Claims
- 1. A method of recovering shale oil from a subterranean formation containing oil shale which comprises the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below such a void, such a zone of unfragmented formation having a center and a substantially horizontal free face adjoining the void;
- placing explosive into at least one of the zones of unfragmented formation;
- forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort in the subterranean formation by detonating such explosive for explosively expanding the unfragmented formation in such a zone of unfragmented formation in a single round for moving formation located at about the center of such zone of unfragmented formation a greater distance in a given time interval after beginning of the single round than formation located in such zone of unfragmented formation outward from about the center of such zone of unfragmented formation;
- introducing gas into the fragmented permeable mass in the in situ oil shale retort for establishing a retorting zone in the fragmented permeable mass wherein oil shale is retorted to produce gaseous and liquid products, and for advancing the retorting zone through the fragmented permeable mass; and
- withdrawing the gaseous and liquid products from the in situ oil shale retort.
- 2. The method according to claim 1 comprising explosively expanding the unfragmented formation in such a zone of unfragmented formation by detonating explosive located at about the center of such zone of unfragmented formation, followed by detonations of explosive in such zone of unfragmented formation progressing generally radially outwardly from the center of such zone of unfragmented formation.
- 3. The method according to claim 1 comprising explosively expanding the zone of unfragmented formation below such a void and the zone of unfragmented formation above such a void toward the void comprising:
- detonating explosive in the zone of unfragmented formation below the void at about the center of such zone of unfragmented formation first, thereafter detonating explosive in the zone of unfragmented formation below the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation below the void; and
- detonating explosive in the zone of unfragmented formation above the void at about the center of such zone of unfragmented formation first, thereafter detonating explosive in the zone of unfragmented formation above the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation above the void.
- 4. The method according to claim 3 wherein the first detonation in the zone of unfragmented formation below the void and the first detonation in the zone of unfragmented formation above the void occur substantially simultaneously, and the rate of progression of detonation generally radially outwardly in the zone of unfragmented formation below the void and the rate of progression of detonation generally radially outwardly in the zone of unfragmented formation above the void are substantially equal.
- 5. A method of recovering shale oil from a subterranean formation containing oil shale which comprises the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below such a void, such a zone of unfragmented formation having a center and a substantially horizontal free face adjoining the void, and leaving at least one support pillar in such a void meeting each adjacent zone of unfragmented formation at a juncture of such a support pillar and such a zone of unfragmented formation;
- placing explosive into at least one of the zones of unfragmented formation;
- placing explosive into such a pillar;
- detonating explosive in the pillar and thereafter in a single round with detonation of explosive in the pillar, detonating explosive in such a zone of unfragmented formation adjacent the pillar for moving formation located at about the center of such zone of unfragmented formation a greater distance in a given time interval after the start of the single round than formation located in the zone of unfragmented formation outward from about the center of the zone of unfragmented formation, thereby forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort in the subterranean formation;
- introducing gas to the fragmented permeable mass in the in situ oil shale retort for establishing a retorting zone in the fragmented permeable mass wherein oil shale is retorted to produce gaseous and liquid products, and for advancing the retorting zone through the fragmented permeable mass; and
- withdrawing the gaseous and liquid products from the in situ oil shale retort.
- 6. The method according to claim 5 comprising explosively expanding the unfragmented formation in such a zone of unfragmented formation by detonating explosive located at about the center of such zone of unfragmented formation followed by detonation of explosive in the zone of unfragmented formation progressing generally radially outwardly from first detonation in such a zone of unfragmented formation.
- 7. The method according to claim 6 comprising explosively expanding the zone of unfragmented formation below such a void and the zone of unfragmented formation above such a void toward the void comprising:
- detonating explosive in the zone of unfragmented formation below the void at about the center of such zone of unfragmented formation first, thereafter detonating explosive in the zone of unfragmented formation below the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation below the void; and
- detonating explosive in the zone of unfragmented formation above the void at about the center of such a zone of unfragmented formation first, thereafter detonating explosive in the zone of unfragmented formation above the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation above the void where the first detonation in the zone of unfragmented formation below the void and the first detonation in the zone of unfragmented formation above the void occur substantially simultaneously, and the rate of progression of detonation generally radially outwardly in the zone of unfragmented formation below the void and the rate of progression of detonation generally radially outwardly in the zone of unfragmented formation above the void are substantially equal.
