[Truncated abstract] Pipelines are the main conduits in offshore hydrocarbon developments and for economical and environmental reasons must be designed to safely operate in remote locations and under harsh environments. For pipelines laid directly on the seabed, pipeline on-bottom stability is critical and analysis techniques should accurately simulate the real offshore processes occurring. This thesis is concerned with the on-bottom stability analysis of offshore pipelines under the action of wave and current loading. It details how hydrodynamic load modeling, pipe-soil interaction modeling and the coupling effect between the hydrodynamic load and the pipe-soil interaction can be properly considered. The motivation is to develop an integrated pipeline on-bottom stability analysis program and design methodology, and to use it to achieve a better understanding of hydrodynamicpipe- soil interaction. A hydrodynamic modeling program that generates a 3-D ocean surface, estimates the wave kinematics at the pipeline level and calculates the hydrodynamic loads on the pipeline was coded in FORTRAN. It has been named UWAHYDRO. Pipe-soil interaction is modeled using plasticity based techniques, again coded in FORTRAN in the UWAPIPE program. A unique pipeline on-bottom stability simulation program was developed by integrating UWAHYDRO and UWAPIPE with the commercial finite element program ABAQUS. The developed modeling program can efficiently evaluate the movement of a long pipeline under storm conditions, as shown by a parametric study of 1250 m of pipeline under one-hour of storm characteristic of the Australian North West Shelf region. Probabilistic methods are also discussed in this thesis and are used to develop further understanding of the pipeline on-bottom stability and to estimate the reliability of the pipeline under different design conditions.
|Qualification||Doctor of Philosophy|
|Publication status||Unpublished - 2011|