The British Petroleum Co. Ltd. achieved an important milestone recently when its equity stake in the Standard Oil Co. of Ohio rose above 50 percent, giving BP - which is itself 51 percent owned by the British government - majority control of one of this country's major marketers and refiners.

THe BP share of Sohio currently stands at 51.2 percent, but it eventually slated to rise to 60 percent. BP plans to consolidate the Sohio financial results on its books for the first time this year.

The acquisition of Sohio completes a dramatic retrenchment for BP over the five years since the Arab oil embargo and the nationalization of its own once vast Iranian and Kuwait oil interests.

It results from the fact that when oil was first discovered in Prudhoe Bay on Alaska's North Slope in 1969, BP found that 53 percent of the western hemisphere's largest oil pool lay on its leases.

The company relishes the opportunity to enter the large U.S. market in force for the first time, having long envied rival Royal Dutch-Shell's 69 percent stake in Shell Oil U.S.A.

But with large capital outlays already committed to the North sea, where BP pioneered exploration, the company decided to go on an unusual indirect route to acquire a U.S. refining and marketing presence.

BP bartered its 53 percent share of the Pruhoe Bay oil reserves for an initial 25 percent interest in Sohio, a compact, efficient relaively debt-free and already established U.S. oil marketer which had sales last year of $3.5 billion.

Under the arrangement, as production has gone up, so has BP's Sohio share. Some analysts figure the ultimate value of the unique buy-in tracsaction will total $12 billion, as income from the oil is realized.

The North Slope was not proved to be the immediate bonanza that BP and Sohio both hoped. Delays in construction of the pipeline sent costs soaring. And the current oil glut on the West Coast of the United States has forced the company to ship 350,000 barrels of its 600,000 barrel daily Alaskan production through the Panama Canal to Gulf Coast refineries, at an additional transportation cost of $2 a barrel.

Meanwhile, BP has continued to score heavily with its massive Forties Field in the NOrth Sea where production this year is expected to reach 500,00 barrels a day, allowing a big payoff on its heavy past investment and an apportunity to reduce some of its debt.

Oil from the North Sea, where BP also has other extensive acreage, provides BP with profits estimated at $3 a barrel, considerably higher than the 25 cents a barrel it receives from Iran where its once sizeable stake was nationalized.

The large crude supplies from the North Slope and the North Sea have come on stream just in time for BP, with seven years ago controlled 12 percent of the free world's crude supplies and this year finds itself down to 1 percent.

The five-old increase in oil costs dictated by the Organization of Petroleum Exporting Countries (OPEC) has had th beneficial effect of making the North Slope and North Sea - with the immense production costs - economical where they otherwise would not have been.

Fifth in size among the "seven Sisters," of international oil in terms of revenues, BP lags the group in profitability. Last year it earned $688 million on $23.5 billion in sales. Its return on invested capital was only 7.7 percent last year, down sharply from 17.7 percent in 1974, but considerably higher than its 1972 return of 3.9 percent.

The current low rate of return results from huge amounts BP has had to borrow to capitalize recent investments, as well as sizeable losses on its European refinery operations.

BP's history goes back to 1901, when the legendary William Knox d'Arcy, hearing tales of large Persian oil finds, pursued the information and wound up negotiating a concession agreement with the Grand Vizier of Tehran for 480,000 square miles, or twice the size of Texas. The company was originally called the Anglo Persian Oil Co.

In 1914, Winston Churchill acquired the U.K. government's 51 percent stake in the company. Churchill, who was first Lord of the British Admiralty at tht time, pursuaded Parliament to make the investment in the undercapitalized company as a way to obtain secure oil supplies for the British navy.

In 1975, the Bank of England picked up another 20 percent in BP when the failing Burmah Oil Co. was bailed out in exchange for its BP stock holdings. The Bank of England's holdings wre sold off in 1977 in two public offerings in Britain and the United States that netted $1 billion for the British government.

Today, the British government continues to hold 51 percent of BP but has never altered its stance as a passive equity investor in the company with no voice in its operations, according to BP chairman Sir David Steel.

"They do not interfere in the commercial decisions of the company, and it has been that way for 60 years," said Sir David who was in New York this week.

Meanwhile, BP is in the strange position of having to negotiate with the British government on a proposal the Labor Party has made to increase the petroleum revenue tax on North Sea production next year.

"We just talk to them like any other company," Sir David said.

With 40 percent of BP's assets now tied up in the United States, Sir David, in a speech to the British-American Chamber of Commerce in New York, felt he could give the U.S. government "an earbashing" for what he still considers an inadequate U.S. energy policy.

With the United States now absorbing 25 percent of the oil moving in international trade, "the level of world prices will be largely set by the level of U.S. imports - in future years he told the audience.

Projections are for the United States to be importing some 12 million barrels a day by 1985, without any energy plan to reduce this. He indicated that while the plan passed last weekend by Congress was "better than having no bill at all," it was still short of required actions to raise U.S. energy prices to world levels to cut demand.

"Unless there is a substantial reduction in the import figure of 12 million barrels a day . . . a severe energy crisis could develop, and you must reduce your dependence on oil if we in the west are to survive," Sir David told the audience.

Looking back at the events of the past two decades that culminated in the 1973 oil embargo, and OPEC price surge, Sie David later told reporters the major mistake the western oil companies may have made was trying to drive down prices of crude oil when OPEC was originally formed in 1959.

"One should maybe have encouraged governments to accept that there should have been gradual price increases," saidr Sir David. "In the 1960s, if we had gotten consumer governments to accept higher prices" the "real shock" of 1973-1974 could possibly have been avoided, he said.

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