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Drawing Oil from Turbulent Waters

By “Awake!” correspondent in the British Isles

AT A point where some of the world’s wildest weather rages, oil has been found beneath the sea. On an average, winds here are calm only one percent of the time in winter and 5 percent in midsummer. Hurricane-force storms batter the oil rigs as 90-foot (27-m) waves crash over the drilling decks. Supply ships have foundered. Most serious of all, however, is the ever-increasing loss of human life. These factors, added to the normal overheads of such a project, make it incredibly expensive to draw oil from the troubled waters of the northern North Sea.

In 1964 the British government issued licenses authorizing oil companies to explore the North Sea for petroleum resources, and by 1969 the first small discovery of oil was made. Since then the oil rush has been on until today 14 fields are considered commercial.

Preparing for the Harvest

When the possibility of drawing oil in commercial quantities from under the sea became a reality, much installation had to be undertaken. First, 32-inch (81-cm)-diameter submarine pipelines with three-quarter-inch (19-mm) steel walls had to be laid from the mainland out into the middle of the sea. These were specially protected by bituminous felt to stop corrosion and then they were clad with cement two to five inches (5 to 13 cm) thick to give weight against currents while the line was being laid in a trench.

The seabed had to be surveyed mile by mile to make sure that the lines were adequately buried. In places this meant going down about 450 feet (137 m), a depth at which pipelines had never been laid before.

The oil production platforms brought their own problems. Because of size and weight each had to be assembled on land and then towed out to the site. The largest task was to move each steel platform support structure out in one piece, sometimes 155 miles (250 km) or more, and drop it into the sea at exactly the right spot, standing in an upright position. Finally, supporting piles were driven about 400 feet (120 m) into the seabed to secure each installation.

Not all production platforms, however, were made of steel, held by supporting piles. Concrete platforms relying on gravity alone were also used. In May 1978, one of these concrete platforms, weighing 600,000 tons, was towed out from Loch Kishorn on the west coast of Scotland to the Ninian oil field in the North Sea. It was claimed to be the largest object ever moved on earth, standing some 776 feet (237 m) high. Today the greater part of it is not even visible above sea level.

Questions as to the safety of these offshore gravity platforms were bound to be raised. Such hazards as ice adhesion, gale-force winds of 100 m.p.h. (160 km/​hr), gigantic waves and even sea-floor movement all attack the structures ceaselessly, often in dangerous combination. And as one top designer has admitted, the dynamic forces of the North Sea are not yet fully understood.

On an Oil Platform

Oil fields are reached mainly by helicopter, and on leaving Aberdeen, Scotland, in one of these you are likely to pass over one of the outlying portable drilling rigs first. The “Ocean Victory” is a typical example. She is self-propelled and semisubmersible, which means that she floats and can be moved. When operating she has her hull about 70 feet (20 m) below the surface, as this amount of structure being submerged contributes largely to the rig’s stability. To hold her in position she is encircled by eight 13-ton anchors, each one running out 3,300 feet (1,000 m). Her derrick houses a hydropneumatic system that maintains constant weight on the drill when it is in operation, regardless of how much she may roll. Practically all semisubmersibles are capable of drilling in 1,000 feet (300 m) of water, although they can usually be modified to drill in water as deep as 3,000 feet (900 m) if required.

A short distance farther east lies one of the standard-type production platforms surmounted by its tapering steel derrick and three decks. The top deck is little more than a helicopter landing pad, while the middle one is taken up by the main working area where the actual drilling is done. The lowest deck holds a storage area where lengths of steel used in the operation are stacked. Also on this deck are the crew’s living quarters, which can accommodate about 150 men, together with two dining rooms, a games room in which there is television, facilities for showing films and a library. Below all of this lies the platform’s main support structure.

Some production platforms can draw from up to 27 wells. On land, with few exceptions, wells are drilled vertically, but out in the North Sea the ratio of one well to one installation would be prohibitively expensive, so directional drilling has been employed. This requires that, while the wells are bored vertically for a short distance down from the sea floor, they are then diverted along planned courses to points located at specific distances, depths and directions from the platform.

Problems of Divers

The underwater world of offshore oil development in the North Sea always needs divers, who frequently earn more than £30,000 ($60,000, U.S.) a year. This is in spite of the fact that they can work only for 25 minutes at a time at a depth of 300 feet (90 m). The hazards are frightful and at the current accident rate a diver has only one chance in five of surviving for 20 years. In fact, the British Medical Association regards the occupation as “fifty times more dangerous than coal mining.”

