HP/HT Pipelines Designed for Lateral Buckling in the South China Sea
- Chris Carpenter (JPT Technology Editor)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- August 2013
- Document Type
- Journal Paper
- 112 - 115
- 2013. International Petroleum Technology Conference
- 0 in the last 30 days
- 50 since 2007
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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 17181, "HP/HT Pipelines Designed for Lateral Buckling in the South China Sea," by H. Brian Skeels, Kwok Lun Lee, and Anand Venkatesh, FMC Technologies, prepared for the 2013 International Petroleum Technology Conference, Beijing, 26-28 March. The paper has not been peer reviewed.
Gas production in the South China Sea has seen an increasing trend of pipelines operating in high-pressure, high-temperature (HP/HT) conditions. This has led operators to look beyond the conventional stress-based design and move into strain-based design using the lateral-buckling-design approach. This paper presents both construction challenges and operational works post-startup, aiming to provide operators with cost-effective construction solutions and a risk-based maintenance philosophy when considering lateral-buckling design.
Lateral-buckling design is a strain-based design that allows the pipeline to expand laterally at locations in a controlled manner. This allows the pipeline to relieve its thermal expansion by lateral movement rather than being axially restrained (i.e., through trenching and burial).
As with any unconventional methodology, such design has certain limit states that require careful consideration. These limit states include local buckling, low cycle fatigue, fracture, and pipeline walking. These limit states are addressed during the design phase, except for fracture, which is addressed during the construction phase. During operation, these limit states are also monitored periodically to ensure that design thresholds are not exceeded.
Construction Challenges and Solutions
Initiation Method. Lateral-buckling design requires suitable initiation methods to ensure that the planned lateral buckles for a pipeline are initiated at the designated locations during startup. The initiation methods are typically executed during the pipeline installation itself rather than before or after the installation. It is therefore important that the initiation method be as practicable as possible for construction, and also effective, to guarantee the success of the lateral-buckling design.The purpose of an initiation method is to provide a low critical buckling force at the designated location, thus providing a higher probability that the planned buckle will initiate at the location intended. This can be achieved by creating an artificial imperfection either vertically or laterally on the seabed. One of the most frequently used methods, which combines both vertical and lateral imperfections, is the zero-radius-bend (ZRB) with buckle-trigger method.
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