Abstract: An in situ oil shale retort is formed in a subterranean formation containing oil shale. Such an in situ oil shale retort contains a fragmented permeable mass of formation particles containing oil shale including a lower moiety and an upper moiety of said fragmented mass. The fragmented permeable mass of formation particles has top, bottom and side boundaries. A first portion of the formation is excavated from within the boundaries of the fragmented mass being formed to form a void. A second portion of the formation is excavated from within the boundaries of the fragmented mass being formed to form at least one additional void in communication with the first void and leaving a third portion to be expanded toward such an additional void. Fragmented particles from the excavation of such an additional void are deposited in the first void to provide a lower moiety of the fragmented permeable mass of formation particles.

Abstract: A method for recovering liquid and gaseous products from an in situ oil shale retort in a subterranean formation containing oil shale is disclosed. The method is practiced on an in situ oil shale retort having a plurality of fragmented permeable masses of formation particles with an upper and at least one lower fragmented mass. A zone of unfragmented formation intervenes between such fragmented masses and has a plurality of vertically extending holes for distributing fluid from the fragmented mass above to the fragmented mass below the zone of unfragmented formation. A processing gas is introduced to the upper fragmented mass and an off gas is withdrawn from the lower fragmented mass establishing a retorting zone in the upper fragmented mass and advancing the retorting zone downwardly through the upper fragmented mass, through such holes in the zone of unfragmented formation, and into and through the lower fragmented mass.

Abstract: A method of forming an in situ oil shale retort with an open space or inlet plenum void between the top boundary of the fragmented permeable mass of oil shale particles and the unfragmented formation above the retort. The method comprises excavating at least one horizontal void in the formation, placing explosive into the unfragmented formation above and below the void, and then explosively expanding formation above the void prior to explosively expanding formation below the void. The additional time for expansion of formation above the void, as compared with that below the void, permits non-uniform expansion and leaves an open space over the top of the fragmented mass.

Abstract: A method is disclosed for recovering liquid and gaseous products from an in situ oil shale retort having a plurality of strata of formation extending through the retort site with at least one stratum of formation having a higher average kerogen content than the average kerogen content of the formation within the retort site. The method includes the steps of excavating at least one void within the retort site and explosively expanding unfragmented formation toward such a void for forming a fragmented permeable mass of formation particles containing oil shale. The fragmented mass has a lower portion and an upper layer containing fragmented particles substantially from the stratum of formation having a higher average kerogen content. The upper layer of the fragmented mass has a higher average kerogen content than the average kerogen content of the fragmented mass. The upper layer is ignited for establishing a combustion zone in the fragmented mass.

Abstract: A secondary combustion zone is established and its location controlled in a fragmented mass of particles containing oil shale in an in situ oil shale retort.A processing zone including a primary combustion zone is established in the retort by igniting a portion of the mass of particles. An oxygen supplying gas is introduced into the retort to advance the processing zone through the fragmented mass. If the primary combustion zone is not substantially planar or has not progressed uniformly, a secondary combustion zone is established upstream of the primary combustion zone by introducing into the retort a retort inlet mixture comprising fuel and at least sufficient oxygen for combustion of the fuel at a temperature no greater than the primary combustion zone temperature.The secondary combustion zone is caused to move upstream from its initial location in the in situ oil shale retort by reducing the ignition temperature of the retort inlet mixture.

Abstract: A processing zone advances through a fragmented permeable mass of particles containing oil shale in an in-situ oil shale retort in a subterranean formation containing oil shale. The retort has an effluent water passing therefrom. The effluent water carries a constituent which is formed, by advancement of the processing zone through the fragmented mass, from a precursor contained in the formation. In a first aspect of the invention, the locus of the processing zone is determined by assaying the formation at selected locations in the retort for content of the precursor before processing the selected locations, and effluent water from the retort is monitored for concentration of the selected constituent. For example, the nitrogen content of kerogen can be the precursor and effluent water from the retort can be monitored for the concentration of ammonia and/or ammonium sulfate produced by retorting of kerogen in the oil shale.

Abstract: 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.

Abstract: When processing a fragmented permeable mass of particles containing oil shale for recovering liquid and gaseous values, a portion of the oil shale is thermally metamorphosed. However, a zone of non-thermally metamorphosed particles can be left in the fragmented mass after completion of processing. To inhibit leaching by water of water-soluble constituents of such non-thermally metamorphosed particles, a heating fluid, such as a mixture of fuel and an oxygen-containing gas, is introduced to the fragmented mass containing non-thermally metamorphosed particles for heating at least a portion of the non-metamorphosed particles to a sufficiently high temperature for forming water-insoluble metamorphic minerals at at least the surfaces of such particles.

Abstract: 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.

Abstract: An in situ oil shale retort is formed in a subterranean formation containing oil shale. The retort contains a fragmented permeable mass of formation particles containing oil shale. During retorting, oxygen-supplying gas is introduced into an upper level of the fragmented mass for establishing a combustion zone and for advancing the combustion zone downwardly through the fragmented mass. Liquid and gaseous products, including shale oil and off gas, are withdrawn from a generally U-shaped production level drift at a lower level of the fragmented mass. Liquid in a lower portion of the U seals against the roof of the drift to provide a gas seal which inhibits passage of off gas from a first leg of the drift in communication with the retort to a second leg of the drift remote from the retort. A retaining wall in the second leg of the drift can provide lateral support for the liquid forming the gas seal, and help minimize the depth of excavation of the U-shaped drift.

