BACTERIAL CHARACTERIZATION AND BIOCIDE QUALIFICATION FOR FULL WELLSTREAM CRUDE OIL PIPELINES

A 30 year old offshore pipeline system in Nigeria was found to have severe internal corrosion, which was attributed to microbiologically influenced corrosion (MIC). MIC became the predominant factor after the field matured and water cut increased. The inability to pig the majority of the system, the difficulties associated with treating sump tanks that likely harbor large quantity of bacteria, and results from pipeline intelligent tool inspections triggered an evaluation of potential treatment alternatives that could provide enhanced solids and biofilm penetration. The operator and chemical supplier performed a comprehensive system-wide bacterial characterization and biocide evaluation, which included testing in the presence of solid and liquid samples obtained from the sumps and main lines. The inherent bacterial populations were characterized by denaturing gradient gel electrophoresis and DNA sequencing. More specifically, a dynamic closed flow loop was developed that recreated many of the parameters in this system, including bacteria growth within pits, and allowed evaluation of more effective biocides using planktonic and sessile kill studies. This work identified a synergistic two-component product that: enhanced biofilm penetration, increased bacterial kill, and delayed biofilm regrowth in laboratory studies. Field trials are in progress to evaluate the effectiveness of this new product.