Method for controlling void in an in situ oil shale retort

摘要

Liquid and gaseous products are recovered from an in situ oil shale retort formed in a retort site in a subterranean formation containing oil shale. A void is excavated in the subterranean formation within the boundaries of the retort site and a zone of unfragmented formation is left in the retort site adjacent the void. A retort inlet is at one upper edge of the retort site and a retort outlet is at the lower edge of the retort site opposite the retort inlet. Explosive charges are placed in the zone of unfragmented formation and detonated in an asymmetrical time delay sequence for forming a fragmented permeable mass of formation particles which substantially fills the retort to the top boundary in the region of the retort inlet. A combustion zone is formed in the fragmented permeable mass adjacent the inlet and a retort inlet mixture comprising an oxygen-supplying gas is introduced into the fragmented mass for sustaining the combustion zone and advancing the combustion zone diagonally through the fragmented mass from the inlet toward the outlet. A retorting zone is on the advancing side of the combustion zone for producing liquid and gaseous products and the liquid and gaseous products are withdrawn through the retort outlet.