Eastern Utah may have less than a quarter of the oil-shale resources that had previously been estimated, according to a study released Wednesday by the Utah Geological Survey.

The report indicated that the Uintah Basin's potential oil-shale resource would amount to about 77 billion barrels of shale oil, far less than the 321 billion barrels first estimated in 1964, said state geologist Michael Vanden Berg. The numbers that had been quoted in the past were based on extrapolations that had been estimated for areas of the Uintah Basin for which there was no scientifically recorded data.

The findings come as Utah's congressional delegation has pushed for further development of the state's petroleum resources, including oil shale and tar sands. Meanwhile, the federal government is opening up more public lands for oil development, and the Bureau of Land Management is scheduled to conduct a sale Friday to auction off thousands of acres in Utah that are considered prime parcels for oil and gas development.

Amid the push for more development of domestic oil resources, an analysis released Wednesday by the Energy Department's Energy Information Administration projects virtually no growth in U.S. petroleum use through the year 2030, due to increased use of ethanol and biodiesel and a push toward greater automobile fuel efficiency, including the growing popularity of gasoline-electric hybrid vehicles.

Even so, Vanden Berg said that while the current estimate of the Uintah Basin's oil-shale resources was considerably less than the past estimate, the amount was still deserving of attention.

"A domestic resource of this size is very significant," he said. "A conventional field with just 1 billion barrels is considered 'giant.'"

The new study was initiated due to concerns over diminishing conventional oil reserves. The assessment answered the questions of where and how much oil shale exists in the Uintah Basin and includes detailed basinwide resource maps.

The Utah Geological Survey analyzed data from 293 wells located throughout the Uintah Basin to create a comprehensive picture of Utah's oil-shale resource. The data was then used to calculate new estimates that offer a better representation of what actually is available for possible oil-shale production, Vanden Berg said.

The agency's assessment considered richness and thickness of deposits, underground accessibility, deposits that were not in direct conflict with current conventional oil and gas operations and location of deposits. The thickest and richest oil-shale zones are in central Uintah County, the report stated.