Abstract: Methods of remedially treating coal bed methane wells to enhance the production of methane therefrom are provided. The methods basically comprise pumping a clean out fluid into the well and into producing zones communicated with the well by perforations therein. The pumping of the clean out fluid is continued while adding perforation sealers thereto to thereby seal perforations and producing zones which are not plugged and to divert the clean out fluid into perforations and producing zones which are partially plugged. An aqueous acid solution is next pumped into the partially plugged perforations and producing zones whereby acid soluble solid materials in the perforations and producing zones are dissolved. The well is shut in, reverse flowed and then returned to production.

Abstract: In the removal of particulates from a wellbore, such as in air drilling for hydrocarbon recovery, a mixture of an amphoteric foaming agent and, typically, an anionic surfactant is employed. An aqueous solution thereof having a pH of at least 9.5 is used to generate a foam for removing the particulates; then the foam is collapsed by the introduction of acid to reduce the pH below about 4, the particles are removed mechanically, the pH is restored to greater than 9.5, and the foaming solution is returned to the wellbore. The solution may be used several times; partial losses of foaming agent in the process may be easily replenished with each cycle. Cationic surfactants may be used instead of anionic, with foaming and foam collapse being controlled at opposite pH's. Savings are realized in water, drilling chemicals, and settling pits and the like for removing particulates from the foam.

Abstract: A method of stimulating a subterranean formation using a foamed cement composition. When hardened, the cement composition has a permeability of at least about 0.3 darcies. The inventive formation stimulation method comprises the steps of: (a) injecting the foamed cement composition into the formation at a pressure sufficient to fracture the formation and (b) allowing the cement composition to harden in the formation.

Abstract: An enhanced oil recovery technique for recovering hydrocarbons from a reservoir during gas injection comprises the at least periodic injection of gas and a foam-forming composition into the reservoir. The foam-forming composition comprises water, an effective foam-forming amount of a C.sub.10-16 .alpha.-olefin sulfonate surfactant including C.sub.10 AOS and/or C.sub.12 AOS, and an effective amount of at least one solubilizing component to increase the brine tolerance of the composition. This solubilizing component is a mixture comprising ##STR1## where M is H, an alkali metal, alkaline earth metal, or ammonium, where R.sub.1 is a linear C.sub.6 -C.sub.16 alkyl group. The method further comprises contacting the hydrocarbons in the reservoir with the foam so as to assist in the recovery of hydrocarbons from the reservoir.

Abstract: A foam generator is provided for in-line installation within a surface tubing network. The generator has a foaming chamber with a plurality of permeable screens positioned in series along a continuous flowpath through the foaming chamber. The screens are separated from one another by spacers that define the radial boundaries of the flowpath. According to one embodiment, the screens and spacers are mounted in a cartridge that fits into the foaming chamber to maintain proper screen alignment and facilitate removal of the screens from the chamber for maintenance. In an alternate embodiment, the screens and spacers are mounted directly in the chamber. In both embodiments, the screens are aligned orthogonal to the flowpath enabling the generator to produce a properly textured foam from shear-sensitive fluids with relatively little shear degradation.

Abstract: A process is provided for promoting oil production from a producing interval of a subterranean hydrocarbon-bearing formation by reducing undesirable gas production therefrom due to gas override or gas channeling in the upper portion of the interval. A polymer enhanced foam containing a polymer, an aqueous solvent, a surfactant, and a gas is placed in the upper portion of the producing interval, thereby substantially inhibiting or blocking the flow of gas therethrough to an oil production wellbore in fluid communication with the producing interval and enabling oil to more readily enter the wellbore for production to the surface.

Abstract: A steam foam method of recovering hydrocarbons from an underground hydrocarbon formation, which comprises injecting steam through an injection well into the formation, injecting an aqueous solution having a salinity greater than about 1% by weight and a pH of about 8 to about 12, comprising about 0.1% to about 5% by weight of a fatty acid salt having about 10 to about 24 carbon atoms, and injecting steam into the formation to sweep hydrocarbons towards the production well for recovery.

