Abstract: Disclosed is a method and apparatus for controlling flame front advance in underground combustion of hydrocarbonaceous material by passing an oxidizing gas into the combustion area comprising providing a plurality of gas removal means positioned so that gas can be removed in the direction of the desired flame front advance; detecting flame front position in the combustion area; selectively removing gas from the retorting area in response to the detected flame front position through one or more of the gas removal means; so that flow of gas to portions of the flame front can be controlled, thereby controlling the advance of portions of the flame front in the desired manner. This method is especially useful in the underground in situ retorting of oil shale.

Abstract: A substantially flat combustion zone is established in a fragmented mass of particles containing oil shale in an in situ oil shale retort. By igniting a portion of the mass of particles, a heated zone including a combustion zone is established in the retort. For a first period of time, an oxidizing gas is introduced into the retort and heated zone at a rate sufficient to advance the heated zone through the fragmented mass. The locus of the combustion zone is monitored to determine if the combustion zone is substantially flat. If the combustion zone is not substantially flat, introduction of oxidizing gas into the retort is reduced temporarily for a second period of time to a rate such that the flow of heated gas through the retort for retorting oil shale in a retorting zone on the advancing side of the combustion zone is substantially reduced for a sufficient time to appreciably flatten the heated zone.

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, the retort is formed by excavating a narrow vertical slot diagonally across a retort site of rectangular horizontal cross-section, leaving separate triangular zones of unfragmented formation within the retort site on opposite sides of the diagonal slot. Explosive is placed in a plurality of vertical blasting holes drilled in each triangular zone of formation, and such explosive is detonated for explosively expanding formation within the triangular zones toward vertical free faces adjacent the slot for forming a fragmented permeable mass of formation particles containing oil shale.

Abstract: Magnesium values are leached from a fragmented mass containing combusted oil shale particles. Magnesium is leached selectively with respect to calcium compounds and silicates with aqueous solutions of a mixture of purgeable, acid-forming gases such as carbon dioxide with a minor proportion of sulfur dioxide. A two-stage leaching process can employ leachant with dissolved carbon dioxide and sulfur dioxide in a first stage and with a carbon dioxide containing solution in the substantial absence of sulfur dioxide in the second stage. An enriched solution containing magnesium values is withdrawn from the fragmented mass and magnesia is recovered from such enriched solution. In one embodiment a fragmented permeable mass of formation particles containing oil shale and carbonates of calcium and magnesium is formed in an in situ oil shale retort.

Abstract: This invention relates to methods and systems for recovering high viscosity oils, petroleum substances and other minerals from subsurface earth formations. In particular, one or more large diameter shaft holes are provided which preferably terminate in an enlarged subterranean chamber. A plurality of drill holes are provided, with perforated piping which extend radially from the chamber into the formation, and from which oil and the like may be recovered. It is a particular feature of this invention to provide means and methods for injecting a mixture of steam and a noncondensable gas into the drill holes, whereby the driving mechanism of the formation may be selectively maintained or enhanced at the same time the viscosity of the oil in the formation is reduced.

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 shale oil passing therefrom. The shale oil contains a constituent which is carried from the formation by advancement of the processing zone through the fragmented mass. To determine the locus of the processing zone, the formation is first assayed at selected locations in the retort for content of the constituent before processing the selected locations, and, during processing, shale oil from the retort is monitored for concentration of the constituent.Preferred constituents are the heavy metals such as iron, vanadium, and arsenic.

Abstract: The locus of a processing zone advancing through a fragmented permeable mass of formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and which generates an effluent fluid is determined by placing a radionuclide source for providing an identifiable radionuclide, and monitoring effluent fluid from the processing zone for presence of such radionuclide. The radionuclide source provides radionuclide at a predetermined temperature.

Abstract: The locus of a processing zone advancing through a fragmented permeable mass of formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and which generates an effluent fluid is determined by placing a halogen source in the permeable mass for providing an identifiable halogen and monitoring effluent fluid from the processing zone for presence of such halocarbon. The halogen source provides halogen at a predetermined temperature.

Abstract: An in situ oil shale retort contains a fragmented permeable mass of formation particles containing oil shale and has a primary combustion zone advancing through a first region having a first fluid flow path, and a second region having a second fluid flow path. The first and second paths have different gas permeabilities. An oxygen containing retort inlet mixture is introduced to the fragmented mass for advancing the primary combustion zone through the fragmented mass and for flow of gas along the first and second flow paths.To maintain a substantially flat primary combustion zone, gas flowing through the first fluid path is maintained at a first average temperature and gas flowing through the second fluid path is maintained at a sufficiently different average temperature to provide substantially equal rates of advancement of the combustion zone through the fragmented mass in the first and second regions.

