The nation's geologists are revising their estimate of the amount of undiscovered oil in the United States to reflect significant new finds in the West.

"There is a general consensus that there are 60 to 100 billion barrels of oil as yet undiscovered and awaiting the drill bit," Charles D. Masters of the U.S. Geological Survey today told the 145th national meeting of the American Association for the Advancement of Science.

"Four years ago, the survey estimated there were 50 to 127 billion barrels of oil undiscovered in the U.S., so we're in the process of reassessing our undiscovered resources," Masters said.

The key number is the low estimate of 60 billion barrels of undiscovered oil, up 10 billion barrels from the low ground is 60 billion barrels, not the 50 billion estimated four years ago.

Masters said the survey will publish a new estimate of undiscovered oil resources in about a year. He gave no hint what it would be, except to suggest the survey felt the new consensus would be more accurate than its own estimate of 1975.

Masters pointed out that the United States found 2 billion barrels of new oil last year -- a slight improvement over the 1.75 billion located in each of the seven previous years -- but is consuming its reserves at the rate of 3 billion barrels annually.

"We need to find 3 billion barrels every year, but even if we do that, we're not likely to go any higher," Masters said. "The U.S. oil industry has rarely found more than 3 billion barrels in any year, even in its heyday."

Overall, U.S. consumption is 6 billion barrels a year, half imported.

One reason geologists are revising their oil estimates has been the recent and surprising find of oil in the western part of the Green River Basin, which embraces parts of Wyoming, Utah, Montana and Colorado. In less than two years, eight discoveries have raised estimates to 37 billion barrels in the basin.

"The discoveries made in this region have been made under circumstances some geologists said were impossible," consulting geologist Don M. Parker said. "But as recently as 1973, the estimates for this region were no more than 1.5 billion barrels of oil."

The oil finds in the Green River Basin have been in what geologists call an "overthrust belt," where many faults (cracks) intersect and overlap. This makes seismic exploration difficult because signals don't easily pass through faults. The terrain itself is rough, interlaced with mountains and canyons that make drilling difficult.

Outside the United States, a geologist panel said, more oil is being found in Mexico and there are signs that large volumes will be found in China. The geologists said the Mexican government estimated last week that its largest offshore field contains 40 billion barrels of oil, double the previous estimate.

"I just returned from China, where there are many sedimentary basins that might contain oil," Masters said. "And the Chinese have promised to drill holes to look for that oil in every one of their basins." Pausing, Masters said: "It will take 10 years to have a good idea of how much oil China has but I think it will be measured in the tens of billions of barrels, not the hundreds of billions."