State geologists have a theory on why wells have failed to find the oil they and petroleum companies believe should be in the Grand Staircase-Escalante National Monument: Maybe it moved.

"Our conclusion is that 30 million years ago, volcanic intrusives north of the monument came up through the layers and created a lot of carbon dioxide that flooded through the oil formations in the new national monument," said M. Lee Allison, director of the Utah Geological Survey.As a result, carbon dioxide gas produced during volcanic eruptions in Wayne and Piute counties could have blown the oil away through deep underground formations that surface in the Grand Canyon, where the Colorado River over millions of years eventually would have washed it to sea.

Allison said the flushing could have dumped a billion barrels (42 billion gallons) of oil into the Colorado River.

Or maybe it is somewhere else in the monument.

The flushing theory will be written by Tom Chidsey, who heads the UGS's petroleum section, geologist Douglas Sprinkel and Allison. The theory was presented orally at the annual convention of the American Association of Petroleum Geologists in Salt Lake City.

Allison's office now will encourage oil explorers to look elsewhere within the monument for oil.

"(The new theory) does not wipe out the chance of oil in the monument," Allison said. "It just means you look in different places . . . We still believe this area is underexplored."

To date, most of the 48 exploratory wells drilled within the monument's boundaries have searched on the crest of rock folds, called "anticlines." Because oil floats on water, it usually makes its way to the top of the folds of porous rocks.

Though the exploratory wells - the most recent of which was the controversial Conoco drilling last year in Reese Canyon - have failed to find oil in the new monument, they have found other hydrocarbons, indicating that there once was oil in those rock formations. The Conoco well, for example, found natural gas.

If the carbon dioxide flushing did not send oil into the Colorado River, it could have shifted it to the flank of the anticlines.

Therefore, the UGS will suggest more drilling on the flanks.

Chidsey noted that it took 100 wells to find the Overthrust Belt in southwestern Wyoming, and it took about 70 wells to find the big reservoir in Alaska's Prudhoe Bay.

Allison said he wants no less than that kind of exploratory rigor in southern Utah. "There is still great potential for oil and natural gas in the national monument."

Only after unsuccessfully drilling on the flanks of the anticlines and in northern Arizona will it be time to throw in the towel, the geologists said.

"Then, you can conclude the oil probably has gone down the Colorado River," said Chidsey. "But as we say in this business, God only knows."