The company raised its 2008 natural gas and oil production outlook.
For the second quarter, the company reported net income of $136.6 million, or 39 cents a share, compared with $47.6 million, or 14 cents a share, a year ago.
Analysts on average were expecting earnings of 37 cents a share, before items, according to Reuters Estimates.
Gas and oil production rose to 45.1 billion cubic feet of natural gas equivalent (Bcfe) from 25.8 Bcfe in the year-ago quarter.
Operating revenue more than doubled to $604.4 million, while gas sales doubled to $368.9 million.
Southwestern's average realized gas price was $8.17 per thousand cubic feet (Mcf), including the effect of hedges, up from $6.90 per Mcf in the same quarter last year.
Average realized oil price was $122.26 per barrel, compared with $61.72 per barrel in the year-ago quarter.
The company raised its 2008 natural gas and oil production outlook to a range of 181.0 to 185.0 Bcfe, from 168.0 to 172.0 Bcfe.