Little wonder, for low temperatures coupled with the high thermal conductivity of the waters can chill an unprotected diver into insensitivity in minutes. At the same time, to avoid being squashed flat he must breathe at sea pressure where he is working, and below 160 feet (50 m) the gas mixture is so critical that it must be carefully and continually monitored. If he is compressed too quickly he may develop tremors; on the other hand, slow compression may take days. The only solution is saturation diving where a diver may have to spend three weeks under continual compression in a confined steel chamber with only other divers for company. Needless to say, such an environment is bound to create serious mental and physical tensions.

Another major hazard lies in getting treatment to an injured diver. Following a very deep dive of say 650 to 740 feet (200 to 225 m), he will have to face at least seven days in decompression. What is done now to solve this problem? The injured diver would first be transferred to the deck compression chamber on his platform. Then a special transfer-under-pressure chamber, built of titanium to keep the weight down to about 2,000 pounds (900 kg), would be brought up to the rig compression chamber and locked on. After the transfer is made, the titanium pressure chamber must then be flown by helicopter to a special pressurized medical unit at Dundee, Scotland.

All of this takes up vital time and if the man’s wounds are very serious he is likely to die before adequate medical aid arrives. Even when a successful transfer is made and an operation is performed in the unit the effects of decompression on sutured wounds is still uncertain. Additionally, normal gas anesthesia by inhalation is impractical in a compression chamber and no electrical apparatus can be used because of the high risk of fire and explosion.

The Norwegians have now developed an operating theatre, built into the aluminium-cased chamber system of their new Underwater Institute overlooking Bergen harbour in Norway. London’s The Observer, however, reported: “There is just one snag. The institute has not yet recruited any doctors willing to give up the time they would have to spend in the space-station-like decompression chamber before and after operations.”

Submersibles

The submersible is a type of submarine vessel that can go to far greater depths than any diver. This makes them indispensable in the quest for offshore oil reserves. These mini-submarines are less than 20 feet (6 m) long. Each vessel carries a two-man crew who, while they cannot leave the submarine underwater, can direct special cameras that record evidence on videotape for subsequent examination by experts on the surface or at the shore base. Although these submersibles are equipped with life support systems for 320 man-hours, they work from a base in pairs so that if one vessel gets into trouble the other can be used on a recovery mission, aided by lifting gear.

The development of the British-made “Seabug,” a remote-controlled sea-floor vehicle, and the Canadian Sub-Sea Chamber have made the task much easier. The latter provides a normal working atmosphere at the bottom of the sea for the crew, who even have supporting shuttle-service capsules to carry them to and from the surface. Even though great care is exercised, diving remains a hazardous occupation. In late 1978 two divers for Mobil Oil Company died in their diving bell after heavy seas caused the lines from their supply ship to part.

Exporting Technology

The efforts to draw oil from the North Sea have resulted in much technological progress. Some time ago The Guardian noted: “From the point of view of the nation [United Kingdom] we stand to earn far more from selling our excellent technology than we will ever make from North Sea oil.” This is proving to be true.

One of the most promising markets at present is South America, particularly Brazil. Brazil’s offshore reserves lie in water of depths similar to those in the North Sea. The location for exploration is the Campos Basin, less than 100 miles (160 km) off the coast of Rio de Janeiro, in water as much as 650 feet (200 m) deep. It is estimated that Brazil will need 30 to 40 production platforms in the next 10 years. This, in turn, will open up markets for inspection submarines, supply boats and other technical equipment. There are other export prospects in the offshore fields of Venezuela, Argentina and Mexico and in the U.S.S.R.’s Caspian Sea.

Future Prospects

What about future prospecting for oil? The United Kingdom Department of Energy, through its Offshore Technology Board, has stated: “To maintain self-sufficiency throughout the 1990’s successful discovery and operation will be needed in deeper U.K. waters in 1985-1990.” The deeper waters referred to would be 1,000 to 6,500 feet (300 to 2,000 m). However, oil explorers have warned that the biggest strikes may already have been made in the North Sea​—as much as three quarters of the total. In fact, attention is turning also to possible oil discoveries on British soil. An optimistic oilman said: “We are in the same position there [southern England] as we were with the North Sea 20 years ago. We know the oil is there. . . . It is only a matter of time.”

Meanwhile, as we leave the North Sea’s drilling rigs and production platforms, we do well to contemplate the real cost of petroleum​—the price paid in human lives, as well as the unique problems of this new technology. Is it really worth it? Most people seem to think so. Perhaps time will tell. In the meantime, the relentless struggle continues to draw ever more oil from the turbulent North Sea.