Failure Analysis of a Ruptured Trunkline

This article reports a detailed analysis of a failure observed in a petroleum trunkline in the Niger Delta region of southwestern Nigeria. The study was carried out using various techniques including metallurgical, chemical, and x-ray analysis. Leakage was observed along a petroleum trunkline route, and excavation of the trunkline revealed that the trunkline had actually fractured along the 6 o’clock position. The pipeline material was found to conform to the API specification for low carbon steel of X52 grade. Wormwood-like interconnecting pits typical of microbial-induced corrosion were noticed at the 6 o’clock position. Scale deposits composed of corrosion products and debris from the crude oil transported by the trunkline were also noticed. The liquid analysis result showed that the produced water was corrosive, and it has a high bacteria count. The failure of the trunkline was found to be due to the thinning of the pipeline at the 6 o’clock position by the combined effect of abrading by debris, erosion, and corrosion aided by bacteria activities, i.e., microbial-induced corrosion (MIC) and eventual rupture.