The application of biocides to inhibit SRB in offshore seawater injection systems has generally been controlled by budgetary requirements rather than chemical effectiveness. This has led to many systems in the North Sea becoming heavily contaminated by SRB (resulting in MIC and reservoir souring) despite the regular application of biocide chemicals over years of operation. With many platforms now remaining in production several years over their anticipated lifetime, greater emphasis is placed on preventative maintenance. As a result, operators are now looking for assurance that failures due to MIC can be minimised by effective treatment. This has resulted in an emphasis on biocide efficacy as the main criteria, although naturally cost considerations remain vitally important. A microbiological audit performed in April 1997 showed high numbers...