Explosive-aided oil shale cavity formation

Claim 1

In forming a rubble-containing cavity in a water-soluble-mineral-containing subterranean oil shale, the improvement comprising: forming a relatively areally extensive void in or above an upper portion of the oil shale by selectively leaching solids from a water-soluble mineral-rich layer in that location; forming a relatively areally extensive permeable zone or void in or continguous with a lower portion of the oil shale by selectively leaching solids from a water-soluble mineral-rich layer in that location; displacing explosive liquid into the lower void or permeable zone; displacing fluid having a relatively low density and high compressibility into the upper void; and subsequently, detonating the explosive to fragment the adjacent shale by the combined action of direct and reflected shock waves and solids-displacement.