Ignition of fragmented oil shale below a sill pillar in an in situ oil shale retort

摘要

An in situ oil shale retort is formed in a subterranean formation containing oil shale. The retort contains a fragmented permeable mass of particles containing oil shale. An open base of operation is excavated in the formation above the retort site, and an access drift is excavated to the bottom of the retort site. Formation is explosively expanded to form the fragmented mass in the retort between the access drift and an elevation spaced below the bottom of the base of operation, leaving a horizontal sill pillar of intact formation between the top of the retort and the bottom of the base of operation. The sill pillar has a vertical thickness sufficient to maintain a safe base of operation above the retort after the fragmented mass is formed. Prior to retorting, a particulate combustible material is placed in the blasting holes and ignited, and air is introduced to the ignited particulate combustible material to generate heated ignition gas for heating an upper portion the fragmented mass below the sill pillar to a temperature greater than the spontaneous ignition temperature of carbonaceous materials in the oil shale. Heated organic carbonaceous material is then contacted with oxygen supplying gas to establish a combustion zone in the fragmented mass. The combustion zone is advanced downwardly through the fragmented mass to provide retorting of particles containing oil shale. Liquid and gaseous products of retorting are withdrawn from the fragmented mass.