Vanden Berg said that based on the new information, Utah's large oil-shale deposits warrant further research, including the initiation of pilot-scale projects, so that if the state's oil-shale resources were tapped, they could be extracted in an environmentally responsible manner.

Despite the dramatic decrease in the estimated resources, the president of the Utah Petroleum Association said the deposits considered to be available would be of great prospective benefit to the state's energy future.

"That's still a tremendous amount of crude oil that could be a boon to the energy security and economic vitality of our state," said Lee Peacock, association president. "You're talking years and decades of production and an incredible amount of resource, regardless of what the scaled-back numbers would be."

Experimental oil-shale development is already under way in Utah. Spokesmen for two companies engaged in that work — Oil Shale Exploration Co. and EcoShale, a subsidiary of Salt Lake City-based Red Leaf Resources Inc. — did not return phone calls Wednesday seeking comment on how the reduced estimates might impact their plans.

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