Abstract: A row of horizontally spaced-apart in situ oil shale retorts is formed in a subterranean formation containing oil shale. Each row of retorts is formed by excavating development drifts at different elevations through opposite side boundaries of a plurality of retorts in the row of retorts. Each retort is formed by explosively expanding formation toward one or more voids within the boundaries of the retort site to form a fragmented permeable mass of formation particles containing oil shale in each retort. Following formation of each retort, the retort development drifts on the advancing side of the retort are closed off by covering formation particles within the development drift with a layer of crushed oil shale particles having a particle size smaller than the average particle size of oil shale particles in the adjacent retort.

Abstract: Formation is excavated from within the boundaries of a retort site in formation containing oil shale for forming at least one retort level void extending horizontally across the retort site, leaving at least one remaining zone of unfragmented formation within the retort site. A production level drift is excavated below the retort level void, leaving a lower zone of unfragmented formation between the retort level void and the production level drift. A plurality of raises are formed between the production level drift and the retort level void for providing product withdrawal passages distributed generally uniformly across the horizontal cross section of the retort level void. The product withdrawal passages are backfilled with a permeable mass of particles.

Abstract: Liquid and gaseous products are recovered from an in situ oil shale retort formed in a retort site in a subterranean formation containing oil shale. A void is excavated in the subterranean formation within the boundaries of the retort site and a zone of unfragmented formation is left in the retort site adjacent the void. A retort inlet is at one upper edge of the retort site and a retort outlet is at the lower edge of the retort site opposite the retort inlet.Explosive charges are placed in the zone of unfragmented formation and detonated in an asymmetrical time delay sequence for forming a fragmented permeable mass of formation particles which substantially fills the retort to the top boundary in the region of the retort inlet.

Abstract: A module of in situ oil shale retorts are formed in a row of retort sites in a subterranean formation. Each retort has top, bottom, and side boundaries of unfragmented formation and contains a fragmented permeable mass of formation particles. Two cross drifts are excavated through the retort sites along the row. One of the drifts is at a lower elevation near the floor of voids to be formed in the retort sites and along one side boundary of the retort sites. The other drift ramps upwardly at an end of the row for extending through the retort sites at a higher elevation near the roof of the voids excavated in the retort sites and along the opposite side boundaries of the retort sites. A horizontally extending slice is excavated at the elevation of the higher drift extending substantially to the side boundaries of a retort site for commencing a void within the retort site. The balance of the void is formed by benching from the slice to the elevation of the lower drift.

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: An in situ oil shale retort is formed in a subterranean formation by excavating voids adjacent the top and bottom boundaries of the retort, leaving an intermediate zone of unfragmented formation between the voids. The lower level void is substantially larger than the upper level void. A lower portion of the intermediate zone is explosively expanded downwardly towards the lower level void for forming a first moiety of a fragmented mass of formation particles in the retort and leaving a void space over the top of the first moiety having about the same volume as the upper level void. Thereafter an upper portion of the intermediate zone is explosively expanded upwardly towards the upper level void and downwardly towards the void space for forming a second moiety of the fragmented mass in the retort. The fragmented mass has an average void fraction up to about 25% and no substantial part has a void fraction less than about 20%.

Abstract: An in situ oil shale retort is formed in a subterranean formation containing oil shale and having horizontal cleavage planes extending parallel to the bedding of the formation and approximately orthogonal vertical cleavage plane sets extending perpendicular to the horizontal cleavage planes. The in situ retort is formed by excavating an opening or void in a retort site in the formation and placing explosive in the formation adjacent the void such that the explosive can fracture formation along the vertical cleavage planes and expand remaining formation within the retort site toward the void, forming a fragmented permeable mass of formation particles containing oil shale within the retort site.

Abstract: A method for forming a fragmented permeable mass of oil shale particles in an in situ oil shale retort in a subterranean formation containing oil shale is provided. At least one void is excavated within the retort site in the subterranean formation while zones of unfragmented formation are left adjacent such a void. The zones of unfragmented formation are then explosively expanded toward the void for forming the fragmented permeable mass of formation particles in the retort. To provide a fragmented mass with a flat top surface and reasonably uniform void fraction distribution, at least one of the zones of unfragmented formation is explosively expanded toward the void in a plurality of contiguous regions. Each such contiguous region has a free face adjacent the void and is expanded by first explosively expanding a first portion of that region toward the void. The free face of the first portion expanded is near the center of its respective region.

Abstract: An in situ oil shale retort is formed in a subterranean formation containing oil shale and having a substantially vertically extending first cleavage plane set and a substantially vertically extending second cleavage plane set intersecting the first set. The dispersion of the individual cleavage planes in the first and second cleavage plane sets is determined. The in situ retort is formed by excavating a vertical slot-shaped void within the boundaries of the retort site, leaving a remaining portion of the unfragmented formation within the retort site which is to be explosively expanded toward the slot. The unfragmented formation adjacent the slot has a pair of longer vertical free faces substantially aligned with the cleavage plane set having the lower dispersion. A pair of shorter vertical side walls of the slot can extend substantially perpendicular to the cleavage plane set having the lower dispersion.

