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Client: Marathon Upstream Sakhalin Services Limited
Location: Sakhalin Island, Okhotsk Sea, Russia
Completion Date: 2001
Project Highlights: Geotechnical design
Sakhalin Energy Investment Company Ltd. purchased the “Molikpaq” Arctic-class drilling platform, formerly used for exploration drilling in the Canadian Beaufort Sea, and converted it to a drilling
and production facility for the Piltun-Astohskoye field in the Russian Far East. By taking on this venture, Sakhalin Energy became the first enterprise to develop and produce oil and gas
resources in Russia under a production sharing agreement. The Piltun-Astohskoye site is located about 16km offshore Sakhalin Island, in a water depth of approximately 30m. Klohn Crippen was
retained by Marathon Sakhalin as geotechnical consultants for the project. The site conditions off Sakhalin presented major challenges in geotechnical design including loading events generated
by Magnitude 7 earthquakes, 10m significant wave height storms and highly mobile ice hummock fields. Klohn Crippen worked with the project team on modifications to the Molikpaq. This
included a steel annular caisson extension manufactured in a Russian shipyard, to allow direct set down at the site specific water depth.
Gulf Canada Resources Ltd. originally designed the Molikpaq to allow year round drilling in arctic waters, and therefore, the structure required sufficient resistance to horizontal ice loading. The
Molikpaq is essentially a continuous steel annulus, octagonal in plan, supporting a deck that carries the drilling “topsides” facilities. It now has a height from base to deck level of 44m, while
plan dimensions range from 111m at the base to 86.6m at deck level. An ice and wave deflector is mounted around the perimeter of the deck. The outer face of the caisson is designed to
accommodate extreme ice features and intense localized loading. A picture of the Molikpaq during winter ice conditions in the Canadian Beaufort Sea is shown.
Services:
- Geotechnical design
- Design of structural modifications
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