Method of blasting pillars with vertical blastholes

Claim 1

A method for forming a fragmented permeable mass of formation particles in an in situ oil shale retort in a subterranean formation containing oil shale, comprising the steps of: (a) excavating formation to form at least one horizontally extending void in the subterranean formation, leaving at least one support pillar of unfragmented formation in the void, and leaving zones of unfragmented formation above and below the void and pillar, such a pillar having opposed free faces; (b) forming an array of explosive charges in at least one of such zones of unfragmented formation for explosively expanding such a zone of unfragmented formation toward the void; (c) forming an array of spaced apart, vertical, columnar explosive charges substantially along the centerline between the opposed free faces of such a support pillar, the amount of explosive on each side of the centerline being about equal; (d) detonating explosive in the support pillar for expanding the pillar about equally toward the opposed free faces; and (e) detonating explosive in such a zone of unfragmented formation for explosively expanding the unfragmented formation toward the void for forming a fragmented permeable mass of formation particles containing oil shale in the in situ oil shale retort.

Claim 2

A method for forming a fragmented permeable mass of formation particles in an in situ oil shale retort in a subterranean formation containing oil shale, comprising the steps of: (a) excavating formation to form at least one horizontally extending void in the subterranean formation, leaving at least one support pillar of unfragmented formation in the void, and leaving zones of unfragmented formation above and below the void and pillar, such a pillar having opposed free faces; (b) forming an array of explosive charges in at least one of such zones of unfragmented formation for explosively expanding such a zone of unfragmented formation toward the void; (c) forming an array of spaced apart, vertical, columnar explosive charges substantially along the centerline between the opposed free faces of such a support pillar, the amount of explosive on each side of the centerline being about equal; (d) detonating explosive in the support pillar for expanding the pillar about equally toward the opposed free faces; and (e) detonating explosive in such a zone of unfragmented formation for explosively expanding the unfragmented formation toward the void for forming a fragmented permeable mass of formation particles containing oil shale in the in situ oil shale retort.

Claim 5

A method for forming a fragmented permeable mass of formation particles in an in situ oil shale retort in a subterranean formation containing oil shale, comprising the steps of: (a) excavating formation to form at least one horizontally extending void in the subterranean formation, leaving at least one support pillar of unfragmented formation in the void, and leaving zones of unfragmented formation above and below the void and pillar, such a pillar having opposed free faces; (b) forming an array of explosive charges in at least one of such zones of unfragmented formation for explosively expanding such a zone of unfragmented formation toward the void; (c) forming an array of explosive charges substantially along the centerline between the opposed free faces of such a support pillar by drilling vertical blastholes substantially along the centerline and loading the vertical blastholes with explosive, the amount of explosive on each side of the centerline being about equal; (d) detonating explosive in the support pillar for expanding the pillar about equally toward the opposed free faces; and (e) detonating explosive in such a zone of unfragmented formation for explosively expanding the unfragmented formation toward the void for forming a fragmented permeable mass of formation particles containing oil shale in the in situ oil shale retort.

Claim 6

A method for forming a fragmented permeable mass of formation particles in an in situ oil shale retort in a subterranean formation containing oil shale, comprising the steps of: (a) excavating formation to form at least one horizontally extending void in the subterranean formation, leaving at least one support pillar of unfragmented formation in the void, and leaving zones of unfragmented formation above and below the void and pillar, such a pillar having opposed free faces; (b) forming an array of explosive charges in at least one of such zones of unfragmented formation for explosively expanding such a zone of unfragmented formation toward the void; (c) forming an array of explosive charges substantially along the centerline between the opposed free faces of such a support pillar by drilling vertical blastholes substantially along the centerline and loading the vertical blastholes with explosive, the amount of explosive on each side of the centerline being about equal; (d) detonating explosive in the support pillar for expanding the pillar about equally toward the opposed free faces; and (e) detonating explosive in such a zone of unfragmented formation for explosively expanding the unfragmented formation toward the void for forming a fragmented permeable mass of formation particles containing oil shale in the in situ oil shale retort.

