Arctic Pipeline Engineering Services
INTECSEA provides a full suite of pipeline engineering services for onshore and offshore arctic pipeline systems to encompass the full range of project development and execution including:
- Design basis document
- Safety schematics
- Leak detection system selection and permitting support
- Pipeline hydraulics and sizing
- Pipeline route selection
Ice Scour
Ice scour or gouging of the seafloor is a near-shore feature for most of the northern continents. Sea ice is driven by wind and current forces and tends to pile up creating a pressure ridge. Pressure ridges and icebergs have keels extending below the water surface and they move with the ice sheet and wind/current conditions. Occasionally, these ice keels intrude into water with depths less than the ice keel draft and form a gouge in the seafloor soils. A pipeline on the seafloor in such an environment may not be able to withstand the ice contact loadings and typically must be buried below predicted extreme ice keel scour depths for protection. Further, the pipe must be trenched sufficiently far beneath the influence zone of soil displaced below the ice keel to limit pipe bending to acceptable limits.
Permafrost
An offshore pipeline transporting oil or gas to shore will need to transition through a shore crossing. In some arctic applications, the shore crossing will have ice-bonded permafrost soil underlying the pipeline. When the pipeline becomes operational, the temperature of the pipeline will typically increase, warming surrounding soils and creating a permafrost thaw bulb. This may result in permafrost thaw consolidation and pipeline settlement. If the settlement area is adjacent to an area, which is thaw stable, the result is a highly loaded pipeline span. This differential settlement can induce considerable bending strain in the pipeline and must be accounted for in design.
Limit State Design Application
Limit state design applications for an above ground arctic onshore pipeline may include internal pressure, wind-induced vortex induced vibration (VIV), corrosion and expansion (due to warm pipe contents). Limit state design applications for offshore buried arctic pipelines may include internal pressure, ovalization (due to displacement controlled bending) and unstable weld flaw propagation due to tensile bending strains. In previous designs by INTECSEA, multiple limit state applications have been developed for pipe behavior during extreme bending. INTECSEA has conducted full-scale bend test programs on behalf of clients to quantify these effects and validate design by confirming ultimate design strains.
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