Abstract: An integrated jet perforation and controlled propellant fracture device and method for enhancing production in oil or gas wells, wherein the device is inserted in a well bore to the level of a geological production structure; the fracturing device being constructed with a cylindrical housing of variable cross-section and wall-thickness with the housing filled with combustible propellant gas generating materials surrounding specially oriented and spaced shaped charges, having an abrasive material distributed within the propellant filled volume along the device length to produce enhanced perforations with attendant pressure-controlled gas and fluid injection into the perforations to produce controlled frac entry at point or points desired in the producing zones of the well bore, wherein a high velocity jet penetrates the production zone of the well bore initiating fractures, and is simultaneously followed by a high pressure propellant material which amplifies and propagates the jet initiated fractures.

Abstract: Hydrocarbon liquids and/or gases are recovered from thick underground deposits of oil-bearing limestone or dolomite by drilling two or more boreholes from the earth's surface into the lower part of the deposit, establishing communication between the boreholes, burning the oil in said limestone or dolomite in an area between the boreholes to decompose the alkaline earth carbonate into alkaline earth oxide, flushing out the alkaline earth oxide formed by the combustion with water to form a cavity, collapsing the overlying oil-bearing limestone or dolomite into the cavity to form a rubblized zone extending vertically to a point near the upper boundary of the deposit, driving a flame front vertically through the rubblized zone to liberate hydrocarbon liquids and produce gases, and recovering the liquids and/or gases from the rubblized zone.

Abstract: A portion of an earth well bore is sealed off, and a combustible mixture of gaseous oxidizer and fuel is introduced into a sealed length of the well bore and ignited with substantial momentary pressure rise, fracturing the earth formation adjacent the well bore to increase the flow of fluid from the surrounding earth into the well. A check valve intermediate of the sealed well bore length functions to segregate the well bore into upper and lower sealed portions. By igniting a fuel gas mixture within the first sealed length, there is created a momentary high pressure wave within the sealed volume that is transmitted as a standing pressure into the second sealed volume. Successive firings of combustible mixtures in the first sealed volume create a steady pressure in the second sealed volume nearly equivalent to the peak transitory pressures realized in the first sealed volume during the individual firings.

Abstract: Process and apparatus for electrohydraulic recovery of crude oil wherein an explosive, ablative electric spark is generated at or near a subsurface oil bearing formation and which generates shock waves and hydraulic waves that radiate or propogate outwardly into the formation and cause forcible migration of oil toward adjacent collection wells. Electrical energy, which is well within the load-carrying capacity of an electrical service cable extending into the well, is stored at or near the level of the oil bearing formation by a capacitor bank. A spark gap across electrodes is broken down by discharging current from an injector capacitor bank after which a current of substantial magnitude is discharged from a main capacitor bank into the broken down spark gap, thus generating the explosive spark.

Abstract: A method of fabrication and the resulting structure for an economical and reliable anchor assembly to retain a conventional bridge plug within the production casing of an oil or gas well. The anchor assembly is efficiently loaded into the well and interfaced with the bridge plug via a packer and tubing, thereby eliminating the necessity of employing an expensive workover rig, which is common to many conventional well plugging techniques. The preferred method includes the step of deforming (i.e. perforating) the production casing for interlocking the anchor assembly therein. By virtue of the instant anchor assembly, a reliable plug may be installed to effectively plug back a depleted zone of an oil or gas well, while withstanding the generally large differential pressures that may be encountered at relatively deep subsurface production zones during a subsequent stimulation of the well.

Abstract: An in situ oil shale retort in a subterranean formation contains a fragmented permeable mass of formation particles. Such a fragmented mass is formed by excavating a horizontally extending void within the boundaries of the retort, leaving a zone of unfragmented formation above and/or below such a void. A plurality of vertical blasting holes are drilled in such a zone and loaded with explosive charges for forming an array of explosive charges sufficiently close together to interact and fragment formation substantially to a plane at the ends of the charges remote from the void. The scaled depth of burial of such an array is in the range of from about 6 to 12 mm/cal.sup.1/3. The explosive charges are detonated in a single round for expanding such a zone towards the void for forming the fragmented mass of particles in the retort.

