Abstract: Methane is produced from a coal seam penetrated by an injection well and a gas production well by first introducing liquefied or gaseous carbon dioxide through the injection well and into the coal seam and subsequently introducing a weakly adsorbable gas through the injection well and into the coal seam. As the weakly adsorbable gas passes through the coal seam, it forces the carbon dioxide through the seam. If the carbon dioxide is in liquefied form, it evaporates as it moves through the seam, and the carbon dioxide gas desorbs methane from the coal and sweeps it toward the production well. The methane is withdrawn from the seam through the production well.

Abstract: The invention relates to assisting the recovery of petroleum from vertically fractured formations utilizing carbon dioxide gas to lower the interfacial tension between the gas and the petroleum in the vertical fractures and in the formation matrix adjacent the vertical fractures to cause vertical drainage of the petroleum down the fracture system. The invention also includes a method for identifying vertically fractured formations which may be particularly susceptible to such recovery with carbon dioxide gas using the capillary to gravity ratio (1/N.sub.B) to select formations having a value for such ratio of 0.2 or less.

Abstract: The invention is a foam method for improving conformance during a steam flood or carbon dioxide flood in a subterranean, oil-containing formation penetrated by at least one injection well and at least one production well. In a steam flood oil recovery process, sweep efficiency is improved by injecting steam until steam breakthrough occurs at the production well after which a mixture of steam, a noncondensible gas, and an aqueous surfactant-starch solution is injected into the formation. The aqueous surfactant-starch solution forms a stable foam with the formation oil at formation conditions that reduce the permeability of the highly permeable steam swept zones thereby diverting the steam to other portions of the formation containing unswept oil. The starch is used as a partial substitute for the surfactant to improve the cost of the foam-forming mixture without reducing its effectiveness in increasing sweep efficiency.

Abstract: The invention is a method for increasing the effectiveness of steam or carbon dioxide foaming operations for improving conformance during steam or carbon dioxide floods by adding to the surfactant foaming solution a fatty acid having about 12 to about 20 carbon atoms in a concentration such that the ratio of fatty acid to surfactant in the foaming solution is between about 1:4 and about 3:2.

Abstract: A process is provided for recovering oil from a gas cap in a subterranean oil-bearing formation by injecting a water-alternating-gas cycle into the gas cap via an injection well in fluid communication therewith. The cycle includes a slug of an aqueous fluid and a slug of a non-aqueous gas. The aqueous fluid slug is substantially smaller in volume than the non-aqueous gas slug, the aqueous fluid slug being only of sufficient volume to substantially increase the water saturation of the gas cap without substantially increasing the gas saturation of the gas cap. The two slugs are injected into the gas cap sequentially, thereby displacing at least a portion of the oil in place from the gas cap into a production well. Any number of cycles are performed in sequence until the process is terminated.

Abstract: In-depth formation damage is prevented during water injection by adding to the water non-compressible solids of sufficient size and concentration to form an external filter cake within the injection well. Preferably, the non-compressible solids are either diatomite, perlite, saw dust, or calcium carbonate, and the concentration of non-compressible solids is from 0.001 to 5 wt%. When no longer needed, the external filter cake is removed from the injection well by using an acid wash or back-flowing the well.

Abstract: Complex metal anions such as cobaltic hexacyanide are utilized as nonradioactive tracers in reservoir studies. Sensitive analytical procedures enable detection and measurement of very low tracer levels.

Abstract: A foam-forming composition comprising a mixture of at least one anionic surfactant and at least one cationic surfactant can effectively form a foam in a variety of formations including an oil-wet environment. In particular, this composition can be employed in a method which comprises at least periodically injecting a gas and this foam-forming composition into an oil-bearing formation to drive oil to a production well. In this composition, the ratio of the at least one anionic surfactant to the at least one cationic surfactant is selected so that the surfactants do not form substantial amounts of precipitate when mixed together. In certain environments, e.g., when the formation contains upwards of 20% total dissolved solids and/or a divalent metal ion concentration up to about 20,000 ppm, the composition can further contain at least one salt-tolerance additive, e.g., a nonionic surfactant.

