The dramatic financial restructuring of the oil industry through two years of mergers and hostile takeovers may be setting the stage for an oil shock in the early part of the next decade, some analysts warn.

"Everything that's going on just points to . . .a reversal of the oil glut in the 1990s," said Bruce Lazier, an oil-industry analyst for the Wall Street firm of Prescott Ball & Turben. "The companies are acting rationally individually, but they're setting us up for another price trap by the Persian Gulf countries in the 1990s."

As oil companies go heavily into debt to buy their own stock and as they roll back exploration and production efforts to cut costs, they may be jeopardizing the development of new sources of oil, some experts fear. In time, that could make the United States seriously vulnerable once again to interruptions in politically sensitive Middle Eastern petroleum shipments, these experts warn. "The exploration they're cutting back, given the lead time for exploration, is exploration that would have brought in oil for the 1990s," Lazier said.

But advocates of the industry shakeup, notably corporate raider T. Boone Pickens Jr., chairman of Mesa Petroleum Co., argue that the financial reorganizations merely recognize the new realities of the oil industry -- an oil glut, slumping prices, dwindling prospects for new sources of oil, rising exploration costs and undervalued stock prices.

"You now have an industry in decline," said Pickens, whose raids on companies such as Gulf Corp. and Phillips Petroleum Co. have prompted many of the recent changes in the industry.

"The primary asset for those companies is the reserve base of oil and gas in the United States, and they cannot protect it any longer," Pickens said in an interview last week. "There are not that many prospects. There are not that many opportunities. . . . The reserves are going down." Depressed oil prices mean those reserves are a relatively poor investment for shareholders -- they also mean that companies can't justify the costs of new exploration, he said. "You're never going to attain the real value of these companies for the stockholders," he asserted.

Therefore, oil companies are better off spending their money to repurchase their stock, selling U.S. reserves or exploring for oil overseas, where prospects are better, Pickens and others say.

"Clearly, it's going to mean a downturn in U.S. exploration and production, but frankly that's just a continuation of a trend that's gone on for some time," said John Sawhill, former deputy secretary of Energy and now a consultant for McKinsey & Co. "It probably means we'll be more dependent on imports, but the real question is, 'Is it going to affect our national security?' . . .As long as we maintain diversified sources of supply and maintain a strategic petroleum reserve, these will compensate."

The makeover of the oil industry has taken a variety of forms: gargantuan mergers such as Chevron Inc.'s takeover of Gulf and Texaco Inc.'s purchase of Getty Oil Co. last year; fine-tuning adjustments such as write-offs or sales of unprofitable operations or cutbacks in drilling programs; or out-and-out financial reorganizations such as those being undertaken by Phillips and Atlantic Richfield Co.

Arco said last week it would go heavily into debt to buy back $4 billion worth of its stock (more than half the amount outstanding); wrote off $1.3 billion worth of operations; announced plans to close or sell a variety of business, including all of its gasoline refining and marketing operations east of the Mississippi; and said it would reduce its capital spending on petroleum exploration and other ventures to $2.8 billion annually from the current $3.6 billion.

The effects of Arco's actions will be to leave it a much leaner, more efficient company, temporarily heavy with debt, and to give its stock owners increased value for their holdings. The stock market thought so: The price of Arco shares jumped by nearly $10 in the days after the announcement.

But while some Wall Street analysts applauded the plan as innovative and even overdue, many others said Arco seemed to be playing for short-term gain at the expense of long-term energy needs. And they warned that such changes increase the chances of short supplies and higher prices of oil in the years ahead.

"If everybody does what they're doing, everybody's going to cut back on exploration and, inevitably, prices are going to get higher," Lazier said.

Many observers blame the oil industry's upheaval on a somewhat cynical view of the future of the oil industry that is advocated primarily by Pickens -- a theory, simply put, that the oil industry is doomed in the long run, so investors might as well make a killing now.

"There is such a thing that I would call the Boone Pickens factor in the oil industry. . . . He started it. It's an emphasis on the short term," said John Lichtblau, executive director of the Petroleum Industry Research Foundation, a New York-based analysis group partly funded by the oil industry. "There's a shift now to emphasize the shareholders' interests by raising the dividend, by buying up the stock. . . . which inevitably means they're going to have less money available for exploration."

What makes the "Pickens factor" possible is the relatively depressed prices of oil company stocks. Years removed from the spiraling oil-product prices of the 1970s -- and the gushing profits that went along with them -- oil company stocks have dropped, in many cases to roughly half the level of a company's underlying asset value. That is, a company whose petroleum and other holdings have a theoretical value of $100 a share may be trading at about $50 a share.

