Quicksilver Resources posted earnings of $48.9 million, or 28 cents a share, in the fourth quarter as revenues declined to $216 million on lower natural gas prices.

The numbers compared unfavorably to earnings of $331.8 million, or $1.82 per share, on revenues of $240 million in the corresponding period of 2010, when the Fort Worth-based natural gas and oil producer recorded a $494 million gain from the sale of Quicksilver Gas Services.

Despite a prolonged weakness in gas prices, Quicksilver's production averaged the equivalent of 412 million cubic feet of gas per day in the fourth quarter, 6 percent more than a year earlier. For all of 2011, the company's output also averaged the equivalent of 412 million cubic feet of gas per day, a record-high annual production level and a 16 percent rise from 2010.

The production gain was driven by a 19 percent jump in output from the Barnett Shale, which accounts for the bulk of Quicksilver's production. However Quicksilver, like other energy companies, is focusing on increased production in other areas where there is more attractively priced oil and natural gas liquids.