Multiple level preparation of oil shale retort

Claim 1

A method for forming an in situ oil shale retort containing a fragmented permeable mass of oil shale particles in a subterranean deposit containing oil shale comprising the steps of: excavating at least a lower void and an upper void, each void having a horizontal cross section substantially similar to the horizontal cross section of the in situ oil shale retort being formed, the upper void being located substantially directly above the lower void, leaving an intervening unfragmented zone of deposit between the upper and lower voids; placing explosive in a lower portion of the unfragmented zone; detonating the explosive to explosively expand the lower portion of the unfragmented zone into at least the lower void and produce a fragmented permeable mass of particles and a space free of fragmented particles below a remaining portion of the unfragmented zone. placing explosive in the remaining portion of the unfragmented zone; and detonating the explosive in the remaining portion to explosively expand the remaining portion of the unfragmented zone into the upper void and the space free of fragmented particles below the remaining portion of the unfragmented zone to thereby produce a fragmented, permeable mass of particles within the boundaries of the in situ oil shale retort being formed, wherein the void volume of the fragmented permeable mass of particles is substantially equal to the total initial volumes of the upper and lower voids.

Claim 2

A method for forming an in situ oil shale retort containing a fragmented permeable mass of oil shale particles in a subterranean deposit containing oil shale comprising the steps of: excavating at least a lower void and an upper void, each void having a horizontal cross section substantially similar to the horizontal cross section of the in situ oil shale retort being formed, the upper void being located substantially directly above the lower void, leaving an intervening unfragmented zone of deposit between the upper and lower voids; placing explosive in a lower portion of the unfragmented zone; detonating the explosive to explosively expand the lower portion of the unfragmented zone into at least the lower void and produce a fragmented permeable mass of particles and a space free of fragmented particles below a remaining portion of the unfragmented zone. placing explosive in the remaining portion of the unfragmented zone; and detonating the explosive in the remaining portion to explosively expand the remaining portion of the unfragmented zone into the upper void and the space free of fragmented particles below the remaining portion of the unfragmented zone to thereby produce a fragmented, permeable mass of particles within the boundaries of the in situ oil shale retort being formed, wherein the void volume of the fragmented permeable mass of particles is substantially equal to the total initial volumes of the upper and lower voids.

Claim 9

A method of recovering shale oil from a subterranean deposit containing oil shale comprising the steps of: excavating at least a lower void and an upper void, each void having a horizontal cross section substantially similar to the horizontal cross section of the in situ oil shale retort being formed, the upper void being located substantially directly above the lower void, leaving an intervening unfragmented zone of the deposit between the upper and lower voids, the unfragmented zone having a thickness greater than the smallest lateral dimension of either the upper or lower void; placing explosive in a lower portion of the unfragmented zone; detonating the explosive to explosively expand the lower portion of the unfragmented zone into at least the lower void and produce a fragmented permeable mass of particles and a space free of fragmented particles below a remaining portion of the unfragmented zone; thereafter placing explosive in the remaining portion of the unfragmented zone; thereafter detonating the explosive in the remaining portion to explosively expand the remaining portion of the unfragmented zone into the upper void and the space free of fragmented particles below the remaining portion of the unfragmented zone to thereby produce a fragmented, permeable mass of particles within the boundaries of an in situ oil shale retort being formed and having a void volume substantially equal to the total initial volume of the upper and lower voids; heating the expanded portion of the oil shale deposit to liquefy carbonaceous values therein by maintaining a downward pressure differential of gas through the fragmented permeable mass; and recovering shale oil from the base of in situ retort.

Claim 10

A method of recovering shale oil from a subterranean deposit containing oil shale comprising the steps of: excavating at least a lower void and an upper void, each void having a horizontal cross section substantially similar to the horizontal cross section of the in situ oil shale retort being formed, the upper void being located substantially directly above the lower void, leaving an intervening unfragmented zone of the deposit between the upper and lower voids, the unfragmented zone having a thickness greater than the smallest lateral dimension of either the upper or lower void; placing explosive in a lower portion of the unfragmented zone; detonating the explosive to explosively expand the lower portion of the unfragmented zone into at least the lower void and produce a fragmented permeable mass of particles and a space free of fragmented particles below a remaining portion of the unfragmented zone; thereafter placing explosive in the remaining portion of the unfragmented zone; thereafter detonating the explosive in the remaining portion to explosively expand the remaining portion of the unfragmented zone into the upper void and the space free of fragmented particles below the remaining portion of the unfragmented zone to thereby produce a fragmented, permeable mass of particles within the boundaries of an in situ oil shale retort being formed and having a void volume substantially equal to the total initial volume of the upper and lower voids; heating the expanded portion of the oil shale deposit to liquefy carbonaceous values therein by maintaining a downward pressure differential of gas through the fragmented permeable mass; and recovering shale oil from the base of in situ retort.

