Abstract: Sulfur dioxide is removed from a process gas by passing the process gas through a first fragmented permeable mass of particles containing treated oil shale and including alkaline earth metal oxides at a sufficient temperature to remove sulfur dioxide from the process gas. Gas containing sulfur dioxide from the first fragmented mass is passed through a second fragmented permeable mass of particles containing treated oil shale and including alkaline earth metal oxides. Water in the second fragmented mass combines with alkaline earth metal oxides in the second fragmented mass and sulfur dioxide in the gas from the first fragmented mass with resultant removal of sulfur dioxide from gas from the first fragmented mass.

Abstract: Liquid and gaseous products are recovered from oil shale in an in situ oil shale retort containing a fragmented permeable mass of particles containing oil shale by retorting oil shale in the fragmented mass to produce gaseous and liquid products. The liquid products are withdrawn from the retort to a first level in unfragmented formation below the elevation of the bottom boundary of the retort. Gaseous products are withdrawn from the retort to a second level below the elevation of the first level.

Abstract: Leaching of water-soluble constituents from particles containing treated oil shale and including oxides of alkaline earth metals, such as particles in an in situ oil shale retort, is inhibited by contacting the particles with carbon dioxide in the presence of water for a sufficient time to produce a substantially water-insoluble and/or impermeable barrier of carbonates of alkaline earth metals at the surface of the particles.

Abstract: 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.

Abstract: To recover liquid and gaseous products from a fragmented permeable mass of particles containing oil shale, a buffer zone containing retorted oil shale is established in the fragmented mass by passing a hot processing gas substantially free of free oxygen through at least a portion of the fragmented mass. Thereafter, a combustion zone is established in the buffer zone, and a combustion zone feed containing oxygen is introduced into the fragmented mass on the trailing side of the combustion zone. This advances the combustion zone through the fragmented mass and retorts oil shale in a retorting zone on the advancing side of the combustion zone. The thickness of the buffer zone is sufficient for reaction of most of the oxygen in the combustion zone feed with residual carbonaceous material in retorted oil shale in the buffer zone.

Abstract: Sulfur dioxide is removed from a gas stream by passing the gas through retorted oil shale particles containing alkaline earth metal oxides.

Abstract: The hydrogen sulfide concentration of a gas of relatively higher hydrogen sulfide concentration is reduced by introducing the gas to a fragmented permeable mass of oil shale for contacting the oil shale in the substantial absence of free oxygen. This yields a gas with relatively lower hydrogen sulfide concentration which is withdrawn from the fragmented permeable mass of oil shale.

Abstract: The locus of a processing zone advancing through a fragmented permeable mass of particles in an in situ oil shale retort in a subterranean formation containing oil shale is determined by monitoring pressure in the retort. Monitoring can be effected by placing a pressure transducer in a well extending through the formation adjacent the retort and/or in the fragmented mass such as in a well extending into the fragmented mass.

Abstract: Values are recovered from a subterranean in situ oil shale retort containing a fragmented permeable mass of formation particles by passing a measuring gas through the retort to determine the presence of a blockage in the fragmented mass. If there is such a blockage, only a portion of the fragmented mass is processed and the portion of the fragmented mass having the blockage is left unprocessed. This is effected by introducing a processing gas to the retort at an intermediate location between opposing ends of the fragmented mass and withdrawing gaseous and liquid products of processing at an end of the fragmented mass remote from such blockage.

Abstract: 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.

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. An open base of operation is excavated in the formation at an elevation above the fragmented mass to be formed, and an access drift is excavated to provide access to the bottom of the retort site. Formation is explosively expanded to form the fragmented mass between the access drift and an elevation spaced below the bottom of the base of operation, leaving a horizontal sill pillar of unfragmented formation between the top of the fragmented mass and the bottom of the base of operation. The sill pillar provides a safe base of operation above the fragmented mass after it is formed. The fragmented mass is formed by, among other steps, drilling blasting holes from the base of operation down through the sill pillar and then detonating explosive in such holes to form the fragmented mass of particles in the retort below the sill pillar.

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 heating it to a temperature of at least about 120.degree. F. and holding at a temperature in the range of from about 120.degree. to 180.degree. F. for about one day. Preferably the shale oil and water are held in the range of from about 130.degree. to 150.degree. F. for about one day and the phases separated by gravity. Heat for the process can be obtained by injecting water into a spent in situ oil shale retort for generating steam and transferring heat from the steam to the emulsion.

Abstract: A technique is provided for forming, in a subterranean deposit containing oil shale, an in situ oil shale retort having boundaries of unfragmented deposit containing a fragmented permeable mass of particles containing oil shale. The technique is particularly useful where at least a portion of the deposition layers of the oil shale deposit within the boundaries of the retort being formed are bonded together as a competent or relatively strong bed resistant to fragmenting. A portion of the deposit within the boundaries of the retort being formed is excavated to form a void with a free face within the boundaries. A second portion of the deposit within the boundaries extending away from the free face includes at least one competent bed. At least one competent bed within the boundaries is fractured substantially parallel to the deposition layers for reducing the effective thickness of the competent bed.

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

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

Abstract: Sulfur dioxide is removed from a process gas by passing the process gas through a fragmented permeable mass of particles containing treated oil shale and including alkaline earth oxides. Water in the fragmented mass combines with alkaline earth oxides in the fragmented mass and sulfur dioxide in the process gas with resultant removal of sulfur dioxide from the process gas.

Abstract: A combustion zone is advanced through an in situ oil shale retort containing a fragmented permeable mass of oil shale particles by introducing into the retort on the trailing side of the combustion zone: water, at least sufficient fuel to vaporize the water, and sufficient oxygen to oxidize the fuel for vaporizing the water and to form a gaseous combustion zone feed containing water vapor and oxygen. The gaseous combustion zone feed is for introduction into the combustion zone to advance the combustion zone through the fragmented mass of particles and produce combustion gas in the combustion zone.

Abstract: The hydrogen sulfide concentration of a gas is reduced by reacting hydrogen sulfide in the gas with oxygen in the presence of raw oil shale. The ratio of sulfur dioxide to sulfur produced by this reaction depends upon the molar ratio of oxygen to hydrogen sulfide present. Sulfur is the predominant product when hydrogen sulfide is reacted in the presence of oil shale with less than about 1 mole of oxygen for each 2 moles of hydrogen sulfide.

Abstract: The hydrogen sulfide concentration and total sulfur concentration of a gas of relatively higher hydrogen sulfide and total sulfur concentration are reduced by combining hydrogen sulfide in the gas with oxygen in the presence of a fragmented permeable mass of particles containing oil shale treated to remove organic materials to yield a gas with relatively lower hydrogen sulfide and total sulfur concentration for withdrawal from the fragmented permeable mass.

Abstract: The locus of a processing zone advancing through a fragmented permeable mass of particles in an in situ oil shale retort in a subterranean formation containing oil shale is determined by monitoring for sound produced in the retort, preferably by monitoring for sound at at least two locations in a plane substantially normal to the direction of advancement of the processing zone. Monitoring can be effected by placing a sound transducer in a well extending through the formation adjacent the retort and/or in the fragmented mass such as in a well extending into the fragmented mass.