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