Abstract: A pressure actuated vent assembly for completing a slanted wellbore. The assembly is connected in series relationship within a tubing string at a location below a packer, and the packer elements are located between the casing and the tubing string, thereby dividing the casing annulus into an upper and lower annular area. The vent assembly includes a ported sliding sleeve which is slidably received about a ported main body member. The sleeve is held into position by a shear pin. Guide pins maintain the ports of the sleeve and main body member aligned with one another. When pressure is applied to the inside of the tubing, the sliding sleeve is forced to slide from an upper closed position, in a downward direction, where the sleeve locks into the opened position.

Abstract: An improvement in an apparatus for fracturing subterranean formation by explosive fracture wherein opposed end charges are detonated to enhance the explosive capability of a central charge, the improvement comprising intermediate driver charges intermediate the central charge in each of the respective end charges; the driver charges being detonated by the end charges to provide a sustained pressure wave for enhancing the rubblizing and fracturing of the subterranean formation and extend the fracture more deeply into the subterranean formation. Also disclosed are improved apparatus enabling carrying out the split second detonating of the respective explosive charges, containing the explosive charges without entangling cable and the like downhole and preventing misfiring.

Abstract: Disclosed are systems for removing hydrocarbons from subterranean deposits thereof. A fluid-impervious barrier screen is formed to isolate parts of the deposit or to isolate the deposit from adjacent fluid-permeable earth formations. The barrier screens are formed by fracturing a vertical zone in the formation by micropercussive fracturing or detonation of microexplosive charges in a series of closely-spaced bore-holes to form a vertically extending fractured plane. The fractured plane is sealed with a sealing medium to form a fluid-impervious screen.Hydrocarbons trapped in the enclosed deposit zone are flushed from the formation by recirculating a fluid medium such as superheated brine and/or hot gases through the enclosed deposit zone under sufficient pressure to cause turbulent flow through the pore formations and to relieve the overburden pressure. The flushing medium may be injected in a series of pressure pulses to force the fluid through the pores by hydraulic ramming.

Abstract: Methane is recovered from an underground coal seam via a borehole which extends from the earth's surface through the overburden to a cavity that is in, partly in or proximate to the coal seam. The cavity is constructed and arranged to be collapsible. Coal from the coal seam moves toward the coal seam under the influence of triaxial compression converting adsorbed methane to free form methane that is recovered.

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, 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 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 room can lie above the columnar void, below the columnar void, or intermediate the ends of the columnar void. The expanded or fragmented shale has a low average void volume. The void volume of the fragmented shale increases at the bottom of the in situ retort.

Abstract: There is disclosed an arming and disarming device which is run into a well bore on a wireline and which is part of an explosive tool to conduct some type explosive operation in the well bore. In the disarmed configuration, the arming sub acts to separate the hot lead in the wireline from the explosive tool, to short circuit the hot and ground leads of the explosive well tool together and to connect the short circuited tool leads to ground. In one mode of use of the arming sub, hydrostatic pressure applied to the tool as it is being run into the well bore acts to move a piston inside the device. As the piston moves, the hot lead of the wireline is electrically connected to the short circuited hot and ground connections of the explosive tool. Continued movement of the piston breaks the short circuit between the hot and ground connections of the explosive tool thereby arming the tool.

Abstract: A fragmented recovery zone in a subterranean ore seam has a polygonal cross section with a low void volume and a conical funnel-shaped bottom with a high void volume. Recovered constituents are removed from the recovery zone at the point of convergence of the funnel.

Abstract: A method of producing fractures or gaps in geological formations of crystalline rocks in order to utilize the heat of the earth surrounding the gaps, comprises, drilling at least one bore into the rock, producing a pressure fluid in the bore adjacent the rock by introducing pressure gas-producing propellants into the bores to a location within the rock formation and reacting the pellants after they have been sealed off from the top of the bore and discharging the fluid pressure into the bore to put the rock under a pressure above its breaking limit so as to produce a large surface gap. The apparatus advantageously comprises a pressure gas generator which operates from a monergolic propellant which is decomposed catalytically and which includes a sealing bellows arranged around a reaction chamber at the bottom of the bore which is sealed at the upper end or to the rear and is connected with the pressure gas chamber and an outlet into the forming gap having a non-return valve therein.