Abstract: 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.

Abstract: In situ oil shale retorts are formed in formation containing oil shale by excavating at least one void in each retort site. Explosive is placed in a remaining portion of unfragmented formation within each retort site adjacent such a void, and such explosive is detonated in a single round for explosively expanding formation within the retort site toward such a void for forming a fragmented permeable mass of formation particles containing oil shale in each retort. This produces a large explosion which generates seismic shock waves traveling outwardly from the blast site through the underground formation. Sensitive equipment which could be damaged by seismic shock traveling to it straight through unfragmented formation is shielded from such an explosion by placing such equipment in the shadow of a fragmented mass in an in situ retort formed prior to the explosion.

Abstract: Liquid and gaseous products are recovered from an in situ oil shale retort containing a fragmented permeable mass of formation particles by establishing a combustion zone in the fragmented permeable mass of particles. The combustion zone is advanced through the fragmented mass of particles by introducing a retort inlet mixture comprising oxygen into the retort on the trailing side of the combustion zone. The retort inlet mixture is maintained at a sufficiently high temperature of at least 1150.degree. F. so that the temperature of at least a portion of the fragmented mass on the trailing side of the combustion zone is maintained at a temperature of at least 1150.degree. F. for increasing the yield of hydrocarbon products obtained from the retort.

Abstract: Formation is excavated from within a retort site in formation containing oil shale 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. Explosive is placed in each zone, and such explosive is detonated in a single round for forming an in situ retort containing a fragmented permeable mass of formation particles containing oil shale. The same amount of formation is explosively expanded upwardly and downwardly toward each void. A horizontal void excavated at a production level has a smaller horizontal cross-sectional area than a void excavated at a lower level of the retort site immediately above the production level void.

Abstract: An in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale is formed in a subterranean formation containing oil shale. To retort oil shale in the retort, a primary combustion zone is established in the fragmented mass. A primary combustion zone feed containing oxygen is introduced to the primary combustion zone for advancing the primary combustion zone through the fragmented mass. A secondary combustion zone is established in the fragmented mass on the trailing side of the primary combustion zone. A retort feed mixture is introduced into the secondary combustion zone. The retort feed mixture contains sufficient fuel and oxygen for maintaining the secondary combustion zone and for forming a primary combustion zone feed containing oxygen for advancing the primary combustion zone through the fragmented mass.

Abstract: An in situ oil shale retort is formed in a subterranean formation containing oil shale. The retort contains a fragmented permeable mass of formation particles containing oil shale. During retorting, oxygen-supplying gas is introduced into an upper level of the fragmented mass for establishing a combustion zone and for advancing the combustion zone through the fragmented mass. Liquid and gaseous products, including shale oil and off gas, are withdrawn from a sealed portion of a production level drift which extends laterally away from the lower level of the fragmented mass. A bulkhead sealed across the drift inhibits passage of off gas from behind the bulkhead to the portion of the drift on the side of the bulkhead opposite the fragmented mass. Off gas, shale oil and water are separately withdrawn from behind the bulkhead.

Abstract: An in situ oil shale retort in which a cavity filled with broken particles of oil shale is formed within the subsurface oil shale formation and air is forced down through the cavity to sustain combustion of the top layer of oil shale particles, the products of combustion being withdrawn at the bottom of the cavity. A plurality of exhaust pipes traverse the bottom of the cavity and extend out through the sealed entrance to the retort cavity. The pipes are supported above the floor of the cavity and have holes opening on the bottom side of the pipes through which the product gases are withdrawn from the cavity. Valves in each pipe control the flow so as to balance the flow distribution of air and exhaust gases through the retorting cavity.

Abstract: An in situ fragmented permeable mass of particles containing treated oil shale is formed by excavating a void in a subterranean formation containing oil shale, explosively expanding formation toward such a void to form a fragmented permeable mass of formation particles containing oil shale, and retorting the particles containing oil shale in the fragmented mass. Water containing impurities is introduced into such an in situ fragmented permeable mass of particles containing treated oil shale, i.e., retorted or combusted oil shale or both, for disposal, purification, or generation of steam. The water introduced can be water containing hydrocarbons such as process water from retorting oil shale or water containing suspended solids such as blowdown from a steam generator. When the fragmented permeable mass is still hot from retorting, steam is generated which can be withdrawn for use in oil shale recovery operations.

Abstract: 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.

Abstract: A technique is described for breaking the very strong emulsion of shale oil and water produced by an in situ oil shale retorting process so that separate shale oil and water phases can be recovered. The emulsion is broken by maintaining a volume of such emulsion at a bulk temperature of at least about 120.degree. F., and momentarily heating portions of emulsion to a temperature substantially higher than the bulk temperature of the emulsion. Preferably the emulsion of shale oil and water is held at a bulk temperature in the range of from about 120.degree. to 190.degree. F. in contact with heating means maintained in the range of from about 170.degree. F. to about 240.degree. F. Momentary localized heating of emulsion to a temperature substantially higher than the bulk temperature of the emulsion accelerates the breaking of the emulsion.