National Geographic : 1981 Feb 28
10 11 PAINTING BY ROYANDERSEN Burning out in about 300 days (12), a retort will produce some 175,000 barrels of oil. Sixty re torts burning simultaneously, along with surface processing, will yield 95,000 barrelsa day. Environmental monitoring rubble, pipes are inserted at the top. These bring in diesel fuel to ignite the ore, air to aid in com bustion, and steam to control the rate of burn. When the fuel is lighted (9), it heats the surround ing ore to about 900°F. This drives oilfrom the rubble, leaving behinda carbon residue that sus tains the fire. As the burn smol ders down through the columns (10 and 11), the retreatingoilmi grates to the bottom of the retort. There it gathers in a collecting drift and is pumped to the surface as synthetic crude. parallelsevery step of the mine's development. Yet uncertainties remain. One concerns pollutants that might be leached by ground water as it percolates through burned retorts-a problem the companies hope to minimize by sealingthe retortswith injections of grout.