A plan is afoot to use the Glomar Explorer, which recovered parts of a sunken Soviet submarine for the Central Intelligence Agency four years ago, to explore for oil in the deep oceans at the edge of the Outer Continental Shelf.

With the backing of some of the world's leading scientists, the National Science Foundation and the U.S. Geological Survey are considering putting up $50 million to convert the 240-foot Glomar Explorer into a ship that could safely explore for oil and natural gas and conduct scientific drilling operations in as much as 12,000 feet of water going as deep as 20,000 feet into the ocean floor.

"Nobody has ever drilled that deep at sea," said Dr. Peter Wilkniss of the NSF. "And the Glomar Explorer is the only vessel there is that could suspend 32,000 feet of drill string."

The plan to use the Glomar for the dual purpose of oil exploration and scientific study also has the support of five other countries, including the Soviet Union. The others are Japan, West Germany, France and Britain.

The NSF and the USGS would put up the money to convert the Glomar and finance its day-to-day operations when it drills in coastal U.S. waters. The five other nations would finance Glomar operations when the ship moves out of U.S. coastal waters.

The bill for running the Glomar would be a big one. The NSF estimates that the Glomar costs about $40,000 a day to operate.

The plan is for the Glomar to drill at the edge of the Continental Shelf, in regions scientists call the "oceanic margins" where the continents end and the ocean begin. Nobody has drilled the margins because the water is too deep and the sediments on the ocean floor too thick.

"Nobody knows what the oil and gas potential of the margins are," said Wilkniss. "The oceanic margins are the last major unexplored regions of the earth."

Geologists want to recover sediments from the floors of the oceanic margins in both the Atlantic and the Pacific, which are vastly different.

Some of the $50 million it would cost to convert the Glomar Explorer into the right kind of drilling ship would go toward buying the 32,000 feet of drill string it would need to operate in the oceanic margins. Part of the cost would be for protective devices to prevent "blowouts" if the drill pipe punctured oil and gas reservoirs.

Currently the property of the Navy and in mothballs in California's Suisin Bay, the Glomar Explorer on June 1 will be turned over to a consortium led by Lockheed Aircraft Corp. and the Global Marine Co. to test out equipment and concepts in deep-sea mining.

The lease the Navy signed with Lockheed and Global Marine runs for 13 months, at which time both companies have four options to renew the lease for six months at a time. The last two options are subject to approval by the Navy.