Halliburton Co , the world's second-largest oilfield services company, posted a higher-than-expected quarterly profit on Monday as more drillers tapped its expertise in extracting gas from U.S. shale rock.

Demand for shale energy continues to climb across the United States, despite low natural gas prices, among the clamor for energy independence and a push for cheap supply from the chemical and transportation sectors.

Third-quarter net profit climbed to $683 million, or 74 cents per share, from $544 million, or 60 cents per share, a year earlier.

Excluding one-time items, Halliburton earned 94 cents per share, exceeding analysts' average estimate of 92 cents, according to Thomson Reuters I/B/E/S.

Revenue rose 40 percent to $6.55 billion. Analysts had expected $6.39 billion.

Producers are plowing billions of dollars into developing U.S. oil shale fields, tightening the market for equipment and allowing the services companies to maintain higher prices.

Many analysts expect the North American shale boom to last at least through 2012 even with the weak American economy.

Despite short-term macroeconomic concerns, I continue to believe in the long-term prospects for our business, Halliburton Chief Executive Dave Lesar said in a statement.

Halliburton said profit from operations outside the United States recovered at the rate we expected during the third quarter.

Delays in Iraq and an operational shutdown in Libya during the third quarter hurt results, the company said.

Three rigs did start operating in Iraq toward the end of the third quarter, however. And in Libya, where ruler Muammar Gaddafi has nearly been overthrown, the company is assessing whether to reopen.

Halliburton has now put behind it a major liability attached to former unit KBR Inc , which just settled a five-year dispute over failed bolts on subsea oilfield flow lines off Brazil for $200 million.

Shares of Houston-based Halliburton rose 0.7 percent to $37.68 in premarket trading. The stock has dropped 8.3 percent so far this year.

(Reporting by Ernest Scheyder in New York, with additional reporting by Braden Reddall in San Francisco; Editing by Lisa Von Ahn and Gerald E. McCormick)