Abstract: A flame front is ignited and passed through an underground oil shale retort to produce shale oil. The flame front is supported by a specially blended feed gas consisting essentially of air, steam and retort off gases. Product yield and quality are increased by varying the volumetric ratio of air, steam and retort off gases in the feed gas during retorting in proportion to the oil yield, or the relative richness, leanness and kerogen content of the oil shale being heated by the flame front, or in proportion to the amount of carbon residue on the retorted shale being combusted.

Abstract: A method for forming an in situ oil shale retort in a subterranean formation containing oil shale is provided. The in situ oil shale retort has top, bottom, and generally vertically extending side boundaries of unfragmented formation and contains a body of expanded oil shale formation that completely fills the retort to its top boundary. The retort is bulked full by explosively expanding a layer above a fragmented permeable mass of formation particles forming part of the body of expanded formation in the retort. The layer is expanded with an available void fraction of no more than about ten percent.

Abstract: A method for recovering liquid and gaseous products from an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale is provided. A hot ignition gas comprising oxygen at a first selected concentration is introduced into the fragmented mass for heating the fragmented mass top surface. The percentage of the fragmented mass surface that is at a temperature no less than the ignition temperature of oil shale is determined. Thereafter, the concentration of oxygen in the ignition gas is increased by an amount proportional to the determined percentage. Such heating of the fragmented mass top surface establishes a combustion zone in the retort. After the combustion zone has spread horizontally across the retort, introduction of the hot ignition gas is discontinued. Thereafter, an oxygen-supplying gas is introduced into the retort for advancing the combustion zone downwardly through the fragmented mass.

Abstract: A method for initiating combustion in a subterranean carbonaceous deposit by positioning at least two wellbores from the surface into the subterranean deposit; extending a first borehole substantially horizontally from a first wellbore into the vicinity of a second wellbore; extending a second borehole substantially horizontally from a second wellbore into the vicinity of the first wellbore; positioning an explosive charge in at least one of the boreholes; detonating the explosive charge to produce a rubblized zone between the first wellbore and the second wellbore; injecting a free-oxygen containing gas into the carbonaceous deposit through one of the wellbores; and igniting the carbonaceous deposit at one of the wellbores.

Abstract: Method for the underground gasification of solid fuels in which an underground fuel deposit is initially opened up and then converted into a gaseous fuel by means of a gasification medium. The opening of the fuel deposit is effected by treatment with a gas which is in the supercritical state, which takes on the volatile organic substances of the solid fuel and the water contained in the solid fuel. The dissolved organic compounds and the water are separated from the charged supercritical gas phase above ground in at least two fractions by pressure reduction and/or a change in temperature.

Abstract: An in situ oil shale retort is formed in a subterranean formation containing oil shale. The formation comprises at least one region of relatively richer oil shale and another region of relatively leaner oil shale. According to one embodiment, formation is excavated from within a retort site for forming at least one void extending horizontally across the retort site, leaving a portion of unfragmented formation including the regions of richer and leaner oil shale adjacent such a void space. A first array of vertical blast holes are drilled in the regions of richer and leaner oil shale, and a second array of blast holes are drilled at least in the region of richer oil shale. Explosive charges are placed in portions of the blast holes in the first and second arrays which extend into the richer oil shale, and separate explosive charges are placed in portions of the blast holes in the first array which extend into the leaner oil shale.

Abstract: A method for igniting an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale is provided. A void space is in the retort between the top surface of the fragmented mass and the top boundary of overlying unfragmented formation. A hot ignition gas comprising oxygen is introduced into the void space to form a combustion zone across the surface of the fragmented mass. An oxygen-supplying gas is then introduced into the void space for sustaining the combustion zone and for advancing the combustion zone downwardly through the retort. The combustion zone is then extinguished and a cool inert gas is introduced into the retort to cool carbonaceous materials comprising the surface of the fragmented mass to a temperature below the self-ignition temperature of such carbonaceous materials, while leaving carbonaceous materials below the fragmented mass surface at temperatures greater than the self-ignition temperature of such materials.

Abstract: A method for forming an in situ oil shale retort in a retort site in a subterranean formation is provided. The in situ oil shale retort contains a fragmented permeable mass of oil shale particles formed within top, bottom, and side boundaries of the retort site. At least one void is excavated in the subterranean formation within the boundaries of the retort site, while a zone of unfragmented formation is left within the boundaries of the retort site adjacent such a void. An inlet is formed in a zone of the retort adjacent the intersection of a first side boundary of the retort site and the top boundary of the retort site and an outlet is formed in a zone of the retort adjacent the intersection of a second side boundary of the retort site and the bottom boundary of the retort site. The second side boundary is on the opposite side of the retort site from the first side boundary.

