Arctic Offshore Pipeline Design and Installation Challenges

Abstract

With the oil industry's continued quest for oil and gas in frontier offshore locations, several developments have taken place in regions characterized by seasonal ice cover including the US Beaufort, North Caspian, and Sakhalin Island. In these projects, pipeline transportation systems have been used, which are a cost effective, safe and reliable mode of hydrocarbon transport to shore. Ice gouging is one of the key design issues that affect engineering considerations with respect to strain based design, target burial depth requirements, cost, and safety.It is generally accepted that offshore pipelines in ice environments will need to be trenched and backfilled for protection. Burial depths can be greater than those that might normally be required for pipelines in temperate climates. Burial depth requirements will be a function of the design ice gouge depth (to prevent interaction between the ice and pipe) and an acceptable level of subgouge deformation beneath a gouging ice keel (which potentially strains the pipeline). There still exists uncertainty on the magnitude and extent of subgouge soil deformations due to ice gouging and the importance of sediment transport mechanisms for biasing gouge statistics.Other challenges that must be considered include strudel and hydrodrnamic scour, thaw settlement and frost heave, and upheaval buckling. These considerations may also influence burial depth requirements.