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 an alcohol having about 8 to about 20 carbon atoms in a concentration such that the ratio of alcohol to surfactant in the foaming solution is between about 1:6 and about 1:2.

Abstract: A method for enhanced oil recovery in a reservoir having a substantial silicon content where an organosilicone surfactant is co-injected with steam to generate a foam. The organosilicone surfactant component of the foam prevents a dissolution of the silicon-containing formation since local equilibrium is assured. Prevention of formation dissolution reduces caving near the wellbore and minimizes permeability reduction away from the wellbore.

Abstract: A process is provided for reducing the inhibiting effect of gas coning on liquid hydrocarbon production at a production wellbore penetrating a subterranean reservoir having a gas cap overlying a liquid hydrocarbon producing zone in fluid communication with the gas cap across vertical flowpaths of gas-permeable matrix. A foamed gel containing a crosslinkable polymer, a crosslinking agent, an aqueous solvent, a surfactant, and a gas is injected through the production wellbore into gas-permeable matrix between the gas cap and wellbore, thereby effectively blocking or reducing the downward flow of gas from the gas cap to the production wellbore and enabling the more desirable liquid hydrocarbons to enter the wellbore for production to the surface.

Abstract: An additive for addition to conventional well treatment fluids to enhance the ability of the fluids to be recovered from subterranean formations, to generate a foam in association with the fluids and/or to enhance the ability of the fluids to remove water and other connate fluids interlocked with gas in the formations. The additive includes about 25% to about 50% by volume of a microemulsion generating component which forms an acid and/or water external microemulsion when added to the treatment fluid, and about 50% to about 75% by volume of a foaming agent component. The foaming agent component includes at least one nonionic surface active agent having an HLB of from 12 to 22. The additive is particularly suitable for addition to foam fracturing fluids useful for stimulating tight or otherwise unconventional gas formations. Also provided are a gas well treatment composition employing the inventive additive and a method of treating a subterranean formation in which the inventive composition is employed.

Abstract: A process is provided for reducing the inhibiting effect of gas coning on liquid hydrocarbon production into a production wellbore penetrating a subterranean formation having a gas cap overlying a liquid hydrocarbon producing zone in fluid communication with the gas cap. A polymer enhanced foam containing a polymer, an aqueous solvent, a surfactant, and a gas is placed in gas-permeable anomalies or matrix between the production wellbore and gas cap, thereby effectively blocking the downward flow of gas from the gas cap to the production wellbore and enabling desirable liquid hydrocarbons to more readily enter the wellbore for production to the surface.

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 blast joint resistant to erosion including an inner pipe joint having a substantially smooth outer surface and an upper end and a lower end. A cylindrical lower assembly having an exterior surface suitable for gripping with power tongs is mounted on the lower end of the inner pipe joint with a torque transfer assembly for transferring torque from the lower assembly to the smooth outer surface of the inner pipe joint. A cylindrical upper assembly having an exterior surface suitable for gripping with power tongs is mounted on the upper end of the inner pipe joint. A plurality of erosion resistant rings are concentrically mounted on the inner pipe joint in a vertically continuous arrangement from a point near the lower end to a point near the upper end of the inner pipe joint without a vertical gap between the rings. A hydrostatic piston and cylinder loader provides a vertical load on the plurality of rings to prevent separations between the rings.

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: A method for improving the sweep efficiency of gas or steam flooding operations by reducing the permeability of relatively high permeability thief zones of an oil bearing subterranean reservoir having heterogeneous and/or fracture permeability and that is penetrated by at least one well is disclosed. A controlled quantity of a surfactant is injected into a high-permeability zone of a reservoir. Controlled quantities of a gas and a subsequent surfactant are then injected, simultaneously or alternatively into the same well, so that a controlled amount of foam having a controlled quality is generated in the high permeability zone, thereby reducing permeability. Following foam emplacement, a chase gas may be injected, and the steps of injecting surfactant and gas may be repeated as necessary to lower the gas-oil ration of non-problem offset producing wells to a preset limit.

