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.

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 gas passing therefrom. The effluent gas contains a constituent which is formed, by advancement of the processing zone through the fragmented mass, from a precursor contained in the formation. To determine the locus of the processing zone, formation is assayed at selected locations in the retort for content of the precursor before processing the selected locations, and effluent gas from the retort is monitored for concentration of the selected constituent.For example, kerogen can be the precursor and effluent gas from the retort can be monitored for the concentration of methane produced by retorting of kerogen in the oil shale.

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 fragmented mass has layers of formation particles of differing composition, such as kerogen content, corresponding to strata of differing composition in the formation. The processing zone advances in a direction substantially perpendicular to such layers in the fragmented mass. Kerogen in oil shale is decomposed to produce gaseous and liquid products including shale oil, and shale oil is withdrawn from the retort. At least one characteristic of the shale oil withdrawn from the retort varies in response to differences in composition of such layers of formation particles through which the processing zone advances. Such a characteristic can be a physical property of the shale oil such as viscosity or specific gravity, or a chemical property such as sulfur content or trace metal content.

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 inlet gas introduced thereto and an effluent gas withdrawn therefrom. To determine the locus of the processing zone, kerogen content of formation at selected locations in the retort is determined before processing the selected locations. Because the difference in pressure between the inlet gas and the effluent gas increases as the kerogen content of formation being processed increases, changes in pressure drop across the fragmented mass can be predicted. By comparing actual changes in pressure drop with predicted change in pressure drop, the locus of the processing zone can be determined.

Abstract: The concentration of hydrocarbons, hydrogen, and carbon monoxide in a gas is reduced by combining these constituents in the gas with oxygen in the presence of a fragmented permeable mass of particles containing oil shale treated to remove organic materials.

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 above the retort site, and an access drift is excavated to the bottom of the retort site. Formation is explosively expanded to form the fragmented mass in the retort between the access drift and an elevation spaced below the bottom of the base of operation, leaving a horizontal sill pillar of intact formation between the top of the retort and the bottom of the base of operation. The sill pillar has a vertical thickness sufficient to maintain a safe base of operation above the retort after the fragmented mass is formed.

Abstract: A subterranean formation containing oil shale is prepared for in situ retorting by initially excavating at least one void adjacent a zone of unfragmented formation to be expanded. The zone of unfragmented formation has a substantially horizontal free face adjoining the void. At least one support pillar of unfragmented formation is left in the void for supporting overlying formation. Explosive is placed in the zone of unfragmented formation, and in such a support pillar. Explosive in such a pillar and in the zone of unfragmented formation is detonated in a single round of explosions with a time delay between detonation of explosive in such a pillar and detonation of explosive in the zone of unfragmented formation for first expanding such a pillar toward the void and then expanding unfragmented formation toward the void. The time delay is sufficient for creation of free face at the juncture of such a pillar and the zone of unfragmented formation.

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 above the retort site, and an access drift is excavated 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 from which to control retorting operations. A plurality of blasting holes used in explosively expanding the formation extend from the base of operation, through the sill pillar, and open into the top of the fragmented 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 withdrawing a sample of gas passing through the retort through a channel through unfragmented formation and in fluid communication with the retort, and analyzing the composition of withdrawn gas. The channel can be artificially formed such as by hydraulic fracturing of unfragmented formation, or can be a naturally occurring permeable layer such as a tuff bed in the formation containing oil shale.

Abstract: A retorting 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 fragmented mass comprises layers of formation particles of differing kerogen content corresponding to strata of differing kerogen content in the subterranean formation. The retorting zone advances in a direction substantially perpendicular to such layers in the fragmented mass. Kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil, and shale oil is withdrawn from the fragmented mass. The rate of shale oil production in the retort depends upon th kerogen content of such a layer in such a fragmented mass through which the retorting zone advances.

Abstract: An in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale is formed in a subterranean formation. The void fraction of the fragmented mass is from about 10 to about 25 percent, and the weight average diameter of particles in the fragmented mass is from about 0.02 to about 0.3 foot. Combustion zone feed containing oxygen is introduced to a combustion zone established in the fragmented mass. The rate at which the combustion zone feed is introduced to the combustion zone is controlled for maintaining the modified Reynolds number of gas passing through the combustion zone in the range of from about 0.1 to about 20.

