Placement of explosive for forming in situ oil shale retort

• Main Authors: FRENCH; GORDON B, COOK; MELVIN A, MCCARTHY; HARRY E
• Format: Patent
• Language: English
• Published: 24.08.1982
• Subjects: EARTH DRILLING; EARTH DRILLING, e.g. DEEP DRILLING; FIXED CONSTRUCTIONS; MINING; MINING OR QUARRYING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR ASLURRY OF MINERALS FROM WELLS

A subterranean formation containing oil shale is prepared for in situ retorting by initially excavating a plurality of vertically spaced apart voids within a retort site, leaving an intervening zone of unfragmented formation between an adjacent pair of such voids. The intervening zone has substantially parallel upper and lower horizontal free faces adjoining the voids. At least one pancake-shaped load of explosive is placed in the intervening zone. The pancake-shaped explosive load has faces which are substantially parallel to the upper and lower free faces, and the length of the axis of the explosive load is less than the radius of the load. The explosive load is detonated for explosively expanding formation toward the upper and lower free faces for forming an in situ retort containing a fragmented permeable mass of formation particles. In one embodiment, a plurality of such pancake-shaped explosive charges are placed at horizontally spaced apart locations at substantially the same level and approximately in the middle of the intervening zone, and the explosive charges are detonated in a single round of explosions for forming the fragmented mass.