A material test for microbiologically influenced corrosion (MIC) is presented. This laboratory based test evaluates the material resistance to MIC caused by corrosive, methane-producing microorganisms. Material testing and corrosion modeling is a natural and important step to ensure material integrity during oil production. Currently, good models for physical and chemical parameters exist, but MIC remains very hard to predict in spite of many years of research, and failures continue to occur prematurely.
MIC can to some degree be mitigated by biocide treatment. However, the effect can be limited because responsible microorganisms are part of a protective biofilm of the metal surface. Parts of the biofilms often survive even the best biocide program, and the surviving microorganisms will quickly re-establish their activity in the system. Metal alloys react differently to these biofilms, and the choice of material is a crucial parameter in minimizing MIC.
Biofilms formed by methane-producing microorganisms are known to cause MIC. These microorganisms are not detected in standard monitoring tests, such as bottle incubations, widely used by the industry. However, several recent studies employing Molecular Microbiology Methods (MMM) have shown that these microorganisms are numerous, widespread, and highly corrosive in off- as well as on-shore oil fields. The new material test described in this paper uses methane-producing microorganisms to test the MIC resistance of metal alloys. This enables petroleum companies to choose a suitable material for an environment with high MIC potential and to predict the corrosion rate at close to in situ conditions.