Biological souring and mitigation in oil reservoirs

Abstract

Souring in oil field systems is most commonly due to the action of sulfate-reducing prokaryotes, a diverse group of anaerobic microorganisms that respire sulfate and produce sulfide (the key souring agent) while oxidizing diverse electron donors. Such biological sulfide production is a detrimental, widespread phenomenon in the petroleum industry, occurring within oil reservoirs or in topside processing facilities, under low- and high-temperature conditions, and in onshore or offshore operations. Sulfate reducers can exist either indigenously in deep subsurface reservoirs or can be "inoculated" into a reservoir system during oil field development (e.g., via drilling operations) or during the oil production phase. In the latter, souring most commonly occurs during water flooding, a secondary recovery strategy wherein water is injected to re-pressurize the reservoir and sweep the oil towards production wells to extend the production life of an oil field. The water source and type of production operation can provide multiple components such as sulfate, labile carbon sources, and sulfate-reducing communities that influence whether oil field souring occurs. Souring can be controlled by biocides, which can non-specifically suppress microbial populations, and by the addition of nitrate (and/or nitrite) that directly impacts the sulfate-reducing population by numerous competitive or inhibitory mechanisms. In this review, we report on the diversity of sulfate reducers associated with oil reservoirs, approaches for determining their presence and effects, the factors that control souring, and the approaches (along with the current understanding of their underlying mechanisms) that may be used to successfully mitigate souring in low-temperature and high-temperature oil field operations.

Thermal effects on microbial composition and microbiologically induced corrosion and mineral precipitation affecting operation of a geothermal plant in a deep saline aquifer

“…Even if the availability of organic matter in the investigated geothermal aquifer is lower than in fluids of oil reservoirs, inferences between the investigated geothermal aquifer and oilfield reservoirs can be done since commonalities concerning the casing and physico-chemical properties of fluids like temperature, salinity, and sulfate content exist. In addition, sulfate reducers closely related to Desulfotomaculum and Desulfohalobium are also commonly found in oil reservoirs (Magot et al 2000;Birkeland 2005;Grigoryan and Voordouw 2008;Gieg et al 2011) as seen for the saline heat store. Thus, chemical constraints in deep reservoirs select for similar microbial communities, while abundant sulfate reducers lead to the widespread phenomenon of biological sulfide production that adversely affects operational materials in reservoirs or in topside processing facilities.…”

Anaerobic utilization of toluene by marine alpha- and gammaproteobacteria reducing nitrate

“…However, nitrate, although less abundant in the ocean than sulphate, is an energetically favourable electron acceptor and one would expect that it is utilized preferably over sulphate. The use of nitrate and nitrite by the oil industry to prevent souring and control corrosion in oil reservoirs and surface facilities (Gieg et al, 2011;Hubert et al, 2005) could provide conditions favourable for marine denitrifying bacteria. Although detrimental production of sulphite might be reduced by the addition of nitrate, the degradation of hydrocarbons accompanied by the production of large amounts of nitrogen gas would be the consequence.…”

“…The activity of sulphate-reducing bacteria in oil reservoirs and in onshore and offshore oil operation has been of great interest from an industrial perspective, as detrimental souring (production of sulphide) has been associated with this group of bacteria. One of the strategies used to control souring has been the addition of nitrate to oil reservoirs and surface facilities, which can have a direct impact on the sulphate-reducing population (Gieg et al, 2011). The anaerobic degradation of aromatic hydrocarbons and alkanes with nitrate as terminal electron acceptor has been previously demonstrated and extensively studied in freshwater environments.…”

The dual role of microbes in corrosion

“…Another corrosion control approach is biocompetitive exclusion (BE) (Videla and Herrera, 2005), which is applied in oil industries to exclude SRB from the local microbial community by promoting the growth of competing bacteria such as nitratereducing bacteria (Gieg et al, 2011).…”