Microbiologically influenced corrosion has been attributed to the activity of sulfate reducing and acid producing bacteria. Advances in DNA isolation and sequencing have revealed that these classes of bacteria often represent only a small portion of the corrosive microbial population present in the oil and gas environment.
We have identified a class of inhibitory molecules that abrogate sulfidogenesis in oilfield produced fluids. Bottle tests and laboratory-scale bioreactors to mimic field conditions, found that very low doses of two versions of this class of compounds were found to effectively prevent H2S generation.
By far, the microbiological species most associated with corrosion has been Sulphate-Reducing Bacteria (SRB). Majority of Microbiologically Influenced Corrosion (MIC) research has focused on the activities of this type of bacteria. One of the primary reasons for this has been the presence of iron sulfides in corrosion products associated with MIC. SRB reduce sulfates to sulfides, which then react with iron and steel. However, an accepted fact is that MIC is also caused by the action of the biofilm produced by bacteria, in a similar way to under-deposit corrosion.
The primary method used to prevent MIC in the oil and gas industry is by use of biocides. The criteria used for selection of biocides is often their proficiency to kill SRB. The danger with this is that one can neglect the ability of other bacteria frequently found in oil and gas environment, such as general aerobes and general anaerobes to cause corrosion by biofilm production. This became evident when severe general & pitting corrosion was observed in two oil and gas separators in one of the facilities in Kuwait Oil Company (KOC), where SRB levels were zero but significant numbers of sessile and planktonic general aerobes and general anaerobes were found to be present in the process.
Using microbiological and chemical analysis, the mechanism of this type of MIC, specially the relationship between the quantity of various biofilm-forming bacteria and nature and magnitude of corrosion has been studied and the findings are presented in this paper.