Abstract: The hydrogen sulfide concentration of a gas of relatively higher hydrogen sulfide concentration is reduced by combining at a temperature less than about 650.degree. F hydrogen sulfide in the gas with oxygen in the presence of a fragmented permeable mass of particles containing oil shale to yield a gas with relatively lower hydrogen sulfide concentration for withdrawing from the fragmented permeable mass.

Abstract: In a process for retorting oil shale in an situ oil shale retort having a tunnel adjacent the retort, off gas is produced. Leakage of the off gas into the tunnel is prevented by withdrawing off gas from the retort at a rate sufficient to reduce the pressure in the retort adjacent the tunnel to a pressure below the ambient pressure within the tunnel.

Abstract: A raise bore drilling rig is provided for use with a drill string of non-round cross-sectional configuration; the drill string is connectible through a pilot hole from a raise bore bit at the lower end of the pilot hole to the raise bore drilling rig at the upper end of the hole. To enable simple assembly of the drill string, the upper end of each length of drill string is circular in way of the female component of a threaded coupling. The drilling rig includes a rotary drive mechanism which mates with the non-round cross-section of individual lengths of drill string and which is rotatably driven to apply torque to the drill string as it is raised axially during the raise bore drilling process. The torque applying component of the drilling rig which is directly engageable with the drill string includes a vertically floating "bushing" which enables torque to be applied to the string as a coupling is raised through a normal "at rest" position of the bushing.

Abstract: A method of processing oil shale in which an in situ oil shale retort comprising an elongated cavity containing a fragmented permeable mass of formation particles containing oil shale is formed in a subterranean formation containing oil shale to recover liquid and gaseous products. Access to the cavity is by a drift or conduit at each end of the cavity and through a drift at an intermediate position. A processing zone is established in the fragmented mass at one end of the cavity and processing gas is introduced at that end of the retort and heating of the fragmented mass of formation particles is conducted from that end towards the other end. Initially, off gas is withdrawn at the intermediate drift. When the processing zone passes the intermediate drift, processing gas is introduced through the intermediate drift and off gas including gaseous products is withdrawn by way of the drift at the other end.

Abstract: An in situ oil shape retort is provided in a subterranean oil shale formation. An inlet gas access is provided to an end of the in situ retort through which gas is supplied to initiate and advance a retorting zone through the in situ retort for converting kerogen in the oil shale to liquid and gaseous products. A zone of fragmented oil shale fills the in situ retort and extends from the inlet gas access means to the product recovery end of the in situ oil shale retort. The zone of fragmented oil shale has a length from the inlet gas access means to the product recovery end of the in situ retort in the range of from about two to five times the width of the zone of fragmented oil shale and an average void fraction of about 10 to 25 percent of the volume of the zone of fragmented oil shale. In a preferred embodiment the in situ retort is vertical with a height between two and three times its width and the average void fraction is about 15%.

Abstract: An underground in situ oil shale retort, having predetermined boundaries, contains a bed of fragmented oil shale particles having an appreciable void volume distributed therethrough. Air passed through this bed of fragmented oil shale supports combustion of some of the carbonaceous material in the oil shale and provides heat for retorting oil therefrom. A number of such retorts may be formed in an area and pillars are left to support the overburden. Pillars forming walls between adjacent retorts also prevent gas leakage. Oil recovery from intact oil shale pillars is enhanced by fracturing the pillars as well as fragmenting the shale in the retort. The pillars are fractured by hydraulic fracturing, electrical fracturing, liquid explosive fissuring, or the like. The fractures are propagated from access holes in the vicinity of the pillars, typically between similar holes adjacent the next retort volume when the pillars are between retorts.

Abstract: A subterranean deposit containing oil shale is prepared for in situ retorting by initially excavating a plurality of vertically spaced apart voids of similar horizontal cross section located one above another within the deposit. A zone of unfragmented deposit temporarily left between each adjacent pair of voids has a thickness greater than the smallest lateral dimension of the voids above and below it. Explosive placed in a lower portion of the unfragmented zone is detonated to expand the lower portion of the unfragmented zone into the lower void, leaving the upper portion of the zone intact and creating a space free of fragmented particles below it. Thereafter, the remaining portion of the unfragmented zone is explosively expanded into the open space below it and into the upper void, forming a subterranean room filled with a fragmented mass of particles having a void volume substantially equal to the total initial volume of the voids.

