An analytical parametric study of lateral pipeline-soil interaction in partially embedded pipelines

ABSTRACT: Pipelines can transport either liquid hydrocarbon or natural gas products and are a key component in offshore oil and gas development. Offshore pipelines are often laid on the seabed. However, factors such as the hydrodynamic force, the weight of the pipe and its contents, and laying effects, can cause a portion of the diameter of the pipeline to penetrate the seabed. A pipeline which was designed to lay on the seabed or be buried can become a partially embedded pipeline due to seabed mobility. Accounting for lateral pipeline soil interaction in partially embedded pipelines is therefore an important consideration for offshore pipeline design. Closed form solutions such as an analytical parametric study are an effective way of understanding engineering problems such as lateral pipeline-spill interaction in partially embedded pipelines. Although advanced experimental studies or finite element analysis would be able to more accurately predict the effects lateral pipeline-soil interaction in partially embedded pipelines, these approaches can be quite costly and impractical. An analytical parametric study was conducted to investigate the order of magnitude of various key parameters influencing soil interaction in partially embedded pipelines. Both drained and undrained conditions were studied and plots relating lateral breakout resistance to penetration were produced. For the undrained condition, the undrained shear strength was manipulated and three different models were plotted. For the drained condition, the angle of internal friction was varied to show the change in drained lateral breakout resistance with penetration for each of the roughness parameters. Two different models were plotted. Environmental and seabed soil properties were selected from Canadian offshore regions. The study revealed interesting trends, which can be useful for engineers designing pipelines in an offshore environment.