- 8. The method according to claim 5 comprising detonating explosive in such zone of unfragmented formation for explosive expansion of such unfragmented formation with a sufficient time delay after explosive expansion of such pillar to distribute fragments of the pillar substantially uniformly across the void.
- 9. A method of recovering shale oil from a subterranean formation containing oil shale which comprises the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below such a void, such a zone of unfragmented formation having a center and a substantially horizontal free face adjoining the void, and leaving at least one support pillar in such a void meeting each adjacent zone of unfragmented formation at a juncture of such a support pillar and such a zone of unfragmented formation;
- placing explosive into at least one of the zones of unfragmented formation;
- placing explosive into such a pillar;
- detonating explosive in the pillar and detonating explosive in such a zone of unfragmented formation such that formation located at about the center of such a zone of unfragmented formation is moved a greater distance in a given time interval after a first detonation of explosive than formation located in the unfragmented formation outward from about the center of such a zone of unfragmented formation, thereby forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort in the subterranean formation;
- introducing gas into the fragmented permeable mass in the in situ oil shale retort for establishing a retorting zone in the fragmented permeable mass wherein oil shale is retorted to produce gaseous and liquid products, and for advancing the retorting zone through the fragmented permeable mass; and
- withdrawing the gaseous and liquid products from the in situ oil shale retort.
- 10. The method according to claim 9 comprising explosively expanding the unfragmented formation in such a zone of unfragmented formation by detonating explosive located at about the center of such zone of unfragmented formation followed by detonation of explosive in the zone of unfragmented formation progressing generally radially outwardly from a first detonation in such zone of unfragmented formation.
- 11. The method according to claim 9 comprising explosively expanding the zone of unfragmented formation below such a void and the zone of unfragmented formation above such a void toward the void comprising:
- detonating explosive in the zone of unfragmented formation below the void at about the center of such a zone of unfragmented formation first, thereafter detonating explosive in the zone of unfragmented formation below the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation below the void; and
- detonating explosive in the zone of unfragmented formation above the void at about the center of such a zone of unfragmented formation first, thereafter detonating explosive in the zone of unfragmented formation above the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation above the void where the first detonation in the zone of unfragmented formation below the void and the first detonation in the zone of unfragmented formation above the void occur substantially simultaneously, and the rate of progression of detonations generally radially outwardly in the zone of unfragmented formation below the void and the rate of progression of detonations generally radially outwardly in the zone of unfragmented formation above the void are substantially equal.
- 12. The method according to claim 9 comprising detonating explosive in such a zone of unfragmented formation for explosive expansion of such unfragmented formation with a sufficient time delay after explosive expansion of such a pillar to distribute fragments of the pillar substantially uniformly across the void.
- 13. A method for forming an in situ oil shale retort in a retort site within a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale comprising the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below each void, each zone of unfragmented formation having a substantially horizontal free face adjoining the void, and leaving at least one support pillar of unfragmented formation in such a void;
- placing explosive into at least one of the zones of unfragmented formation;
- placing explosive into the pillar;
- detonating explosive in the pillar and thereafter in a single round with detonation of explosive in the pillar, detonating explosive in such a zone of unfragmented formation for moving formation located in the zone of unfragmented formation substantially vertically spaced apart from about the locus of the center of mass of such a pillar a greater distance in a given time interval after the start of the round than formation located in the zone of unfragmented formation outward from about the locus of the center of mass of such a pillar, thereby forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort in the subterranean formation.
- 14. The method according to claim 13 comprising explosively expanding at least one of the zones of unfragmented formation above and below such a void by a first detonation of explosive located in the zone of unfragmented formation substantially vertically spaced apart from the locus of the center of mass of such a pillar followed by detonation of explosive in the zone of unfragmented formation progressing generally radially outwardly from the first detonation.