Abstract: A method is provided for recovering shale oil from a subterranean formation containing oil shale. Unfragmented formation is prepared for explosive expansion to form an oil shale retort by excavating at least one limited void in the subterranean formation and forming an array of spaced apart blastholes in the formation. A substantially horizontal array of explosive charges is formed by placing explosive into each blasthole wherein the scaled point charge depth of burial of the explosive charge in each blasthole is substantially equal to the equivalent scaled point charge depth of burial of the array of the explosive charges. Explosive charges are detonated in a single round for explosively expanding the unfragmented formation to form the in situ oil shale retort.Retorting is commenced and liquid and gaseous products of retorting are withdrawn from the retort.

Abstract: An improved method for the in situ recovery of methane from a plurality of coal seams beneath the earth's surface. At least one borehole is driven from the surface into a selected coal seam wherein a plurality of cavities are formed. The coal walls intermediate said cavities and the strata overlying said cavities are caused to collapse suddenly thereby forming fissure systems into the coal bearing rock strata from which methane is released. The methane is withdrawn via the fissure systems, cavities and the borehole. The cavities may be formed by chemical, physical or mechanical recovery of the coal.

Abstract: An in situ oil shale retort is formed with an upper surface of a fragmented permeable mass in the retort separated from a top boundary of unfragmented formation, creating an inlet plenum void. A primary combustion zone is established in the fragmented mass, and such primary combustion zone is caused to spread laterally by the establishment of a secondary combustion zone. During a first period of time, the temperature in the inlet plenum void is maintained at less than the temperature at which unfragmented formation from above the top boundary will slough into the void. The primary combustion zone is advanced through the retort and liquid and gaseous products of retorting are withdrawn. During a second period of time the temperature in the inlet plenum void is increased to increase the temperature of the top boundary of unfragmented formation to a temperature which will cause unfragmented formation from above the top boundary to slough into the void.

Abstract: Disclosed is an apparatus and method for the recovery of hydrocarbon values from underground hydrocarbonaceous deposits comprising forming an underground reaction zone containing a mass of rubblized hydrocarbonaceous material; forming an essentially surface reaction zone containing a mass of rubblized hydrocarbonaceous material in fluid communication with the underground reaction zone; forming an underground product collection zone for the gathering and collection of hydrocarbon values, said zone being in fluid communication with the surface and underground reaction zones; passing a suitable fluid capable of removing hydrocarbon values from the rubblized material through the surface and underground reaction zones so as to effectively remove hydrocarbon values from such material; and passing the hydrocarbon values to the underground collection zone for recovery.

Abstract: A fragmented permeable mass of formation particles containing oil shale and carbonates of calcium and magnesium is formed in an in situ oil shale retort. A combustion zone is advanced through the fragmented mass, whereby kerogen in oil shale in the fragmented mass is decomposed in a retorting zone on the advancing side of the combustion zone to produce gaseous and liquid products including shale oil. The combustion zone also converts the magnesium values in the particles of retorted oil shale to a more leachable form such as magnesium oxide. Magnesium values are selectively leached from the combusted particles, with respect to calcium compounds, with an aqueous solution of a purgeable, acid-forming gas such as carbon dioxide and a minor amount of a polyelectrolyte such as polyacrylic acid, polysulfonic acid, polyphosphonic acid, or the salts thereof. An enriched solution containing magnesium values is withdrawn from the fragmented mass and magnesia is recovered from such enriched solution.

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: 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.

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 for the recovery of products from nahcolite-bearing oil shale ore deposits which comprises, in pertinent part, in situ retorting of oil shale ore from which a major portion of the nahcolite has been separated.

Abstract: Shale oil is recovered from an underground oil shale deposit by in-situ retorting of rubblized shale in a retort formed in the deposit. Oil shale in a volume in the range of ten to fifty percent of the volume of the retort is mined from the deposit and delivered to the surface to provide void space for the expansion of the shale that occurs on rubblization to form the in-situ retort. The oil shale delivered to the surface is retorted at the surface. After completion of the in-situ retorting, boreholes are drilled downwardly through the retorted shale and a pipe lowered through the borehole to a level near the bottom of the retort. Spent shale from the surface retorting operation is slurried and pumped into the lower end of the in-situ retort. Pumping is continued to squeeze the slurry into the fissures between blocks of spent shale. The slurry is delivered into successively higher levels of the retort and the pumping and squeezing operation repeated at each level.