Claim 16

A method for forming an in situ oil shale retort containing a fragmented permeable mass of particles in a subterranean deposit containing oil shale comprising the steps of excavating a plurality of vertically spaced apart voids, wherein the horizontal cross section of each void is substantially similar to the horizontal cross section of the in situ oil shale retort being formed and including a lower void and at least one void is located substantially directly above said lower void, and leaving an intervening unfragmented zone of deposit between adjacent voids; and explosively expanding each unfragmented zone downwardly toward a lower void in a plurality of sequential portions from the bottom up, the final portion also expanding upwardly toward the void above the zone to produce a fragmented, permeable mass of particles within the boundaries of the in situ oil shale retort having a void volume substantially equal to the total volume of the voids within the boundaries of the in situ oil shale retort being formed.

Claim 17

A method for forming an in situ oil shale retort containing a fragmented permeable mass of particles in a subterranean deposit containing oil shale comprising the steps of excavating a plurality of vertically spaced apart voids, wherein the horizontal cross section of each void is substantially similar to the horizontal cross section of the in situ oil shale retort being formed and including a lower void and at least one void is located substantially directly above said lower void, and leaving an intervening unfragmented zone of deposit between adjacent voids; and explosively expanding each unfragmented zone downwardly toward a lower void in a plurality of sequential portions from the bottom up, the final portion also expanding upwardly toward the void above the zone to produce a fragmented, permeable mass of particles within the boundaries of the in situ oil shale retort having a void volume substantially equal to the total volume of the voids within the boundaries of the in situ oil shale retort being formed.

Claim 22

A method of forming an in situ oil shale retort containing a fragmented permeable mass of oil shale particles in a subterranean deposit, which comprises the steps of: excavating a plurality of vertically spaced apart voids with a zone of unfragmented deposit between adjacent voids and within the boundaries of the in situ oil shale retort being formed; explosively expanding at least one lower portion of such an unfragmented zone downwardly toward a lower void; and thereafter explosively expanding an upper remaining portion of such an unfragmented zone at least partly toward an upper void to form a fragmented permeable mass of particles within the boundaries of the in situ oil shale retort being formed, wherein the void volume of the fragmented permeable mass of particles in the in situ oil shale retort is substantially equal to the total volume of the voids within the boundaries of the in situ oil shale retort being formed.

Claim 23

A method of forming an in situ oil shale retort containing a fragmented permeable mass of oil shale particles in a subterranean deposit, which comprises the steps of: excavating a plurality of vertically spaced apart voids with a zone of unfragmented deposit between adjacent voids and within the boundaries of the in situ oil shale retort being formed; explosively expanding at least one lower portion of such an unfragmented zone downwardly toward a lower void; and thereafter explosively expanding an upper remaining portion of such an unfragmented zone at least partly toward an upper void to form a fragmented permeable mass of particles within the boundaries of the in situ oil shale retort being formed, wherein the void volume of the fragmented permeable mass of particles in the in situ oil shale retort is substantially equal to the total volume of the voids within the boundaries of the in situ oil shale retort being formed.

Claim 30

A method for forming an in situ oil shale retort in a subterranean oil shale deposit comprising the steps of: excavating a lower void having a horizontal cross section corresponding to a desired horizontal cross section of an in situ oil shale retort; excavating an upper void having a horizontal cross section corresponding to the horizontal cross section of the lower void and spaced substantially directly above the lower void a distance greater than about the minimum lateral dimension of either void, thereby leaving a zone of unfragmented oil shale deposit between the lower void and the upper void; excavating an intermediate void having a horizontal cross section corresponding to the horizontal cross section of the lower void and spaced directly above the lower void and directly below the upper void and spaced from each void a distance greater than about the minimum lateral dimension of either void, thereby subdividing the oil shale deposit into two zones of unfragmented oil shale deposit each having a thickness not appreciably less than the smallest lateral dimension of the void into which the oil shale is to be expanded; explosively expanding a lower portion of the lower unfragmented zone toward the lower void to produce a permeable mass of fragmented particles and a space free of fragmented particles below the remaining portion of the lower unfragmented zone; explosively expanding the remaining portion of the lower unfragmented zone toward the intermediate void and the space free of fragmented particles below the remaining portion of the lower unfragmented zone; explosively expanding a lower portion of the upper unfragmented zone toward the intermediate void to produce a permeable mass of fragmented particles and a space free of fragmented particles below the remaining portion of the upper unfragmented zone; and explosively expanding the remaining portion of the upper unfragmented zone toward the upper void and the space free of fragmented particles below the remaining portion of the upper unfragmented zone.

