Changes

Since the beginning of the oil-shale industry, more than 1 billion tons of oil shale are believed to have been mined in 19 countries, 80% of it in China and Estonia.

Since the beginning of the oil-shale industry, more than 1 billion tons of oil shale are believed to have been mined in 19 countries, 80% of it in China and Estonia.

Two general processes of recovery of shale oil have been attempted: * mining the oil shales, either underground or in open pits, crushing, and above-ground retorting (the process so far used in all oil-shale projects) * in-situ processing, involving drilling into the oil-shale unit, fracturing it to increase its permeability, igniting the shale, and recovering the oil thus generated through other wells.

Two general processes of recovery of shale oil have been attempted:  

* mining the oil shales, either underground or in open pits, crushing, and above-ground retorting (the process so far used in all oil-shale projects)  

* in-situ processing, involving drilling into the oil-shale unit, fracturing it to increase its permeability, igniting the shale, and recovering the oil thus generated through other wells.

This second process is, as of 2005, still in an experimental stage but holds promise, because it reduces the harm to the environment.

This second process is, as of 2005, still in an experimental stage but holds promise, because it reduces the harm to the environment.