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 comprising kerogen and various inorganic carbonates. A processing zone is established in the fragmented mass of formation particles and advanced therethrough. Off-gas, including carbon dioxide from carbonate decomposition, is withdrawn from the retort. The carbon dioxide content of the withdrawn off-gas, being a function of the processing zone temperature, is then determined. The determined carbon dioxide content of the withdrawn off-gas is then compared to values of carbon dioxide content of off-gas predicted as a function of processing zone temperature.

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. A crack is propagated in at least one of the zones of unfragmented formation along the side boundaries of the retort site and thereafter the zone of unfragmented formation is explosively expanded towards such a void for forming a fragmented permeable mass of formation particles in the retort. Such a fragmented permeable mass is retorted in situ to produce shale oil.

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 has a heating value which is dependent on the kerogen content of the oil shale then in contact with the processing zone. To determine the locus of the processing zone, the formation is assayed at selected locations in the retort for kerogen content before processing the selected locations, and effluent gas from the retort is monitored for its heating value.

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: 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: 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: 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 secondary combustion zone is established and its location controlled in a fragmented mass of particles containing oil shale in an in situ oil shale retort.A processing zone including a primary combustion zone is established in the retort by igniting a portion of the mass of particles. An oxygen supplying gas is introduced into the retort to advance the processing zone through the fragmented mass. If the primary combustion zone is not substantially planar or has not progressed uniformly, a secondary combustion zone is established upstream of the primary combustion zone by introducing into the retort a retort inlet mixture comprising fuel and at least sufficient oxygen for combustion of the fuel at a temperature no greater than the primary combustion zone temperature.The secondary combustion zone is caused to move upstream from its initial location in the in situ oil shale retort by reducing the ignition temperature of the retort inlet mixture.

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: 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: 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 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 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: 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 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 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 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.