"While the retorting of oil shale under pressure is not a new concept, past investigators have not thoroughly explored the field especially as it applies to gas circulation type retorting processes. Jacomini obtained an Austral1an patent for a pressurized system heated indirectly; Laramie's work on the thermal solution process involved the use of pressure; and the work at the University of Colorado on the hydrogenation of oil shale is a form of pressurized retorting. Several unique effects would result from the application of pressure to the Gas-Combustion process retorting system. Among the beneficial effects which might be anticipated are a reduction in power requirements for gas circulation, recovery of the lighter hydrocarbons lost in the product gas under atmospheric pressure operation, a higher retorting rate owing to the use of a denser heat transfer medium, suppression of carbonate decomposition, smaller gas lines and gas handling equipment, and the possibility of using gas turbines to advantage to drive process blowers and generate electric power. Offsetting disadvantages are the necessity for introducing shale into and discharging ash from a pressurized system) and heavier lines and vessels owing to the higher pressure. It is the purpose of this study to determine whether the advantages of operating the Gas -Combustion process under pressure outweigh the disadvantages and to compare the estimated costs of producing crude shale oil by this method to shale oil production by conventional atmospheric procedures."