| 摘要 |
An in situ oil shale retort is formed in a subterranean formation containing oil shale. The formation comprises at least one region of relatively richer oil shale and another region of relatively leaner oil shale. According to one embodiment, formation is excavated from within a retort site for forming at least one void extending horizontally across the retort site, leaving a portion of unfragmented formation including the regions of richer and leaner oil shale adjacent such a void space. A first array of vertical blast holes are drilled in the regions of richer and leaner oil shale, and a second array of blast holes are drilled at least in the region of richer oil shale. Explosive charges are placed in portions of the blast holes in the first and second arrays which extend into the richer oil shale, and separate explosive charges are placed in portions of the blast holes in the first array which extend into the leaner oil shale. This provides an array with a smaller scaled depth of burial (sdob) and closer spacing distance between explosive charges in the richer oil shale than the sdob and spacing distance of the array of explosive charges in the leaner oil shale. The explosive charges are detonated for explosively expanding the regions of richer and leaner oil shale toward the horizontal void for forming a fragmented mass of particles. Upon detonation of the explosive, greater explosive energy is provided collectively by the explosive charges in the richer oil shale, compared with the explosive energy produced by the explosive charges in the leaner oil shale, resulting in comparable fragmentation in both grades of oil shale.
|
