Abstract: The effective permeability of subterranean hydrocarbon bearing formations with respect to surfactant and drive fluid injection processes is enhanced by preceding the surfactant fluid injection step with creation of multiple formation fractures using tailored pressure pulses produced by gas generating propellant canisters disposed in the injection well. Fluid injectivity rates are increased by subsequent fracture extensions provided by repeated steps of generating high pressure gas pulses at selected intervals.

Abstract: This process comprises positioning along a predetermined direction two walls penetrating a geological formation to be fractured. During a preliminary period a predetermined amount of hydraulic fluid in injected.During a preliminary period/hydraulic fluid is injected simultaneously into both wells during for a sufficient time interval at a pressure insufficient to fracture the formation, either at a substantially constant flow rate, or in a stepwise manner at progressively increasing pressure levels. This preliminary injection is followed by the injection of hydraulic fluid into at least one of the wells at a pressure higher than the pressure of fractuation of the formation.

Abstract: A two-phase ceramic particulate useful as a proppant in hydraulic fracturing operations is provided which comprises a vitreous matrix phase containing a crystalline alumina phase. The new ceramic particles are characterized by:(i) a concentration gradient of alumina which increases from very low in the center to relatively high near the surface of the particles;(ii) a fired density less than about 2.9 g/cc; and(iii) closed cell microporosity.Certain embodiments of the inventive ceramic particulate are also characterized by a Krumbein roundness of at least 0.8 and are chemically stable.The ceramic is made by a process comprising the steps of:a. mixing and pelletizing, with the aid of water, the dry raw materials including a mineral particulate such as nepheline syenite and a binder such as bentonite;b. drying the wet pelletizer product;c. mixing the dried pellets with a parting agent; andd.

Abstract: Disclosed is a method and apparatus for enhancing oil and/or gas production from a subterranean well by using high energy, short duration electrical pulses to fracture underground rock formations containing entrapped oil or gas. The invention obviates the large power requirements of the prior art devices by generating a series of constant pulses having different durations into the rock formation to determine its characteristic impedance. Once the characteristic impedance has been determined, a second pulse having an amplitude and duration matching this characteristic impedance is discharged into the rock formation to alter its dynamic characteristics. A third pulse is then discharged into the rock formation to cause its fracture.

Abstract: A process for establishing well-to-well flow communication between a plurality of wells penetrating a subsurface formation is provided. A common fracture network is created by initiating a fracture from a first well, and then propagating that fracture from the first well to a second well. When the fracture has reached the second well, fracturing fluid is injected into the second well and thereby further propagates the fracture to a third well, and so on, so that the fracture is successively propagated to all of the wells. Such a fracture can be located adjacent either a lower or an upper boundary of a tilted subsurface formation, as desired. Techniques are also provided for reducing uneven areal distribution of injection fluids which are injected into fractures.

Abstract: An enhanced oil recovery technique includes the predetermination of a desired steam distribution within a steam flood pattern, which preferably is proportional to the volumes of oil in place within various sectors of an area of a subsurface formation. These sectors are associated with the various producing wells of the steam flood pattern. Initial steam distribution is then determined. Subsequently, one or more of the producing wells has its production rate modified so that the final steam distribution within the formation will more closely approximate the predetermined preferred steam distribution.

Abstract: Disclosed is a method for removing phenols from an underground gasification zone by injecting an alkaline material to convert at least a portion of the phenols to the corresponding salt and producing the solution of said salt. Thereafter, the salt can be converted to the free phenol or merely evaporated to dryness. In both of these cases, the phenol or salt can be incinerated.

Abstract: This invention is a method for recovering viscous hydrocarbonaceous fluids from a subterranean formation containing one or more vertically extensive, narrow, high permeability conduits. At least one injection well communicates with at least one production well via said conduits. Steam is injected into said injection well until the water-oil ratio becomes excessive at the production well. The production well is then shut in until the formation is pressurized. Stem injection is then stopped and the production well is opened for production by pressure depletion. This cycle is repeated until oil recovery becomes uneconomical.