Abstract: A method and apparatus for well perforations and fracturing operations includes a shaped charge having a generally spherical container, a conical liner positioned therein, an explosive substantially filling the container around the liner, and a booster charge in the form of an annular wafer of compressed high speed explosive positioned against the wall of the container in axial alignment with and adjacent the apex of the liner. The outside diameter of the booster charge is at least as large as one-half the diameter of the base of the conical liner and in proximity to a primer cord positioned in contact with the exterior of the container. The spherical container is composed of a frangible material, and it is positioned in a cylindrical carrier also composed of a frangible material which disintegrates upon detonation of the explosive. A secondary explosive of slower detonating speed than the primary explosive is packed around the shaped charge container in the carrier, and the carrier is sealed at both ends.

Abstract: Method of and apparatus for fracturing and creating multiple fissures in hydrocarbon impregnated rock. The invention uses a sequence of explosive charges involving a main, centrally located high velocity, shape charge shot directed out horizontally into the stratum to be fractured, and two supplemental charges of bulk explosives of a lower detonation velocity positioned above and below the main shot and simultaneously detonated following the main charge, the purpose of the sequence and the physical arrangements being to effect greater penetration of the stratum. In the preferred embodiment a metal shaped charge containing a liquid explosive is used for the centrally located main shot comprising a number of longitudinally extended tined spokes directed radially outward from a common center (note FIG. 3). The diameter of the shaped charge can be varied to fit and preferably generally fills up the diameter of the well bore.

Abstract: The process of the present invention involves the following steps:producing, as by hydrofracing, a substantially horizontal fracture in the subterranean rock mass to be processed;emplacing an explosive charge in the mass in spaced juxtaposed position to the fracture;enlarging the fracture to create a void space thereat, an initial lifting of the overburden, and to provide a free face juxtaposed to and arranged to cooperate with the emplaced explosive charge; andexploding the charge against the free face for fragmenting the rock and to distribute the space, thus providing fractured, pervious, rubble-ized rock in an enclosed subterranean chamber.Firing of the charge provides a further lifting of the overburden, an enlargement of the chamber and a larger void space to distribute throughout the rubble-ized rock within the chamber.

Abstract: A fracture that conducts fluid within the confines of an underground rock formation without the need for particulate proppant materials to hold opposing fracture faces apart is created by a method in which a long portion of a hole drilled into the formation has its axis slanted with respect to the directions of the principal stresses, and is pressurized rapidly over its entire length with fluid, preferably by detonating an explosive therein.A hypothetical fracture plane is defined as that plane containing the axis of the hole which is under the least compressive normal stress. When the orientation of the hole axis is such that there is a substantial shear stress on the hypothetical fracture plane, but the normal stress thereon does not greatly exceed the minimum principal stress, the fracture created lies close to the hypothetical fracture plane, and is conductive to fluids.

Abstract: Downhole method and apparatus for efficient well completions wherein natural earth energy is utilized by the exploitation of a maximum pressure differential into a given well bore. The method and tools of the apparatus function to back surge the well, enhancing reservoir communication, saving time and reducing costs. Tools of the apparatus include a tubular nipple, a surge plug inserted operationally into the nipple, and an optional catcher sub connected thereto. The entire tool assembly is production actuated by dropping a recoverable bar of sufficient weight to overcome that buoyant force which seals the plug within the nipple. The essence of invention resides in the economy of time and material.

