North Sea — a test bed for oil technology

Press, 15 July 1980, Page 17

North Sea — a test bed for oil technology

By

MICHAEL GUNTON,

London Press

Service industrial correspondent

The discovery of oil in the United Kingdom sector of the North Sea in September, 1969, has led not only to the growth of a vital industry, but to major developments within that industry. Feats of offshore construction, innovations in deep-sea drilling, the handling of heavy equipment at sea, and even accurate methods of positioning vessels without the use of anchors, thought to be practically impossible some years ago, are now

an accepted feature of oil industry life. “We are doing things in the North Sea never thought of before. They have been forced upon us by violent weather, the need, to work in deep water, and to get to the oil as quickly as possible,” says Mr Luke Lewis, offshore installations manager with British Petroleum. “The development of new techniques continues as we move into deeper and deeper waters in the continuous search for oil.” Drilling a hole, which in

the North Sea is usually three to five kilometres deep, into what is virtually unknown territory, is a task which calls for a great deal of expensive equipment and specialist knowledge of a very high order.

The North Sea can be one of the most inhospitable places on earth. Winds of up to 210 km an hour can whip up waves of 30m or more. Mist, rain, fog, snow, and ice are the rule rather than the exception. It is expected that 273 days in

any one year will be officially “bad” as far as the weather is concerned, 49 will be “marginal,” leaving only 43 for a description of “fair” or “good."

The force of North Sea waves is phenomenal. In the “splash area” of a platform — that is the section which is near the surface of the sea — the impact of a wave can be the equivalent of several

thousand tonnes both sideways and downwards at the same time. Having passed by, the wave then reverses its power and sucks with almost equal impetus. To combat this gigantic force the oil companies have had to develop giant platforms which must not only withstand the bad temper of the North Sea but also carry production

and other equipment weighing around 10,000 tonnes. Platforms are now constructed of either concrete or steel, the choice dependant on cost, delivery, and technical considerations such as the nature of the seabed. For example, in BP’s Forties Field, one of the biggest in the North Sea currently producing about 500,000 barrels of oil a day, four steel drillingproduction platforms each weighing some 57,000 tonnes are in place.

Accommodating almost 200 men, they are installed in a water depth reaching 128 m. They are 210 m high from the seabed to the top of the derrick and 167 m ’ high from the seabed to the top deck. Each platform has three decks and they are pinned to the sea bed by 11 piles for each leg driven to a depth of up to 76m. Up to 27 wells can be directionally drilled from a platform at angles up to 55 degrees to drilled depths, up to 3000 metres.

Concrete platforms, with similar capabilities, are held in position on the seabed by their sheer weight.

The design, construction of these platforms, and their transportation to the oilfields called for innovation and new technology. Another major North Sea development has been the semi-submersible vessel which can be used as a drilling rig, a maintenance or support vessel, a pipe-laying or crane barge.