Minus 56° Celsius, 24 hours of absolute darkness and tightest safety standards: extreme conditions for offshore oil production along the northern coast of Alaska. The project partners for this technically challenging pipeline undertaking are INTEC Engineering, USA, and Pioneer Natural Resources Alaska Inc. The pipes are from Mannesmann Fuchs Rohr, Germany.
An artificial island rises seven metres out of the sea nine kilometres off the northern Alaskan coast. Some 15 million cubic metres of gravel were heaped up here to hold the production facilities for the Oooguruk project.
Current offshore projects reap the benefit of these engineering advances. Oooguruk - some 65 kilometres west of Prudhoe Bay and about nine kilometres from shore is the second oil project in this region. Even though the water is only 1.80 metres deep, the gruelling conditions make lifting the deposits from their depth of about two kilometres a tremendously complex technical undertaking.
Account has to be taken not only of production and transport temperatures as low as minus 56 degrees Celsius but also and particularly of the geographical conditions. A brief ice-free summer period of only 6-8 weeks and the long winter make speedy progress all the more difficult.
It is estimated that the Oooguruk oilfield contains about 50 to 90 billion barrels of oil. The development concept was drawn up in 2000 as part of the Northstar project. It soon became apparent that HFI welded pipe was superior to seamless pipe in terms of production time, economy and quality demands. Very tight production tolerances in diameter, ovality and wall thickness were also convincing, while the flexibility in the production of individual pipe lengths was an enormous advantage when planning the pipeline sections.
The pipes are being laid in two sections, the first subsea and the second on land. The oil platform, an artificial island, will be connected with the mainland by an open bundle of four pipelines laid under the sea bed. The pipeline from the production island to the mainland is due to be laid in February 2007. First the solidly frozen water has to be milled out before a 2.7-metre trench can be dug in the seabed. The pipe bundle will then be installed in it and the trench backfilled.
A 3.7-kilometre-long overland section will be laid on stilt-like vertical supports, also designed and supplied by Mannesmann Fuchs Rohr, to connect with Conoco‘s processing plant. A hole will be drilled into the permafrost for each 10-meter-high support, which will freeze naturally into the special water and sand mixture filling the hole. This section of the pipeline will not be installed as a straight line. Pipe bends will create a serpentine shape designed to guard against thermal fluctuations and damage.
Safety is one of the major themes in the project as a whole for so much is at stake, particularly in these new offshore projects.