Abstract: In a petroliferous zone surmounting an aquifer, a lateral sweep stimulation is achieved by means of a fluid capable of displacing the petroleum effluents (a warm fluid such as steam, a solvent, etc), which is injected into the formation through a deflected injection drain, i.e. a first drain, horizontal for example), and the oil displaced by the displacement fluid is withdrawn through a withdrawing drain, i.e. a second drain, laterally offset in relation to the first drain and substantially parallel to it. In order to prevent the oil from being displaced into the aquifer and remaining trapped therein, a third drain and possibly a fourth drain closer to the interface (I) with the aquifer than the first and the second drain are bored into the petroliferous zone.

Abstract: A process is provided for recovering liquid hydrocarbons from a subterranean hydrocarbon-bearing formation by sequential injection of a pair of immiscible gases of differing composition which displace the liquid hydrocarbons from the formation. The compositions of the displacement gases are selected such that one gas is characterized as a swelling gas and the other is characterized as a non-swelling gas with respect to the liquid hydrocarbons in place.

Abstract: The recovery of hydrocarbons from subterranean formations is improved by the use of a mobility control fluid comprising a mixture of at least one alkylated diphenyl oxide and at least one amphoteric surfactant. A preferred mobility control fluid comprises the disodium salt of hexyldiphenyloxide disulfonate and cocamido-2-hydroxypropyl sultaine.

Abstract: In an oilfield production system, a water driven jet pump is used to evacuate vapors from storage tanks to thereby recover the vapors and prevent emissions from passing to the atmosphere. The jet pump entrains the vapors in process water which is passed to a process separator already in the system. The gas is separated for recovery.

Abstract: The present invention resides in a three directional horizontal drilling process which is suitable for the in-situ treatment or extraction of undesirable contaminants from subsurface formations. A first extraction well is drilled utilizing three directional horizontal drilling techniques in the general vicinity of a contaminated subsurface formation. A second injection well is strategically drilled to direct contaminants into a subsurface screen system in the extraction well, thus facilitating the extraction and collection of undesirable contaminants.

Abstract: Gas-condensate having an API gravity value greater than 55.degree. is produced by injecting (1) a light noncondensable gas and (2) a foaming agent comprising a surfactant and water into a subterranean formation containing the gas condensate.

Abstract: A method of microbial enhanced oil recovery for recovering oil from an oil-bearing rock formation. A population of aerobic bacteria is introduced into the formation at a position spaced from a production borehole. The micro-organisms are adapted to use oil as a carbon source. Pressurised injection water is introduced into the formation via an injection borehole, the water including a source of oxygen and mineral nutrients. The bacteria multiply using the oil as their main carbon source and the oxygen in the injection water as their main oxygen source. In so doing, they dissociate the oil from the rock formation and the dissociated oil is removed via the production borehole by the injection water.

Abstract: A polysiloxane polymer having pendant aromatic groups that is useful in increasing the viscosity of carbon dioxide. That polymer can be formed by reacting a polysiloxane containing at least one olefinic group with a phenyldialkylsilane. That polymer can be used in a method for recovering oil from an underground oil-bearing earth formation penetrated by an injection well and a producing well, in which method carbon dioxide is injected into the formation to displace oil towards the producing well from which oil is produced to the surface. The viscosity of the carbon dioxide injected into the formatin is increased at least three-fold by the presence of a sufficient amount of the polymer and a sufficient amount of a cosolvent to form a solution of the polymer in the carbon dioxide.

Abstract: A method for generating oxygen-depleted air for injection into a subterranean coal seam for increasing production of methane. Air and produced fluids comprising methane are input into a fuel cell power system; and fuel cell power system exhaust comprising oxygen-depleted air is injected into the coal seam.

Abstract: A polymer enhanced foam comprising a polymer selected from a synthetic polymer or a biopolymer, a surfactant, an aqueous solvent and a gas is injected into a fractured subterranean formation via a first well in fluid communication with the formation and preferentially enters fractures present in the formation. The injected polymer enhanced foam promotes the recovery of liquid hydrocarbons from said formation via the first well or a second well in fluid communication with the formation.

