Occidental Oil Shale, Inc.

Ned M Hutchins

Irving G Studebaker

Thomas E Ricketts

Richard D Ridley

Leon G Holbrook

J Walter Enyeart

Rudolf Kvapil

In situ oil shale retorts are formed in spaced apart rows, with adjacent rows of such retorts being separated by load-bearing barrier pillars of unfragmented formation sufficiently strong for preventing substantial subsidence at the ground surface. Each retort contains a fragmented permeable mass of formation particles containing oil shale. Separate air level drifts are excavated on an upper level of the retorts within alternating barrier pillars, and separate production level drifts are excavated at a lower production level of the retorts within intervening barrier pillars between the barrier pillars having the air level drifts. Each air level drift extends between a pair of adjacent rows of retorts adjacent upper edges of the retorts in the adjacent rows, and each production level drift extends between a pair of adjacent rows of retorts adjacent lower edges of the retorts on sides of the retorts opposite the air level drifts. During retorting operations, air is introduced along the upper edge of each retort through lateral air inlet passages extending from the adjacent air level drift. Off gas and liquid products are withdrawn from each retort through one or more lateral production level passages extending from the lower edge of the retort to the adjacent production level drift. Withdrawal of off gas along the lower edge of each retort opposite the upper edge where air is introduced causes a generally diagonal flow pattern of combustion gas through the fragmented mass from one upper edge toward the opposite lower edge of the retort.

In situ oil shale retort system

Formation is excavated from within the boundaries of a retort site in formation containing oil shale for forming at least one retort level void extending horizontally across the retort site, leaving at least one remaining zone of unfragmented formation within the retort site. A production level drift is excavated below the retort level void, leaving a lower zone of unfragmented formation between the retort level void and the production level drift. A plurality of raises are formed between the production level drift and the retort level void for providing product withdrawal passages distributed generally uniformly across the horizontal cross section of the retort level void. The product withdrawal passages are backfilled with a permeable mass of particles. Explosive placed within the remaining zone of unfragmented formation above the retort level void is detonated for explosively expanding formation within the retort site toward at least the retort level void for forming a fragmented permeable mass of formation particles containing oil shale within the boundaries of the retort site. During retorting operations products of retorting are conducted from the fragmented mass in the retort through the product withdrawal passages to the production level void. The products are withdrawn from the production level void.

Fluid outlet at the bottom of an in situ oil shale retort

A module of in situ oil shale retorts are formed in a row of retort sites in a subterranean formation. Each retort has top, bottom, and side boundaries of unfragmented formation and contains a fragmented permeable mass of formation particles. Two cross drifts are excavated through the retort sites along the row. One of the drifts is at a lower elevation near the floor of voids to be formed in the retort sites and along one side boundary of the retort sites. The other drift ramps upwardly at an end of the row for extending through the retort sites at a higher elevation near the roof of the voids excavated in the retort sites and along the opposite side boundaries of the retort sites. A horizontally extending slice is excavated at the elevation of the higher drift extending substantially to the side boundaries of a retort site for commencing a void within the retort site. The balance of the void is formed by benching from the slice to the elevation of the lower drift. This leaves at least one zone of unfragmented formation remaining in the retort site with a horizontally extending free face adjacent to the void. Such a zone of formation is explosively expanded toward the void for forming a fragmented permeable mass of formation particles in the retort.

Method for forming a module of in situ oil shale retorts

A non-subsidence method for developing an in situ oil shale retort tract in a subterranean formation containing oil shale includes forming a number of spaced apart rows of in situ oil shale retorts, leaving intervening zones of unfragmented formation between adjacent rows of retorts for supporting the overburden loads without substantial subsidence. Each retort contains a fragmented permeable mass of formation particles containing oil shale. The retorts in each row are separated by gas barriers that provide support for the overburden load above each row of retorts. After retorting, a stabilizing material is introduced into the void spaces in the spent in situ oil shale retorts for increasing the compressive strength of the fragmented masses of spent oil shale particles in the spent in situ retorts. Thereafter, separate rows of in situ oil shale retorts are formed in corresponding intervening zones of unfragmented formation. The retorts in each intervening row are separated by gas barriers that provide partial support for the overburden load above each row of intervening retorts. Separate barriers of unfragmented formation are left between the retorts in each intervening row and adjacent rows of spent retorts. This shifts the overburden load to the spent retorts and to the intervening barriers of unfragmented formation, as well as to the barriers of formation between individual retorts in the intervening rows of retorts, which collectively support overburden loads without substantial subsidence during the operating life of the retorts in the intervening rows.

Non-subsidence method for developing an in situ oil shale retort

An in situ oil shale retort is formed in a subterranean formation containing oil shale. Formation is excavated from within a retort site for forming a plurality of vertically spaced apart voids extending horizontally across different levels of the retort site, leaving a separate zone of unfragmented formation between each pair of adjacent voids, and leaving one or more pillars within each void for providing temporary roof support for unfragmented formation above each void. A plurality of horizontally spaced apart vertical blast holes are drilled in each zone of unfragmented formation below the voids. A pillar within a first void is offset horizontally from at least a portion of a pillar in a second void excavated directly below the first void. This provides an access region in the first void above at least a portion of the pillar in the second void so that vertical blast holes can be drilled into a zone of unfragmented formation below the pillar in the second void from the access region in the first void. Explosive is placed in the blast holes and such explosive in detonated for explosively expanding the zones of unfragmented formation toward the voids for forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort. By horizontally offsetting pillars in adjacent voids, a combination of upwardly drilled and downwardly drilled blast holes can be used to place explosive throughout a zone of unfragmented formation between such voids.