- 15. The method according to claim 13 comprising:
- detonating explosive in such a zone of unfragmented formation below the void at about the locus of the center of mass of such a pillar first, thereafter detonating explosive in such a zone below the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation below the void; and
- detonating explosive in such a zone of unfragmented formation above the void at about the locus of the center of mass of such a pillar first, thereafter detonating explosive in such a zone of unfragmented formation above the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation above the void, wherein the first detonation in the zone of unfragmented formation below the void and the first detonation in the zone of unfragmented formation above the void occur substantially simultaneously, and the rate of progression of detonations generally radially outwardly in the zone of unfragmented formation below the void and the rate of progression of detonations generally radially outwardly in the zone of unfragmented formation above the void are substantially equal.
- 16. The method according to claim 13 comprising detonating explosive in such zone of unfragmented formation for explosive expansion of such unfragmented formation with a sufficient time delay after explosive expansion of the pillar to distribute fragments of such pillar substantially uniformly across the void.
- 17. A method of forming an in situ oil shale retort in a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale, which comprises the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below such a void, each zone of unfragmented formation having a substantially horizontal free face adjoining such a void, and leaving at least one support pillar of unfragmented formation in such a void;
- placing explosive into at least one of the zones of unfragmented formation for explosively expanding such zone of unfragmented formation;
- placing explosive into the pillar;
- detonating explosive in the pillar and in such a zone of unfragmented formation in a single round wherein the first detonation of explosive is at about the center of the zone of unfragmented formation followed by detonation of explosive in the zone of unfragmented formation progressing generally radially outwardly from the first detonation, thereby forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort in the subterranean formation.
- 18. The method according to claim 17 comprising explosively expanding the zone of unfragmented formation below such a void and the zone of unfragmented formation above such a void toward the void comprising:
- detonating explosive in the zone of unfragmented formation below the void at about the center of such a zone of unfragmented formation first, thereafter detonating explosive in the zone of unfragmented formation below the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation below the void; and
- detonating explosive in the zone of unfragmented formation above the void at about the center of such a zone of unfragmented formation first, thereafter detonating explosive in the zone of unfragmented formation above the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation above the void, wherein the first detonation in the zone of unfragmented formation below the void and the first detonation in the zone of unfragmented formation above the void occur substantially simultaneously, and the rate of progression of detonations generally radially outwardly in the zone of unfragmented formation below the void and the rate of progression of detonations generally radially outwardly in the zone of unfragmented formation above the void are substantially equal.
- 19. The method according to claim 17 comprising detonating explosive in such a zone of unfragmented formation for explosive expansion of such zone of unfragmented formation with a sufficient time delay after explosive expansion of the pillar to spread fragments of such pillar substantially uniformly across the void.
- 20. The method according to claim 17 comprising detonating explosive in such a zone of unfragmented formation for providing a burden velocity of about 75 to about 100 feet per second and detonating explosive in the pillar for providing a burden velocity of pillar fragments of about 125 feet per second.
- 21. A method for forming an in situ oil shale retort in a retort site within a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale comprising the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below each void, each zone of unfragmented formation having a substantially horizontal free face adjoining the void, and leaving at least one support pillar of unfragmented formation in the void, each such support pillar meeting each zone of unfragmented formation at a juncture of such a pillar and such a zone of unfragmented formation;
- placing explosive into at least one of the zones of unfragmented formation for explosively expanding such zone of unfragmented formation;
- placing explosive into the pillar;
- detonating explosive in the pillar and in such a zone of unfragmented formation in a single round wherein the first detonation of explosive in the zone of unfragmented formation is substantially vertically spaced apart from at about the locus of the center of mass of such a pillar, thereafter followed by detonation of explosive in the zone of unfragmented formation progressing generally radially outwardly from the first detonation, thereby forming a fragmented permeable mass of formation particles containing oil shale in the subterranean formation forming an in situ oil shale retort.
