Reports of corrosion failures implicating bacterial activity – and in particular the activity of Sulphate-reducing Bacteria (SRB) – continue to appear in the literature and documented case histories. In many cases, the Microbially Influenced Corrosion (MIC) has occurred despite the application of biocide chemicals into the affected system. It is not uncommon to hear of ‘ineffective biocides’, the implication being that the efficacy of the chemical to kill bacteria is questionable. It is clear, however, that the most commonly applied generic formulations of oilfield biocides (such as Glutaraldehyde, THPS, etc.) are effective killers of bacteria. If the field application of these chemicals does not result in acceptable microbiological control then the inference should be, not that the chemical is an ineffective biocide, but that the application of the chemical is such that it is not contacting the target bacteria with sufficient concentration, retention time and/or frequency to achieve a kill.

This paper presents an overview of how oilfield biocides can be applied such that those bacteria with a role in corrosion are controlled to sufficiently low levels to inhibit MIC. The emphasis is on seawater injection systems, where the majority of the total tonnage of oilfield biocide is applied. However, the key parameters are also relevant to oil production systems.

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