Abstract: A method of in-situ leaching is disclosed in which the ore body is incapsulated by impermeable barriers. A grid of injection and production wells are drilled into the ore body. Horizontal barriers are formed at the top and bottom of the ore body by creating an overlapping pattern of horizontally-oriented fractures filled with polymer, above and below the ore body, radiating from each of the injection and production wells. A ring of boundary wells may also be drilled surrounding the ore body. The strata around each boundary well is fractured and a polymer is then injected to form a vertical barrier around the periphery of the ore body. The lixiviant is then introduced to extract the desired mineral values. In addition, water may be injected under pressure into guard wells between the ore body and the vertical and/or horizontal barrier wells to further reduce any migration of lixiviant into neighboring formations.

Abstract: Oil is produced by drilling parallel horizontal wells within a deep subterranean reservoir, extending parallel vertical fractures between the wells, heating the reservoir by flowing hot fluid through all fractures and producing oil by displacing fluid between the fractures.

Abstract: A water permeability contrast correction process to improve the sweep efficiency of waterflooding in carbonate-bearing strata which involves a sequential injection of (1) an optional aqueous preflush slug to adjust connate water salinity, (2) a slug of aqueous polymer gelable with polyvalent metal cations, such as an polyacrylamide, (3) an acidic aqueous solution effective to dissolve some of the carbonate and at least therefrom polyvalent metal cations specifically calcium or magnesium or both effective to gel said polymer, wherein said aqueous polymer and acidic solution can be injected together in a single slug, followed by (4) an additional aqueous polymer solution injection, wherein the acidic solution provides polyvalent metal cations in-situ for gelation of said polymer slug to preferentially decrease water permeability in highly permeable thief zones, and (5) an aqueous drive fluid.

Abstract: Circulating and non-circulating well-drilling fluids are provided comprising parenchymal cell cellulose. In accordance with a preferred embodiment, improved viscosity and fluid loss control in circulating well-drilling fluids are obtained from the inclusion of parenchymal cell cellulose in such fluids. In accordance with another preferred embodiment, certain polymers, especially anionic polymers, and polymers derived from hemicellulosic materials are admixed with parenchymal cell cellulsoe in well fluids to provide synergistic fluid loss control and other beneficial properties. Methods for the employment of circulating and non-circulating well fluids employing parenchymal cell cellulose are also disclosed.

Abstract: A method of recovering hydrocarbon from an argillaceous subterranean rock formation involving the flooding of the formation with an aqueous fluid to displace the hydrocarbon from the formation. The method involves first subjecting the formation to an acid stimulation treatment by injecting a strongly acidic solution to dissolve acid soluble pore clogging materials, although this first step can be omitted, if desired. The formation is then treated with a solution containing an acid, a surfactant and a clay stabilizing agent. The concentration of the treatment solution is initially quite high but is gradually reduced until a certain threshold concentration is reached, after which a treatment solution having this threshold concentration is continuously injected into the formation to displace the hydrocarbon.

Abstract: Polymers used in enhanced oil recovery operations, including polysaccharides, polyamides and cellulose derivatives may be crosslinked by the use of organic nitrogen compounds bearing at least two positively charged nitrogen atoms. Suitable crosslinking agents include the salts of aliphatic and aromatic diamines and bis (quaternary ammonium) compounds. The crosslinked copolymers may be used for mobility and permeability control purposes. The crosslinking agents are effective over a wide range of pH conditions to form stable gel structures with the polymers.

Abstract: Performing steam drive operations in critical manipulative steps can improve the recovery of viscous hydrocarbons from tar sand deposits. Steam is injected into an injection well at a rate that is less than the rate needed to fracture the formation, and fluids are simultaneously produced from a communicating production well. When steam breakthrough occurs at the production well, the production well is shut-in, and the injection rate is increased to a rate at least sufficient to fracture the formation. After the reservoir is sufficiently heated, injection ceases and production resumes. Once the production rate declines to a rate that is no longer efficient, the process can be repeated.

Abstract: The present invention relates to a method of treating a carbonate-containing subterranean formation to increase the production of hydrocarbons therefrom. The subterranean formation is contacted with an aqueous solution of a composition represented by the formula: ##STR1## wherein a is a whole number or fraction thereof in the range of from about 4 to about 18;wherein b is a whole number or fraction thereof in the range of from about 0 to about 30;wherein c is a whole number or fraction thereof in the range of from about 0 to about 3;wherein d is independently a whole number or fraction thereof in the range of from about 0 to about 3;wherein e is a whole number or fraction thereof in the range of from about 1 to about 3;R is independently selected from the group consisting of hydrogen and a methyl group whereby mixtures containing both groups may result; andX.sup.