Abstract: A method of producing hydrocarbonaceous liquids and gases from subterranean kerogen-containing oil shale formations comprising (a) penetrating the oil shale deposits with at least two well bores; (b) fracturing the oil shale deposits in a lower vertical portion thereof; (c) igniting the hydrocarbonaceous deposit; (d) introducing through the first well bore a free oxygen-containing gas to the ignited point of the oil shale deposit to effect thermal decomposition of the hydrocarbonaceous material therein and to propagate a combustion zone through the fractured communication area and the second well bore, thereby forming a region of combusted shale between the first well bore and the second well bore; (e) allowing the combustion to continue until a sufficient volume of combusted shale has been formed; (f) then jetting an aqueous liquid into and through the combusted shale zone to remove the mineral residue remaining after combustion; (g) positioning conventional explosives in the oil shale deposit in the vicinit

Abstract: Method and apparatus are disclosed for recovering submerged equipment, such as a guide base and wellhead used in offshore well operations. A recovery tool, which includes an elongated member capable of extending from above the equipment into a well pipe and means for latching the recovery tool to the equipment and explosive means attached to the elongated member for severing the well pipe, is lowered from the water's surface to the equipment and then latched thereto. The explosive is then detonated to sever the well pipe. The recovery tool, together with the equipment and severed portion of the well pipe, is raised to the water's surface.

Abstract: The subterranean fragmented and pervious zone is formed beneath an overburden which, as a first step of the process, is lifted as a substantially monolithic land mass to produce a void space and a free space proximate the rock to be fragmented, the raised overburden thus providing a substantially impervious lid or closure for the fragmented zone as formed by the present invention. Explosive charges are then placed proximate to and for blasting against the free face formed on raising the overburden. The charges are exploded to fragment the rock to distribute the space, thus producing fractured, pervious rubble-ized rock in a defined and enclosed zone. Different techniques are disclosed for the critical raising of the overburden and subsequent fragmenting of the rock.

Abstract: An earth fracturing apparatus has a casing of reactive metal containing a central, double ended charge load that is simultaneously detonated from both ends; and a pair of opposed end charges at opposite sides of the central charge load, the end charges being concavely dished toward the central charge load and having a liner of reactive metal on the dished face. The end charges are simultaneously peripherally initiated to explode with a collapsing detonation wave toward the central charge load. Void spaces between each end charge and the central charge load contain an oxidizer that may be under pressure. In a modified form of the apparatus, the end charges are omitted and the central charge load alone acts as a perforator for well pipe.

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.

Abstract: A method for creating a zone of relatively high permeability within a subterranean carbonaceous deposit which includes gasifying a portion of the carbonaceous deposit to provide a cavity, placing at least one explosive device in the deposit in the vicinity of the cavity so that energy generated upon detonation of the explosive device extends into the cavity, and detonating the explosive device thereby causing a portion of the carbonaceous deposit to be fragmented and to collapse into the cavity.

Abstract: Disclosed is a process for generating synthetic fuels from carbonaceous minerals such as oil shale and coal by dispersing a catalytic agent by suitable explosive means into carbonaceous deposits. The explosives serve to fracture and rubblize the carbonaceous mineral as well as conveying the catalyst onto and in close proximity to the fractured particles. The catalyst coated particles are then converted, in whole or part, to gaseous and liquid products by conventional processes such as retorting, gasification, hydroretorting, hydrogenation, or the like, wherein this process or part of it is accelerated, decelerated, or otherwise favored by the presence of the catalytic agent. This process is capable of producing an increased yield and/or better quality product since it is possible to maintain greater control over the conversion step.

Abstract: In the representative manner of practicing the new and improved method disclosed herein, a so-called "stuck-point indicator" or "freepoint-indicator" tool including a unique deformation-responsive sensor tandemly arranged between unique upper and lower tool anchors is positioned in a string of well pipe believed to be stuck in a well bore. The tool is then moved to a selected depth location in the pipe string and, in keeping with the principles of the present invention, operated so that the upper anchor is engaged with the pipe string wall before the lower anchor is engaged. Thereafter, upon application of forces to the upper end of the pipe string, independent measurements are produced by the sensor which are respectively representative of tensional forces and torsional forces acting on that portion of the pipe string between the upper and lower anchors.

Abstract: A method and means for chemically treating water wells to increase the production thereof. Liquid chemical, usually acid, is initially placed in the well through the water discharge conduit of the well head or pump apparatus at the upper end thereof. Compressed air is initially forced downwardly into the interior of the column pipe in the casing to sense the depth of the water therein so that pressure sensitive gauges in the circuitry may be set according to the water depth. Compressed air is then forced downwardly into the column pipe to force some of the water outwardly therefrom into the water bearing formation. A combustible mixture of air and gas is then introduced into the upper end of the column pipe and ignited so that the force of combustion expels the water and acid in the casing outwardly through the slits in the well casing into the water bearing formation.

