Hess Corp. (HES) has up to $2 billion in potential asset sales "well under way" as the independent oil and gas producer tries to raise enough cash to keep up with its spending, the company said Wednesday.

Hess expects to close the deals by mid-2013, but did not say which assets it had on the sales block. The New York company has oil and gas assets throughout the world and a small refinery in Port Reading, N.J.

"They will be more mature, not as strategic," Chief Executive John Hess said of what the company is trying to sell. "We're going to be shedding assets that are smaller-interest, that have capital expenses associated with them that are not attractive."

Hess is also identifying more assets it can sell after 2013, the company said. Hess is rearranging its assets to focus on oil and gas fields it sees as the most profitable. In January, it closed its Hovensa LLC refinery joint venture with Petroleos de Venezuela SA, keeping the small Port Reading refinery as its only fuel processing plant.

Hess raised its 2012 capital expenditure estimate 25% to $8.5 billion, as it works to complete oil and gas wells in the Bakken and Eagle Ford shale formations in the U.S. The company was nearing completion of some wells just as infrastructure prices were increasing.

"We're at the peak of our capex," Mr. Hess said. "As we move forward, we expect significantly lower capital costs."

Still, the news of the increased spending may trouble investors who may have been happy with the company's increased production in the Bakken region of North Dakota. Hess is producing nearly 60,000 barrels of oil equivalent a day in the Bakken area, and is shipping about 29,000 barrels of oil a day out of the Bakken area via rail after building a rail terminal there in April, the company said.

The "current capex run-rate of more than $8 billion is not sitting well with investors," said Barclays analyst Paul Cheng in a note to clients.

Hess's second-quarter earnings fell 10%, to $549 million, as lower oil prices hurt its exploration and production segment's bottom line. Revenue fell 5.1% to $9.31 billion.

Hess said it would produce 395,000 to 405,000 barrels of oil equivalent a day in 2012, up 5% from its previous estimate. The company expects Brent oil to reach $90 a barrel by 2014.

Hess shares were $44.24 in recent trading, up 0.7%.

Write to Ben Lefebvre at ben.lefebvre@dowjones.com