Abstract: Underground formation fracturing compositions comprise a fracturing fluid composition for use in fracturing underground formations, such as oil or gas wells, comprising at least one substantially anhydrous aliphatic alcohol, a non-ionic homopolymer to form a gel with the alcohol and having a molecular weight from about 4 million to about 5 million, and as gel activating agent an alkali metal halide or an alkaline earth metal halide. A gel breaker comprising a salt containing iron or chromium, can be present.

Abstract: In a process for preparing crosslinked gels from aqueous polygalactomannans using potassium pyroantimonates, the rate of gel formation is decreased by chelating the potassium pyroantimonate with di or tri alkali metal or ammonium citrate.

Abstract: Mineral values, particularly uranium, are recovered "in situ" from a subsurface earth formation by completing at least one well in the mineralized formation adjacent either the top or the bottom of the mineralized formation, completing at least one second well in the mineralized formation adjacent the opposite of the top and the bottom of the mineralized formation, forming a horizontally-oriented fracture in the mineralized formation adjacent at least one of the top and the bottom of the mineralized formation, each of which fractures is in open communication with that well which has been completed at a corresponding vertical level, injecting a leach solution, adapted to solvate the mineral values, into the first or the second well, which thus becomes an injection well, and thence into that fracture which is in communication with the injection well and producing the leach solution, containing solvated mineral values, from the other of the first and second wells, which thus becomes the production well, whereby

Abstract: An aqueous composition has been developed to treat subterranean formations whereby the compositions can maintain for a period of time a sufficient viscosity to function as a hydraulic fluid and optionally to support particulate matter. Subsequently, the viscosity of the composition decreases to facilitate the removal of the composition.

Abstract: An aqueous composition has been developed to treat subterranean formations whereby the compositions can maintain for a period of time a sufficient viscosity to function as a hydraulic fluid and optionally to support particulate matter. Subsequently, the viscosity of the composition decreases to facilitate the removal of the composition.

Abstract: In a method for performing a step rate test on an injection well, a portable pumping unit is employed to increase the pressure on the injected water to a predetermined level in order to carry out the step rate test, and the predetermined pressure and flow rate are maintained and controlled by separating a portion of the pressurized water outflow from the portable pump from the main stream thereof, and the separated portion of pressurized water is returned to the water storage tank which feeds the input to the portable pump.

Abstract: Metal chelates of water soluble copolymers with polyvalent metal ions contain a statistical distribution of 1-86% by weight of structural units of the formula ##STR1## 9-80% by weight of units of the formula ##STR2## 5-90% by weight of units of the formula ##STR3## and up to 30% by weight of one or more units of the formulae ##STR4## wherein R.sup.1 is alkyl having 1 to 4 carbon atoms; R.sup.2 and R.sup.5 independently of one another are each hydrogen or methyl;R.sup.3 and R.sup.4 independently of one another are each hydrogen, methyl or ethyl or together are a trimethylene or pentamethylene;Y is a direct bond, phenylene or a moiety of the formula --CO--NH--C(CH.sub.3).sub.2 --CH.sub.2 --; andX.sup..sym. is a cation or H.sup..crclbar.

Abstract: A method for enhancing steam drive recovery of oil from an oil zone disposed below an overburden (18) including injecting a surfactant continuously into a supply (20) of driving steam to uniformly mix the surfactant with the steam and thereby provide a driving fluid. The driving fluid is then introduced into the oil zone (16) under sufficient pressure to cause the fluid to drive through a flow channel (S) between the interface I and the overburden (18) thereabove. The surfactant reacts with the oil to enable the fluid to strip away a top layer of the oil which is driven to a production well 14 for removal thereof.

Abstract: A store for storing heat in rock is produced in that the rock is split up hydraulically in approximately plane parallel fissure planes from a number of boreholes (9, 9', 9", 26). One or more production holes (12, 12', 12", 24, 29) are drilled down to the bottom of the cracked store. Hot water is supplied to the system in that the water is conveyed down to the upper portion of the store, from where the water is conveyed down through the store along zig-zag paths defined by the fissure planes (10, 10', 10", 10a-e) and transverse channels (11, 11', 11", 26,27). Alternatively, the hot water can be supplied along the whole height of the store and travel sideways along the horizontal fissure planes (10'") to the production hole.