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 and parallel to the free face, 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 in layers severed in a sequence progressing away from the free face and 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 blasting holes are drilled and loaded with explosive from the room. The room can lie above the columnar void, below the columnar void, or intermediate the ends of the columnar void.

Abstract: An in situ oil shale retort is formed in a subterranean oil shale deposit by excavating one or more slot-shaped columnar voids each having a pair of vertically extending, planar free faces, drilling blasting holes adjacent to the columnar void and parallel to the free faces, loading the blasting holes with explosive, and detonating the explosive in a single round to expand the shale adjacent to the columnar void one directionally toward each free face in one or more planar layers severed in a sequence progressing away from each free face and 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. The pair of free faces extend across the entire width (or length) of the retort being formed. 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.

Abstract: A subterranean deposit containing oil shale is prepared for in situ retorting by initially excavating a plurality of vertically spaced apart voids of similar horizontal cross section located one above another within the deposit. A plurality of vertically spaced apart zones of unfragmented deposit are temporarily left between the voids, each unfragmented zone having a thickness of less than about 190 percent of the smallest lateral dimension of the voids above and below it. Explosive placed in each of the unfragmented zones is detonated, preferably in a single round to expand each unfragmented zone into the voids on either side of it and form a subterranean room containing a fragmented mass of particles having a void volume equal to the void violume of the initial voids. Retorting of the expanded mass is then carried out to recover shale oil from the oil shale.

Abstract: Liquid and gaseous products are recovered from oil shale in an in situ oil shale retort in which a combustion zone is advanced therethrough by a method which includes the steps of establishing a combustion zone in the oil shale in the in situ oil shale retort and introducing a gaseous feed mixture into the combustion zone in the direction the combustion zone is to be advanced through the in situ oil shale retort. The gaseous feed mixture comprises an oxygen supplying gas and water vapor and is introduced into the combustion zone at a rate sufficient to maintain the temperature in the combustion zone within a predetermined range of temperatures above the retorting temperature of the oil shale in the in situ oil shale retort and sufficient to advance the combustion zone through the in situ oil shale retort.

Abstract: A technique is provided for loading an ammonium nitrate-fuel oil (ANFO) explosive mixture upwardly into a vertical blast hole extending as much as 70 feet or more from the open end at the face of the rock structure into which the blast hole is drilled. In order to achieve adequate packing in the hole the ANFO is maintained "soft" by keeping the ammonium nitrate particles substantially free of anti-caking materials. First the hole surface is moistened with water. If the surface dries before the hole is completely loaded, the remaining unloaded length is again moistened. The particles of explosive are blown into the hole through a hose as a mixture with air at a velocity sufficient to bring about packing and sticking of the ANFO in the blast hole. The packing is sufficient to keep the ANFO from falling out of an upwardly extending blast hole.

Abstract: A technique is described for reducing the content of oil and water in the flue gas recovered from the bottom of an underground in situ oil shale retort. In such a retort air is passed downwardly to sustain a combustion zone for retorting oil which is recovered at the bottom. Flue gas recovered from the bottom of the retort contains water vapor and oil and water aerosols. These are removed from the flue gas by passing it a substantial distance upwardly through cool overburden so that the flue gas is cooled below its dew point so that water condenses in the vertical conduit and aerosols are dropped out on the walls. The oil and water are recovered at the bottom of the conduit and stored in an underground sump.

Abstract: A technique is provided for cooling the flue gas or off gas from the bottom of an in situ oil shale retort. The gas is collected in a conduit that has a vertical portion through which the gas flows upwardly. It is then withdrawn from the retort through a gas tight bulkhead. Water is sparged downwardly through the vertical portion of the conduit for cooling and cleaning the gas. Means are provided for draining the sparged water into a sump at the bottom of the retort wherein oil and water are collected. Water and oil are separated and the water may be recycled for additional cooling.