A sulfur and nitrogen cycle informed model to simulate nitrate treatment of reservoir souring

Abstract

Nitrate treatment has been widely used in various seawater injection projects to treat biologic sulfate reduction or reservoir souring. To design a promising nitrate treatment plan, it is essential to have a comprehensive understanding of reactions that represent the microbial communities of the reservoir and mechanisms through which the souring process is inhibited. We employ a new approach of evaluating different reaction pathways to design reaction models that reflect governing microbial processes in a set of batch and flow experiments. Utilizing the designed models, we suggest dissimilatory nitrate reduction to ammonium is the main reaction pathway. Additionally, we illustrate nitrite inhibition is the major mechanism of nitrate treatment process; independent of nitrate reduction being autotrophic or heterotrophic. We introduce an inhibitory nitrate injection concentration that can inhibit souring regardless of nitrite inhibition effect and the distance between injection and production wells. Furthermore, we demonstrate that the ratio of the nitrite-nitrate reduction rate can be used to estimate nitrate treatment effectiveness. Our findings in regard to importance of nitrite inhibition mechanism and the inhibitory nitrate concentration are in accordance with the field observations.

Nitrate and oxygen significantly changed the abundance rather than structure of sulphate‐reducing and sulphur‐oxidising bacteria in water retrieved from petroleum reservoirs

“…Moreover, An et al (2017) and Marietou et al (2020) confirmed that nitrite inhibition is the most effective nitrate‐based souring mitigation mechanism. The SOB distributions of samples collected from oil fields were affected by the levels of nitrate and nitrite, which could stimulate the growth of NR‐SOB (Greene et al, 2003; Hubert et al, 2005; Jahanbani Veshareh & Nick, 2019; Qi et al, 2022). In addition, the concentration of acetate had an obvious influence on the SOB communities.…”

“…To avoid hydrogen sulphide formation in oil fields, the injection of oxygen-containing nitrate solutions is a widely used measure for the petroleum industry to stimulate NRB to compete with SRB for degradable organics in oil, oxidise hydrogen sulphide to sulphur or sulphate, and suppress sulphate reduction by nitrite or by the higher redox potential that is created by nitrate and oxygen injection (Bødtker et al, 2008;Hubert & Voordouw, 2007;Jurelevicius et al, 2020;Kaster et al, 2007;Marietou et al, 2020;Qi et al, 2022;Voordouw et al, 2009). Studies have also shown that many sulphur-oxidising bacteria (SOB), which can catalyse sulphide oxidation coupled with nitrate reduction, are stimulated by nitrate (Aoyagi et al, 2021;Hubert & Voordouw, 2007;Jahanbani Veshareh & Nick, 2019;Qi et al, 2022). As reservoir environments contain numerous reduced sulphur compounds (e.g., thiosulphate, sulphide and ferrous sulphide and elemental sulphur), SOB, including Thiobacillus, Sulfurospirillum, Sulfuricurvum, Sulfurovum and Sulfurimonas, are commonly detected in reservoir environments (Gao et al, 2015(Gao et al, , 2022Gao & Fan, 2023;Hubbard et al, 2014;Tian et al, 2017).…”

“…The phylogeny of SOB is highly diverse, and they can catalyse sulphur oxidation coupled with carbon and nitrogen cycling under both aerobic and anaerobic conditions (Friedrich, 1998; Ghosh & Dam, 2009). Jahanbani Veshareh and Nick (2019) reported that nitrite inhibition by nitrate‐reducing sulphur‐oxidising bacteria (NR‐SOB) is a significant contributor to nitrate treatment and that the sulphide oxidisation rate by NR‐SOB is equal to or greater than that of SRB. Qi et al (2021) isolated a potential bioaugmenter, Gordonia sp.…”

Assessing Microbial Corrosion Risk on Offshore Crude Oil Production Topsides under Conditions of Nitrate and Nitrite Treatment for Souring

“…It has also been found that adding nitrite to injection water is more effective than other treatment chemicals in oilfields, including in high-temperature scenarios [ 49 ]. Modeling simulations based on several case studies asserted that nitrite is the main inhibitory chemical in nitrate-treated sour oilfield systems [ 50 ]. In the present study, the produced fluid samples were from a high-temperature reservoir that can reach temperatures of up to 90 °C.…”

“…In the present study, the produced fluid samples were from a high-temperature reservoir that can reach temperatures of up to 90 °C. The mode of action of nitrite in sulfate reduction inhibition, in addition to its efficacy in high-temperature oil fields, may be the reason that nitrite performed better across both platform samples for reducing sulfate reduction, as opposed to the variability in efficacy of the nitrate treatments [ 23 , 24 , 50 ]. The corrosion rates (assessed after the 156-day incubation) measured for the nitrite-treated microcosms in our study indicate a low corrosion risk ( Figure 6 ), however the potential chemical corrosivity of nitrite can be observed in the nitrite-treated sterile controls that showed a moderate corrosion rate of 0.07 mm/year [ 27 ].…”