In photo, Rex W. Tillerson, the current Chairman, President, and CEO of Exxon Mobil Corporation, From [HERE] Exxon reported a 2% rise in fourth-quarter earnings Tuesday as higher oil prices offset declining production volumes. The largest U.S. oil company also defended its focus on natural gas, which is part of its plan to develop unconventional energy sources in the United States.

Prices for natural gas have remained in a deep slump, falling more than 25% in the fourth quarter.

David Rosenthal, the company's vice president of investor relations, blamed mild winter weather and weak economic growth in Europe for cutting into demand. But Exxon is optimistic about the future prospects for the fuel that's used to heat buildings and generate electricity.

"We remain bullish on the future of natural gas as an energy source," Rosenthal told analysts in a conference call. "Given the steep decline in conventional gas, unconventional gas will pay dominant roll going forward." Natural gas prices fell 8% Tuesday, while oil prices edged higher.

The biggest winners of Obama's natural gas push

Before the market opened Tuesday, Exxon reported net income of $9.4 billion, or $1.97 a share, in the fourth quarter. That's up from $9.25 billion, or $1.86 a share, in the same period in 2010.

Analysts were expecting earnings of $1.96 a share, according to a survey by Thomson Reuters.

Revenue rose 15% to $121.6 billion, the company said.

For the full year, Exxon earned $8.43 per share, in 2011. Analysts were expecting annual profits of $8.42 per share.

Shares of Exxon (XOM, Fortune 500) were down 2% in midday trading.