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Project Number 332
Date of Summary April 09, 2002
Subject An Engineering Assessment of Double Wall Versus Single Wall Designs for Offshore Pipelines in an Arctic Environment
Performing Activity C-CORE
Principal Investigator Dr. Ryan Phillips
Contracting Agency Minerals Management Service
Completion Completed
Description This study had several objectives. The main objective of this study is to conduct an extensive, non bias engineering and environmental assessment, considering both pro's and con's, of single versus double walled designs for offshore pipelines in an Arctic environment. The principal rationale for conducting this study is to assess if a double walled design provides the same or a greater degree of engineering integrity and environmental robustness as compared to a thicker walled single pipe design for an Arctic offshore application and to appraise the economics of one selection over the other relative to the potential risks (real and/or perceived) associated with either application. The assessment will provide an extensive general review of all engineering and environmental pro's and con's for using either single wall or double wall pipeline designs for offshore oil and gas pipelines located in an Arctic environment. It will consider specific existing and/or planned pipelines projects of either design methodology located in the Gulf of Mexico, the North Sea and/or other international locations. For double wall pipelines, the assessment shall document, with references, the technical and non-technical reasons as to why that type of design was selected for the project as opposed to an alternative single wall design relative to construction, operations, and maintenance issues.

The intent of the desired study IS NOT to assess the alternatives for a single, specific ongoing Arctic pipeline project. It is understood that to assess the actual benefits versus costs and risks associated with either a single walled or double walled design would require project specific analyzes. The purpose of the assessment IS to accurately document the advantages and disadvantages (technical and non-technical) of either a robust single thick walled design to a pipe-in-pipe design considering the constraints associated with an offshore Arctic pipeline project, i.e. ice cover, permafrost, scouring of the seafloor by ice, etc. and based on supporting quantitative information. The assessment will provide a comprehensive technical reference on double walled pipeline concepts relative to single walled designs considering long-term structural integrity and environmental issues. The assessment will consider aspects of both alternatives such as, but not limited to designed performance versus actual performance, potential for construction and installation problems, inspection, risks associated with more complex design and construction requirements, quality assurance and quality control, corrosion, leak detection, costs versus perceived risk mitigation, long term operations and maintenance, structural integrity, secondary containment in the event of a leak occurring. A primary purpose of the study is to see if it is feasible to design a double wall pipe for Arctic conditions and to assess advantages/disadvantages, risks/challenges and what resources would be required to meet or mitigate those challenges.

All results stated will be specific as to how the conclusions were determined and if they are, in fact, based on thorough and defendable engineering or environmental assessments and/or analyzes of critical issues. The assessment shall be presented in a format so that engineers, biologists, scientists and the public can comprehend the results and resulting conclusions. Also the results and conclusions must be presented in a way so that they are useful, concise, and defendable to all concerned in making decisions relative to long term integrity and environmental issues typical for an offshore Arctic pipeline.

Workshop Proceedings are available at http://www.mms.gov/tarworkshops/Proceedings/workshop25.htm.

Progress Project is now completed.
   

Reports
AA (269 pages) PDF An Engineering Assessment of Double Wall Versus Single Wall Designs for Offshore Pipelines in an Arctic Environment, Final Report,   C-CORE, Memorial University of Newfoundland, St. John's, NF, April 2000.
AB (31 pages) PDF

Proceedings for "ALASKAN ARCTIC PIPELINE WORKSHOP" Captain Cook Hotel --Anchorage, Alaska, November 8 - 9, 1999, C-CORE, Memorial University of Newfoundland, St. John's, NF.
 

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Last Updated: 07/23/2008, 08:02 AM