Abstract: A subterranean, viscous oil-containing formation not greater than 2500 feet in depth is penetrated by at least one injection well extending into the lower portion thereof. A horizontal fracture is formed in the lower portion of the formation through the injection well. At least one spaced-apart production well penetrates the formation in fluid communication with the upper two-thirds or less of the formation. A slug of steam, about 0.35 to 0.45 pore volume, is injected into the injection well and fluids including oil are recovered from the formation via the production well. The injection well is shut-in for a predetermined period of time while continuing production of oil. Thereafter, a predetermined amount, about 0.03 to 0.10 pore volume, of hot water or low quality steam is injected into the injection well and production is continued until there is an unfavorable amount of water or steam in the fluids recovered.

Abstract: There are provided polymeric pyrrolidinium methanesulfonate viscosifiers which are useful in chemical waterflooding and in drilling fluids. These compounds may be formed by an unexpected cyclization reaction of quaternary diallyl amino groups on polymeric backbones involving the reaction of such groups with bisulfite salts.

Abstract: A process for recovering heavy hydrocarbonaceous oil in situ is disclosed. After a communication path is established between injection and production wells, a hot viscous fluid at least 20% of which is produced hydrocarbonaceous oil from the production well is circulated between the wells providing high sweep efficiency and good recovery of oil in place. In a preferred embodiment, the fluid comprises recirculated bitumen from the production well, steam, and small amounts of inert gas and emulsified water. The final stage is a recovery by conventional means.

Abstract: A method for recovering oil from a bed of tight reservoir rock in which a chamber is formed at the base of the bed followed by alternately combusting rubble in the chamber while recovering oil liberated by pyrolysis and spalling the walls of the chamber by injection of a coolant when oil production decreases. The method is practiced from a single well by extending a casing into the chamber and extending a tubing through the casing so that oxidant and coolant can be introduced into the chamber through the annulus between the casing and tubing while oil is recovered by a pump disposed in the tubing. Multiple well operation is practiced by forming a pancake fracture between the chamber and a laterally displaced well from which the oil can be pumped after seepage through the fracture. Oxidant and coolant are injected into the chamber in multiple well operation via a well at the bottom of which the chamber is formed.

Abstract: A method for the recovery of heavy oil from a subterranean silica-containing oil-containing formation comprising treating the formation with a slug of a hot aqueous solution containing sodium hydroxide and sodium bicarbonate capable of forming in-situ CO.sub.2 and metasilicate followed by injection of a drive fluid to aid in recovering the oil.

Abstract: Apparatus and a method of producing fluid organic products from kerogen in situ in a body of oil shale by the application of alternating electric fields having a frequency between 100 kilohertz and 100 megahertz to heat the kerogen in the oil shale to a temperature in the range of 200.degree. C. to 360.degree. C. and to maintain the kerogen in this temperature range for a period of time sufficient to convert a substantial portion of the kerogen in oil shale to fluid organic products which may be collected through passages produced in the oil shale formation by flowing to a well bore having a collection sump.

Abstract: An in-situ process for recovering hydrocarbons from a diatomite-type formation which comprises contacting the diatomite formation with a C.sub.4 -C.sub.10 alcohol and thereafter displacing the hydrocarbon-alcohol mixture with an aqueous alkaline solution towards a production well. The aqueous alkaline solution can be displaced with additional solution or another suitable medium such as a connate water drive.

Abstract: This invention provides in the production of heavy oil from a shallow subterranean tar sand bed penetrated by spaced injection and recovery systems, the method comprising:(a) forming a plurality of horizontal fractures spanning the distance between said injection system and said recovery system, said fractures being spaced apart in a vertical direction with respect to each other throughout the depth of the tar sand bed;(b) injecting a solvent for heavy oil and/or steam into said fractures,(c) shutting in the injection and recovery systems for a predetermined period of time to form a heavy oil/solvent mixture by gravity-driven convective mixing, and(d) recovering said heavy oil/solvent mixture in said recovery system by conventional recovery techniques.

