Control of Sulfide Production in High Salinity Bakken Shale Oil Reservoirs by Halophilic Bacteria Reducing Nitrate to Nitrite

Abstract

Microbial communities in shale oil fields are still poorly known. We obtained samples of injection, produced and facility waters from a Bakken shale oil field in Saskatchewan, Canada with a resident temperature of 60°C. The injection water had a lower salinity (0.7 Meq of NaCl) than produced or facility waters (0.6–3.6 Meq of NaCl). Salinities of the latter decreased with time, likely due to injection of low salinity water, which had 15–30 mM sulfate. Batch cultures of field samples showed sulfate-reducing and nitrate-reducing bacteria activities at different salinities (0, 0.5, 0.75, 1.0, 1.5, and 2.5 M NaCl). Notably, at high salinity nitrite accumulated, which was not observed at low salinity, indicating potential for nitrate-mediated souring control at high salinity. Continuous culture chemostats were established in media with volatile fatty acids (a mixture of acetate, propionate and butyrate) or lactate as electron donor and nitrate or sulfate as electron acceptor at 0.5 to 2.5 M NaCl. Microbial community analyses of these cultures indicated high proportions of Halanaerobium, Desulfovermiculus, Halomonas, and Marinobacter in cultures at 2.5 M NaCl, whereas Desulfovibrio, Geoalkalibacter, and Dethiosulfatibacter were dominant at 0.5 M NaCl. Use of bioreactors to study the effect of nitrate injection on sulfate reduction showed that accumulation of nitrite inhibited SRB activity at 2.5 M but not at 0.5 M NaCl. High proportions of Halanaerobium and Desulfovermiculus were found at 2.5 M NaCl in the absence of nitrate, whereas high proportions of Halomonas and no SRB were found in the presence of nitrate. A diverse microbial community dominated by the SRB Desulfovibrio was observed at 0.5 M NaCl both in the presence and absence of nitrate. Our results suggest that nitrate injection can prevent souring provided that the salinity is maintained at a high level. Thus, reinjection of high salinity produced water amended with nitrate maybe be a cost effective method for souring control.

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

“…Sand grains can shield microorganism from mechanical sheer stress, while providing necessary porosity for substrate availability (Probandt et al, 2018). A comparison between incubation time was additionally conducted, where an incubation of 7 days, selected based on previous bioreactor studies (Callbeck et al, 2011;An et al, 2017;Chen et al, 2017), was compared with 3.5 days and 24 h. Results showed a linear relationship between incubation time and corrosion rate (Supplementary Figure S3), indicating a possible role of biofilm in the corrosion mechanism of methanogens that can be further amplified in sand-packed environments. Additionally, sand grains can further mimic environmental conditions in marine sediments, soil and oil reservoir.…”

“…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.…”

“…The detection limit for methane is 20 ppm. The dissolved hydrogen sulfide concentration in the medium and enrichments of D. alaskensis 16109 and D. ferrophilus IS5, were determined using the diamine or methylene blue method (Trüper and Schlegel, 1964;Xue and Voordouw, 2015;An et al, 2017).…”

Halophilic Methylotrophic Methanogens May Contribute to the High Ammonium Concentrations Found in Shale Oil and Shale Gas Reservoirs

“…Halophiles are often isolated from highly saline environments such as the Great Salt Lake and the Dead Sea (Oren, 2001(Oren, , 2008Roberts et al, 2005). Recent exploration of highly saline shale oil and shale gas reservoirs has also indicated the presence of halophilic microbial communities (Cluff et al, 2014;Tucker et al, 2015;An et al, 2017).…”

“…Hence, there are multiple incentives for controlling microbial activities in shale gas reservoirs. Creating multiple environments by changing salinity and temperature through injection of cold fresh water and by storing produced water above ground complicates the problem of microbial control, e.g., when temperature and/or salinity are kept high nitrate-reducing bacteria (NRB) reduce nitrate only to nitrite, which is a powerful SRB inhibitor (Fida et al, 2016;An et al, 2017). Hence, SRB control with nitrate is easier if environments with low salinity and temperature are not allowed to emerge in shale gas or shale oil operations.…”