Abstract: 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.

Abstract: A fragmented permeable mass of formation particles containing oil shale and having a substantially uniformly distributed void fraction is formed in an in situ oil shale retort in a subterranean formation containing oil shale. The fragmented mass is formed by explosive expansion towards a horizontal free face. At least one generally horizontally extending void is formed in the subterranean formation and zones of unfragmented formation are left above and below such a void. An array of horizontally spaced apart substantially vertical columnar explosive charges is formed in at least one of the zones of unfragmented formation. The array of explosive charges includes a plurality of central explosive charges which are spaced apart from side boundaries of the retort and a plurality of outer explosive charges surrounding the central charges.

Abstract: A portion of crude shale oil produced from an in situ oil shale retort is blended with shale oil produced from a Tosco II retorting process to produce a blended shale oil composition having a pour point lower than the pour point of the shale oil produced from the Tosco II retorting process.

Abstract: A method of controlled thermal linking of an injection well and a production well, both penetrating an underground formation, accomplished by injecting oxidant into the annulus of the injection well and fuel into the tubing of an injection well in stoichiometric proportions, and initiating a combustion zone at the production well which propagates along a predictable path in the formation which is a deviated or horizontal portion of the injection well.

Abstract: Product yield and quality is increased during in situ retorting of oil shale by pulsed combustion in which the flow of feed gas to the flame front is intermittently stopped while continuously retorting the oil shale. A purge gas can be injected into the retort between pulses of feed gas to enhance transfer of sensible heat from the combustion zone to the retorting zone and enlarge the separation between the combustion zone and the advancing front of the retorting zone.

Abstract: An in situ retort and process are provided for underground retorting of oil shale. The in situ retort is formed with at least one flame front-stabilizing layer of minute lean oil shale particles which serves as a redistribution region or grid. When the flame front is ignited and passed through the retort with a feed gas, the flame front-stabilizing layer will stabilize and enhance horizontal uniformity of the flame front to substantially minimize burning of the product shale oil.

Abstract: An in situ process and ignition procedure are provided to retort oil shale which increases product yield and enhances uniformity of the flame front in an underground retort. In the process, a portion of the rubblized mass of oil shale is preheated with steam, nitrogen or some other inert gas, to at least the minimum oil shale ignition temperature and preferably retorted. Thereafter, the preheated oil shale is ignited with hot excess air or some other oxygen-containing gas above the maximum desired retorting temperature to establish a generally uniform flame front across the retort. In the preferred form, the preheating gas and oxygen-containing gas are introduced into the retort at different times from the same specially configured downhole burner.

Abstract: A process for enlarging or widening rock fractures in order to facilitate the recovery of deposits, such as oil or gas, comprising the emplacement of an aluminothermic mixture of aluminum and ferric oxide, and its subsequent ignition. Preferably, slag-forming products are also placed into the cavity, so as to prevent closure of the fractures after termination of the combustion process.

Abstract: An array of explosive charges is formed in a retort site in a subterranean formation containing oil shale. The explosive charges that are located around the perimeter of the retort site are smaller than the explosive charges located more remote from the perimeter. Formation within the retort site is explosively expanded toward a void formed in the site by detonating the explosive charges. This explosive expansion of formation results in a fragmented permeable mass of formation particles in the retort. Damage to objects near the retort site, which is caused by seismic shock from the detonations, is minimized by using smaller explosive charges around the perimeter than in the center of the retort site.

Abstract: Hot retorting gas for pyrolysis of kerogen in a bed of rubblized oil shale is supplied by a pressure pulsing technique.

Abstract: This invention is a comminution process for treating coal with a drying gas to form fractures which weaken the structure of the coal and make it easier to disintegrate mechanically, chemically or by fluid force. Another aspect of this invention is a process for treating an underground formation of coal with a dry gas for a time sufficient to form cracks and fractures in a portion of the formation in order to increase the permeability of the coal formation to the flow of fluids therethrough. Processes for in-situ combustion of the coal formation are therefore more efficient since the coal formation is more permeable to the flow of gas therethrough.

Abstract: A method for controlling the flow of subterranean water into a selected zone in a permeable subterranean carbonaceous deposit by injecting an aqueous plugging material into the permeable deposit through a plurality of wells to produce a plurality of injected areas of a size such that the injected areas overlap to form a barrier to the flow of subterranean water into the selected zone.

