A contribution to risk-informed inspection and maintenance planning for unpiggable pipelines subject to internal corrosion
Date
2020-12-10
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Abstract
Pipelines are the safest transportation mode for hydrocarbons, but internal corrosion is still a major cause of failure for energy pipelines. Inspection and repair strategies are implemented to avoid pipeline failures and their consequences. In-line inspection is the most detailed examination technique for pipelines, but almost half of existing pipelines are unpiggable and cannot be inspected using this technique. Direct assessment, based on models that numerically assess corrosion in a pipeline, was developed to overcome this limitation and to facilitate inspection at certain sites. However, most of these models do not take localized corrosion into consideration, which is the main cause of pipeline failure. Industry standards provide guidance for selecting inspection sites based on the results of direct assessment models. However, this process is based only on the likelihood of pipeline failure and can lead to decisions which imply elevated risk and increased pipeline lifecycle costs. The aim of this dissertation is to expand the state of knowledge in risk-based inspection and maintenance planning for upstream unpiggable pipelines subject to internal corrosion. The research focuses on unpiggable pipelines in production and gathering systems operated in the upstream oil and gas industry. A framework for probabilistic risk and integrity assessment of unpiggable pipelines is developed. The framework combines advanced flow and corrosion models with risk-based inspection and maintenance planning. It also includes uncertainty analysis and lifecycle-cost optimization. An extreme value analysis is developed to model localized corrosion and microbiologically-influenced corrosion, which are the main causes of internal corrosion failure in pipelines. A method for decision optimization of unpiggable pipeline inspections based on the value of information is proposed. For maintenance decision optimization at specified safety levels, the research considers both risk-constrained optimization and lifecycle-cost optimization. The research outcomes provide pipeline operators with a methodology for developing optimal inspection and maintenance plans, while maintaining adequate safety levels.
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Keywords
internal corrosion, risk based inspection, decision making, probabilistic analysis, unpiggable pipelines, upstream
Citation
Melo Gonzalez, C. A. (2020). A contribution to risk-informed inspection and maintenance planning for unpiggable pipelines subject to internal corrosion (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.