Abstract: A polymer is disclosed that is useful in increasing the viscosity of carbon dioxide. That polymer comprises a polysilylenesiloxane polymer, preferably polydimethylsilylenedimethylsiloxane. That polymer can be used in a method for recovering oil from an underground oil-bearing earth formation penetrated by an injection well and a producing well, in which method carbon dioxide is injected into the formation to displace oil towards the producing well from which oil is produced to the surface. The viscosity of the carbon dioxide injected into the formation is increased at least three-fold by the presence of a sufficient amount of the polysilylenesiloxane polymer and a sufficient amount of a cosolvent to form a solution of the polymer in the carbon dioxide.

Abstract: A soluble or crosslinked graft copolymer of lignin-(2-propenamide)-(2-methyl-3-oxo-4-oxyhex-1-ene-6-ol) having a central lignin network and at least one grafted side chain, R, having randomly repeating units of the formula: ##STR1## such that the central lignin network has a molecular weight of about 1,000 to 150,000 and the total number of randomly repeating units in the grafted side chain or chains is in the range of 1 to 300,000, such that the total copolymer molecular weight is in the range of 1,000 to 30,000,000 for use as thickeners for water and aqueous solutions and may be advantageously used in the recovery of oil from subterranean wells, in the preparation and use of drilling fluid compositions, or in plastics and elastomers.

Abstract: The invention is a method of recovering petroleum hydrocarbons from an underground formation penetrated by at least one injection well and at least one production well, which comprises injecting through an injection well a mixture of carbon dioxide and about 0.1% to about 20% by weight trichloroethane at a temperature and pressure above the bubble point of the mixture, and recovering hydrocarbons and other fluids at a production well.

Abstract: An improved process for the remediation of soil contaminated by the presence therein of organic or semi-volatile inorganic contaminants which comprises (1) supplying thermal energy to the soil at one or more locations under the surface of the soil, (2) collecting the vapors resulting from contaminant vaporization or decomposition under the influence of the thermal energy, after passage horizontally through the soil, at one or more locations under the surface of the soil and separating from the collected vapors the environmentally undesirable components thereof.

Abstract: A process for improved delivery of mobility control agents. The drive solvent is designed such that the plugging agent, e.g. surfactant or polymer, is soluble in the drive solvent under the injection conditions of temperature and pressure but is substantially insoluble under the conditions of temperature and pressure in the formation. Typically, miscible drive solvents have more favorable solvent properties at the low injection temperature than at the higher formation temperature. Preferably, solute solubility in miscible drive solvents is increased by the use of appropriate cosolvents. Cosolvent concentration is maintained below the amount needed for solute solubility at reservoir temperatures so that the solute will drop out of solution at some increased temperature depending on the concentration of the cosolvent added to the primary drive solvent.

Abstract: For selectively reducing permeability to water in an underground formation producing oil and/or gas, injecting into the formation a composition comprising water, at least one water soluble aldehyde compound at a concentration (by weight) of 180 to 20,000 ppm and at least one non-ionic polysaccharide at a concentration (by weight) of 200 to 5000 ppm, the concentration of aldehyde compound being higher than that of polysaccharide. The composition may be used in the water injection well or the hydrocarbon producing well and may assist in the recovery of hydrocarbons.

Abstract: A polymer is disclosed that is useful in increasing the viscosity of carbon dioxide. That polymer comprises a polysilalkylenesilane polymer, preferably polydimethylsilmethylenedimethylsilane. That polymer can be used in a method for recovering oil from an underground oil-bearing earth formation penetrated by an injection well and a producing well, in which method carbon dioxide is injected into the formation to displace oil towards the producing well from which oil is produced to the surface. The viscosity of the carbon dioxide injected into the formation is increased at least three-fold by the presence of a sufficient amount of a polysilalkylenesilane polymer and a sufficient amount of a cosolvent to form a solution of the polymer in the carbon dioxide.