Claim 7

A method for forming a fragmented permeable mass of formation particles in an in situ oil shale retort in a subterranean formation containing oil shale comprising the steps of: (a) excavating formation to form at least one horizontally extending void in the subterranean formation leaving at least one support pillar of unfragmented formation in the void, and leaving zones of unfragmented formation above and below the void and pillar, such a pillar having opposed free faces; (b) forming an array of spaced apart vertical blastholes in such a zone of unfragmented formation, at least a portion of the blastholes extending into the pillar substantially along the centerline between the opposed free faces of the pillar; (c) placing explosive into a portion of such vertical blastholes for forming an array of explosive charges in at least one of the zones of unfragmented formation for explosively expanding such a zone of unfragmented formation toward the void; (d) placing explosive into blastholes formed substantially along the centerline of the support pillar for forming an array of substantially vertical columnar exlosive charges in the support pillar so that the amount of explosive on each side of the centerline is about equal; (e) detonating explosive in the support pillar for expanding the pillar about equally toward the opposed free faces; and (f) detonating explosive in such a zone of unfragmented formation for explosively expanding the zone of unfragmented formation toward the void for forming a fragmented permeable mass of formation particles containing oil shale in the in situ oil shale retort.

Claim 8

A method for forming a fragmented permeable mass of formation particles in an in situ oil shale retort in a subterranean formation containing oil shale comprising the steps of: (a) excavating formation to form at least one horizontally extending void in the subterranean formation leaving at least one support pillar of unfragmented formation in the void, and leaving zones of unfragmented formation above and below the void and pillar, such a pillar having opposed free faces; (b) forming an array of spaced apart vertical blastholes in such a zone of unfragmented formation, at least a portion of the blastholes extending into the pillar substantially along the centerline between the opposed free faces of the pillar; (c) placing explosive into a portion of such vertical blastholes for forming an array of explosive charges in at least one of the zones of unfragmented formation for explosively expanding such a zone of unfragmented formation toward the void; (d) placing explosive into blastholes formed substantially along the centerline of the support pillar for forming an array of substantially vertical columnar exlosive charges in the support pillar so that the amount of explosive on each side of the centerline is about equal; (e) detonating explosive in the support pillar for expanding the pillar about equally toward the opposed free faces; and (f) detonating explosive in such a zone of unfragmented formation for explosively expanding the zone of unfragmented formation toward the void for forming a fragmented permeable mass of formation particles containing oil shale in the in situ oil shale retort.

Claim 11

A method for explosively expanding a generally rectangular support pillar of unfragmented formation in an excavation in a subterranean formation, such a pillar having opposed long free faces, comprising the steps of: forming a plurality of spaced apart vertical columnar explosive charges substantially along the centerline between the opposed long free faces of the pillar, a plurality of equal squares being defined across the entire horizontal cross-section of the pillar by the centerline and lines perpendicular to the centerline which pass through the center of each explosive charge and extend to the edges of the pillar; forming a vertical columnar explosive charge at about the center of each square; and detonating explosive in the support pillar for expanding the pillar about equally toward the opposed free faces.

Claim 12

A method for explosively expanding a generally rectangular support pillar of unfragmented formation in an excavation in a subterranean formation, such a pillar having opposed long free faces, comprising the steps of: forming a plurality of spaced apart vertical columnar explosive charges substantially along the centerline between the opposed long free faces of the pillar, a plurality of equal squares being defined across the entire horizontal cross-section of the pillar by the centerline and lines perpendicular to the centerline which pass through the center of each explosive charge and extend to the edges of the pillar; forming a vertical columnar explosive charge at about the center of each square; and detonating explosive in the support pillar for expanding the pillar about equally toward the opposed free faces.

Claim 15

A method for explosively expanding a support pillar having a generally square horizontal cross-section of unfragmented formation in an excavation in a subterranean formation comprising the steps of: forming an array of spaced apart vertical columnar explosive charges in the pillar and detonating a portion of the explosive charges for expanding a first portion of the pillar toward the void, leaving a second portion of the pillar having a generally rectangular horizontal cross-section in the void, the second portion of the pillar having opposed long free faces, a plurality of such explosive charges remaining substantially along the centerline of the second portion of the pillar between the opposed long free faces, a plurality of equal squares being defined across the entire horizontal cross-section of the second portion of the pillar by the centerline and lines extending to the edges of the second portion of the pillar which are perpendicular to the centerline and pass through the center of each explosive charge along the centerline, an explosive charge being at about the center of each equal square; and detonating explosive in the second portion of the pillar for expanding the second portion about equally toward the opposed long free faces.

Claim 16

A method for explosively expanding a support pillar having a generally square horizontal cross-section of unfragmented formation in an excavation in a subterranean formation comprising the steps of: forming an array of spaced apart vertical columnar explosive charges in the pillar and detonating a portion of the explosive charges for expanding a first portion of the pillar toward the void, leaving a second portion of the pillar having a generally rectangular horizontal cross-section in the void, the second portion of the pillar having opposed long free faces, a plurality of such explosive charges remaining substantially along the centerline of the second portion of the pillar between the opposed long free faces, a plurality of equal squares being defined across the entire horizontal cross-section of the second portion of the pillar by the centerline and lines extending to the edges of the second portion of the pillar which are perpendicular to the centerline and pass through the center of each explosive charge along the centerline, an explosive charge being at about the center of each equal square; and detonating explosive in the second portion of the pillar for expanding the second portion about equally toward the opposed long free faces.

