Pipeline shore crossing approaches in Arctic conditions

Abstract

The development of the Arctic region will entail the construction of new infrastructure, in particular, subsea pipelines. Considering the lack of actual field practice, ecosystem vulnerability and lack of common Arctic international standards, their development will be a big challenge, in particular, in the shore crossing zone. The design and construction of pipelines in the shore crossing area require a special approach that takes into account environmental and technological aspects of development. This work is aimed at analysing and determining environmental and technological factors influencing the design of offshore pipelines in the Arctic coastline. The paper presents theoretical and analytical work and the research is applied to a specific case study (pipelines from the Leningraskoye field to shore), through engineering calculations. Currently, there are five Arctic projects with shore transition areas for which trenching has been implemented. In order to determine the best shore crossing approach, it is important to consider the following environmental conditions: ice encroachment; ice ridges; shoreline erosion; permafrost thawing. Environmental characteristics should predetermine the choice of approach. Among three existing methods: trenching, tunnelling and horizontal directional drilling (HDD), the micro-tunnelling method is recommended for the Leningradskoye field in combination with a cofferdam corridor to protect the buried pipe from waves and ice in the nearshore area. In order to protect the surrounded permafrost from melting seasonal cooling-device is recommended to be used. The burial depth is determined to be more than 3.52 m in accordance with Force model calculations of ice ridges scouring depth. On the basis of research, the general choice-making diagram was proposed for Arctic shore crossing areas.