Abstract: A method for enhancing the recovery of petroleum from an oil bearing formation during injection of a non-condensible gas comprises the at least periodic injection of a foam forming composition or a preformed foam into the reservoir. The foam comprises a mixture of a non-condensible gas, preferably CO.sub.2, water and an alpha-olefin sulfonate. The alpha-olefin sulfonate comprises a mixture of hydroxy-sulfonates and alkene-sulfonates wherein the ratio of alkene-sulfonates to hydroxy-sulfonates is preferably not greater than about 4. In addition, the hydroxy-sulfonates comprises 3-hydroxy and 4-hydroxy-sulfonates wherein the ratio of 3-hydroxy-sulfonates to 4-hydroxy-sulfonates is at least about 2. The method is preferably employed within a light oil bearing formation comprising sandstone.

Abstract: A foam is provided for use in a subterranean oil-bearing formation for reducing and controlling the mobility of a gaseous drive fluid. The foam is generated using an inert gas and a fluorocarbon surfactant solution in admixture with an amphoteric or anionic hydrocarbon surfactant solution. A relatively small amount of the fluorocarbon surfactant is operative, when mixed with the hydrocarbon surfactant and foamed, to generate a foam that has better stability when in contact with oil than a foam made with hydrocarbon surfactant alone.

Abstract: A process for in-situ enrichment of gas used in miscible flooding in a subterranean hydrocarbon-bearing reservoir. A drive gas such as methane, lean natural gas, nitrogen, carbon dioxide or mixtures thereof is used to immiscibly displace formation hydrocarbons. After gas breakthrough the produced fluid is separated into oil and gas components. The separated gas, which has been enriched with intermediate hydrocarbon compounds extracted from the formation hydrocarbons, is mixed with the drive gas injected into the reservoir so as to enrich the injected gas sufficiently to cause miscible displacement of the formation hydrocarbons. When the drive gas is carbon dioxide, methane and/or nitrogen may be extracted from the separated gas prior to being mixed with the drive gas.

Abstract: The invention has application only to a first oil well producing oil having a high water cut, said oil well being completed in a reservoir having an increased gas saturation, in the vicinity of the first oil well, arising from injection of gas through an adjacent injection well. The first oil well is treated by injecting through it into the reservoir a slug of non-condensible gas in an amount between about 40,000 m.sup.3 and 200,000 m.sup.3. The first well is then placed back on production and its water cut is significantly reduced.

Abstract: A process is provided for enhancing the recovery of oil in a subterranean formation. The process involves injecting a surfactant-containing foam having oil-imbibing and transporting properties. A foam having such properties is selected either by determination of the lamella number or by micro-visualization techniques.

Abstract: A method for recovering oil from a subterranean formation is disclosed wherein an aqueous surfactant solution is injected into the formation to reduce the mobility of gas in a gas-flooding process. The gas may include hydrocarbon gas, inert gas, carbon dioxide, and steam, or mixtures thereof. The surfactant is represented by the general formula ##STR1## where R is a linear or branched chain alkyl group with n carbon atoms wherein n ranges from about 6 to about 50, except that if the gas is steam n ranges from about 9 to about 50;Ar is a mononuclear or fused ring dinuclear aryl group;Z is an ionic group consisting of --SO.sub.3.sup.- M.sup.+ or --R'SO.sub.3.sup.- M.sup.+ wherein M.sup.+ is a cation and R' is a linear or branched chain alkyl group of from one to about six carbon atoms;x ranges from 0 to about 20; andy ranges from 3 to about 100.

Abstract: Oil recovery by carbon dioxide flooding is increased by adding surfactants to the carbon dioxide at high pressures such that an emulsion with water will be formed in the pore spaces of rock. The emulsion diverts flow of carbon dioxide to rock containing higher oil saturations.