Claim 19

A method for explosively expanding a generally rectangular support pillar of unfragmented formation in an excavation in a subterranean formation, such a pillar having opposed long free faces, comprising the steps of: forming a plurality of spaced apart vertical columnar explosive charges substantially along the centerline between the opposed long free faces of the pillar, a plurality of equal squares being defined across the entire horizontal cross-section of the pillar by the centerline and by lines perpendicular to the centerline which pass through a first portion of the explosive charges along the centerline, the perpendicular lines extending to the edges of the pillar; forming a vertical columnar explosive charge at about the center of each square; forming the second portion of the explosive charges along the centerline at about the intersection of the centerline and lines perpendicular to the centerline which extend between the explosive charges at about the center of adjacent squares; and detonating explosive in the support pillar for expanding the pillar about equally toward the opposed long free faces.

Claim 20

A method for explosively expanding a generally rectangular support pillar of unfragmented formation in an excavation in a subterranean formation, such a pillar having opposed long free faces, comprising the steps of: forming a plurality of spaced apart vertical columnar explosive charges substantially along the centerline between the opposed long free faces of the pillar, a plurality of equal squares being defined across the entire horizontal cross-section of the pillar by the centerline and by lines perpendicular to the centerline which pass through a first portion of the explosive charges along the centerline, the perpendicular lines extending to the edges of the pillar; forming a vertical columnar explosive charge at about the center of each square; forming the second portion of the explosive charges along the centerline at about the intersection of the centerline and lines perpendicular to the centerline which extend between the explosive charges at about the center of adjacent squares; and detonating explosive in the support pillar for expanding the pillar about equally toward the opposed long free faces.

Claim 23

A method for explosively expanding a support pillar having a generally square horizontal cross-section of unfragmented formation in an excavation in a subterranean formation, comprising the steps of: forming an array of spaced apart vertical columnar explosive charges in the pillar and detonating a portion of the explosive charges for expanding a first portion of the pillar toward the void, leaving a second portion of the pillar in the void, the second portion having a generally rectangular horizontal cross-section and opposed long free faces, a plurality of such explosive charges remaining substantially along the centerline of the second portion of the pillar between the opposed long free faces, a plurality of equal squares being defined across the entire horizontal cross-section of the pillar by the centerline and lines extending to the edges of the pillar perpendicular to the centerline which pass through a first portion of the explosive charges along the centerline, a vertical columnar explosive charge being at about the center of each square and at about the intersection of the centerline and lines perpendicular to the centerline which extend between explosive charges at about the center of adjacent squares; and detonating explosive in the second portion of the pillar for explosively expanding the second portion about equally toward the opposed long free faces.

Claim 24

A method for explosively expanding a support pillar having a generally square horizontal cross-section of unfragmented formation in an excavation in a subterranean formation, comprising the steps of: forming an array of spaced apart vertical columnar explosive charges in the pillar and detonating a portion of the explosive charges for expanding a first portion of the pillar toward the void, leaving a second portion of the pillar in the void, the second portion having a generally rectangular horizontal cross-section and opposed long free faces, a plurality of such explosive charges remaining substantially along the centerline of the second portion of the pillar between the opposed long free faces, a plurality of equal squares being defined across the entire horizontal cross-section of the pillar by the centerline and lines extending to the edges of the pillar perpendicular to the centerline which pass through a first portion of the explosive charges along the centerline, a vertical columnar explosive charge being at about the center of each square and at about the intersection of the centerline and lines perpendicular to the centerline which extend between explosive charges at about the center of adjacent squares; and detonating explosive in the second portion of the pillar for explosively expanding the second portion about equally toward the opposed long free faces.

Claim 27

A method for explosively expanding a support pillar having a generally square horizontal cross-section of unfragmented formation in an excavation in a subterranean formation, such a support pillar having a first pair of opposed free faces and a second pair of opposed free faces, comprising the steps of: forming a first vertical columnar explosive charge at about the center of the pillar and a plurality of spaced apart second vertical columnar explosive charges spaced apart from the first explosive charge substantially along a first centerline between the first pair of opposed free faces and substantially along a second centerline between the second pair of opposed free faces, sixteen equal squares being defined across the entire horizontal cross-section of the pillar by the first and second centerlines, by lines extending to the edges of the pillar perpendicular to the first centerline which pass through the center of each second charge on the first centerline and by lines extending to the edges of the pillar perpendicular to the second centerline, which pass through the center of each second charge on the second centerline; forming a vertical columnar explosive charge at about the corner of each of the four interior squares located about on diagonal lines from the center of the pillar to each of its corners; forming a vertical columnar explosive charge in each of the four interior squares located about on a diagonal line from the center of the pillar to its corner at a distance from the center of the pillar no greater than about one-half the diagonal dimension of such an interior square; and detonating explosive in the support pillar for expanding the pillar about equally toward the free faces.