In situ oil shale retort having horizontally offset pillars

An array of in situ oil shale retorts is formed in a development region in a subterranean formation containing oil shale. At least one void is excavated in each retort site, and remaining formation within each retort site is explosively expanded toward the void for forming a fragmented permeable mass of formation particles containing oil shale in each in situ retort. Overburden loads over an area of the development region are carried largely by the fragmented masses and partly by unfragmented partitions between retorts. Subsidence of overburden following explosive expansion is controlled at the boundary of the development region to avoid an abrupt change in the overburden load supported largely by the fragmented masses inside the boundary and the overburden load supported by unfragmented formation outside the boundary. Subsidence can be controlled by providing a gradual transition in overburden load support inside the boundary by progressively decreasing the proportion of horizontal area of formation explosively expanded to form the fragmented masses as the fragmented masses approach the boundary. This can be achieved by progressively reducing the area of the fragmented masses, or progressively spacing the fragmented masses farther apart, or both.

Subsidence control at boundaries of an in situ oil shale retort

Oil shale formation is explosively expanded toward a limited void volume for forming an in situ oil shale retort in a subterranean formation containing oil shale. In one embodiment, a void in the form a narrow vertical slot is excavated within a retort site, leaving at least one portion of unfragmented formation within the retort site adjacent a vertical free face of the slot. Explosive is placed in a row of vertical blasting holes in the remaining portion of unfragmented formation adjacent the vertical free face. The blasting holes are mutually spaced apart along the length of the slot, and the row of blasting holes extends generally parallel to the vertical free face. Explosive in the blasting holes is detonated in a time delay sequence starting near one end of the slot and progressing along the length of the slot for explosively expanding formation in the remaining portion of unfragmented formation toward the vertical free face for forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort.

Method of detonating explosives for fragmenting oil shale formation

An in situ oil shale retort is formed in a subterranean formation containing oil shale. Underground workings excavated within the formation provide a means for access to a retort site in the formation. At least one void is excavated in the retort site via access provided by the underground workings, leaving a remaining portion of the unfragmented formation within the retort site adjacent the void. Explosive placed in the remaining unfragmented formation adjacent such a void is detonated in a single round for explosively expanding the unfragmented formation toward such a void for forming a fragmented permeable mass of formation particles containing oil shale. Prior to such explosive expansion, a barrier of unfragmented formation is left between such a void and underground workings providing means for access to such a void. At least one gas flow passage extends through the barrier of unfragmented formation between the means for access and the retort site. Such a gas flow passage has a substantially smaller cross-section for gas flow than the transverse cross-section of the means for access to the retort site. The smaller cross-section of such a gas flow passage temporarily confines the high gas pressure generated by the explosion and limits the flow of gas to the means for access for attenuating airblast in the means for access and other underground workings in gas communication with the means for access.

Control of airblast during explosive expansion in an in situ oil shale

Oil shale formation is explosively expanded toward a limited void volume for forming an in situ oil shale retort in a subterranean formation containing oil shale. In one embodiment, a void in the form of a vertical slot is excavated within a retort site, leaving at least one portion of unfragmented formation within the retort site adjacent a vertical free face of the slot. Explosive is placed in at least two rows of vertical blasting holes in the remaining portion of unfragmented formation adjacent the vertical free face. The blasting holes in each row are mutually spaced apart along the length of the slot and longitudinally offset from blasting holes in the next adjacent row, and the row of blasting holes extends generally parallel to the vertical free face. Explosive in the blasting holes is detonated in a time delay sequence starting near one end of the slot and progressing along the length of the slot for explosively expanding formation in the remaining portion of unfragmented formation toward the vertical free face for forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort.

Staggered array of explosives for fragmented oil shale formation toward

A group of spaced apart in situ oil shale retorts is formed in a subterranean formation containing oil shale. At least one void is excavated in each retort site, and remaining formation within each retort site is explosively expanded toward such a void for forming a fragmented permeable mass of formation particles containing oil shale in each retort. A vertically extending partition of substantially unfragmented formation forms a gas barrier between the fragmented masses in a pair of adjacent retorts. Such a gas barrier yields structurally but retains sufficient integrity to inhibit gas flow between the fragmented masses of adjacent retorts. Such a gas barrier is sufficiently thin that it independently supports substantially the same proportionate amount of load from overburden at elevations above the retorts as the fragmented masses on either side of the gas barrier. Subsidence of such a gas barrier is substantially the same as subsidence of adjacent fragmented masses, permitting uniform subsidence of overburden.

In situ oil shale retorts with gas barriers for maximizing product

A bridging plug for a circular blast hole has a relatively longer major axis and a relatively shorter minor axis. The plug is hinged to pivot about the minor axis. A tension line is secured to the minor axis for lowering the plug into an explosive placement hole. The plug pivots into an angular open position when lowered into the hole. An upward force on the tension line jams the hinged portions of the plug in a closed position to plug the hole. An explosive charge can be placed in the hole at the location defined by the closed plug.

Hinged bridging plug for explosive placement holes

An in situ oil shale retort is formed in a subterranean formation containing oil shale. The retort with top, bottom and side boundaries contains a fragmented permeable mass of particles containing oil shale. A base of operation is excavated at a working level in the formation. Means are excavated through the formation for access to a location underlying the base of operation. In one embodiment, a void in the form of a vertical slot is excavated in the site between the means for access and an elevation below the bottom of the base of operation, leaving a remaining portion which is to be expanded toward the void. This is designed to leave a horizontal sill pillar of intact formation between the top of the void and the bottom of the base of operation with a vertical thickness sufficient to maintain a safe base of operation after explosive expansion of formation to form the fragmented permeable mass of particles. The void provides at least one free face extending vertically through the formation within the boundaries of the in situ oil shale retort site. This remaining portion is explosively expanded toward the void with a single round of explosions.

Growing community of inventors

Grand Junction, CO, United States of America

Ned M Hutchins