Abstract: Oil shale is retorted, preferably in situ, by passing velocity flow of super-heated air through one or more conduit-like passages in direct contact with exposed surfaces of oil shale. Kerogen pyrolysis products are recovered by condensation of the vapors and collection of the condensate and by collection of the gases and separation of the valuable gases from the normally waste gases. Some of the waste gases may be recycled with the air for controlling combustion of the kerogen content of the shale.

Abstract: There is provided a process for recovery of metal values from an ore body containing sulfide minerals. The ore body is fractured for increasing its permeability. The fractured ore body is then roasted in situ to increase the permeability and porosity of ore body to liquid leach solutions. The roasted sulfide minerals in the ore body are thereafter contacted with a leach solution to extract metal values therefrom and the extracted metal values are recovered.

Abstract: 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 which is ignited by introducing fuel and air through a passage leading to the fragmented mass. The amount of air provided is in the range of from about 1/3 more than the amount of air required to stoichiometrically combine with the fuel to about twice the amount of air required to stoichiometrically combine with the fuel. The fuel/air mixture is ignited and hot combustion gases pass downwardly into the fragmented mass. The hot combustion gases heat oil shale particles above the self-ignition temperature of such particles, thereby forming a primary combustion zone in the fragmented mass. Introduction of fuel is discontinued when the concentration of oxygen in off gas from the retort decreases to below a first selected value.

Abstract: In-situ retorting methods include forming an in-situ mass of rubblized, hydrocarbon-containing minerals covering at least part of that mass with a nonflammable liquid such as water, uncovering part of the mass and retorting to produce hydrocarbon values from that part, and then progressively or sequentially uncovering other parts of the mass and retorting hydrocarbons from those parts. Methods for forming highly permeable rubblized masses include forming a retorting zone in a kerogen-bearing formation wherein two walls of the retorting zone form a low angle to one another, and cleaving oil shale from the upper wall beginning near the intersection of the two walls and proceeding upwardly.

Abstract: Hydrocarbon liquids and/or gases are recovered from thick underground deposits of oil-bearing limestone or dolomite by drilling two or more boreholes from the earth's surface into the lower part of the deposit, establishing communication between the boreholes, burning the oil in said limestone or dolomite in an area between the boreholes to decompose the alkaline earth carbonate into alkaline earth oxide, flushing out the alkaline earth oxide formed by the combustion with water to form a cavity, collapsing the overlying oil-bearing limestone or dolomite into the cavity to form a rubblized zone extending vertically to a point near the upper boundary of the deposit, driving a flame front vertically through the rubblized zone to liberate hydrocarbon liquids and produce gases, and recovering the liquids and/or gases from the rubblized zone.

Abstract: A method is provided for flattening a non-planar combustion zone which is advancing through a fragmented permeable mass of formation particles in an in situ oil shale retort. To effect flattening of the non-planar combustion zone, a fragmented permeable mass of formation particles having generally horizontally extending layers of various void fraction is provided in the in situ retort. At least one layer has a substantially higher effective average void fraction than adjacent layers above and below this layer. When the advancing non-planar combustion zone enters the high void fraction layer, it spreads laterally across the layer. The resulting combustion zone is approximately flat in a plane transverse to its direction of advance when it exits the high void fraction layer.

Abstract: Disclosed are a method and apparatus for the in situ retorting of oil shale and purification products comprising establishing an underground in situ retort containing a mass of rubblized matter comprising oil shale and establishing a flame front within the rubblized matter. Oxygen containing gas comprising at least about 90 weight percent oxygen and diluent are passed into the retort to support combustion and form combustion gases suitable for the retorting of the rubblized mass and formation of off-gas comprising hydrogen, hydrocarbons, and contaminants. Off-gas comprising hydrogen, hydrocarbons, and contaminants is recovered from the retort and hydrocarbons and contaminants are substantially separated from at least a portion of the off-gas to produce a purified gas stream comprising hydrogen.

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 is determined by monitoring in a well extending through unfragmented formation adjacent the retort, for condition in the retort affected by the advancement of such a processing zone through the retort. Monitoring can be effected by placing means for monitoring such a condition in such a well extending through unfragmented formation adjacent the retort.

Abstract: Disclosed is a method for controlling the flame front during the in situ combustion of a subterranean carbonaceous stratum which involves monitoring the extent and movement of said flame front to determine the location of one or more segments of the flame front which exhibit unfavorable combustion characteristics, and injecting one or more gases into the vicinity of one or more of said segments to control and optimize the combustion in said segment.