- 22. The method according to claim 21 comprising explosively expanding the zone of unfragmented formation below such a void and the zone of unfragmented formation above such a void toward the void comprising:
- detonating explosive in the zone of unfragmented formation below the void at about the locus of the center of mass of such a pillar first, thereafter detonating explosive in the zone of unfragmented formation below the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation below the void;
- detonating explosive in the zone of unfragmented formation above the void at about the locus of the center of mass of such a pillar first, thereafter detonating explosive in the zone of unfragmented formation above the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation above the void, where the first detonation in the zone of unfragmented formation below the void and the first detonation in the zone of unfragmented formation above the void occur substantially simultaneously, and the rate of progression of detonations generally radially outwardly in the zone of unfragmented formation below the void and the rate of progression of detonations generally radially outwardly in the zone of unfragmented formation above the void are substantially equal.
- 23. The method according to claim 21 comprising detonating explosive in the pillar first, and thereafter detonating explosive in such a zone of unfragmented formation at about the locus of the center of mass of the pillar, after a time delay sufficient to allow formation of a free face at the juncture of such pillar and such a zone of unfragmented formation owing to explosive expansion of the pillar.
- 24. The method according to claim 21 comprising detonating explosive in such a zone of unfragmented formation for explosive expansion of such zone of unfragmented formation with a sufficient time delay after explosive expansion of the pillar to distribute the fragments of such pillar substantially uniformly across the void.
- 25. The method according to claim 21 comprising detonating explosive in such a zone of unfragmented formation above such a void and in such a zone of unfragmented formation below such void for providing a burden velocity of about 75 to about 100 feet per second and detonating explosive in the pillar for providing a burden velocity of pillar fragments of about 125 feet per second.
- 26. A method of recovering shale oil from a subterranean formation containing oil shale which comprises the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below each void, each zone of unfragmented formation having a substantially horizontal free face adjoining the void;
- placing explosive into at least one of the zones of unfragmented formation for explosively expanding such a zone of unfragmented formation;
- forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort in the subterranean formation by explosively expanding at least one of the zones of unfragmented formation above and below such a void toward the void in a single round wherein the first explosive expansion is at about the center of the zone of unfragmented formation, thereafter followed by explosive expansion of unfragmented formation progressing outwardly from the center;
- introducing gas to the fragmented permeable mass in the in situ oil shale retort for establishing a retorting zone in the fragmented permeable mass wherein oil shale is retorted to produce gaseous and liquid products, and for advancing the retorting zone through the fragmented mass; and
- withdrawing the gaseous and liquid products from the retort.
- 27. The method according to claim 26 comprising explosively expanding the zone of unfragmented formation below the void and the zone of unfragmented formation above the void toward the void comprising:
- detonating explosive in the zone below the void at about the center of such a zone first, thereafter detonating explosive in the zone below the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation below the void; and
- detonating explosive in the zone above the void at about the center of such a zone first, thereafter detonating explosive in the zone above the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation above the void where the first detonation in the zone of unfragmented formation above the void and the first detonation in the zone of unfragmented formation below the void occur simultaneously, and the rate of progression of detonations generally radially outwardly in the zone of unfragmented formation below the void and the rate of progression of detonations generally radially outwardly in the zone of unfragmented formation above the void are substantially equal.
- 28. A method for forming an in situ oil shale retort in a retort site within a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale comprising the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below each void, each zone of unfragmented formation having a substantially horizontal free face adjoining such a void, and leaving at least one support pillar of unfragmented formation in such a void, each such support pillar meeting each zone of unfragmented formation at a juncture of such a pillar and such a zone of unfragmented formation;
- placing an array of explosive charges into at least one of the zones of unfragmented formation for explosively expanding such a zone of unfragmented formation;
- placing explosive into the pillar;
- detonating explosive in the pillar and thereafter detonating the explosive charges in such a zone of unfragmented formation in a single round wherein the first detonation of explosive charges is of a first group of explosive charges at about the center of the array of explosive charges, followed by detonation of explosive charges in at least a first band of explosive charges substantially surrounding the first group, thereby forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort in the subterranean formation.
