Nearshore FE Based Pipeline On-Bottom Stability Design
2 x 42” Ras Markaz Crude Oil Pipelines were installed by shore-pull operation on the eastern coast of Oman. Immediately after shore-pull operation the pipelines were supposed to be trenched. However, as a result of the spread of the COVID19 pandemic, the trenching equipment could not be mobilised to the site. This resulted in the pipeline to be abandoned on the seabed after shore-pull and to be recovered at a later stage. This would result in the pipelines exposed to harsh shore approach environmental loading which had potential to make the pipeline unstable.
FE based on-bottom stability assessment was performed using Abaqus general purpose FE software package to determine stability status of the pipelines. The pipelines were found to be unstable on the seabed with a potential to laterally displace by approximately 73 m as a result of wave and current loading. This had a potential of excessive bending of the pipeline at the exit of the cofferdam in which the pipelines were supposed to be backfilled.
It was recommended to flood the line immediately after shore-pull operation and also to install bollards to restrain the lateral displacement of the pipelines as a result of environmental loading.