Role of Microbial Induced Corrosion in Subsea Water Pipe Line Failure

Abstract Premature failure of subsea water injection pipelines due to rupture was observed in Indian offshore facilities. In this connection various contributing factors like metallurgy of pipeline, operating conditions and corrosion related parameters have been examined. Material defects that can lead to premature failure of pipelines like microstructural anomalies, variation in hardness and elemental composition and tensile strength etc. have been found within the specified limits of material specification. Analysis of various operating parameters and water quality data indicated failure due to microbial induced internal corrosion. Due to low flow velocities, suspended insoluble corrosion products, bacteria and other microbes, present in the water, accumulated inside the pipeline surface mostly in low areas. Deposit provided hiding place for bacteria and shielded them from effective treatment by bactericides. Deposits also resulted in the formation of oxygen concentration cells resulting in localised corrosion. Non-pigging of pipe lines, even after long shut down, also resulted in accumulation of deposits. During this period, microbial activities dominated resulting in the formation of acidic metabolites which ultimately led to internal corrosion. In this paper, all above aspects have been examined with special reference to the role of microbiologically induced corrosion for failure of subsea water injection pipe lines.