Occidental Oil Shale, Inc.

Occidental Petroleum

Science Applications International Corporation

Gordon B French

Richard D Ridley

Chang Y Cha

Harry E McCarthy

Robert S Burton, Iii

Donald E Garrett

William J Bartel

Eugene A Mills

Melvin A Cook

David E Miall

Kanaan Hanna

Following the conventional mining of rich oil shale for conventional above ground retorting, by horizontally extensive room and pillar mining operations, additional shale oil and related product may be secondarily recovered from the oil shale formation by in-situ retort formation and combustion. The secondary recovery steps would involve initially the identification of a large horizontally extending area, normally located between barrier pillars, which may be blocked off for the in-situ retort. Suitable shale oil drain arrangements may then be provided along one lower edge of this in-situ retorting area. Along the opposite lower edge of the in-situ retorting area, conduits may be provided for withdrawing product gas from the retort area. The retort area may then be sealed, and rubblized by blasting the pillars and caving in the roof to provide the appropriate 15% to 30% void volume for in-situ retorting. Conduits for input air to the rubblized retort volume may be provided along an upper edge of the rubblized volume, diagonally opposed from the product gas conduits, and above the shale oil drainage removal point. The retorting of the rubblized volume, which extends horizontally for a substantially greater distance than its vertical extent, is characterized by a diagonal direction of combustion extending from the air input conduits to the product gas outlet conduits.

Secondary oil shale recovery technique

A ventilation and process air distribution system is provided for an in situ oil shale retort system which includes a production region having a cluster of retorts producing gaseous and liquid products and a retort preparation region where in situ retorts are being prepared for production. An underground air delivery drift system distributes process air to the production region and ventilation air to underground workings in the retort preparation region. A liquid collection drift system extends at or below the bottoms of the retorts in the production region and in the retort preparation region. The liquid collection drifts connect to an exhaust airway leading above ground and having an induction fan for inducing ventilation air to flow through the retort preparation region at a pressure lower than ambient air pressure above ground. A gas collection level located below the retorts connects to a product gas way leading above ground and having a centrifugal fan for withdrawing off gas from the retorts in the production region at a pressure lower than that of the ventilation air, which continually draws process air from the air delivery drifts into active retorts to promote combustion in the retorts. The suction produced in the exhaust airway and the product gas airway continually draws fresh air into an inlet airway at ambient air pressure above ground for distribution as process air and ventilation air.

Ventilation air and process air distribution for in situ oil shale

A subterranean formation containing oil shale is prepared for in situ retorting by initially excavating a plurality of vertically spaced apart voids within a retort site, leaving an intervening zone of unfragmented formation between an adjacent pair of such voids. The intervening zone has substantially parallel upper and lower horizontal free faces adjoining the voids. At least one pancake-shaped load of explosive is placed in the intervening zone. The pancake-shaped explosive load has faces which are substantially parallel to the upper and lower free faces, and the length of the axis of the explosive load is less than the radius of the load. The explosive load is detonated for explosively expanding formation toward the upper and lower free faces for forming an in situ retort containing a fragmented permeable mass of formation particles. In one embodiment, a plurality of such pancake-shaped explosive charges are placed at horizontally spaced apart locations at substantially the same level and approximately in the middle of the intervening zone, and the explosive charges are detonated in a single round of explosions for forming the fragmented mass.

Placement of explosive for forming in situ oil shale retort

An in situ oil shale retort is formed in a subterranean oil shale deposit by excavating a columnar void having a vertically extending free face, drilling blasting holes adjacent to the columnar void, loading the blasting holes with explosive, and detonating the explosive in a single round to expand the shale adjacent to the columnar void toward the free face to fill with fragmented oil shale the columnar void and the space in the in situ retort originally occupied by the expanded shale prior to the expansion. A room having a horizontal floor plan that coincides approximately with the horizontal cross section of the retort to be formed is excavated so as to intersect the columnar void. The room can lie above the columnar void, below the columnar void, or intermediate the ends of the columnar void. The expanded or fragmented shale has a low average void volume. The void volume of the fragmented shale increases at the bottom of the in situ retort. In one embodiment the higher void volume is obtained since the ratio of the cross-sectional area of the columnar void to the horizontal cross-sectional area of the retort is decreased near the bottom. Backfilling part of a void with fragmented shale prior to explosive expansion provides a high void volume in another embodiment. In an embodiment with a room at the bottom of the columnar void, shale in one region can expand downwardly toward the room as well as toward the columnar void and hence has a higher void volume than a region where shale expands only toward the columnar void.

