Oct. 6--Last October, just as the economy was tilting into crisis, a small oil and gas company in Houston quietly announced the discovery of a mammoth natural gas field in South Texas that at any other time might have garnered bigger headlines.

Petrohawk Energy's find, however, did not go unnoticed in the oil and gas industry -- and it didn't take long before oil companies large and small began making their moves.

Today, though the economy and natural gas prices remain weak, the Eagle Ford shale remains one of the hottest prospects in North America, and energy companies are moving forward there even as they're pulling back elsewhere.

That's because of what some companies suggest is a virtually recession-proof combination of highly productive wells and low drilling costs they say can yield profits even as natural gas prices hover near seven-year lows.

Also attractive: the flat South Texas ranch land, where obstacles are few and Gulf Coast oil and gas infrastructure is nearby; and landowners have grown comfortable with the industry after decades of oil drilling.

"You can certainly make more money from wells than cows," said Joe Martin, whose family leased nearly 20,000 acres of land to Petrohawk in LaSalle County for drilling.

But it may still be a while before the full potential of the Eagle Ford shale is known. Though early results are promising, companies have been cautious about overstating what could be in the ground, especially since so few wells have been drilled so far.

"What we're going to find out, as with most shale plays, is there's going to be sweet spots," said Bob Banks, chief operating officer at Swift Energy, a Houston-based oil company with nearly 90,000 acres leased in the Eagle Ford. "That's what we don't know yet, which areas are really going to work better than the others because it's pretty early days."

Recently discovered U.S. shale plays, including the Haynesville in Louisiana and Marcellus in Pennsylvania, are expected to provide a major boost to U.S. natural gas supplies in coming years. The dense rock formations, once thought too difficult to explore, have been unlocked with the help of recent advances in drilling technology.

The core areas of the eight largest U.S. shale plays may contain 475 trillion cubic feet of recoverable resources, according to an estimate by Ross Smith Energy Group, an industry research firm in Calgary, Alberta. That's roughly ten times the size of Texas' famed Barnett shale play in the Dallas-Fort Worth area, which supplies nearly 10 percent of U.S. natural gas production, excluding Alaska.