Abstract: A method for reducing the time during which steam moves in a lateral direction between two parallel superimposed horizontal wells when utilizing a Steam Assisted Gravity Drainage (SAGD) process. Foam is added while injecting steam into an upper horizontal well once steam breakthrough occurs in an interwell region. Foam enters the interwell region thereby causing an increased pressure gradient. This increased pressure gradient adds to the gravity force thereby providing a greater interstitial oil velocity which increases oil drainage between wells during startup.

Abstract: A foam/steam injection method for forming fractures is a for reservoir penetrated by a horizontal wellbore. Steam is injected into said wellbore at a pressure sufficient to fracture the formation. Water which is used to make the steam contains a foamable composition in an amount sufficient to make a foam upon contact with steam. Steam and foam enter the wellbore and create a fracture in an oil-rich zone. Thereafter, foam blocks further steam entry into the created fracture which causes another fracture to form at a second interval along the horizontal wellbore. These steps are repeated until a fracture system is made along the length of the wellbore.

Abstract: The invention relates to the treatment by a fluid, or more generally by an acid fluid, of subterranean formations located in particular around an oil, gas, water or geothermal well.Acid is diverted towards the zone to be treated by a surfactant flush, the injection of a foam and then the injection of an acid/surfactant composition. These operations are repeated as often as required, increasing at each stage representing approximately 80 cm (20 to 25 inches) of treatment in terms of height the quantity of foam injected.

Abstract: Pathway-containing foamed gels enhance the recovery of the nonaqueous fluids from subterranean formations by selectively reducing the flow of aqueous fluids with respect to the flow of nonaqueous fluids.

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: A method for recovering hydrocarbons from a reservoir during gas injection into the reservoir comprises at least periodically injecting a gas comprising steam and a foam-forming composition which includes at least one steam foam diversion surfactant into a reservoir which contains at least one multivalent cation. The foam forming composition comprises water, an effective foam-forming amount of the surfactant which preferably comprises an alkyl aromatic sulfonate and a precipitation control additive. This precipitation-control additive preferably comprises an alpha-olefin sulfonate dimer (AOSD). The method further comprises contacting the hydrocarbons in the resevoir with the foam and the gas so as to assist in the recovery of hydrocarbons from the reservoir.

Abstract: A method for introducing a surfactant into an oil bearing formation includes plurality of a micro-slug injections of surfactant. Each micro-slug injection comprises an "on time" in which the surfactant is introduced into the formation and which is based upon the time needed for the surfactant to generate foam in the formation and a "off time" in which surfactant flow is stopped and is based upon the time period for the generated foam to degrade to a predetermined degree in the formation.

Abstract: Alkaline earth metal scales, especially barium sulfate scale is removed from a well (the wellbore and the adjacent formation) by contacting the scale with a scale-removing solvent and thereafter sparging the solvent with air or insert gas to dissolve the scale. The sparging aids in achieving a flushing action by the solvent relative to the scale thereby enabling the solvent to more effectively dissolve the scale in the well. Temperature and caustic compatible surfactuants (anionic and non-ionic) may be used in the solvent to generate a column of foam which increases the extent of cleaning oil from the scale surfaces, enabling the solvent to more effectively remove the scale.

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 microbial system is provided for selective plugging of permeable regions of a subterranean formation, for use in conjunction with injection of surfactant-containing foams. Bacteria indigenous to the target formation are isolated, and selected for ability to degrade the surfactant of interest. Small, non-adherent ultramicrobacteria, or UMB, are prepared from the selected culture by starvation. The UMB and the surfactant-containing foam are then injected into the target formation. The surfactant allows the foam to penetrate into the formation. The UMB then revive to their vegetative state, degrade the surfactant and produce exopolymer, thus plugging the formation.

