservoir oil well were prospective for use in MEOR.