- 29. The method according to claim 28 comprising explosively expanding the zone of unfragmented formation below the void and the zone of unfragmented formation above the void toward the void comprising:
- detonating explosive in the zone of unfragmented formation below the void at about the center of such a zone of unfragmented formation first, thereafter detonating explosive in the zone of unfragmented formation below the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation below the void; and
- detonating explosive in the zone of unfragmented formation above the void at about the center of such a zone of unfragmented formation first, thereafter detonating explosive in the zone of unfragmented formation above the void progressing generally radially outwardly from the first detonation in the zone of unfragmented formation above the void where the first detonation in the zone of unfragmented formation below the void and the first detonation in the zone of unfragmented formation above the void occur substantially simultaneously, and the rate of progression of detonations generally radially outwardly in the zone of unfragmented formation below the void and the rate of progression of detonations generally radially outwardly in the zone of unfragmented formation above the void are substantially equal.
- 30. The method according to claim 28 comprising detonating explosive in such a zone of unfragmented formation for explosive expansion of such unfragmented formation with a sufficient time delay after explosive expansion of the pillar to spread the fragments of such pillar substantially uniformly across the void.
- 31. A method of recovering shale oil from a subterranean formation containing oil shale which comprises the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below such a void, each such zone of unfragmented formation having a center;
- placing an array of explosive charges into at least one of the zones of unfragmented formation;
- detonating such an array of explosive charges for explosively expanding unfragmented formation in such a zone of unfragmented formation for forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort in the subterranean formation wherein the explosive charges in the array are detonated in a sequence such that formation located at about the center of the zone of unfragmented formation is moved a greater distance in a given time interval after the beginning of the detonation sequence than formation located in the zone of unfragmented formation outward from about the center of the zone of unfragmented formation;
- introducing gas into the fragmented permeable mass in the in situ oil shale retort for establishing a retorting zone in the fragmented permeable mass wherein oil shale is retorted to produce gaseous and liquid products, and for advancing the retorting zone through the fragmented permeable mass; and
- withdrawing the gaseous and liquid products from the in situ oil shale retort.
- 32. A method of recovering shale oil from a subterranean formation containing oil shale which comprises the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below such a void, each such zone of unfragmented formation having a center, and leaving at least one support pillar in such a void;
- placing a plurality of explosive charges into at least one of the zones of unfragmented formation;
- placing at least one explosive charge into such a pillar;
- detonating such explosive charge in the pillar and thereafter detonating the explosive charges in such a zone of unfragmented formation adjacent the pillar such that formation located at about the center of the zone of unfragmented formation is moved a greater distance in a given time interval after the start of the detonation of such explosive charges than formation located in the zone of unfragmented formation outward from about the center of the zone of unfragmented formation, thereby forming a fragmented permeable mass of formation particles containing oil shale in the subterranean formation;
- introducing gas to the fragmented permeable mass for establishing a retorting zone in the fragmented permeable mass wherein oil shale is retorted to produce gaseous and liquid products, and for advancing the retorting zone through the fragmented permeable mass; and
- withdrawing the gaseous and liquid products from the fragmented permeable mass.
- 33. A method for forming a fragmented permeable mass within a subterranean formation comprising the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation immediately adjacent each such void having a substantially horizontal free face adjoining the void, and leaving at least one support pillar of unfragmented formation in such a void;
- placing a plurality of explosive charges into at least one of the zones of unfragmented formation;
- placing at least one explosive charge into the pillar; and detonating the explosive charges in the pillar and in such a zone of unfragmented formation in a sequence such that formation located in the zone of unfragmented formation substantially vertically spaced apart from about the locus of the center of mass of the pillar is moved a greater distance in a given time interval after the start of the detonation sequence than formation located in the zone of unfragmented formation horizontally spaced from about the locus of the center of mass of the pillar for forming a fragmented permeable mass of formation particles in the subterranean formation.
- 34. A method of forming a fragmented permeable mass of formation particles in a subterranean formation, which comprises the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below such a void, each zone of unfragmented formation having a substantially horizontal free face adjoining such a void;
- placing a plurality of explosive charges into at least one of the zones of unfragmented formation for explosively expanding such zone of unfragmented formation; and
- detonating the explosive charges in the zone of unfragmented formation in a sequence progressing generally radially outwardly from the center of the zone of unfragmented formation thereby forming a fragmented permeable mass of formation particles in the subterranean formation.
