2) California

The offshore of southern California and particularly the Santa Barbara Channel area, must be classed as a major U.S. petroleum source. The State of California estimates its offshore potential to be 30 billion barrels. The OCS waters off California almost certainly have an even larger potential.

3) Alaska

The Gulf of Alaska, the Bering Sea, the Chukchi Sea and the Beaufort Sea shelf have potential for large amounts of petroleum when appraised on the basis of broad geologic favorability. Geologic structures and sizeable sedimentary basins are known. Various estimates of potential have been made, but with exception of the north Alaska coastal area, reservoir conditions in the areas otherwise favorable are unknown and must stand the test of the drill before meaningful estimates of potential can be made.

4) Atlantic Continental Margin

Along the submerged continental margin off the U.S. from Florida to Canada are three known sedimentary basins of the size and thickness favorable for the occurrence of petroleum. These are the Georges Bank basin, the Baltimore Canyon basin and the Blake Plateau basin. (Maher, 1971, p. 65). These basinal areas lie beneath the outer continental shelf and extend seaward beneath the continental slope and possibly beneath at least part of the continental rise as well. Although geophysical exploration has been underway along the U.S. Atlantic margin for some eight years, reservoir characteristics offshore remain as yet untested by drilling. Nevertheless the extent of the area and the size of its sedimentary basins are such that it must be considered at this time as a very important area for prospect drilling. Until this is done estimates of ultimate potential must be classed as speculative.

To summarize the status of knowledge about the petroleum prospects of the submerged continental margin of the U.S., it can be safely stated that less than five percent has been studied in the detail necessary to make meaningful estimates of the ultimate offshore petroleum potential of the U.S.

Other large areas of the offshore as yet unexplored

For completeness, mention must be made of three of the world's most extensive shelf areas that are unexplored: the shallow sea floor beneath the Laptev and East Siberia Seas north of Siberia; the shelf area off China, extending for 2,000 miles southwest from the Yellow Sea, through the East China Sea to Hainan off southeast China; and the vast shelf areas of Antarctica. The geology of the vast Arctic Siberian shelf

is not well known, but the area is a potential oil-producing province for the somewhat distant future. A recent offshore discovery of rumored major size was made in an inland arm of the Yellow Sea off China. Recent reconnaissance exploration off Antarctica suggests a potential in spite of severe operational constraints.

Also, the sizeable shelf areas of the Norwegian Sea off Central and Northern Norway and the Northern Barents Sea shelf off southern Sptzbergen and Franz Josef Land have potential. Much of the shelf areas around New Zealand is yet to be fully explored. Much of the shelf areas off east and southeast Africa and that off eastern Central America has received some exploration attention but significant discoveries have not been made.

Technology and future trends

Offshore drilling to the present time has been conducted as a seasurface operation, either from platforms that stand on the sea floor or from drilling ships and barges. A short ten to twelve years ago, most offshore drilling and production operations were in water depths measured in tens of feet; relatively few operations were underway in depths of more than a hundred and fifty feet. Today operations in depths exceeding 300 feet are common and oil well drilling has been done in water depth of just over 2,000 feet. Recently, concessions and leases have been granted for offshore drilling in depths of up to 4,000 feet.

The rapid pace at which offshore oil well drilling has been moving into increasingly greater depths of water attests to the rapid advances that have been made in the techological know-how for conducting offshore petroleum operations. A platform just being completed for the North Sea will stand 700 feet above the sea floor and another under construction will exceed the Empire State Building in height.

The advance into deeper water, however, has been accompanied by substantially increased costs because of the requirement for bigger and more elaborate drilling rigs and production platforms. As a means of reducing the cost of deep water drilling and production, sea floor completion units have been under development for some ten years (Bleakley, 1973). Development on these has now reached the sea trail stage and this summer Phillips Petroleum Company will field test a subsea unit in the North Sea in 250 feet of water at a point 200 miles from the coast.

The ability to complete and maintain petroleum wells on the sea floor will have a profound effect on offshore petroleum operations. Not only will operations costs be reduced but development time also will be shortened. Furthermore, by the end of the next decade, sea floor completion and maintenance in water depths greater than 5,000 feet likely will be a reality.

AFRICA

Table 1-PROVISIONAL WORLDWIDE ULTIMATE RECOVERABLE OFFSHORE

OIL RESERVES AND CUMULATIVE PRODUCTION⭑

Extensive exploration now underway over the shelves of Africa plus recent discoveries in five other countries not listed here will doubtless add substantially to this figure.

*Reserve and production statistics and identification of oil fields have been compiled from the following sources: International Petroleum Encyclopedia, 1972; McCaslin, 1973; Halbouty and others, 1970; Albers and others 1973; U.S. Geol. Survey, 1972; and news items in 1973 issues of Oil and Gas Journal, World Oil, and Ocean Industry.

Reserves estimates not available

2/ Reserves estimates not available for Fateh, SW Fields, but thought to be > 500 million

barrels

3/ Opinions have been expressed that the potential for additional large discoveries in the Persian Gulf is high.

4/ Extensive exploration over the Sunda Shelf, the waters of Indonesia, the South China Sea, and the Andaman Sea, which began about two years ago, is expected to add

substantially to this figure.

5/ Production from three fields

2/ Dr. J. Birks, Director--technical, British Trading Executive Committee places ultimate recoverable oil reserves for total North Sea south the 62° parallel at 42 billion barrels.

3/ Production scheduled to begin 1974

4/ Includes conservative estimate of 1 billion barrels recoverable reserves for Edda Field which had the highest daily initial test flow for any discovery to date in the North Sea (1972 discovery).

5/ Includes Edda Field (1972) as a giant discovery

6/ Considered a conservative estimate. Development is reported rapid in the Caspian Sea where Russian sources state only that reserves discovered are "enormous".