Root-Cause Analysis of Offshore Pipeline Failures
- Chris Carpenter (JPT Technology Editor)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- November 2018
- Document Type
- Journal Paper
- 99 - 100
- 2017. Society of Petroleum Engineers
- 0 in the last 30 days
- 73 since 2007
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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 188717, “Offshore-Pipeline-Failure Root-Cause Analysis,” by Emmanuel Iyeh, SPE, Addax Petroleum, and Grant Adams, JEE Subsea, prepared for the 2017 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 13–16 November. The paper has not been peer reviewed.
This paper evaluates potential causes of failure for nine pipelines operating in shallow waters (8 to 14 m) in the Gulf of Guinea. The authors develop an analytical method to identify root causes and provide recommendations for pipeline design and placement.
Once the subject pipelines had been identified, field visits and failed-section analyses were conducted. Pipeline properties and conditions are provided in Tables 1 through 5 of the complete paper. Mechanical-failure, hydrodynamic, and third-party-interference assessments were performed. Design-stability assessment was reviewed and gaps identified. A further stability assessment of the pipelines was performed in accordance with Det Norske Veritas- Germanischer Lloyd Recommended Practice (DNVGL-RP) F109. The authors then developed the best remedial option by use of a scoring matrix based on weighting with respect to business drivers.
For a new tie-in spool, a subsea flexible spool can be used. This approach has been used safely and successfully to accommodate instability. This approach may be adopted for pipelines, with the following caveats:
- An unbonded subsea flexible spool verified for use in a multiphase system should be used.
- A flexible spool should be combined with a rigid riser.
- The flexible spool does not represent a solution to pipeline instability but rather a method to prevent failure of the riser caused by a mobile pipeline. The pipeline may continue to move over time, and the flexible spool may eventually enter tension and fail. An unstable pipeline is also at significant risk of fatigue if instability continues.
A flexible spool could be used with a concrete mattress. This will allow a degree of movement (e.g., if the mattresses take some time to settle into the seabed). The position of the flexible tie-in can also be monitored and, in the event that the pipeline continues to move after mattresses have been installed, will give warning that the pipeline is still unstable.
The majority of the studied failures occurred between the months of May and October, the rainy season in the Gulf of Guinea. This season features the region’s most extreme weather, likely contributing to the failures. Most failures involved pipeline movement or riser kinks.
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