Abstract: The present method involves the initial mining of horizontally extending layers of oil-rich or "kerogen phase continuous" shale. The oil-rich shale is brought to the surface where it is retorted in above-ground retorts of one of the known types. The leaner oil shale which is still "in situ" is then explosively fragmented into the voids created when the oil-rich shale was mined, and oil is obtained as the fragmented shale is ignited, in accordance with known horizontal type modified in situ oil shale retorting techniques.

Abstract: Bituminous coal is processed in situ for the recovery of values therefrom by drilling at least one borehole into the underground deposit, introducing a solvent for inclusions of resinous and other uncarbonized vegetable matter present in the coal, which solvent may or may not also be effective in some degree to dissolve carbonaceous matter, removing the solvent pregnant with the dissolved matter, so as to leave a substantially permeable area of coal in the deposit at and adjacent to the end of the borehole, igniting the coal at the end of the borehole, and removing products of combustion from the permeablized area while introducing a combustion-supporting gas into the area for advancing a heat front through the permeablized area.

Abstract: A method for elevating extremely large blocks of earth by displacement with a slurry composed of water and locally excavated materials. The blocks are separated on lateral faces by variously drilling, jetting, fracturing, and kerf cutting operations. The blocks are separated at the lower end by notching and hydraulic fracturing. Block movement is started by injecting gelled fluid into the narrow separations.In one set of applications the high density slurry filling the side clearances is less dense than the block being elevated. In these cases the earth blocks are displaced upward by injecting fluid into the underside, and the non hydrostatic component of the displacement pressure is contained by the gel strength of the slurry filling the narrow side clearance. In a second set of applications the blocks being elevated contain a high percentage of coal, and slurry filling the side clearances exceeds the block density. The blocks are then displaced upward by hydrostatic pressure.

Abstract: The method of thermal-mine recovery of oil and fluent bitumens or kerogens includes providing a system of mine workings above an oil-bearing formation and drilling from these workings and from the ground surface a series of injection wells into the oil-bearing formation. An operation gallery is provided within the oil-bearing formation, from which a system of horizontal and inclined recovery wells is drilled. Then a heat carrier is positively injected into the oil-bearing formation to heat it to a temperature whereat the oil attains the required fluidity within the formation. Then a fluid is charged into the formation to force the oil from the oil-bearing formation into the horizontal and inclined recovery wells, toward the operation gallery, from which the oil is directed to the ground surface.

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 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: A method for maximizing shale oil recovery from an underground oil shale formation which has previously been processed by in situ retorting such that there is provided in the formation a column of substantially intact oil shale intervening between adjacent spent retorts, which method includes the steps of back filling the spent retorts with an aqueous slurry of spent shale. The slurry is permitted to harden into a cement-like substance which stabilizes the spent retorts. Shale oil is then recovered from the intervening column of intact oil shale by retorting the column in situ, the stabilized spent retorts providing support for the newly developed retorts.

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: A method of oil recovery by thermal mining from oil deposit sections into which the mine field is divided, according to which a plurality of underground workings are provided ensuring a successive recovery of oil from the mine field sections. The plurality of underground workings include intake and development wells. Thereupon, an overall mine ventilation system is set up ensuring the ventilation of the workings. Prior to the supply of heating medium to the development wells, the flow of heating medium is throttled. Then, the throttled heating medium flow is force-fed via pipes into the development wells for heating the oil bed to the temperature at which oil assumes the required fluidity in the oil bed. A fluid medium is then force-fed to the intake wells to force oil from the oil bed into the development wells and pump it up to the surface.

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: An in-situ retort is formed in an oil shale deposit by a sublevel caving method in which the starting slot for the sublevel caving is at opposite ends of the retort on adjacent sublevels. Any zones of high permeability that are formed adjacent to the starting slots are limited in vertical extent to the vertical spacing of the sublevels and are spaced from the zones of high permeability in adjacent sublevels by the length of the retort. A source of channeling through the retort that is caused by the usual sublevel caving mining method is thereby eliminated.

