ABSTRACT
Retorting is the only commercially attractive method for extracting raw shale oil from oil shale deposits. In retorting, the oil shale is heated until it breaks down into crude shale oil, its by-products and waste materials. A surface retort is a heating vessel situated aboveground, Crushed oil shale is placed in this retort and heated to a temperature between 900° F and 1500° F depending upon the particular retorting process used. The oil shale must be crushed before it is fed into surface retorts--and the degree of crushing required varies with the type of retort. Modified in-situ processing is actually mining-assisted in-situ retorting. A vertical, underground retort is prepared by mining enough oil shale from the bottom of the shale deposit to create a room. Crude shale oil, after recovery from the oil shale deposits, must go through one more step--upgrading, or partial refining--to convert the shale oil into premium petroleum feedstock.
