Buckle propagation in deep sub-sea pipelines

Khalilpasha, Hossein (2013). Buckle propagation in deep sub-sea pipelines PhD Thesis, School of Civil Engineering, The University of Queensland.

       
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Author Khalilpasha, Hossein
Thesis Title Buckle propagation in deep sub-sea pipelines
Formatted title
Buckle Propagation in deep sub-sea pipelines
School, Centre or Institute School of Civil Engineering
Institution The University of Queensland
Publication date 2013
Thesis type PhD Thesis
Supervisor Faris Albermani
Yicai Wang
Total pages 248
Total colour pages 71
Total black and white pages 177
Language eng
Subjects 090506 Structural Engineering
Abstract/Summary The recent oil spill in the Gulf of Mexico (2010) and the resulting environmental vandalism and massive economical loss, highlight the engineering challenges in deep subsea operations. In Australia, 80% of hydrocarbon reserve is located in frontier deep subsea regions. Safe and economical realisation of these resources requires innovative engineering solutions suitable for platform-free operations. Long and deep subsea pipelines can experience a number of structural instabilities such as lateral and upheaval buckling, spanning and buckle propagation. Among these, buckle propagation result in a catastrophic failure of a long stretch of the pipeline. A local buckle, ovalization, dent or corrosion in the pipe wall can quickly transform the pipe cross-section into a dumb-bell shape that travels along the pipeline as long as the external pressure is high enough to sustain propagation. The lowest pressure that maintains propagation is the propagation pressure which is only a small fraction of the elastic collapse pressure of the intact pipe. This results in a substantial increase in material and installation cost of the pipeline, since design is therefore governed by propagation pressure. A number of solutions to mitigate buckle propagation (and the necessary increase in wall-thickness were proposed such as buckle arrestors, pipe-in-pipe system, sandwich pipe system and ring-stiffened pipelines. This thesis investigates buckle propagation in deep subsea pipelines. An experimental work is conducted to determine buckle initiation and buckle propagation pressures in hyperbaric chamber test using aluminium and steel sample pipes with various diameter-to-thickness ratios (D/t). Intact and dented pipes are used in these tests to determine imperfection sensitivity of buckle propagation. Based on experimental observations, a modification to the available analytical solution of buckle propagation is proposed that accounts for circumferential bending as well as circumferential membrane actions. Nonlinear finite element (FE) modelling of the hyperbaric chamber tests was conducted and the predicted FE results of initiation and propagation pressures were verified against the experimental results. In order to increase the buckle propagation capacity and alleviate the inherent imperfection sensitivity, two issues that are relevant to deep subsea pipelines, a novel form of pipeline is proposed. The new form is a textured pipeline which is cylindrical in the global sense with local textured rather than smooth wall. Nonlinear FE analysis is used to evaluate the performance of textured pipeline. Based on obtained results, the textured pipeline offer superior performance in comparison to a conventional cylindrical pipe made of the same material and the same D/t ratio.
Formatted abstract
The recent oil spill in the Gulf of Mexico (2010) and the resulting environmental vandalism and massive economical loss, highlight the engineering challenges in deep subsea operations. In Australia, 80% of hydrocarbon reserve is located in frontier deep subsea regions. Safe and economical realisation of these resources requires innovative engineering solutions suitable for platform-free operations.

Long and deep subsea pipelines can experience a number of structural instabilities such as lateral and upheaval buckling, spanning and buckle propagation. Among these, buckle propagation result in a catastrophic failure of a long stretch of the pipeline. A local buckle, ovalization, dent or corrosion in the pipe wall can quickly transform the pipe cross-section into a dumb-bell shape that travels along the pipeline as long as the external pressure is high enough to sustain propagation. The lowest pressure that maintains propagation is the propagation pressure which is only a small fraction of the elastic collapse pressure of the intact pipe. This results in a substantial increase in material and installation cost of the pipeline, since design is therefore governed by propagation pressure. A number of solutions to mitigate buckle propagation (and the necessary increase in wall-thickness were proposed such as buckle arrestors, pipe-in-pipe system, sandwich pipe system and ring-stiffened pipelines.

This thesis investigates buckle propagation in deep subsea pipelines. An experimental work is conducted to determine buckle initiation and buckle propagation pressures in hyperbaric chamber test using aluminium and steel sample pipes with various diameter-to-thickness ratios (D/t). Intact and dented pipes are used in these tests to determine imperfection sensitivity of buckle propagation. Based on experimental observations, a modification to the available analytical solution of buckle propagation is proposed that accounts for circumferential bending as well as circumferential membrane actions. Nonlinear finite element (FE) modelling of the hyperbaric chamber tests was conducted and the predicted FE results of initiation and propagation pressures were verified against the experimental results.

In order to increase the buckle propagation capacity and alleviate the inherent imperfection sensitivity, two issues that are relevant to deep subsea pipelines, a novel form of pipeline is proposed. The new form is a textured pipeline which is cylindrical in the global sense with local textured rather than smooth wall. Nonlinear FE analysis is used to evaluate the performance of textured pipeline. Based on obtained results, the textured pipeline offer superior performance in comparison to a conventional cylindrical pipe made of the same material and the same D/t ratio.
Keyword Offshore Pipeline
Buckle Propagation
Collapse Pressure
Propagation Pressure
Finite Element Analysis (FEA)
Textured Pipe
Subsea Pipelines
Hydrostatic Pressure
Hyperbaric Chamber Test
Ring Squash Test
Nonlinear Analysis
Cylindrical Pipe

 
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Created: Tue, 18 Jun 2013, 13:42:59 EST by Hossein Khalilpasha on behalf of Scholarly Communication and Digitisation Service