Problems Caused by Microbes and Treatment Strategies The Effect of Nitrate Injection in Oil Reservoirs – Experience with Nitrate Injection in the Halfdan Oilfield
This chapter deals with the use of nitrate injection for reservoir souring mitigation in an oilfield with seawater injection in the Danish sector of the North Sea. Nitrate impacts on the activity of sulphate-reducing bacteria (SRB) and biofilm redox potential (Larsen et al., 2007), as a result of which corrosion due to SRB activity will be reduced, souring inhibited and previously formed sulphide removed (Larsen, 2002). One important aspect is that the microbiological reduction of nitrate provides approximately three times more energy to SRB than the reduction of sulphate. Therefore, when both nitrate and sulphate are present, nitrate becomes the preferred electron acceptor and SRB capable of growing on nitrate will dominate. Nitrate provides a competitive advantage to nitrate-utilising bacteria (indicated by the general acronym NUB) during competition for available carbon sources as the NUB are capable of much faster growth than SRB.
KeywordsHorizontal Well Total Bacterial Count Fish Technique Total Bacterial Abundance Nitrate Injection
Laboratory experiments and field monitoring were sponsored by DUC Partners (A.P. Møller-Mærsk, Shell and Chevron).
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