Abstract: The invention is a foam method for improving conformance during a steam flood or carbon dioxide flood in an underground hydrocarbon formation penetrated by at least one injection well and at least one production well, which comprises injecting into an injection well about 0.05% to about 2% by weight aqueous surfactant solution, and then injecting into the injection well a flooding medium of steam or carbon dioxide, said surfactant solution comprising a surfactant having the formulaR(C.sub.2 H.sub.4 O).sub.n SO.sup.4 M.sup.+where R is a lignin phenol produced by reducing lignin in the presence of a reducing agent of carbon monoxide or hydrogen at a temperature greater than about 200.degree. C. and a pressure greater than about 100 psi, n has an average value of about 2 to about 25, and M.sup.+ is an alkali metal or ammonium cation.

Abstract: A polymer having pendant silyl ether groups is disclosed having a minimum solubility parameter of 6.85 (cal/cc).sup.1/2 or less. That minimum solubility parameter is reduced to 6.85 (cal/cc).sup.1/2 or less by control of the number of pendant silyl ether groups and by the selection of said silyl ether groups. The polymer can be formed by reacting a olefin monomer with a silyl monomer or by grafting a silyl monomer onto an unsaturated polyolefin. Preferably, the silyl monomer is either a vinyl trimethylsilyl ether monomer, a vinyl dimethylchlorosilane monomer, or a vinyl methyldichlorosilane monomer. Preferably, the olefin monomer is decene, and the unsaturated polyolefin is polydecene.

Abstract: The present invention provides a system and method for producing an effluent contained in a geological formation forming a reservoir for said effluent or producing formation, including a central well, at least one subhorizontal drain as well as a displacing or displacement agent, the displacement agent being injected into the formation either from the central well or from the subhorizontal drain and the displacement agent causes migration of the effluent to be produced.

Abstract: A polymer is disclosed that is useful in increasing the viscosity of carbon dioxide. That polymer comprises an organosilicon polymer having nonrandom crosslinkages that enhance backbone rigidity. Preferably, that polymer is a polyalkylsilsesquioxane. That polymer can be used in a method for recovering oil from an underground oil-bearing earth formation penetrated by an injection well and a producing well, in which method carbon dioxide is injected into the formation to displace oil towards the producing well from which oil is produced to the surface. The viscosity of the carbon dioxide injected into the formation is increased at least three-fold by the presence of a sufficient amount of the polymer and a sufficient amount of a cosolvent to form a solution of the polymer in the carbon dioxide.

Abstract: A method for positioning at least one plug, or screen, between two fluids in a geological formation, a product intended to form said plug being injected through at least one substantially horizontal plane situated in the vicinity of the interface formed by said two fluids.

Abstract: A method of fracturing a subterranean formation involving the use of crosslinked gels to form a fracture and deposit particulate proppant therein followed by the introduction of dilute aqueous solutions of chlorine dioxide in the propped fracture to degrade the gel.

Abstract: A method of treating a subterranean formation is provided using a treating fluid comprising from about 0% up to about 80% by volume liquid carbon dioxide. The remainder of the treating fluid comprises a viscous substantially anhydrous liquid which may be crosslinked by a metal ion source. The treating fluid is formed by the addition of polymers or copolymers of dimethylacrylamide to the substantially anhydrous fluid.

Abstract: An enhanced oil recovery process is described wherein oil is recovered from a depleted water-wet formation by the application of a gas to the formation. The flow of gas through the formation causes oil droplets to spontaneously form an oil film on connate water, which is extruded and discharged from the pores. The films pass through the formation under the influence of gravity, gradually accumulating more oil to form an oil mass which enters the producing well bore. A sem-permeable membrane may be used to prevent the inert gas from entering the well bore from the formation.

Abstract: A flowing crosslinked polymer gel is employed as a kill fluid or as an additive to a kill fluid in a process for preventing the intrusion of formation fluid into a wellbore while minimizing wellbore fluid leakoff in the formation during conventional oil field operations in the wellbore. The gel comprises a carboxylate-containing polymer and a chromic carboxylate crosslinking agent.

Abstract: A process for removing and disposing of or neutralizing volatile contaminants existing in the vadose zone of earth and also in a below ground aquifer. The process includes the injection of substantially oxygen free air into the aquifer to retard the formation of aerobic bacteria and injection of oxygen rich air into the vadose zone to stimulate bacterial growth which aids contaminant recovery. Volatilized contaminants are pulled out of the soil through withdrawal wells which terminate in the vadose zone.