Abstract: A field instrument for measuring the chemical composition of a solid core sample includes means for forming a smooth surface along the core sample, a light source for illuminating the smoothed surface, a photocell for sensing monochromatic light reflected from the surface of the core sample, means for providing relative movement between the core sample and the photocell, and means for converting the photocell output into a measurement of the amount of a chemical component being analyzed contained in the core sample. To avoid wide variations in measured chemical content, caused by non-uniform distribution of the material being analyzed within the core sample, reflected light is integrated over a selected area of the core sample.

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 lower surface area per unit volume than the average surface area per unit volume of the fragmented mass.

Abstract: An apparatus is provided for determining the locus of a processing zone which advances through a fragmented permeable mass of particles in an in situ oil shale retort in a subterranean formation containing oil shale. The apparatus, which functions by releasing means for providing an indicator at a preselected temperature, comprises container means, means for providing an indicator in the container, and means for releasing the indicator providing means at a selected temperature greater than ambient.

Abstract: The kerogen content of oil shale is measured by illuminating the surface of a solid piece of oil shale so that the amount of light not absorbed by the oil shale is reflected from the illuminated surface. A monochromatic portion of the reflected light is sensed, the wavelength of the sensed light being within the absorption band for kerogen in oil shale. The amount of light absorbed by the piece of oil shale is proportional to its kerogen content, and the amount of sensed reflected light, which is inversely proportional to kerogen content, is converted into a measurement of kerogen content. To avoid wide variations in measured kerogen content, caused by nonuniform kerogen distribution within the sample being analyzed, reflected light is integrated over an area of the sample likely to have numerous varves containing kerogen.

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 and which generates an effluent fluid is determined by placing an indicator source for providing an indicator, and monitoring effluent fluid from the processing zone for presence of indicator. The indicator source provides indicator at a predetermind temperature.

Abstract: Oil shale is pyrolyzed by introducing an oil shale feed to a retorting zone fluidized bed to yield, as products of retorting, retorted oil shale containing residual carbonaceous material and volatilized hydrocarbons. The retorted oil shale particles are passed to the top of a combustion zone fluidized bed into which a gaseous source of oxygen is introduced for fluidizing the combustion zone fluidized bed and oxidizing residual carbonaceous material contained in the retorted oil shale particles to yield combustion gases for fluidizing the retorting zone fluidized bed and for maintaining the retorting zone fluidized bed at a temperature sufficient to retort oil shale.

Abstract: A tunnel is formed above an in situ oil shale retort in a subterranean deposit containing oil shale. A void is excavated in the retort site and remaining deposit in the retort site is fragmented by explosively expanding toward the void to form a subterranean cavity containing a fragmented permeable mass of particles containing oil shale. The top of the fragmented mass is spaced downwardly from the tunnel to leave therebetween a pillar of unfragmented deposit. A retorting gas is introduced into the retort through a plurality of sloping passages from the tunnel for retorting oil shale in the fragmented mass. The liquid and gaseous products of such retorting are removed from the bottom of the retort. A portion of the carbonaceous products are used for generating electricity. In working a large area of deposit, a plurality of retorts are arranged in rows and columns.

Abstract: A method for retorting oil shale in an in situ oil shale retort includes the steps of excavating a void in a subterranean formation containing oil shale and placing combustible material in the void adjacent an ignition situs. Formation is then explosively expanded toward the void to form a retort containing a fragmented permeable mass of formation particles containing oil shale, the top layer of the fragmented mass adjacent an ignition situs containing such combustible material. The combustible material is then ignited for establishing a combustion zone in the retort.

Abstract: A subterranean formation containing oil shale is prepared for in situ retorting by initially excavating a pair of spaced apart voids, leaving an intervening zone of unfragmented formation between the voids. The intervening zone has substantially parallel free faces adjoining the void. A plurality of elongated blasting holes are formed in the intervening zone of unfragmented formation, the longitudinal axis of each blasting hole being substantially perpendicular to the parallel free faces of the intervening zone. At least two deck loads of explosives are placed in each blasting hole, with each load being longitudinally spaced apart from each adjacent load by stemming. The loads of explosive are then detonated in a single round of explosions with a time delay between adjacent loads for expanding formation in the intervening zones toward both voids. The fragmented mass of formation particles is then retorted to recover shale oil from the oil shale.