In situ recovery of shale oil

A fragmented recovery zone in a subterranean ore seam has a polygonal cross section with a low void volume and a conical funnel-shaped bottom with a high void volume. Recovered constituents are removed from the recovery zone at the point of convergence of the funnel.

In-situ recovery of constituents from fragmented ore

An in situ oil shale retort is formed in a subterranean formation containing oil shale and including underground workings by excavating a means for access to a retort site in the formation, excavating a void in the retort site at least in part from the means for access, leaving a remaining portion of the unfragmented formation in the retort site adjacent the void, placing explosive in the remaining portion of formation, and detonating the explosive in such unfragmented formation in a single round to explosively expand formation toward the void for forming a fragmented permeable mass of formation particles containing oil shale in an in situ retort. A permeable barrier is provided between the void and the underground workings which provide means for access to such a void. The permeable barrier has a cross-section for gas flow which is substantially smaller than the transverse cross-section of such means for access, and the cross-section of such permeable barrier temporarily confines gas from such explosive expansion and limits flow of such gas to such means for access to attentuate airblast in underground workings. A fragmented permeable mass of formation particles produced during excavation of the void can provide such a permeable barrier.

Method of attenuating airblast from detonating explosive in an in situ

A subterranean formation containing oil shale is prepared for in situ retorting by initially excavating at least one void adjacent a zone of unfragmented formation to be expanded. The zone of unfragmented formation has a substantially horizontal free face adjoining the void. At least one support pillar of unfragmented formation is left in the void for supporting overlying formation. Explosive is placed in the zone of unfragmented formation, and in such a support pillar. Explosive in such a pillar and in the zone of unfragmented formation is detonated in a single round of explosions with a time delay between detonation of explosive in such a pillar and detonation of explosive in the zone of unfragmented formation for first expanding such a pillar toward the void and then expanding unfragmented formation toward the void. The time delay is sufficient for creation of free face at the juncture of such a pillar and the zone of unfragmented formation. The time delay is preferably short enough that explosive in the zone of unfragmented formation is detonated before particles formed by explosive expansion of the pillars have come to rest on the floor of the void. The fragmented permeable mass of formation particles so formed in an in situ oil shale retort is then retorted to recover shale oil from oil shale in the fragmented mass.

Removal of pillars from a void for explosive expansion toward the void

The locus of a processing zone advancing through a fragmented permeable mass of particles in an in situ oil shale retort in a subterranean formation containing oil shale is determined by withdrawing a sample of gas passing through the retort through a channel through unfragmented formation and in fluid communication with the retort, and analyzing the composition of withdrawn gas. The channel can be artificially formed such as by hydraulic fracturing of unfragmented formation, or can be a naturally occurring permeable layer such as a tuff bed in the formation containing oil shale.

Determining the locus of a processing zone in a retort through channels

A tunnel is formed above an in situ oil shale retort in a subterranean deposit containing oil shale. A void is excavated in the retort site and remaining deposit in the retort site is fragmented by explosively expanding toward the void to form a subterranean cavity containing a fragmented permeable mass of particles containing oil shale. The top of the fragmented mass is spaced downwardly from the tunnel to leave therebetween a pillar of unfragmented deposit. A retorting gas is introduced into the retort through a plurality of sloping passages from the tunnel for retorting oil shale in the fragmented mass. The liquid and gaseous products of such retorting are removed from the bottom of the retort. A portion of the carbonaceous products are used for generating electricity. In working a large area of deposit, a plurality of retorts are arranged in rows and columns. The tunnel is part of a tunnel system communicating with the tops of the retorts and having a peripheral double entry tunnel surrounding the rows and columns of retorts. Tunnel systems are also provided at a level adjacent the bottom of the retorts and at a level between the bottom and top.

Method for in situ recovery of liquid and gaseous products from oil

A subterranean formation containing oil shale is prepared for in situ retorting by initially excavating a pair of spaced apart voids, leaving an intervening zone of unfragmented formation between the voids. The intervening zone has substantially parallel free faces adjoining the void. A plurality of elongated blasting holes are formed in the intervening zone of unfragmented formation, the longitudinal axis of each blasting hole being substantially perpendicular to the parallel free faces of the intervening zone. At least two deck loads of explosives are placed in each blasting hole, with each load being longitudinally spaced apart from each adjacent load by stemming. The loads of explosive are then detonated in a single round of explosions with a time delay between adjacent loads for expanding formation in the intervening zones toward both voids. The fragmented mass of formation particles is then retorted to recover shale oil from the oil shale.