Claim 28

A method for explosively expanding a support pillar having a generally square horizontal cross-section of unfragmented formation in an excavation in a subterranean formation, such a support pillar having a first pair of opposed free faces and a second pair of opposed free faces, comprising the steps of: forming a first vertical columnar explosive charge at about the center of the pillar and a plurality of spaced apart second vertical columnar explosive charges spaced apart from the first explosive charge substantially along a first centerline between the first pair of opposed free faces and substantially along a second centerline between the second pair of opposed free faces, sixteen equal squares being defined across the entire horizontal cross-section of the pillar by the first and second centerlines, by lines extending to the edges of the pillar perpendicular to the first centerline which pass through the center of each second charge on the first centerline and by lines extending to the edges of the pillar perpendicular to the second centerline, which pass through the center of each second charge on the second centerline; forming a vertical columnar explosive charge at about the corner of each of the four interior squares located about on diagonal lines from the center of the pillar to each of its corners; forming a vertical columnar explosive charge in each of the four interior squares located about on a diagonal line from the center of the pillar to its corner at a distance from the center of the pillar no greater than about one-half the diagonal dimension of such an interior square; and detonating explosive in the support pillar for expanding the pillar about equally toward the free faces.

Claim 31

A method for explosively expanding a generally rectangular support pillar of unfragmented formation in an excavation in a subterranean formation comprising the steps of: forming an array of spaced apart vertical columnar explosive charges in such a pillar and detonating a portion of the charges for explosively expanding a first portion of the pillar toward the void, leaving a second portion of the pillar in the void, the second portion having a generally square horizontal cross-section, and a first and second pair of opposed free faces, there being: a first vertical columnar explosive charge at about the center of the pillar and a plurality of second vertical columnar explosive charges spaced apart from the first explosive charge substantially along a first centerline between the first pair of opposed free faces and substantially along a second centerline between the second pair of opposed free faces, sixteen equal squares being defined across the entire horizontal cross-section of the second portion by the first and second centerlines, lines extending to the edges of the pillar perpendicular to the first centerline which pass through about the center of each second charge on the first centerline and lines extending to the edges of the pillar perpendicular to the second centerline which pass through about the center of each second charge on the second centerline; a vertical columnar explosive charge at about the corner of each of the four interior squares located on diagonal lines from the center of the second portion of the pillar to each of its corners; a vertical columnar explosive charge in each of the four interior squares located about on a diagonal line from the center of the second portion of the pillar to its corner at a distance from the center of the second portion of the pillar no greater than about one-half the diagonal dimension of such an interior square; and detonating explosive in the second portion of the support pillar for expanding the pillar equally toward each of the opposed free faces.

Claim 32

A method for explosively expanding a generally rectangular support pillar of unfragmented formation in an excavation in a subterranean formation comprising the steps of: forming an array of spaced apart vertical columnar explosive charges in such a pillar and detonating a portion of the charges for explosively expanding a first portion of the pillar toward the void, leaving a second portion of the pillar in the void, the second portion having a generally square horizontal cross-section, and a first and second pair of opposed free faces, there being: a first vertical columnar explosive charge at about the center of the pillar and a plurality of second vertical columnar explosive charges spaced apart from the first explosive charge substantially along a first centerline between the first pair of opposed free faces and substantially along a second centerline between the second pair of opposed free faces, sixteen equal squares being defined across the entire horizontal cross-section of the second portion by the first and second centerlines, lines extending to the edges of the pillar perpendicular to the first centerline which pass through about the center of each second charge on the first centerline and lines extending to the edges of the pillar perpendicular to the second centerline which pass through about the center of each second charge on the second centerline; a vertical columnar explosive charge at about the corner of each of the four interior squares located on diagonal lines from the center of the second portion of the pillar to each of its corners; a vertical columnar explosive charge in each of the four interior squares located about on a diagonal line from the center of the second portion of the pillar to its corner at a distance from the center of the second portion of the pillar no greater than about one-half the diagonal dimension of such an interior square; and detonating explosive in the second portion of the support pillar for expanding the pillar equally toward each of the opposed free faces.