Abstract: A method for generating a horizontal fracture through a wellbore by causing two explosively induced shear waves to intersect. This is achieved by placing, within a coupling fluid within a wellbore, a length of high explosives whose center is adjacent the location where a fracture is desired. Both ends of the high explosive are ignited simultaneously.

Abstract: A method of stimulation oil well production uses a gas generating chemical charge that is placed in the oil well bore at a depth of known oil productivity where it is ignited to generate a gas pressure-volume pulse of known pressure-time characteristics and time duration, the pressure time characteristics includes a pulsating pressure for greater penetration effect.

Abstract: A method for stimulating a producing well by introducing an explosive into perforation tunnels which communicate between the reservoir and the well bore and detonating the explosive while maintaining the well bore at about reservoir pressure and relatively free of explosive.

Abstract: Apparatus for stimulation of oil well production utilizes a gas generating chemical charge that is placed in the oil well bore at a depth of known oil productivity and ignited to produce a gas pressure-volume pulse of known pressure-time characteristics and time duration, including means for generating a pulsating gas pressure-volume pulse.

Abstract: A method for stimulating oil and gas wells to increase production including filling the lower portion of the well above the pay zone level having exposed rock with a fracturing fluid, and sealing the well above the lower portion. A shock wave is then applied to the fracturing fluid, which, when applied thereby to the rock at the pay zone creates a stress wave in the rock having a rise time faster than the time required for sound to traverse one half the periphery of the rock at the pay zone, and having an amplitude which will fracture but not crush the rock.

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: A method and means for stimulating oil and gas wells to increase production comprises filling a well above the pay zone level with a fracturing fluid, then suspending a cylinder of high explosive centrally within the wellbore adjacent to the pay zone. Thereafter a propellant is suspended within tens of feet above the high explosive and the well above the propellant is enclosed. The application of high explosive is chosen to cause multiple radiating fractures but will not crush the rock in the well. Also, the rise time of the shock wave created by the explosive should be less than the time required for sound to traverse one-half of the periphery of the well opening in the rock at the pay zone. The propellant is detonated first, followed by the detonation of the high explosive. The purpose of using the propellant is to maintain pressure caused by the high explosive over a longer period, thereby extending the fractures caused by the high explosive.

Abstract: Subterranean carbonaceous deposits, such as oil shale or the like, that are located at or close to the surface, are prepared for retorting by drilling blast holes from the surface into the deposit, and blasting, creating a rubble pile that reaches the surface. The surface is sealed by suitable means, and the oil shale is retorted in place. Where a stratum of barren rock lies between the carbonaceous deposit and the surface, the blast holes are drilled and blasted in such a manner as to maximize the fragmentation of the carbonaceous deposit, and minimize the fragmentation of the overlying barren stratum. Where overburden conditions are not suitable for treatment by this method, the overburden is removed by strip mining methods, and the carbonaceous deposits are exposed for treatment by the method described above.

Abstract: In the disclosed method, an aqueous solution of alkaline earth metal hydroxides and a salt of an alkaline earth metal is injected down a well bore and into a hydrocarbon reservoir in volume quantities sufficient to fill the pore spaces of said reservoir to some distance from the well bore. The concentration of the alkaline earth metal cations is greater than 10,000 ppm and the pH of the aqueous solution is greater than 10. The solution is forced under pressure out into the subterranean reservoir for a time period which is insufficient to consolidate sand but which is sufficient to permanently alter the properties of indigenous, intergranular clay sized particles and thereby achieve desirable permeability effects in certain fluid sensitive reservoirs. After a sufficient time period has elapsed, the well head pressure is released thereby allowing the solution to flow back into the well bore.

