Estimation of Corrosion Induced Flaw Sizes on Buried Gas Pipeline in the Nigerian Sector of Niger Delta

摘要

A geoelectrical survey was conducted to investigate pipeline corrosion in the coastal plain sands of the Nigerian sector of the Niger Delta. The objective is to estimate corrosion flaw sizes on the pipeline quantitatively instead of direct excavation of the pipeline and eventual use of measuring tape to measure the flaws on the pipeline. The pipelines buried in the Benin sands at Ikot Abasi, South of the Niger Delta Basin became instructive for this study. The survey consisted of electrical potential profiling using Close Interval Pipe-Soil potential survey (CIPS) and Horizontal Electrical Profiling (HEP) according to Wenner electrodes arrangement. Two permanent test points (PS) were used for the study and the flaw sizes were estimated at points delineated to be of high corrosion risk in the study area. The data for close interval potential and HEP were analyzed and interpreted in line with the threshold protective potential (-850 mV) as well as the American Water Works Association (AWWA) soil corrosivity rating. Results indicate high risk zones due to external corrosion at pipeline length 25-30 m from PS1 and 80 m from PS2. These locations contain significant saline groundwater that facilitates corrosion of metal pipes buried within the area. The results also suggest that the corrosion protection systems for the pipeline need to be reinforced to mitigate further growth of the flaws on the pipeline segment. The impact of the flaws could be severe if allowed to continue.