With the advent of $4-a-gallon gasoline has come a bruising debate in Congress over whether to intensify efforts to drill on federal lands, including part of the Arctic National Wildlife Refuge in Alaska. But while those hoping to lower prices at the pump are clamoring for new oil, most new onshore drilling in the past seven years has produced natural gas, not oil.

The Bush administration, in its effort to expand energy production, has issued more than three times the number of well-drilling permits on Western lands as in the Clinton administration's last six years. But oil production in that region during the Bush years is 12 percent below average levels from the Clinton era, according to federal data.

Meanwhile, natural gas production has increased by 34 percent during President Bush's term in office, compared with the annual production levels during President Clinton's term.

Meanwhile, the wellhead price of natural gas is about five times higher than it was in the 1990s.

Dusty Horwitt, a senior analyst for public lands at the Environmental Working Group, said that opening more lands to drilling would not bring down the price of natural gas. "We've turned our Western lands into a pincushion and gasoline is $4 a gallon and the price of natural gas has gone through the roof," he said.

Horwitt added, "On the oil side, the data show that there's just not that much oil out there in the West."

But industry representatives contend that the high prices, and the technical skills learned in recovering hard-to-retrieve oil in places like Texas, provide an opportunity to find oil and natural gas that would not have seemed worth the trouble a few years ago.

Marc Smith, the executive director of the Independent Petroleum Association of the Mountain States, said that in the last six years more than $20 billion had been invested in his region to increase energy production.

"Because we are a frontier region," Smith said, "it's heavier lifting to build the infrastructure to ship energy from where it's produced to where it's needed."

Also, Pete Stark, of the energy analysis firm IHS, said: "It takes an increasing number of wells to be drilled each year to replace lost production. The industry is running very hard just to stay in place."

But for all this activity, the Wilderness Society says, in a state like Colorado, where 4.9 million acres are leased out, just 1.4 million acres are under production. And of 7,124 drilling permits approved on public lands in fiscal year 2007, 5,343 wells were drilled. Using such data, House Democrats tried -- and failed -- to pass legislation setting tighter requirements for companies to develop their leases.

Whether the cause of the lag time between leasing federal lands and producing oil and natural gas is due to environmental restrictions or strategy by energy companies, the delays mean that "opening protected areas of the coasts or public lands to new leasing is not going to lower the price of gasoline," said David Alberswerth, a senior policy adviser at the Wilderness Society.

But Richard Ranger, a senior policy adviser with the American Petroleum Institute, takes the long view.

"There is obviously in the Rockies a tremendous amount of industry investment," he said. "It is reasonable to expect that surge will bear fruit with new production over the coming decade."