- 35. A method for forming a fragmented mass of formation particles within a subterranean formation comprising the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below each void;
- placing an array of explosive charges into at least one of the zones of unfragmented formation for explosively expanding such zone of unfragmented formation;
- detonating the array of explosive charges in such a zone of unfragmented formation in a single round in a sequence wherein the first explosive charge detonated in the zone of unfragmented formation is substantially at the center of the zone of unfragmented formation and thereafter explosive charges are detonated progressing generally radially outwardly from the first detonation, thereby forming a fragmented permeable mass of formation particles in the subterranean formation.
- 36. A method of recovering shale oil from a subterranean formation containing oil shale which comprises the steps of:
- excavating formation to form at least one void in the subterranean formation leaving zones of unfragmented formation above and below each void, each zone of unfragmented formation having a substantially horizontal free face adjoining the void;
- placing a plurality of explosive charges into at least one of the zones of unfragmented formation for explosively expanding such a zone of unfragmented formation;
- forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort in the subterranean formation by detonating such explosive charges to thereby explosively expand such zone of unfragmented formation toward the void wherein the first explosive charge detonated is at about the center of the zone of unfragmented formation, thereafter followed by explosive expansion of unfragmented formation progressing outwardly from the center;
- introducing gas to the fragmented permeable mass in the in situ oil shale retort for establishing a retorting zone in the fragmented permeable mass wherein oil shale is retorted to produce gaseous and liquid products, and for advancing the retorting zone through the fragmented mass; and
- withdrawing the gaseous and liquid products from the retort.
- 37. A method for forming an in situ oil shale retort in a retort site within a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale comprising the steps of:
- excavating formation to form at least one void in the subterranean formation, leaving a zone of unfragmented formation above such a void having a substantially horizontal free face adjoining the void;
- placing a plurality of explosive charges into the zone of unfragmented formation for explosively expanding the zone of unfragmented formation; and
- detonating such explosive charges for forming a fragmented permeable mass of formation particles containing oil shale in the in situ oil shale retort by explosively expanding the zone of unfragmented formation above the void toward the void, wherein the first explosive expansion is at about the center of the zone of unfragmented formation, thereafter followed by explosive expansion of formation progressing outwardly from the center.
- 38. A method of recovering shale oil from a subterranean formation containing oil shale which comprises the steps of:
- excavating formation to form at least one void in the subterranean formation leaving a zone of unfragmented formation above such a void, such a zone of unfragmented formation having a center and a substantially horizontal free face adjoining the void;
- placing a plurality of explosive charges into the zone of unfragmented formation;
- detonating such explosive charges in a time delay sequence for explosively expanding the zone of unfragmented formation and forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort, the time delay sequence being sufficient for moving formation located at about the center of the zone of unfragmented formation a greater distance in a given time interval after beginning of the time delay sequence than formation located in the zone of unfragmented formation outward from about the center of the zone of unfragmented formation;
- introducing gas into the fragmented permeable mass in the in situ oil shale retort for establishing a retorting zone in the fragmented permeable mass wherein oil shale is retorted to produce gaseous and liquid products, and for advancing the retorting zone through the fragmented permeable mass; and
- withdrawing the gaseous and liquid products from the in situ oil shale retort.
- 39. A method for forming an in situ oil shale retort in a retort site within a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale comprising the steps of:
- excavating formation to form at least one void in the subterranean formation, leaving a zone of unfragmented formation above such a void having a substantially horizontal free face adjoining the void;
- placing a plurality of explosive charges into the zone of unfragmented formation for explosively expanding the zone of unfragmented formation; and
- detonating at least one such explosive charge at about the center of the zone of unfragmented formation, thereafter followed by detonation of a plurality of such explosive charges progressing outwardly from the center for explosively expanding the zone of unfragmented formation above the void toward the void for forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort.
CROSS REFERENCE TO RELATED APPLICATIONS
This is a continuation of application Ser. No. 075,846, filed Sept. 14, 1979, now abandoned.
US Referenced Citations (7)
Continuations (1)
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Number |
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75846 |
Sep 1979 |
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