Development of a Probabilistic Corrosion Degradation Model for Ageing Crude Oil Pipeline Infrastructure in the Niger Delta

This study develops a probabilistic corrosion degradation model for ageing crude oil pipelines in the Niger Delta, South South Nigeria, incorporating the stochastic variability of corrosion rate, wall thickness, and inspection measurement uncertainty to support risk-based inspection planning. A significant proportion of Nigeria's onshore pipeline network was installed in the 1960s and 1970s and has exceeded design service life, and the probabilistic modelling of remaining wall thickness distribution is fundamental to evidence-based inspection interval setting under the DNV-RP-F101 and ASME B31.8S risk-based inspection frameworks. The model is developed using a Bayesian updating framework that integrates prior corrosion rate distributions established from published field data and the Nigerian pipeline literature with in-line inspection (ILI) measurement datasets from two cooperating operating companies. Monte Carlo simulation is applied to propagate uncertainty in corrosion rate and ILI tool measurement accuracy through a limit state function for wall loss exceedance. The posterior distribution of remaining life is updated as successive ILI rounds are incorporated. Sensitivity analysis quantifies the relative contribution of corrosion rate variability, initial wall thickness uncertainty, and ILI tool accuracy to overall remaining life uncertainty. The model is applied to three pipeline segments of different ages and corrosion histories to demonstrate comparative risk ranking. The study produces an original probabilistic framework calibrated to Niger Delta pipeline integrity data. Keywords: probabilistic corrosion model, pipeline integrity, Niger Delta, Bayesian updating, risk-based inspection.