UPDATE 1-Devon Energy has well blowout at oil sands project

* Blowout sprayed oil and steam mist

* Regulators investigating, shut nearby wells

* Devon says cleanup has begun (Adds details, company comments; in U.S. dollars)

CALGARY, Alberta, July 13 (Reuters) - A well at Devon Energy Corp's DVN.N Canadian oil sands operations had a blowout on Saturday that took nearly 35 hours to get under control, Alberta regulators said.

The well, part of Devon’s Jackfish project in northern Alberta, blew a mixture of steam and oil over the project area. Regulators are as yet unsure how much oil was released and will audit production records to determine how much was spilled.

In the interim, the Alberta Energy Resources Conservation Board, which oversees energy projects in the province, has shut down six other nearby wells at the 35,000-barrel-per-day oil project.

“We are taking this very seriously,” said Darin Barter, a spokesman for the ERCB. “If there is an issue on the site, we want to make sure it’s resolved.”

Nadine Barber, a spokeswoman for Devon, said the shutdown would reduce output from the project by “a couple of thousand barrels” a day.

The Jackfish project uses the steam-assisted gravity drainage process to produce the oil sands reserves. The technology uses paired wells: an injector well that pumps steam into the oil-bearing sands, liquefying the tarry bitumen, which gathers into a producer well and flows to the surface.

It was the producer well that blew out on the weekend, spraying a mist of steam and oil.

The mist, which Barber said contained about 30 percent oil, spread beyond the project site. Devon said it has already begun a cleanup at the site and is surveying surrounding areas to gauge the extent of the spill.

It has also found some small amounts of oil sheen in the waters of a nearby creek and has put in booms to keep any oil from flowing downstream.

Barber said the company does not yet know how long the affected wells will be shut down while Devon and regulators investigate the cause of the blowout.

Such incidents are rare in oil sands thermal operations.

Shares of Oklahoma City-based Devon were up 29 cents at $63.79 by late Tuesday morning on the New York Stock Exchange. (Reporting by Scott Haggett; editing by Rob Wilson)