Microbial-Induced Corrosion of Subsea Pipeline in the Gulf of Suez

Abstract

Summary In mid-May 1996, a leak developed in a 24-in. crude oil line that transfers the untreated crude oil from El-Morgan field in the Gulf of Suez to the onshore process facilities (Fig. 1). The line, a carbon steel API-5L XS-60 seamless pipeline with a wall thickness of 0.75 in., was installed in April 1993. A diving survey was carried out after an oil spill using side-scan sonar survey and a remote operating vehicle (ROV) video. The ROV inspection identified the leak to be the result of internal corrosion in eight joints located at a depth of 240 to 250 ft. After fixing the leaks, a complete ultrasonic survey was performed using a high-resolution intelligent pig. The ultrasonic data, with the sample analysis of the deposits accumulated ahead of the pig, confirmed the mode of corrosion as internal microbial-influenced corrosion (MIC) at the 6 o'clock position. A comprehensive review of the corroded line history, the available corrosion monitoring data, and the applied corrosion-mitigation program shows the following: corrosion monitoring using weight loss coupons, electrochemical devices, and/or chemical methods installed in the two ends of the subsea pipelines does not show any sign of a high corrosion rate (average 3 MPY); absence of the frequent pigging in the pipeline resulted in the accumulation of sludge that caused underdeposits corrosion; thermophilic sulphate-reducing bacteria (SRB) were not detected; however, some non-SRB were detected. This article reviews the pipeline history, corrosion mechanism, inspection outlines, and reservoir souring modeling. We present a plan of action to prevent this leak from happening again, and a brief introduction for mitigation options strategies and economics.