Microbially Enhanced Oil Recovery by Alkylbenzene-Oxidizing Nitrate-Reducing Bacteria

Abstract

Microbially enhanced oil recovery (MEOR) of heavy oil and bitumen is challenging because light hydrocarbons, which can feed resident microbial communities are present in low concentrations, if at all. We have recently shown that increasing the toluene concentration of heavy oil by aqueous injection followed by injection of nitrate boosts the activity of toluene-oxidizing nitrate-reducing bacteria in heavy oil-containing sand pack columns, giving production of residual oil in place (ROIP). In the current work we found that ethylbenzene is as effective as toluene. Microbial community analyses indicated Thauera and Pseudomonas to be main components of nitrate-containing batch and continuous cultures, regardless whether ethylbenzene or toluene was used as the electron donor. Biomass from batch cultures grown with heavy oil amended with ethylbenzene or toluene and nitrate or biomass from continuous cultures grown on ethylbenzene or toluene and nitrate had similar MEOR activity. Increasing the concentration of injected biomass from continuous cultures increased the fraction of ROIP recovered both in the absence and in the presence of nitrate. Nitrate increased the fraction of ROIP recovered by about 2-fold by increasing the concentration of biomass in the columns. Emulsification of oil by surface-adhering biomass and blocking of aqueous flow channels by oil emulsion droplets are proposed as a possible mechanism of hydrocarbon- and nitrate-mediated MEOR. Pure isolates Thauera sp. NS1 and Pseudomonas sp. NS2, which used both ethylbenzene and toluene, were obtained but did not offer improved MEOR compared to the use of batch and continuous cultures.

Denitrification Biokinetics: Towards Optimization for Industrial Applications

“…In contrast, strain NS1 exhibited similarities to a PO type of DRP and transient accumulation of NO 2 − resulting from reduction of NO 3 − (Figure 1B). This strain is phylogenetically more related to strains K172 and S100 ( > 90% 16S rRNA gene similarity; Suri et al, 2019) but unexpectedly showed lower denitrification rates as compared to the type strain K172 under identical denitrifying culture conditions. At higher NO 3 − concentrations ( > 2 mmol L −1 ), the denitrification kinetics of the three Thauera strains became more similar showing a PO type of DRP and prolonged accumulation of NO 2 − and N 2 O (Figure 2 and Table 4), even at an ideal temperature (30 • C).…”

Iron to Gas: Versatile Multiport Flow-Column Revealed Extremely High Corrosion Potential by Methanogen-Induced Microbiologically Influenced Corrosion (Mi-MIC)

“…Additionally, sand grains can further mimic environmental conditions in marine sediments, soil and oil reservoir. Currently, sand-packed reactors were used to investigate oil reservoir related studies, such as souring control and enhanced oil recovery (Gieg et al, 2011;Gassara et al, 2015;An et al, 2017;Suri et al, 2019) targeting SRB and nitrate-reducing bacteria. Bioreactor or studies under flow regarding methanogens have been largely neglected due to the difficulties maintaining an anaerobic system that allows methane measurements.…”

Comparison of Nitrate and Perchlorate in Controlling Sulfidogenesis in Heavy Oil-Containing Bioreactors

“…Alkylbenzenes were added directly to 50 mL aqueous CSBK medium or to 1 mL of HMN overlaying this medium to minimize toxicity. A 20-fold concentrated 18PW sample (1 mL) or a nitrate-reducing chemostat culture (5 mL), continuously fed with either toluene or ethylbenzene ( Suri, 2017 ), were used as inocula. However, these were unable to use toluene or ethylbenzene for reduction of 10 mM perchlorate within 30 days of incubation.…”