Offshore pipeline integrity assessment considering material and parametric uncertainty

Abstract

This paper presents a methodology that integrates the semi-empirical corrosion models with probabilistic analysis to study steel structural failure behavior considering material and parametric uncertainties. The semi-empirical models are used to assess the asset’s susceptibility, system degradation rate, and defect growth over time under harsh corrosive environment. The developed model is translated into a limit state function in a probabilistic framework to define the asset’s safe operating envelope. The probabilistic framework is simulated considering the variations in the material properties of steel grades, corrosion response parameters, and types of susceptibility models. The variabilities in the ultimate tensile strength, operating pressure, and wall thickness exhibit the highest contributions to pipeline failure behavior in a harsh offshore environment. It is also observed that the failure probability of the pipeline increases with an increase in the coefficient of variation at the lower bound of failure, while it decreases at the upper bound of failure. The coefficient of variation for the tensile strength shows a 32.2% (the highest) impact on the limit state function performance as the year of exposure progresses. The proposed approach offers a systematic framework for an appropriate material selection and risk-based integrity management strategy for offshore structures, including pipelines.

Keywords

• Mixed corrosion environment
• Offshore steel pipelines
• Monte Carlo simulation
• Failure probability
• Uncertainty
• Parametric variability