The fact that Abu Dhabi's government-owned Mubadala Development Company could open its vaults and hand over $1.35 billion for 7.5 percent of the U.S.-based Carlyle Group may be newsworthy, but it's not surprising. What may be more surprising is that Mubadala didn't spring for more.

Simply put, Mubadala is the cash camel of the United Arab Emirates, one of the wealthiest of the oil-and-natural-gas-producing members of the 12-nation Organization of Petroleum Exporting Countries.

In the Gulf, there is a saying: Dubai is the emirate with all the flash, but Abu Dhabi—the biggest and richest of the U.A.E.'s seven sheikhdoms—has the cash.

Need more evidence? Look no further than today's headlines: State-owned Abu Dhabi National Energy Co. agreed to buy PrimeWest Energy Trust of Canada for $5 billion in cash and assumed debt. It is the biggest-ever North American takeover by a United Arab Emirates company.

It has the cash because virtually all of the U.A.E.'s crude oil—10 billion barrels of it, representing almost 10 percent of the world's total of proven reserves—and 5.8 billion cubic meters of natural gas lie in Abu Dhabi.

Nearly 92 percent of the country's gas reserves—4 percent of the world's total—are in Abu Dhabi itself and in the Khuff reservoir beneath the offshore oil fields of Umm Shaif and Abu al-Bukhoosh. It ranks among the largest single gas reservoirs in the world.

At the current production rate of some 2 million barrels a day, estimates suggest the U.A.E.'s reserves could last another 150 years. And if oil prices keep hovering in the range of this week's record $80 a barrel, the U.A.E.'s budget surpluses will grow to a point where it just may run out of places in which to invest.

Under an agreement forged by the late Sheik Zayed Al Nahayan, when the U.A.E. was created in 1971 from the British possession known as the Trucial States, the other six emirates received the equivalent of monthly allowances. Zayed is widely credited with holding together the seven emirates by keeping various sheiks from feuding openly over the country's natural wealth.

How much disposable cash does Abu Dhabi possess? Conservatively speaking, its surplus for 2007 is likely to be in excess of $500 billion. Abu Dhabi has already invested more than $1 trillion abroad, some of it in U.S. Treasury bills.

This year, the six countries comprising the Gulf Cooperation Council—Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates—are expected to invest nearly $70 billion overseas; in 2006, they invested about half that figure. Just last week, for example, the U.A.E.'s bitter rival, neighboring Qatar, announced it was taking a 20 percent stake in the London Stock Exchange.

As for Mubadala, its existence highlights a fundamental premise of modern-day nation building: A country's wealth, especially accruing from its natural resources, must be put in service of economic growth. And in this age of galloping globalization, it isn't enough simply to invest. It is important to invest wisely. It is equally important to invest widely.

That is what Mubadala has been doing since its creation five years ago as a wholly owned unit of the government of the emirate of Abu Dhabi. Its objectives are manifold, but they all underscore a central thesis: The emirate needs to broaden its economy and embrace a variety of enterprises.

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In time, the thesis goes, oil and gas should serve mainly as a fiscal trampoline, a safety net under a diverse economy that also embraces utilities, real estate, aviation, shipbuilding, health care, and information technology.

Little wonder, then, that Mubadala linked up with Carlyle. According to officials of both companies, part of the deal with Abu Dhabi includes a provision that requires Carlyle to guarantee its $20 billion valuation if—as the New York Times put it—the firm ever goes public, hinting that it may be an inevitability.

In the event that Carlyle, which currently manages about $77 billion in assets, is valued at less than $20 billion at the time of an offering, the firm would give Mubadala a larger piece of the business to make up for the difference, according to these officials.

Before the Carlyle deal, Mubadala partnered with Electronic Data Systems, the American outsourcing behemoth that employs some 120,000 around the world, and set up Injazat Data Systems as a 60-40 venture. Among its clients, the joint venture counts the Environment and Wildlife Development Authority, the U.A.E. Offsets Group, and the Abu Dhabi Water and Electricity Authority.

Mubadala has also acquired a 35 percent equity share of the Italian business-aircraft manufacturer Piaggio Aero; a 5 percent interest in automaker Ferrari; 25 percent of LeasePlan Corp., a fleet-management giant in the Netherlands; an unspecified stake in nine oil exploration sites in Libya; and part ownership of a gas processing plant in neighboring Qatar.

The Qatar deal, in fact, was in itself associated with a larger project, Dolphin Energy. The company—of which Mubadala owns 51 percent, with the rest split equally between Total of France and Occidental Petroleum of the U.S.—is creating the first cross-border natural-gas network of the six countries of the Gulf Cooperation Council.

Natural gas from Qatar's North Field moves through Dolphin's gas processing plant at Ras Laffan, where commercial byproducts are extracted. The dry gas—some 2 billion cubic feet daily—is then transported by pipeline to Abu Dhabi via Dolphin's 230-mile pipeline.

Other energy projects also figure prominently in Mubadala's plans, which are increasingly emphasizing regional cooperation. A wholly owned subsidiary, Liwa Energy Limited, for example, has struck an agreement with Oman to develop its Mukhaizna heavy oil field.

The goal is to increase production to 150,000 barrels per day from the current 10,000 barrels. There's the agreement with Oman Oil Company to develop the Salalah Methanol Project, which is designed to produce 3,000 tons per day.

There's significant cooperation with other emirates within the U.A.E. too. Mubadala has, for instance, teamed with Dubai's aluminum-smelting company, Dubal, to build a $6 billion aluminum-smelter complex at Taweelah in Abu Dhabi. It is designed to produce 1.2 million tons annually, which would make it the biggest single-site aluminum smelter in the world. It will also create more than 4,000 jobs, mostly for U.A.E. nationals.

Mubadala is not limiting itself to business and industry. It is reported to be developing educational institutions that would compete with the three national systems of higher education—the U.A.E. University, Zayed University, and the Higher Colleges of Technology. Mubadala's strategy? No surprise: linking up with foreign entities that export educational products and systems, particularly in the United States, Britain, Ireland, and Australia.

There is an old Arab saying: Never compete openly with your brothers. Mubadala's managers are among a new generation writing a new saying: Do whatever it takes.