(FORTUNE Magazine) – The U.S.-led embargo of Iraq and Kuwait, which together produced 20% of OPEC's crude exports last year, will jolt some of the world's leading oil companies and enrich others. Starting on this page are ten scorecards comparing the top companies doing business in the U.S., the world's largest market for oil and the biggest importer as well. These goliaths aren't accustomed to changing their sources of crude from month to month, but some will have to while the crisis lasts. Hardest pressed may be those most reliant on Iraqi oil, but all Persian Gulf supplies, even from friendly Saudi Arabia, are in jeopardy from the hostile troops massed along the Kuwaiti-Saudi border. As petroleum prices rise, the big profits will go to companies that produce high percentages of the crude their refineries need -- and in the long run, to those like Amoco with substantial reserves of natural gas.

BOX: EXXON COMPANY OUTLOOK: Profits sagged after a $1.7 billion writeoff for the Valdez spill . . . Over a fifth of its U.S. imports come from Persian Gulf OPEC members . . . Formidable even so . . . Says CEO Lawrence Rawl: ''Current supplies are adequate, but shortages could occur if shortfalls in Iraq and Kuwait are not replaced.''

ROYAL DUTCH/SHELL COMPANY OUTLOOK: Owns the world's largest proved reserves of oil and natural gas liquids, much located in the U.S. . . . Some offshore rigs in the North Sea are shut down for summer maintenance, temporarily halting their production . . . A big plus: rapidly expanding natural gas production in Britain.

MOBIL COMPANY OUTLOOK: Crude poor but has extensive natural gas holdings . . . Says security analyst William Randol of First Boston: ''Companies like Mobil might whisper in policymakers' ears about natural gas as an oil alternative.'' . . . Has a lucrative chemicals sideline that makes commodity goods and Hefty trash bags.

BRITISH PETROLEUM COMPANY OUTLOOK: Scant exposure to Persian Gulf . . . Big buyers of Nigerian light crude . . . Says BP Oil's general manager, Les Atkinson: ''We would not describe the current situation as a supply crisis, nor is one imminent. Other producers can make up the supply that had been coming out of Iraq and Kuwait.''

TEXACO COMPANY OUTLOOK: Flush with crude . . . Its joint venture with Saudi Arabia in Star Enterprise has the right to buy 600,000 barrels per day of Saudi oil . . . Management is minding the store again after long battle with investor Carl Icahn . . . Says Todd L. Bergman, security analyst at Goldman Sachs: ''I expect to see a big increase in cash flow and more emphasis on exploration.''

CHEVRON COMPANY OUTLOOK: Chevron has shifted from Persian Gulf crude to more from ; Mexico, and holds reserves of domestic natural gas and heavy oils . . . Wrote off $1.2 billion in 1989, partly as a result of environmental concerns that led regulators to bar production from offshore wells near Santa Barbara, California.

AMOCO COMPANY OUTLOOK: Largest nongovernment owner of natural gas reserves in North America; sees future in that fuel -- at least in the U.S. . . . Says H. Laurance Fuller, president: ''I've seen crude prices at all levels. I can say that we won't be making substantial changes in our strategy in the near future because of Iraq.''

USX COMPANY OUTLOOK: The steelmaker that bought Marathon Oil still gets 30% of revenues from steel . . . 7% of its U.S. imports come from Iraq . . . Expects to make up the shortfall with purchases from U.S. independents or on spot market, but that won't be cheap . . . Well positioned in the Brae oil fields of the North Sea.

ATLANTIC RICHFIELD COMPANY OUTLOOK: Rising price of crude means increased profits for oil-rich Arco . . . Produces oil in Alaska and Texas . . . Exposed to Middle Eastern tumult only through its 49.9%-owned Lyondell Petrochemical, a $5.3-billion-a- year refiner that imports the bulk of its crude, over 200,000 barrels per day.

PHILLIPS PETROL COMPANY OUTLOOK: No U.S. imports from Iraq or Kuwait . . . Produces almost 90% of its refinery needs . . . Like Chevron, Phillips is barred from pumping oil from its offshore California field, causing a $280 million write-down in 1989 . . . Expect the company to invest any increased cash flow from higher crude prices in its promising U.S. and Canadian natural gas operations.

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