Oil companies have coped with -- or taken advantage of -- this undervaluation in various ways. At first, it spurred a wave of mergers in the industry. "The best place to drill for oil is the floor of the New York Stock Exchange," went the saying and, indeed, oil companies bought other oil companies because it was cheaper to purchase additional cash-producing oil reserves than it was to drill for new oil.

The same philosophy turned the oil companies in on themselves. Oil companies generate huge amounts of cash, and rather than spend it on drilling for marginal or high-risk prospects or trying to diversify into new businesses -- the cause of some of the industry's biggest recent fiascos -- companies began buying their own stock on the open market. Exxon Corp., Amoco Corp (the former Standard Oil Co. of Indiana), Arco and others have used excess cash in recent years to purchase their own shares, thus pushing the stock prices up closer to the companies' theoretical values.

The massive restructurings undertaken by Arco and Phillips are the latest manifestation of these philosophies, but all of these strategies bother many analysts as diverting attention -- and money -- from long-range oil-drilling needs. They believe that mergers, handcuff the involved companies' finances while they work off the debt incurred taking each other over. At the same time, combined companies spend less looking for oil than they might have separately, analysts say. "If you go to Texaco, sure, they're doing exploration, but I'm sure it's not what the level would have been for Texaco and Getty," Lazier said.

"It's hard to see how you could be a super-aggressive exploration company when you've got 75 percent debt," said Ted Eck, Amoco's chief economist.

"Some of the money that would have been used to search for hydrocarbons in the United States and elsewhere is going to be diverted to paying off the debt," said Sanford Margoshes, an analyst at Shearson/Lehman Brothers.

Proponents of restructuring say it just doesn't make any sense to spend much more than the minimum for oil exploration and development these days, especially in the United States. More holes have been poked in this country in the search for oil than anywhere else in the world, and there may not be much left here to find.

There's still plenty of oil overseas. But most of it is in the Middle East. "We'll still have plenty of oil," Lazier said. "The problem is that all the incremental oil will be out of the Persian Gulf, and that puts us back where we were in 1973."

Many experts say the solution is to concentrate on increasing imports from more politically secure areas, and to diversify supply sources as much as possible. To this end, many American oil companies are directing increasing percentages of their oil and gas drilling budgets away from U.S. prospects and into exploration overseas.

"I think it's sort of rational, given the resource endowment overseas," said Amoco's Eck, whose company has shifted much of its exploration effort overseas in recent years. "The only responsible thing to say about American imports is, if we have to import it, we might as well import it from some place where we have some confidence in security of access."

"If we begin getting oil from Colombia and Canada and Indonesia and China, it seems to me that gives us the kind of diversity so that we're not dependent on just one area," Sawhill said. Mexico is another important source removed from the Middle East.

But other experts believe the U.S. oil industry is still better off looking for its oil at home -- even if it is less economical to do so. "From the national-interest standpoint, to the extent that we replenish as much oil as possible, we strengthen ourself as much as possible in trying to avoid confrontations with other nations in trying to get to politically insecure oil," Margoshes said. "The way we're headed is toward a more destabilized world if we just sit back and deplete our resources instead of fighting the hard fight to replace what we consume."

There is also concern that oil companies are taking on so much debt in these restructurings and takeovers that their corporate financial structures could be rocked should oil prices fall. "If there's a huge drop in oil prices. . . . the companies with huge debts are much more vulnerable," Eck said. "I don't like that. This has always been a risky business, and it's not getting any less risky -- if anything, it's getting more risky."

"Companies are substituting debt for equity to the point where they're making themselves vulnerable if we enter an era of lower oil prices," Margoshes said. "We're weakening the financial strength of the American oil industry."

Traditionally, American oil companies have operated with much less debt than most other industrial companies. That's changing. Arco's restructuring will leave its debt-to-equity ratio at about 55 percent, twice the previous level.

The companies believe that their massive cash flows will give them the wherewithal to pay down the debt -- albeit partially at the expense of exploration spending.

Nevertheless, critics fear that the higher debt loads will strip the companies of flexibility, slowing their ability to react to changes in the industry.

"In the aggregate, it's weakening the oil companies because it's reducing their resiliency in a time of increasingly competitive conditions," Margoshes said.

Other experts disagree, however. "If it becomes attractive to drill for oil because the price of oil begins to go up, I think you will find the capital," Lichtblau said. "If the price of oil will strengthen again, I think the financing system, the banking system, will find the money to drill."