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: A two-pass in situ oil shale retorting system uses two separate gas levels for withdrawing off gas from producing in situ oil shale retorts. During a first pass of retorting through an oil shale tract, spaced apart groups of in situ oil shale retorts are formed, leaving intervening barrier pillars of unfragmented formation between adjacent groups of retorts. During retorting, off gas from the retorts formed in the first pass is withdrawn to a first gas level drift system. Thereafter, during a second pass of retorting, intervening groups of in situ oil shale retorts are formed in the intervening barrier pillars between the groups of in situ retorts formed in the first pass. During retorting in the retorts formed in the second pass, off gas is withdrawn to a second gas level drift system that is formed at a different level and isolated from the first gas level drift system so that gas flow between the two gas levels is avoided.

Abstract: There is provided a method for forming an in situ retort containing a fragmented permeable mass of formation particles in a retort site within a subterranean formation. A void is excavated into the formation and a zone of unfragmented formation is left adjacent the void. A plurality of explosive charges are formed in the zone of unfragmented formation. At least one central explosive charge is in a central portion of the zone of unfragmented formation, and a plurality of outer explosive charges are in the zone of unfragmented formation nearer the side walls of the void than the central explosive charge. The distance from each such outer explosive charge to an adjacent side wall of the void is about equal to the crater radius of the outer explosive charge. The central and outer explosive charges are detonated for explosively expanding the zone of unfragmented formation toward the void for forming a fragmented permeable mass of formation particles in the in situ retort.

Abstract: A retort site in a subterranean formation containing oil shale is prepared for in situ retorting by excavating a void space in the retort site and then explosively expanding at least a portion of the remainder of the formation within the retort site toward the void space. The resultant fragmented mass explosively expanded toward the void space will be permeabilized by the void volume of the void space. The void space is initially formed by excavating at least three substantially parallel drifts through the retort site. At least two of the drifts are along opposed outside edges of the retort site and at least one drift is intermediate the two outside drifts. Excavation of the void space is conducted from the two outside drifts. A vertically extending slot is first excavated from each such drift upwardly into the proposed void space at one end of the retort site. The slot may be fanned above the drift so that the slots from the two outside drifts meet near the top of the void space.

Abstract: Formation is excavated from an in situ oil shale retort site for forming at least one void within the retort site, leaving at least one remaining zone of unfragmented formation within the retort site adjacent such a void. The remaining zone is explosively expanded toward such a void for forming a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort. Oil shale in the in situ retort is retorted to produce liquid and gaseous products, leaving a mass of spent oil shale particles in the in situ retort. Oil shale particles excavated from the in situ retort site are separately retorted, such as in a surface retorting operation, producing liquid and gaseous products and spent surface retorted oil shale particles. The spent surface retorted particles are disposed of by forming an aqueous slurry of the particles, and pumping the slurry into a spent in situ retort.

Abstract: A ventilation and process air distribution system is provided for an in situ oil shale retort system which includes a production region having a cluster of retorts producing gaseous and liquid products and a retort preparation region where in situ retorts are being prepared for production. An underground air delivery drift system distributes process air to the production region and ventilation air to underground workings in the retort preparation region. A liquid collection drift system extends at or below the bottoms of the retorts in the production region and in the retort preparation region. The liquid collection drifts connect to an exhaust airway leading above ground and having an induction fan for inducing ventilation air to flow through the retort preparation region at a pressure lower than ambient air pressure above ground.

Abstract: A generally flat combustion zone is formed across the entire horizontal cross-section of a fragmented permeable mass of formation particles formed in an in situ oil shale retort. The flat combustion zone is formed by either sequentially igniting regions of the surface of the fragmented permeable mass at successively lower elevations or by igniting the entire surface of the fragmented permeable mass and controlling the rate of advance of various portions of the combustion zone.

Abstract: This invention relates to a method of recovering shale oil from a subterranean formation containing oil shale. Unfragmented formation is explosively expanded in a single round of explosions for moving formation located at about the center of a zone of unfragmented formation a greater distance in a given time interval after the beginning of the round than formation located in the unfragmented formation outward from about the center of the unfragmented formation.The explosive expansion forms a fragmented mass of formation particles containing oil shale in the subterranean formation forming an in situ oil shale retort.Gas is introduced into the fragmented permeable mass in the in situ oil shale retort for establishing a retorting zone in the fragmented permeable mass wherein oil shale is retorted to produce gaseous and liquid products, and for advancing the retorting zone through the fragmented mass. Gaseous and liquid products are withdrawn from the bottom of the retort.

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. 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.