Microbially-Enhanced Oil Recovery through Activity of Alkylbenzene-Oxidizing Nitrate-Reducing Bacteria

Date
2017
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Abstract
Heterotrophic nitrate reducing bacteria (hNRB) of the genera Thauera and Pseudomonas can use alkylbenzenes as electron donors for nitrate reduction. The reduction of nitrate by these bacteria increases with the increase in alkylbenzene concentrations of oils especially toluene. The potential of hNRB in microbially enhanced oil recovery (MEOR) was evaluated using sand pack model columns. The concentrations of alkylbenzenes are low in heavy oils. Therefore, water flooded columns were injected with 2-5.6 mM or 1.5 mM of aqueous toluene or ethylbenzene to increase the alkylbenzene content of residual oil in place (ROIP). This was followed by injection of high nitrate (80 mM) to stimulate oil emulsification by hNRB. The hNRB were either cultivated batchwise or in continuous cultures. Injection of sand-packs containing 0.5 pore volumes (PV) of alkylbenzene-amended ROIP with nitrate and a hNRB consortium gave up to 0.10 PV of additional ROIP. Additional oil production was associated with oxidation of alkylbenzenes in the oil phase and reduction of nitrate in the aqueous phase. The dominant microbial species of Thauera and Pseudomonas were isolated from continuous cultures. The isolates were tested for their ability to reduce nitrate with acetate, benzoate, toluene or ethylbenzene as electron donors. Interestingly, only up to 20 mM nitrate was completely reduced to N2 by these isolates with excess toluene or ethylbenzene. Nitrite formed upon reduction of nitrate concentrations of more than 20 mM and was not reduced further to N2. Similar observations were made with the hNRB consortia. Both the isolates had similar MEOR potential either individually or together.
Description
Keywords
Microbiology
Citation
Suri, N. (2017). Microbially-Enhanced Oil Recovery through Activity of Alkylbenzene-Oxidizing Nitrate-Reducing Bacteria (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26901