Abstract: A polymer having pendant tertiary alkyl amine groups is disclosed having a minimum solubility parameter of 6.85 (cal/cc).sup.1/2 or less. That minimum solubility parameter is reduced to 6.85 (cal/cc).sup.1/2 or less by control of the number of pendant tertiary alkyl amine groups and by the selection of said tertiary alkyl amine groups. The polymer can be formed by reacting either polyglycol (such as polypropylene glycol) or a polyolefin (such as polybutadiene) with a secondary amine, such as diisobutylamine.

Abstract: A polymer having pendant vinyl ether groups is disclosed having a minimum solubility parameter of 6.85 (cal/cc).sup.1/2 or less. That minimum solubility parameter is reduced to 6.85 (cal/cc).sup.1/2 or less by control of the number of pendant vinyl ether groups and by the selection of said vinyl ether groups. Preferably, the polymer has a molecular weight of over 1000 and is formed by reacting an olefin monomer (such as decene) with a vinyl(ethyl ether) monomer or by grafting a vinyl ether monomer onto an unsaturated polyolefin (such as polydecene).

Abstract: A method of increasing the viscosity of CO.sub.2 at least three-fold by adding (1) a viscosifying amount of a polymer having a Minimum Solubility Parameter of 6.85 or less and a plurality of electron donor atoms selected from the group consisting of O, N, and S, and (2) a sufficient amount of a cosolvent to form a one-phase solution, said cosolvent being capable of (a) dissolving at least 2% by weight of CO.sub.2 at 25.degree. C. and 900 psig, and (b) forming a one-phase mixture with the polymer when the mixture contains 10 weight percent cosolvent at ambient temperature and a pressure sufficient to maintain the cosolvent in the liquid phase. New compositions containing CO.sub.2, the defined polymer and cosolvent are also claimed as is a method for recovering oil from underground formations using a viscosified CO.sub.2.

Abstract: An improved process for recovering oil by injecting a mixture of noncondensible gas and gas foam surfactant into an oil-containing subterranean reservoir, the improvement provided by using a surfactant enriched in olefin disulfonate. The sulfactant may be used in either a gas drive or a gas soak process. Disulfonate-enriched gas foam surfactants and mixtures are also described.

Abstract: A method for the completion or work-over of a well comprises the step of using a solids-free, non-aqueous well-bore fluid comprising a halogenated organic compound as a completion or work-over fluid. The fluid has a specific gravity in the range 0.9 to 2.3.Preferred halogenated organic compounds are brominated aromatic ethers, diphenyls, aliphatic hydrocarbons, benzene and alkyl benzenes.The halogenated organic compound may be dissolved in an organic solvent. The relative proportions may be chosen to provide a well-bore fluid having a desired specific gravity.The fluids are non-corrosive, thermally stable and non-damaging to formations.

Abstract: A process for modifying the minimum miscibility pressure (MMP) of a drive fluid and hydrocarbonaceous fluid mixture by addition of alcohol to the drive fluid. Alcohols which can be utilized include methanol through octanol. The preferred drive fluid comprises carbon dioxide. Selection of the alcohol will depend on the water saturation in the reservoir and gravity of the crude oil. MMP modification results in an increased and more efficient recovery of reservoir oil.

Abstract: A method for production of nitrogen for application at high pressure, preferably for pressure injection in submarine or substerranean oil or natural gas wells, by combination of natural gas in air, which is compressed prior to the combustion, for binding of the oxygen content of the air in carbon dioxide to be removed from the flue gas by absorption, whereas the remaining nitrogen is pressurized to a predetermined high pressure suitable for such application.

Abstract: A method of producing coalbed methane by injecting inert gas, such as nitrogen, through an injection well into the coal seam and recovering coalbed methane from a production well(s). Methane desorption from coal is achieved by reduction in methane partial pressure rather than by reduction in total pressure alone.