Abstract: Crushed raw oil shale is fed into a geothermal compartment or reservoir under oil shale retorting conditions using the reservoir as a source of heat for retorting. After retorting is completed hydrocarbon products are removed from the compartment or reservoir. The resultant spent shale is subsequently used to fill voids in the reservoir. Hydraulic fluids are then placed into the compartment or reservoir and sufficient pressure applied to fracture the reservoir or compartment causing another geothermal compartment or reservoir to be formed.

Abstract: Auxiliary agents for chemical flooding of petroleum deposits and auxiliary agents used in well drilling fluids are water-soluble copolymers containing a statistical distribution of(a) 5 to 95% by weight of structural units of formula I ##STR1## (b) 0 to 30% by weight of structural units of formula II ##STR2## (c) 0 to 80% by weight of structural units of formula III ##STR3## (d) 5 to 60% by weight of structural units of formula IV ##STR4## wherein R.sup.1 and R.sup.2 are the same or different and represent hydrogen, methyl, or ethyl or together are trimethylene to cyclic pentamethylene;R.sup.3 represents hydrogen or methyl;R.sup.4 represent a imidazolyl-(1) or imidazolyl-(2) moiety;Y is a single covalent bond or the formula --CO--NH--C(CH.sub.3).sub.2 --CH.sub.2 --; andX.sup.+ is a cation.

Abstract: Method for the underground gasification of solid fuels in which an underground fuel deposit is initially opened up and then converted into a gaseous fuel by means of a gasification medium. The opening of the fuel deposit is effected by treatment with a gas which is in the supercritical state, which takes on the volatile organic substances of the solid fuel and the water contained in the solid fuel. The dissolved organic compounds and the water are separated from the charged supercritical gas phase above ground in at least two fractions by pressure reduction and/or a change in temperature.

Abstract: In an acidic in situ leaching system, a short circuit passage through a subterranean formation between a fracture associated with an injection well and a fracture associated with a production well can be plugged by introducing a non-acidic liquid for displacing acidic leach liquid from the short circuit passage, introducing into the injection well a basic composition including a sealing material that gels under acidic conditions, and introducing sufficient liquid into the injection well to displace at least a portion of the basic composition containing sealing material from the injection well into the short circuit passage. Liquid flow between the injection well and the production well is then discontinued for a sufficient time for residual acid in the subterranean formation surrounding the short circuit passage to contact the sealing material and cause gelation of the sealing material in the short circuit passage. The introduction of acidic leach liquid to the formation can then continue.

Abstract: A method of recompleting or controlling the flow of a formation which is inaccessible through the original wellbore and which is losing valuable hydrocarbons to another formation. A second borehole is formed in close proximity to the first wellbore, and at least the bottom end of the new borehole is slanted until it penetrates the hydrocarbon bearing formation within shooting distance of the bottom end of the first wellbore. A large casing gun is run downhole through the new borehole. All of the shaped charges of the gun are oriented in the same direction. Indexing means are included by which all of the shaped charges of the gun are oriented to fire towards the casing of the first wellbore. After the gun is discharged, cement is pumped down the borehole, through the tunnels formed by the shaped charges, and into the perforations of the wellbore casing, thereby killing the flow of hydrocarbons from the damaged wellbore.

Abstract: A method of oil recovery from subterranean formations, and especially water wet sand formation, comprising the steps of sequentially establishing a rate of oil production for the formation as a function of formation characteristics, such as perosity, permeability, depth of formation and past production from the formation. Second, injecting into the formation a bank of chilled water solution containing carbon dioxide gas and citric acid and phosphoric acid. Third, driving the bank of water solution from the injection well by any suitable means to the production well and withdrawing oil from the production well at the established rate of oil production. The method is especially adapted as a tertiary oil recovery method and effectively provides a 70% horizontal and vertical sweep of the formation.

Abstract: An in situ leaching or solution mining process is conducted in a subterranean cavity in communication with a well bore. The subterranean cavity is gradually enlarged by inducing spallation of formation particles and/or collapse of the roof into the cavity by repeatedly cycling the hydraulic pressure in the subterranean cavity. The hydraulic pressure is preferably increased during a period of at least about two hours. The hydraulic pressure can be gradually decreased during a period of at least about two hours or can be suddenly decreased. Rapid pressure pulses can be applied to liquid in the subterranean cavity by detonation of shaped charges of explosive with the axis of force of the charge being directed along the axis of the well.

