Abstract: An underground in situ oil shale retort contains a bed of fragmented oil shale particles having an appreciable void volume distributed therethrough. Air or other retorting gas passed through this bed of fragmented oil shale supports combustion of some of the carbonaceous material in the oil shale and provides heat for retorting oil therefrom. A number of such retorts may be formed in an area and pillars are left to support the overburden. Pillars forming walls between adjacent retorts also prevent gas leakage. Oil recovery from intact oil shale pillars between retorts is enhanced by fracturing the pillars as well as fragmenting the shale in the retort. The pillars are fractured by detonating explosives in bore holes in the region between the retort and pillars, preferably a fraction of a second after explosive fragmentation of the oil shale in the retort.

Abstract: An in situ oil shale retort is provided with a retort off gas cooling zone in the in situ retort at the product outlet end of the in situ retort. The kerogen in the in situ retort is converted to liquid and gaseous products by moving a heated gas through a retorting zone in the in situ retort and toward the product outlet end of the in situ retort. The movement of gas through the retorting zone is terminated when the retort off gas moving from the product outlet end of the in situ retort attains a temperature above which the temperature of the retort off gases will deleteriously effect product collection and removal apparatus in a collection zone adjacent to the product outlet end of the in situ retort. A reduced kerogen content of the oil shale in the retort off gas cooling zone as compared with the average kerogen content of oil shale in the in situ retort improves the yield of products from the in situ retort.

Abstract: An underground room in substantially undisturbed shale is filled with fragmented oil shale particles for in situ retorting. A comprehensive system is provided for feeding air to the top of the retort and recovering oil and flue gas from the bottom of the retort. The oil is separated from admixed water and both are recovered. Flue gas is withdrawn from the bottom of the retort, scrubbed clean and a portion may be recycled through the retort while another portion is vented or burned in a turbine. Means are also provided for passing scrubbed gas through a second spent shale retort prior to venting, burning or recycle.