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: An in situ oil shale retort having a top boundary of unfragmented formation and containing a fragmented permeable mass has a pocket at the top, that is, an open space between a portion of the top of the fragmented mass and the top boundary of unfragmented formation. To establish a combustion zone across the fragmented mass, a combustion zone is established in a portion of the fragmented mass which is proximate to the top boundary. A retort inlet mixture comprising oxygen is introduced to the fragmented mass to propagate the combustion zone across an upper portion of the fragmented mass. Simultaneously, cool fluid is introduced to the pocket to prevent overheating and thermal sloughing of formation from the top boundary into the pocket.

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: A carbonaceous deposit is retorted in an array of in-situ retorts comprising rectangular retorts arranged in rows. Adjacent rows of retorts are separated by an unbroken pillar extending the length of the rows. The bottoms of the in-situ retorts slope downwardly from a first side to the opposite side. An exhaust tunnel for the deliver of products from the retort located below the bottom of the retort extends longitudinally of the row with its outer wall approximately in alignment with, but not extending laterally beyond, the pillar to maintain the integrity of the pillar. The system is especially advantageous in the retorting of oil shale and is described in detail for that application.

Abstract: A crude shale oil is produced by in situ retorting of oil shale in a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort in a subterranean formation containing oil shale. A combustion zone is advanced through the fragmented mass by introducing an oxygen containing gas to the mass on the trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on the advancing side of the combustion zone. Gas flow advances the combustion zone through the fragmented mass and transfers heat of combustion to a retorting zone on the advancing side of the combustion zone. Kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including crude shale oil. Crude shale oil produced by such a process and having characteristics described herein is withdrawn from the fragmented mass on the advancing side of the retorting zone.

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 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 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: The subterranean fragmented and pervious zone is formed beneath an overburden which, as a first step of the process, is lifted as a substantially monolithic land mass to produce a void space and a free space proximate the rock to be fragmented, the raised overburden thus providing a substantially impervious lid or closure for the fragmented zone as formed by the present invention. Explosive charges are then placed proximate to and for blasting against the free face formed on raising the overburden. The charges are exploded to fragment the rock to distribute the space, thus producing fractured, pervious rubble-ized rock in a defined and enclosed zone. Different techniques are disclosed for the critical raising of the overburden and subsequent fragmenting of the rock.

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.

Abstract: A fragmented permeable mass of formation particles containing oil shale and carbonates of calcium and magnesium is formed in an in situ oil shale retort. A combustion zone is advanced through the fragmented mass, whereby kerogen in oil shale in the fragmented mass is decomposed in a retorting zone on the advancing side of the combustion zone to produce gaseous and liquid products including shale oil, and particles containing retorted oil shale are combusted for converting magnesium values to more leachable form such as magnesium oxide. Magnesium values are leached from the combusted particles selectively with respect to calcium compounds and silicates with aqueous solutions of a purgeable, acid-forming gas such as carbon dioxide or sulfur dioxide. An enriched solution containing magnesium values is withdrawn from the fragmented mass and magnesia is recovered from such enriched solution.

Abstract: Disclosed is a process for the in situ retorting of oil shale and energy recovery from generated off gases. An underground retort containing rubblized oil shale is subjected to retorting, thereby forming shale oil and off gases. The off gases are purified and burned in a gas turbine. Commonly this process comprises forming a subterranean in situ retort containing rubblized oil shale having a void space of about 5 to about 40 percent; passing a retorting gas through the in situ retort to effectively retort the oil shale and produce a mixture of shale oil and off gases; subjecting the mixture of shale oil and off gases to a preliminary separation to remove gross quantities of shale oil from the off gases; passing a portion of the off gases to a purification zone so as to remove off gas impurities which would be detrimental to the environment or the operation of downstream equipment; and passing a portion of the purified off gases to a gas turbine where said off gases are burned and power is generated.

Abstract: An in situ oil shale retort is formed in a subterranean formation containing oil shale. The formation comprises at least one stratum of relatively higher average kerogen content which is included in formation of relatively lower average kerogen content. A void is excavated in a retort site in the formation, leaving a remaining portion of unfragmented formation within the retort site adjacent the void. The portion of unfragmented formation within the retort site is explosively expanded toward the void to form a fragmented permeable mass of formation particles containing oil shale in an in situ retort in which fragmented formation particles from the stratum of higher kerogen content have a larger void fraction than the averge void fraction of the fragmented mass. This can be accomplished by enlarging the void in the vicinity of the stratum having the higher kerogen content prior to explosive expansion.