Schlumberger Ltd. (SLB), the world's largest oilfield services group, on Friday posted a 36 percent jump in second-quarter earnings, lifted by strong worldwide demand from oil and gas producers.

Schlumberger also said it had bought an additional 25 percent equity stake in Russia's largest independent oilfield services company, PetroAlliance Services Company Limited (search), for an undisclosed amount, bringing its share to 51 percent.

It expects to purchase the remaining 49 percent of that company in 2006.

The company reported second-quarter net income of $482.2 million, or 80 cents per share, up from $355.6 million, or 59 cents per share, a year earlier.

Income from continuing operations in the period was 78 cents per share. Analysts, on average, expected the company to earn 67 cents per share, according to Reuters Estimates.

"They beat us by 11 cents. Profitability in North America blew the doors off," said James Wicklund, analyst with Bank of America Securities.

High oil and gas prices prompted energy producers to begin ramping up spending last year to boost supply, he said, and that trend was now showing up in the oilfield service companies profits.

Late on Thursday, No. 2 oilfield services group Halliburton Co. (HAL) turned a profit from a year-ago loss, posting second-quarter income from continuing operations of 76 cents per share to beat Wall Street forecasts by 21 cents.

Schlumberger's operating revenue jumped to 21 percent to $3.43 billion versus the same period last year, as high oil and gas prices prompted major energy companies to increase demand for Schlumberger's services to take advantage of high oil prices.

"Second-quarter results showed sharp improvements across all geographical areas and technologies, both year-on-year and sequentially, as customer spending plans accelerated worldwide," Schlumberger Chairman and CEO Andrew Gould said in a statement.

Oilfield services revenue jumped 20 percent to $3.04 billion, with North American revenue up 21 percent year on year.

Pretax operating income in North American oilfield services rose 94 percent from a year ago to $234 million, while Mexico, Europe, former Soviet states, West Africa and the Middle East all showed increases between 28 to 34 percent.

WesternGeco, the company's seismic arm, posted second-quarter operating income of $58 million as revenues grew 31 percent from last year's second quarter to $383 million.

Schlumberger said it repurchased 2.77 million shares during the quarter for about $189 million as part of its 15 million-share buyback program.

The company's shares have risen 16 percent so far this year.