Abstract: Disclosed is a method for controlling the flame front during the in situ combustion of a subterranean carbonaceous stratum which involves monitoring the extent and movement of said flame front to determine the location of one or more segments of the flame front which exhibit unfavorable combustion characteristics, and injecting one or more gases into the vicinity of one or more of said segments to control and optimize the combustion in said segment.

Abstract: An in situ oil shale retort in a subterranean formation contains a fragmented permeable mass of formation particles. Such a fragmented mass is formed by excavating a horizontally extending void within the boundaries of the retort, leaving a zone of unfragmented formation above and/or below such a void. A plurality of vertical blasting holes are drilled in such a zone and loaded with explosive charges for forming an array of explosive charges sufficiently close together to interact and fragment formation substantially to a plane at the ends of the charges remote from the void. The scaled depth of burial of such an array is in the range of from about 6 to 12 mm/cal.sup.1/3. The explosive charges are detonated in a single round for expanding such a zone towards the void for forming the fragmented mass of particles in the retort.

Abstract: There is provided a method of forming an in situ oil shale retort in a retort site within a subterranean formation containing oil shale. The in situ oil shale retort contains a fragmented permeable mass of formation particles. A first portion of formation is excavated from within the boundaries of the retort being formed to form at least one void. The surface of the formation defining such a void provides at least one free face extending through the formation. The second portion of formation is left within the boundaries of the retort being formed to be explosively expanded toward the void.At least two arrays of explosive charges are formed in the second portion of formation wherein the first array of explosive charges has a first burden distance and the second array of explosive charges has a second burden distance wherein the second burden distance is less than the first burden distance.

Abstract: Disclosed is a method for the underground retorting of oil shale comprising introducing retorting fluid from a first direction into a retort containing rubblized mass comprising oil shale until the mass is substantially retorted; and then introducing oxygen containing gas from a second direction substantially opposite to the first direction to combust with coke or hydrocarbonaceous materials in the rubblized mass and retort a portion of unretorted rubblized mass.

Abstract: A process for recovering hydrocarbon products from a body of fragmented or rubblized oil shale. The process includes initiating a combustion zone adjacent the lower end of a body of oil shale and using the thermal energy therefrom for volatilizing the shale oil from the oil shale above the combustion front. Improved recovery of hydrocarbon products is realized by refluxing the heavier fractions in the volatilized shale oil. The heavier fractions are refluxed by condensing the heavier fractions and allowing the resulting condensate to flow downwardly toward the combustion front. Thermal energy from the combustion zone cracks the condensate producing additional lower molecular weight fractions and a carbonaceous residue. The carbonaceous residue is burned in the combustion front to supply the thermal energy. The temperature of the combustion front is maintained by regulating input of oxygen to the combustion zone.

Abstract: Disclosed is a method for controlling the flame front during the in situ combustion of a subterranean carbonaceous stratum which involves monitoring the extent and movement of said flame front to determine the location of one or more segments of the flame front which exhibit unfavorable combustion characteristics, and injecting one or more gases into the vicinity of one or more of said segments to control and optimize the combustion in said segment.

Abstract: Disclosed is a method for controlling the flame front during the in situ combustion of a subterranean carbonaceous stratum which involves monitoring the extent and movement of said flame front to determine the location of one or more segments of the flame front which exhibit unfavorable combustion characteristics, and injecting one or more gases into the vicinity of one or more of said segments to control and optimize the combustion in said segment.

Abstract: In the underground gasification of a swelling coal the high gas-flow link between the injection and the production wells needed for the gasification process is produced by reverse combustion using air heated to a temperature below the softening point of the coal. The heated air pretreats and conditions the coal proximate to the link under formation by increasing its permeability and reducing its swelling properties. Improved combustion and suppression of plugging results in the subsequent gasification stage.

Abstract: An in situ coal gasification process adapted for large scale commercial projects is provided. Techniques are provided to insure establishment of a gasification front over the full seam thickness as each successive injection well in the array is brought on line. This is accomplished by controlling the oxidant introduction in a prescribed manner during the early stages of injection after pneumatic communication between well pairs has been established. Also provided are techniques and standards for avoiding or controlling subsidence and for conducting gasification operations in free water laden seams and in coal seams subject to spontaneous combustion.

Abstract: In the underground gasification of a swelling coal the high gas-flow link between the injection and the production wells is produced by introducing hot air into the injection well at a pressure sufficient to fracture the coal. The bulk permeability of the coal proximate to the link is increased and the plugging of the link during the subsequent in situ combustion and gasification procedure is suppressed by continuing the injection of the hot air, heated to a temperature below the softening point of the coal, into the injection well, through the link to the production well without combustion of the coal.