Abstract: Oil shale is retorted, preferably in situ, by passing velocity flow of super-heated air through one or more conduit-like passages in direct contact with exposed surfaces of oil shale. Kerogen pyrolysis products are recovered by condensation of the vapors and collection of the condensate and by collection of the gases and separation of the valuable gases from the normally waste gases. Some of the waste gases may be recycled with the air for controlling combustion of the kerogen content of the shale.

Abstract: A process for recovering thermal values and organic materials from solid carbonaceous fuels, i.e., bituminous coals and lignites, by contacting such fuels with waste foul condensates, known as black liquor, from pulping operations thereby to solubilize thermal value containing organic materials therefrom and simultaneously provide a use for the heretofore considered unusable black liquors, the disposal of which up to now has presented both an economical and ecological problem.

Abstract: Oil may be recovered from viscous oil-containing formations including tar sand deposits by first establishing a fluid communication path in the lower portion of the formation intermediate at least one injection well and a production well. At least one additional interior production well in fluid communication with the upper portion of the formation is drilled within the formation defined by the injection well and production well. A hydrocarbon solvent having a density less than oil contained in the formation under formation conditions is injected into the fluid communication path via an injection well and fluids including oil are recovered from the production well until solvent is detected in the fluid recovered.

Abstract: Oil may be recovered from viscous oil-containing formations including tar sand deposits by first establishing a fluid communication path in the lower portion of the formation intermediate at least one injection well and a production well. A hydrocarbon solvent having a density less than oil contained in the formation and a viscosity not greater than 1/100 the viscosity of the oil contained in the formation under formation conditions is injected into the communication path and fluids including oil are recovered from the production well until the fluid recovered contains an unfavorable ratio of oil to solvent. The production well is shut-in and an additional quantity of the hydrocarbon solvent is injected into the fluid communication path, preferably until a total amount of between 0.05 to 0.30 pore volume.

Abstract: In a method of treating a subterranean formation, a well treatment composition comprising a dispersion of a water-in-oil emulsion in an aqueous medium is injected into the formation. The water-in-oil emulsion has an internal aqueous phase and an external phase containing a liquid hydrocarbon and a surfactant soluble in the hydrocarbon. The compositions can be designed to perform various well treatment applications including hydraulic fracturing and acidizing and can also be used to encapsulate or to transport well treatment materials and chemicals into the wellbore or formation. Treatment methods may also employ dispersions of a reactive simple or multiple emulsion. The distinct phases of the compositions may be selected to form treatment solutions upon mixing. Thus, improved acidizing may be achieved through an in situ reaction format.

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: This process comprises the three successive following steps of:(a) injecting into a formation a solution of sodium or potassium hydroxide during a limited time interval to perform a chemical leaching treatment of the formation,(b) injecting a saline solution, and(c) establishing a circulation of a heat conveying fluid through the formation.

Abstract: A thermal method is disclosed for recovering normally immobile oil from a tar sand deposit. Two wells are drilled into the deposit, one for injection of heated fluid and one for production of liquids. Thermal communication is established between the wells. The wells are operated such that heated mobilized oil and steam flow without substantially mixing. Oil drains continuously by gravity to the production well where it is recovered.

Abstract: Methods for increasing the permeability of a subterranean igneous rock formation penetrated by at least one well where a hydraulic fluid is injected into the formation at a pressure sufficient to cause diffusion into the natural fractures thereof and thus increase the cross-sectional area thereof, maintaining the pressure and injecting a second fluid which results, by the use thereof, in substantially maintaining the increased cross-sectional area after the pressure is reduced.

Abstract: Lignite is removed from a seam or stratum containing the same in an underground formation by forming within the seam or stratum with aid of a production fluid, which can contain a dispersant or surfactant, a suspension of the lignite in said fluid whereupon the fluid is removed to the surface and the lignite recovered therefrom. The fluid thus recovered is re-used. The production fluid can be heated and/or pulsated and is injected and passed through the formation under conditions to promote the formation of the desired lignite suspension.