ConocoPhillips and Occidental Petroleum reported quarterly results that topped Wall Street estimates as they produced more oil and gas than expected, even as lower prices hurt profits.

During the third quarter the companies increased drilling in North America, where large oil companies are spending more in a bid to increase production. Conoco had record output in the Eagle Ford basin in south Texas, while Occidental saw strong production of higher-priced crude oil in the Permian Basin.

"(Conoco's) ramp-up in the Eagle Ford is on track or exceeding the market's expectations," said Fadel Gheit, an oil analyst at Oppenheimer. "They delivered on everything they said they would, and more."

North American shale fields are increasingly seen as a relatively low-cost, reliable source of both oil and natural gas in an era when nations like Russia and Brazil are tightening control of their resources.

Natural gas prices in the United States fell 30% in the third quarter, compared with a year earlier, to $2.83 per million British thermal units, burdened by heavy supplies.

The average Brent oil price of $110 per barrel in the quarter was down $2, hit by worries about slowing demand.

Conoco's third-quarter profit fell 31% and Occidental's declined 22%, hurt by the lower oil and natural gas prices.

Conoco's oil and gas output in the quarter was 1.53 million barrels of oil equivalent per day (BOE), down from 1.54 million a year earlier.

For the fourth quarter, Conoco sees production gains from the previous quarter, with higher output coming from the Eagle Ford and the company's oil sands properties in Canada.

It expects to spend $15.5 billion to $16 billion this year, reaching the upper end of that range if it buys acreage in shale basins. Conoco's budget for 2013 will be of a similar size, Conoco Chief Executive Ryan Lance told analysts on a conference call.

This was Conoco's first quarter to report earnings as an standalone exploration and production company. Earlier this year, it split off its refining business. Now, Conoco is selling assets and increasing dividends as part of an effort to return cash to shareholders.

Excluding items related to asset sales and taxes, Conoco, the No. 3 U.S. oil company, had a profit of $1.44 per share. Analysts, on average, expected $1.19.

Occidental, the No. 4 U.S. oil company, said net profit fell to $1.38 billion, or $1.69 per share, from $1.77 billion, or $2.17 per share, a year earlier. Analysts looked for $1.63 per share, according to the average on Thomson Reuters I/B/E/S.

"(Occidental's) earnings were strong across the board, driven by higher-than-expected U.S. oil production, lower unit costs and strong chemicals segment income," Sterne Agee analyst Tim Rezvan said.

Output rose 4% from a year ago to 766,000 barrels per day.

Still, Occidental's CEO Stephen Chazen expressed concern about the company's returns when speaking on a conference call with analysts.

"If I don't see real improvements in the returns, you know, in the next couple of quarters, strategy will change," said Chazen, adding that could take the form of higher dividends or even farming out wells to other companies.

Shares of Conoco rose 94 cents to $56.89, while Occidental's shares climbed $1.82 to $82.50 on the NYSE.

Noble records drip in profit

Smaller oil company Noble Energy reported a 50% drop in third-quarter profit as output was hit by disruptions resulting from Hurricane Isaac.

Oil and gas sales were 242,000 barrels of oil equivalent per day, up 11% from a year earlier.

Noble Energy shares rose 2.4% to $91.38.