Chinedu I. Ossai

Estimation of Internal Pit Depth Growth and Reliability of Aged Oil and Gas Pipelines— A Monte Carlo Simulation Approach

To estimate the internal pit depth growth and reliability of aged oil and gas pipelines, a Monte Carlo simulation approach was adopted. The average maximum pit depths of corroded pipelines were correlated with the operating parameters—temperature, CO2 partial pressure, pH, flow rate, sulfate ion concentration, chloride ion concentration, water cut, and wall shear stress via a multivariate regression analysis. Poisson square wave model was used to predict the time lapse of the pit depth growth using the statistical best fit of the maximum pit depth and operating parameters as boundary conditions. Weibull probability function was used to determine the failure intensity and survivability of the pipelines for different distribution types, whereas inspection data from a magnetic flux leakage in-line inspected transmission pipeline were used to test the application of the model. The future pit depth distribution, survivability, and failure rate of this transmission pipeline were also determined, with the result...

Modelling the effects of production rates and physico-chemical parameters on pitting rate and pit depth growth of onshore oil and gas pipelines

To estimate the pitting rate of internally corroded oil and gas gathering pipelines, a multivariate regression modelling was carried out, using pitting rates and operating parameters. These operating parameters, temperature, pH, CO2 partial pressure, water cut, wall shear stress, chloride ion concentration, sulphate ion concentration, operating pressure, oil production rate, gas production rate and water production rate, were obtained from routine monitoring of the pipelines, whereas, the pitting rates (mean pit depths over time) were determined by the ultrasonic thickness measurement technique. The operating parameters and pitting rates were also used to estimate the pit depth growth of the pipelines using Monte Carlo simulation, and field data were used to test the developed models. The results obtained indicated that the pipelines under severe pitting corrosion rate were, more conservatively predicted than those under low, moderate and high pitting corrosion rates.

Reliability Analysis and Performance Predictions of Aged Pipelines Subjected to Internal Corrosion: A Markov Modelling Technique

To maintain the integrity of corroded oil and gas pipelines, the reliability at times of exposure over the lifecycle duration need to be understood. This paper describes the procedures for predicting the performance of internally corroded oil and gas pipelines using a probabilistic-based Markovian process. The Pipeline Corrosivity Index (PCI), which is expressed as a function of the retained pipe-wall thickness was used to describe the condition of the corroded pipelines at exposure durations for low, moderate, high and severe corrosion rates. The time variation of the predicted Pipeline Corrosivity Index (PCI) was compared with field measured Pipeline Corrosivity Indexes (PCIs) of corroded API X52 grade pipelines and the results indicate that the model developed in this research is viable for integrated management of aged corroded pipelines and remaining useful life predictions.Copyright