Claim 31

A method for forming an in situ oil shale retort in a subterranean oil shale deposit comprising the steps of: excavating a lower void having a horizontal cross section corresponding to a desired horizontal cross section of an in situ oil shale retort; excavating an upper void having a horizontal cross section corresponding to the horizontal cross section of the lower void and spaced substantially directly above the lower void a distance greater than about the minimum lateral dimension of either void, thereby leaving a zone of unfragmented oil shale deposit between the lower void and the upper void; excavating an intermediate void having a horizontal cross section corresponding to the horizontal cross section of the lower void and spaced directly above the lower void and directly below the upper void and spaced from each void a distance greater than about the minimum lateral dimension of either void, thereby subdividing the oil shale deposit into two zones of unfragmented oil shale deposit each having a thickness not appreciably less than the smallest lateral dimension of the void into which the oil shale is to be expanded; explosively expanding a lower portion of the lower unfragmented zone toward the lower void to produce a permeable mass of fragmented particles and a space free of fragmented particles below the remaining portion of the lower unfragmented zone; explosively expanding the remaining portion of the lower unfragmented zone toward the intermediate void and the space free of fragmented particles below the remaining portion of the lower unfragmented zone; explosively expanding a lower portion of the upper unfragmented zone toward the intermediate void to produce a permeable mass of fragmented particles and a space free of fragmented particles below the remaining portion of the upper unfragmented zone; and explosively expanding the remaining portion of the upper unfragmented zone toward the upper void and the space free of fragmented particles below the remaining portion of the upper unfragmented zone.

Claim 33

A method of forming an in situ oil shale retort containing a fragmented permeable mass of oil shale particles in a subterranean deposit, which comprises the steps of: excavating a plurality of vertically spaced apart voids with a zone of unfragmented deposit between vertically adjacent voids, wherein the horizontal cross section of each void is substantially similar to the horizontal cross section of the in situ oil shale retort being formed; and explosively expanding at least one lower portion of such an unfragmented zone downwardly toward a lower void; thereafter explosively expanding an upper remaining portion of such an unfragmented zone at least partly toward an upper void to form a fragmented permeable mass of particles in an in situ oil shale retort being formed.

Claim 34

A method of forming an in situ oil shale retort containing a fragmented permeable mass of oil shale particles in a subterranean deposit, which comprises the steps of: excavating a plurality of vertically spaced apart voids with a zone of unfragmented deposit between vertically adjacent voids, wherein the horizontal cross section of each void is substantially similar to the horizontal cross section of the in situ oil shale retort being formed; and explosively expanding at least one lower portion of such an unfragmented zone downwardly toward a lower void; thereafter explosively expanding an upper remaining portion of such an unfragmented zone at least partly toward an upper void to form a fragmented permeable mass of particles in an in situ oil shale retort being formed.

Claim 35

A method of forming an in situ oil shale retort containing a fragmented permeable mass of oil shale particles in a subterranean deposit which comprises the steps of: excavating a plurality of vertically spaced apart voids with a zone of unfragmented deposit between adjacent vertically spaced apart voids, said unfragmented zone having a free face of deposit adjoining each of the adjacent vertically spaced apart voids; forming a plurality of vertically extending blasting holes in such an unfragmented zone; detonating explosive in at least a portion of said blasting holes for explosively expanding at least one lower portion of such an unfragmented zone downwardly toward such a free face of deposit adjacent a lower void; and thereafter detonating explosive in at least a portion of said blasting holes for explosively expanding an upper remaining portion of such an unfragmented zone at least partly toward such a free face of deposit adjacent an upper void to form a fragmented permeable mass of particles within the boundaries of the in situ oil shale retort being formed.

Claim 36

A method of forming an in situ oil shale retort containing a fragmented permeable mass of oil shale particles in a subterranean deposit which comprises the steps of: excavating a plurality of vertically spaced apart voids with a zone of unfragmented deposit between adjacent vertically spaced apart voids, said unfragmented zone having a free face of deposit adjoining each of the adjacent vertically spaced apart voids; forming a plurality of vertically extending blasting holes in such an unfragmented zone; detonating explosive in at least a portion of said blasting holes for explosively expanding at least one lower portion of such an unfragmented zone downwardly toward such a free face of deposit adjacent a lower void; and thereafter detonating explosive in at least a portion of said blasting holes for explosively expanding an upper remaining portion of such an unfragmented zone at least partly toward such a free face of deposit adjacent an upper void to form a fragmented permeable mass of particles within the boundaries of the in situ oil shale retort being formed.