NEW YORK (AP) -- Higher fuel prices have been an elixir this year for Big Oil, covering problems that would have been much more noticeable during leaner times.A 40 percent rise in oil prices boosted ConocoPhillips' adjusted earnings in the third quarter, even though production fell as it shed $8 billion of assets since 2010. BP's profits doubled in the same July-September period even though it still faces hundreds of lawsuits stemming from last year's Gulf of Mexico oil spill.The largest oil company, Exxon Mobil Corp., is up next Thursday. Analysts are expecting another mammoth quarter for Exxon, given the rise in oil prices. But they still wonder about its $29 billion acquisition of natural gas producer XTO Energy.Natural gas prices are a third of what they were in 2008, and Exxon's increasing reliance on the natural gas business has so far been a weakness for the company.Exxon said it made the decision based on long-term assumptions about an increasing shift in the U.S. from coal to natural gas. Still, analysts want to know how the Irving, Texas company plans to increase oil production, which has been more profitable, and how quickly it can do it.WHAT TO WATCH FOR: Analysts want to know which oil fields Exxon is investing in. They also will want to see how Exxon is managing its U.S. natural gas fields as prices remain flat.WHY IT MATTERS: Exxon is the world's largest publicly owned oil company. Its quarterly financial report provides an intimate look into global energy markets.WHAT'S EXPECTED: Analysts expect earnings of $2.12 per share on revenue of $118.5 billion, according to FactSet.LAST YEAR'S QUARTER: Exxon earned $7.35 billion, or $1.44 per share, on revenue of $95.3 billion for the same July-September quarter last year.