Use of Nitrate to Mitigate Reservoir Souring in Bonga Deepwater Development Offshore Nigeria

fax 01-972-952-9435. AbstractThe Bonga field, which is located in deep water off the Nigerian coast, started oil production at the end of 2005. In order to sustain production, seawater injection started from the beginning of the oil production at a rate of 300k bwpd. During the field development it was concluded that seawater injection in Bonga would result in reservoir souring, and that mitigation was necessary. Initially the selected strategy for Bonga seawater injection was to control reservoir souring with biocide and handle low levels of H 2 S with sour service materials and scavenging facilities topside. The maximum H 2 S the existing facilities could handle was set at 50 ppm (v).The decision to control reservoir souring with biocide and handle H 2 S at surface was re-evaluated in 2003, and it was concluded that there would be a risk that the maximum allowable H 2 S content in the facilities (i.e. 50 ppm(v)) might be exceeded during the life time of the project. Given the positive experience with the injection of nitrate in other seawater floods throughout the industry, nitrate was selected as the mitigation method and injection started directly at the beginning of the waterflood at the end of 2005. As such Bonga is one of the first waterfloods where nitrate is being used to prevent reservoir souring, the main application so far has been to reduce H 2 S in already sour fields. This paper presents the experience gained with the nitrate injection during the first period of the Bonga waterflood. Issues like logistics and how to ensure nitrate is applied correctly are discussed in more detail. In addition laboratory testing executed to define an appropriate nitrate injection rate under Bonga conditions are also presented.After several months of operation the Minox unit to remove the bulk of the oxygen broke down and oxygen control was done with chemical oxygen scavenger only. With this different mode of operation, the effectiveness of the nitrate as souring mitigation method was expected to be affected. Additional laboratory experiments, also reported in this paper, were performed and did not indicate any issue with respect to the predicted souring.

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“…1 is limited to injection water only. The adjusted monitoring program as used during the first year of the waterflood is given in Table 1.…”

Section: Monitoring and Surveillancementioning

confidence: 99%

One Year Experience With The Injection of Nitrate To Control Souring in Bonga Deepwater Development Offshore Nigeria

Kuijvenhoven¹,

Noirot²,

Hubbard³

et al. 2007

Proceedings of International Symposium on Oilfield Chemistry

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Biological souring and mitigation in oil reservoirs

Gieg

Jack

Foght

2011

Appl Microbiol Biotechnol

270

228

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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.

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Contribution of make-up water to the microbial community in an oilfield from which oil is produced by produced water re-injection

Folarin¹,

An²,

Caffrey³

et al. 2013

International Biodeterioration & Biodegradation

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Use of Nitrate to Mitigate Reservoir Souring in Bonga Deepwater Development Offshore Nigeria

Cited by 6 publications

References 4 publications

One Year Experience With The Injection of Nitrate To Control Souring in Bonga Deepwater Development Offshore Nigeria

One Year Experience With The Injection of Nitrate To Control Souring in Bonga Deepwater Development Offshore Nigeria

Biological souring and mitigation in oil reservoirs

Contribution of make-up water to the microbial community in an oilfield from which oil is produced by produced water re-injection

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