Abstract: According to the invention, a process and system are disclosed for conditioning an oil or gas formation and the application of the various stimulating fluids to the oil or gas formation. The method consists of drilling from a vertical well hole a horizontal spiralling hole which spirals out into the oil or gas formation and around the vertical well hole. Other embodiments include the drilling of a horizontal inward spiralling well from a vertical well hole that inwardly spirals out into the oil or gas formation from the vertical well hole, and the drilling of a hole from a vertical well hole that spirals out and coils down through an oil or gas formation around the vertical well hole. The application of this process is contingent on the use of my remote control directional drilling system, U.S. Pat. No. 3,811,519, and my flexible drill pipe pending application Ser. No. 465,500, filed Apr. 30, 1974 on related equipment, now abandoned.

Abstract: Method and apparatus for controlled fracturing of a portion of the earth's formations intermediate predetermined depths characterized by positioning adjacent the portion to be fractured explosive charges having exteriorly disposed grooves deep enough to effect a concentration of explosive forces along a predetermined fracture plane, the plane extending radially outwardly from the central longitudinal axis of the groove; and detonating the explosive charge to achieve the desired fracture. Preferred embodiments employ both horizontally-fracturing explosive charges containing peripherally disposed grooves having their central longitudinal axis in a plane perpendicular to the central longitudinal axis of the explosive charge and vertically-fracturing charges having longitudinally extending grooves so as to fracture outwardly in planes that are substantially vertically oriented and passed through the center line of the charge.

Abstract: A new and improved apparatus and method for lowering the apparatus downwardly in a drill string on a wireline to releasably engage a recess in a threaded joint or collar of the drill string to prevent further downward movement of the apparatus and to thereafter detonate an explosive by manipulating a wireline actuated jar with repeated downward blows for exerting a jarring force to the joint as a result of the explosion to release the threads at the joint upon simultaneous application of a back-off torque to the drill string. The apparatus can be released and removed from the well without breaking or damaging the collar locating and supporting portion of the apparatus.

Abstract: There is disclosed herein an improved method of well stimulation involving the use of explosive mixtures performed downhole and employing the combustible components of the fossil fuel producing formation as the fuel component of the explosive mixture.

Abstract: This invention relates generally to petroleum well treatment and more particularly to improvement of production from earthen petroleum reservoirs of low permeability by fracturing the petroleum bearing strata. The present invention accomplishes this purpose by use of energy capsules that upon implosion produce acoustic waves as to cause the formation to undergo periodic stress beyond its elastic endurance limit and to fail by elastic fatigue.A plurality of energy capsules designed to implode at different hydrostatic pressures in order to release shock waves to produce a cavitational action in the areas adjacent to the well bore are transmitted in a fluid medium. The energy capsules may be utilized in conjunction with pressurized fluid that is oscillated such that the combined elements of a pressurized fluid system and the release of shock waves at spaced time intervals from the energy capsules is obtained.

Abstract: A method for recovering coal from deeply buried deposits comprising drilling a hole down into a coal seam, filling the hole with water, and periodically detonating an explosive charge at the bottom of the water-filled hole. The water transmits the explosive shock wave to the face of the coal seam, thereby fracturing and dislodging the coal. The resulting suspension of loose coal in water is then pumped to the surface where the coal is recovered and the water is recycled to the mining operation.

Abstract: The forming of a rubble-containing cavity within a subterranean oil shale is improved by: leaching water-soluble minerals to form an areally extensive void in or above an upper portion and an areally extensive permeable zone or void within or contiguous with a lower portion of the oil shale; displacing an explosive fluid into the lower permeable zone; and detonating the explosive.

Abstract: A highly safe, wholly mechanically operable initiator is disclosed which is particularly suitable for initiating a liquid explosive in well fracturing and numerous other underground mining operations.

Abstract: A rock-exploitation method based on thermodynamic cycles utilizing an in-situ energy source, which includes sinking at least one well as far down as, or deeper than a producing horizon, admitting stratal fluid into the well, discharging the fluid from the well above or below the producing horizon, and injecting a heat-carrying agent into the well where it circulates and exchanges heat with the rock through the fluid which is in contact with the rock and acts as a heat-carrying agent in an underground circuit including said means for admission of fluid, a section of the well between the fluid inlet and the fluid outlet, and the fluid-permeable rock mass adjacent to said section of the well.