The U.S. Department of the Interior’s ha said it supports a proposal by Washington to ease rules on developing shale, which a new estimate says could yield 800 billion barrels of recoverable oil.

The Department is proposing leasing regulations ensure maximum oil shale lease sizes a range of royalty rates.

According to the U.S. Geological Survey, the U.S. holds more than half of the world’s oil shale resources.

Oil shale is a fine-grained sedimentary rock containing organic matter from which oil can be produced. In a report this year in Scandinavian Oil-Gas Magazine, it was learned that Shell had quietly secured a shale concession in Sweden, which is also rich in the alternative energy source.

Commercial development of oil shale will not begin until the technology is ready, “not expected for several years”, according to the Department. The President Bush has called on Congress to remove a ban on finalizing oil shale program regulations.

The largest known deposits of oil shale are in a 16,000-square-mile area in the Green River formation in Colorado, Utah and Wyoming.

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