Buried pipeline response to ice gouging
Arctic region is rich in abundant discovered and undiscovered hydrocarbon resources and is an important area for energy development. In the arctic and other cold regions, subsea pipelines, which are considered to be an economical and convenient way of oil and gas transportation, are exposed to vario...
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| Format: | Thesis |
| Language: | English |
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Memorial University of Newfoundland
2014
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| Online Access: | https://research.library.mun.ca/8479/ https://research.library.mun.ca/8479/1/thesis.pdf |
| Summary: | Arctic region is rich in abundant discovered and undiscovered hydrocarbon resources and is an important area for energy development. In the arctic and other cold regions, subsea pipelines, which are considered to be an economical and convenient way of oil and gas transportation, are exposed to various geohazards such as pressure ridges or icebergs gouging the seabed. These floating ice masses could impose distress to the pipe through interaction with the seabed and ultimately jeopardize the integrity of the pipeline structure. To protect the pipelines the most common and efficient practice is to bury them into the seabed. Efficiency refers to both cost and performance of this method. Comparing to alternative methods, such as ice management or construction of protective structures along the length of the pipeline, trenching would be a more manageable option. In addition to protecting against ice features, trenching can help maintain the structural integrity of the pipelines against other hazards such as lateral buckling or hydrodynamic loads. Trenching is very useful to cope with uneven seabed and mitigate free spans. As the result, finding a safe but economic burial depth to install the pipelines in the subsea is important in offshore pipeline projects. The key to determination of a safe and economical burial depth is the proper understanding of the seabed soil response to the ice gouging and accurate prediction of the sub-gouge deformation under gouging loads. Numerical analysis could be an efficient tool to capture the seabed behaviour during the ice gouging event and simulate the sub-gouge deformations provided an appropriate soil model is applied. The soil constitutive model should be able to account for different stress paths. It should also be simple in terms of estimating input parameters with small number of common tests. Most of the constitutive models available in commercial finite element packages do not appropriately simulate the dilative behaviour of sand. An improvement in hardening law could also ... |
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