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Those sediments are being found round the globe—in troughs running along the continental shelves and around the deltas of major rivers. Recent expeditions of Massachusetts' Woods Hole Oceanographic Institution pinpointed possible oil deposits off the mouths of China's Yellow and Yangtze rivers, among other locations.
Offshore wells supply about 20% of the world's oil and 7% of its gas needs today, and their importance is rising fast. K.O. Emery, a senior geologist at Woods Hole, reckons that offshore oil production "will probably surpass that being recovered on land within a decade." In 1973, the world consumed about 20 billion bbl. By U.N. estimates, proven reserves currently total 640 billion bbl., including at least 115 bbl. in offshore deposits. But many scientists believe that the world's undersea oil supplies are far more extensive.
The controlling factors are technology and cost. Until recently, commercial drilling was feasible only to depths of about 300 ft., but now oil companies are extending their underwater reach. One new U.S. ship called a SEDCO-445 can drill at underwater depths of 6,000 ft., unfazed by huge waves and hurricane winds. Yet exploratory drilling in the stormy North Sea, for example, costs up to $5 million per hole—with no certainty of a strike. Price tags for drilling platforms range from $1 million to $2 million in such accessible areas as the Gulf of Mexico, to as much as $15 million in Alaska's Cook Inlet. The tab will climb even higher as oil companies explore farther offshore. Contrary to popular opinion, there is a possibility of oil finds in the deep oceans. Geophysicist Mahlon M. Ball of the University of Miami's Rosenstiel School of Marine and Atmospheric Science says that there are "hundreds" of promising sites, some buried under 10,000 ft. or more of water.
ENERGY: HARVESTING HEAT
Eventually, mankind may be able to use the energy stored in the seas themselves, rather than in the oil and gas deposits beneath. As early as the 11th century, the ebb and flow of tides in the coastal inlets of Europe were tapped to turn water wheels. Today, the plant that France built in 1966 to tap the 27-ft. tides at the mouth of the Ranee River faithfully produces 240 Mw. of electricity a year—about one-third the output of the average nuclear generating plant.
Recently, scientists have begun to look into a different form of sea energy.
Covering 70% of the globe, the oceans trap a huge amount of solar heat. But much of this heat lies near the surface; sunlight cannot penetrate to lower depths. Thus there is a temperature differential that scientists like Physicist Clarence Zener of Carnegie-Mellon University think can be used to make electricity. For instance, he says, an easily vaporized liquid-like ammonia or the commercial refrigerant Freon could be passed through a closed loop of pipes submerged in the sea. In the warmer water near the surface, it would be vaporized; at depth, it would be liquefied again. The result: a continuous flow that could drive a turbogenerator. And the system would be pollution free.
FISH: DOWN ON THE AQUAFARM