METHOD FOR EXPLOSIVE EXPANSION TOWARD HORIZONTAL FREE FACES FOR FORMING AN IN SITU OIL SHALE RETORT

摘要

METHOD FOR EXPLOSIVE EXPANSION TOWARD HORIZONTAL FREE FACES FOR FORMING AN IN SITU OIL SHALE RETORT Formation is excavated from within a retort site in formation containing oil shale for forming a plurality of vertically spaced apart voids extending horizontally across different levels of the retort site, leaving a separate zone of unfragmented formation beneath each void. Explosive is placed in each zone, and such explosive is detonated in a single round for forming an in situ retort containing a fragmented permeable mass of formation particles containing oil shale. Formation is explosively expanded upwardly and downwardly toward each void. A horizontal void excavated at a production level has a smaller horizontal cross-sectional area than a void excavated at a lower level of the retort site immediately above the production level void. Explosive in a first group of vertical blast holes is detonatedfor explosively expanding formation upwardly toward the lower void, and explosive in a second group of vertical blast holes is detonated in the same round for explosively expanding formation upwardly toward the lower void and downwardly toward the production level void for forming a generally T-shaped bottom of the fragmented mass.