Explosive placement for explosive expansion toward spaced apart voids

A row of horizontally spaced apart in situ oil shale retorts is formed in a subterranean formation containing oil shale. Each row is formed by excavating at least a pair of upper and lower retort access drifts at elevations within the top and bottom boundaries of the retort sites. The access drifts extend through opposite side boundaries of a plurality of retorts in such row. Each retort is formed by excavating upper and lower horizontal voids at the levels of the upper and lower retort access drifts, respectively, such voids being excavated laterally from the access drift within the side boundaries of the retort sites. Each retort is formed by explosively expanding formation toward the upper and lower voids within the boundaries of the retort site to form a fragmented permeable mass of particles containing oil shale in each retort. Following formation of each retort, the retort access drifts on the advancing side of the retort are at least partially sealed, preferably with a mass of formation particles covered by a gas impermeable layer and backfilled with a further mass of formation particles.

Isolation of in situ oil shale retorts

An in situ oil shale retort is formed in a subterranean formation containing oil shale. The retort contains a fragmented permeable mass of particles containing oil shale. An open base of operation is excavated in the formation at an elevation above the fragmented mass to be formed, and an access drift is excavated to provide access to the bottom of the retort site. Formation is explosively expanded to form the fragmented mass between the access drift and an elevation spaced below the bottom of the base of operation, leaving a horizontal sill pillar of unfragmented formation between the top of the fragmented mass and the bottom of the base of operation. The sill pillar provides a safe base of operation above the fragmented mass after it is formed. The fragmented mass is formed by, among other steps, drilling blasting holes from the base of operation down through the sill pillar and then detonating explosive in such holes to form the fragmented mass of particles in the retort below the sill pillar. During retorting, gas is introduced into the fragmented mass through such blasting holes for establishing a combustion zone in the fragmented mass and for advancing the combustion zone through the fragmented mass. The blasting holes have separate valves located in the base of operation for use in controlling gas flow through selected regions of the fragmented mass.

Subterranean in situ oil shale retort and method for making and

A row of horizontally spaced apart in situ oil shale retorts is formed in a subterranean formation containing oil shale. Each row is formed by excavating at least a pair of upper and lower retort access drifts at elevations within the top and bottom boundaries of the retort sites. The access drifts extend through opposite side boundaries of a plurality of retorts in such row. Each retort is formed by excavating upper and lower horizontal voids at the levels of the upper and lower right access drifts, respectively, such voids being excavated laterally from the access drift within the side boundaries of the retort sites. Each retort is formed by explosively expanding formation toward the upper and lower voids within the boundaries of the retort site to form a fragmented permeable mass of particles containing oil shale in each retort. Following formation of each retort, the retort access drifts on the advancing side of the retort are at least partially sealed, preferably with a mass of formation particles covered by a gas impermeable layer and backfilled with a further mass of formation particles.

Method of forming in situ oil shale retorts

In raise bore drilling, a drill string of non-round cross-sectional configuration is connected through a pilot hole from a raise bore bit at the lower end of the pilot hole to a raise bore drilling rig at the upper end of the hole. The drill string is defined by a number of serially connected individual pipe lengths. The drill string configuration preferably is hexagonal except at one end of each length where the pipe length is round for a distance which corresponds to the length of a female threaded connection component defined by that end of the pipe length. The other end of each pipe length defines a cooperating male threaded connection component.

Raise bore drilling

An in situ oil shale retort is formed in a subterranean oil shale deposit by excavating a columnar void having a vertically extending free face, drilling blasting holes adjacent to the columnar void and parallel to the free face, loading the blasting holes with explosive, and detonating the explosive in a single round to expand the shale adjacent to the columnar void toward the free face in layers severed in a sequence progressing away from the free face and to fill with fragmented oil shale the columnar void and the space in the in situ retort originally occupied by the expanded shale prior to the expansion. A room having a horizontal floor plan that coincides approximately, with the horizontal cross section of the retort to be formed is excavated so as to intersect the columnar void. The blasting holes are drilled and loaded with explosive from the room. The room can lie above the columnar void, below the columnar void, or intermediate the ends of the columnar void. In one embodiment, the columnar void is cylindrical and the blasting holes are arranged in concentric rings around the columnar void. In another embodiment, the columnar void is a slot having one or more large parallel, planar vertical free faces, toward which the oil shale in the retort under construction can be explosively expanded. The blasting holes are arranged in planes parallel to these faces. The resulting retort generally has a cross section coinciding with the placement of the blasting holes and a height determined for the greater part by the vertical height of the columnar void. To form a retort having a large cross-sectional area, a plurality of columnar voids can be excavated and the shale in the retort expanded toward the respective columnar voids to form a continuous fragmented permeable mass of oil shale.

Growing community of inventors

Bakersfield, CA, United States of America

Gordon B French