Abstract: In the underground gasification of a swelling coal the bulk permeability of the coal proximate to the linkage between the injection and the production holes is increased and the plugging of the linkage during the in situ combustion and gasification procedure is suppressed by subjecting this coal proximate to the linkage between the injection and production holes to a stream of air heated to a temperature below the softening point of the coal prior to the in situ combustion and gasification procedure.

Abstract: An in situ oil shale retort is formed in a subterranean formation containing oil shale, a horizontally extending void is excavated within the boundaries of the retort site leaving a zone of unfragmented formation above and/or below such a void, at least one pillar of unfragmented formation is left within the side boundaries of such a void for providing temporary support for overburden above the void, such a pillar is explosively expanded so that a principal portion of the pillar fragments travel to the side boundaries of the void and such a zone of unfragmented formation is explosively expanded toward the void. Accumulation of sufficient pillar fragments adjacent the side boundaries of the retort can substantially offset a tendency for fragments of the expanded zone of formation to form a mound thereby forming a fragmented permeable mass of formation particles within the retort with a reasonably flat upper surface. Such a fragmented permeable mass is retorted in situ to produce shale oil.

Abstract: A method for the in situ processing of mineral-bearing oil shale ore includes the establishment of a plurality of underground stopes by removing from each a portion of the oil shale ore therein, rubblizing the remaining ore in each stope, extracting the rubblized ore and crushing it to obtain a nahcolite fraction and an oil shale fraction having a desired particle size for subsequent processing, and restoring sized oil shale particles to the stope by back filling the stope as the rubble is extracted so as to maintain the stope substantially filled with particles to provide lateral support to the side walls and reduce the likelihood of caving in the stope. The nahcolite fraction is recovered from the crushed ore prior to backfilling of the stopes for retorting to recover shale oil, while soda ash and alumina may be recovered from the spent shale by leaching the stopes after retorting.

Abstract: An in situ oil shale retort is formed in a subterranean formation containing oil shale. A void can be formed in formation within the retort site by directing fluid under pressure against a zone of relatively weakened formation, such as tuffs, gravel beds, or fractured oil shale, to erode such weakened formation into particle form, leaving a void space adjacent a remaining zone of unfragmented formation within the retort site. The void space can be formed by drilling a bore hole into the zone of weakened formation, placing a jet nozzle in the bore hole, and forcing a fluid such as water through the nozzle against the weakened formation for eroding it to form the void space. Eroded formation particles are passed to the bottom of the bore hole. Such water jetting techniques can be used to form voids in zones of weakened formation interspersed throughout the retort site.

Abstract: Disclosed is a method for controlling the flame front during the in situ combustion of a subterranean carbonaceous stratum which involves monitoring the extent and movement of said flame front to determine the location of one or more segments of the flame front which exhibit unfavorable combustion characteristics, and injecting one or more gases into the vicinity of one or more of said segments to control and optimize the combustion in said segment.

Abstract: 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.

Abstract: A method for preparing a shale oil deposit for in situ retorting includes providing a drilling and process control level above the deposit with a substantial thickness of personnel isolating and protecting formation between the deposit and the level, providing a collecting and pumping level below the deposit with a substantial thickness of personel isolating and protecting formation between that level and the deposit, and excavation providing voids affording fragmentation of shale in the retorting zones reached from the collecting level. The shale excavated to provide the voids is transported through access risers to the collecting level; closures serving as sumps and protective gratings for the sumps are installed in the upper ends of the risers. Introduction of combustion gases from the control level is accomplished through drill holes provided for this purpose, some of the drill holes also being provided with control or detecting devices.

Abstract: 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.

Abstract: Kerogen and other combustible matter can be extracted from an area of oil shale or tarsand by drilling boreholes in a selected pattern through the overlying soil and rock without removing it. Each borehole mouth is tightly closed by a cover provided with an air inlet pipe and a gas exhaust pipe. In the covers of one or several boreholes, the inlet pipe is centrally guided and longitudinally movable in an upward and downward direction, and a laser beam generated by a laser source is inroduced into the upper end of the pipe and directed centrally to its bottom where it is diverted toward the borehole wall by a mirror assembly. The laser beam moved along the borehole wall irradiates the oil shale or tarsand and ignites the combustible matter contained therein which liquefies and evaporates. Combustion spreads from the initially ignited bore to the remaining bores in the area through the fissures in the formation and likewise serves to liquefy and evaporate the kerogen there.

Abstract: 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.

Abstract: In situ shale oil recovery from oil shale deposits using radio frequency energy as a heat generator is facilitated by rubblizing the shale oil deposits before application of radio frequency energy.