Abstract: The time delay experienced between the commencement of the steam-foam drive and the subsequent incremental increase in oil production rate is reduced by simultaneously (a) injecting steam into the lower level of a subterranean oil-bearing formation and (b) injecting foam into the upper elevation of the formation. Preferably, the elevation where the foam is injected is gradually lowered while maintaining the steam injection elevation substantially constant. The accelerated response rate improves the economics of the steam-foam drive.

Abstract: Foamed well cementing compositions and methods of performing cementing operations in salt containing subterranean environments are provided. The compositions are comprised of hydraulic cement, salt water, dispersed gas and a foaming agent selected from the group consisting of surfactants of the formula R--(OR').sub.n --OSO.sup.-.sub.3 X.sup.+.

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 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 comprises a selective plugging treatment with good penetration for acid diversion or water control. The fluid comprises a foamed delayed gelation system.

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 hydraulic fracturing process in which substantial quantities of both nitrogen and carbon dioxide are incorporated into the fracturing fluid. Nitrogen and carbon dioxide are separately incorporated into an aqueous based fracturing fluid in amounts to provide a volume ratio of nitrogen to carbon dioxide at wellhead conditions within the range of about 0.2-1.0. The volume ratio of the total of carbon dioxide and nitrogen to the aqueous phase of the aqueous fracturing fluid at wellhead conditions within the range of about 1-4. The aqueous fracturing fluid containing the nitrogen and carbon dioxide is injected in the well under a pressure sufficient to implement hydraulic fracturing of the subterranean formation undergoing treatment. A thickening agent may be incorporated into water to provide a viscous aqueous based fracturing fluid to which the carbon dioxide and nitrogen are added. The carbon dioxide is incorporated in liquid phase and the nitrogen in gaseous phase.

Abstract: Device for extracting a liquid out of a tube of great length closed at one of its ends in case a communication between the closed end and a source of a substitution fluid should be difficult to establish, the device includes a mobile member provided with a body connected to a supporting surface apparatus, a piston whose cross-section is adapted to the inner cross-section of the tube controlled valve means allowing for the running of the mobile member along the tube and means in the body for providing a substitution fluid such as liquified gas bottles or substances which provide a great volume of gas when combusted. Such a device is useful for example for emptying tube when production tests are conducted in oil wells,.

Abstract: A process for the recovery of oil from a petroleum reservoir by improving steam sweep efficiency during steam-flooding, wherein a foaming agent is added to divert steam to unswept zones and the reservoir is penetrated by at least one injection well and at least one production well, which process comprises injecting steam and a surfactant solution into an injection well, while concurrently and separately injecting an additional amount of liquid water into the injection well; and recovering oil from a production well.

Abstract: Conductivity damage is decreased in fracturing a high temperature (greater than 200.degree. F.) well by employing a first fracturing fluid which is substantially stable at the bottom hole static temperature and pumping a second fracturing fluid behind the first fracturing fluid which is less stable at bottom hole static temperature than the first-pumped fracturing fluid.

Abstract: A method of enhanced oil recovery using foam to improve the effectiveness of steam to mobilize viscous crude, either for steam stimulation in a single well or for steam drive between wells. A new surfactant composition having branched alkyl aromatic sulfonates as the effective agent for the steam foamer is used because of its ability to foam in the presence of substantial pore volumes of residual oil and thereby mobilize significant amounts of producible oil by diverting steam to less-permeable zones.

Abstract: Hydraulic fracturing process in which a normally gaseous energizing phase is incorporated into an aqueous fracturing fluid in a manner to effect good dissemination and stabilization of the energizing phase in the fracturing liquid. A normally gaseous energizing phase is incorporated into an aqueous fracturing fluid having a viscosity at wellhead conditions within the range of 10-300 centipoises. The fracturing fluid containing the energizing phase is introduced into the well and displaced from the wellhead down the well to the vicinity of the subterranean formation. During the displacement of the fracturing fluid from the wellhead to the vicinity of the formation, the viscosity of the fracturing fluid is increased by a factor about 2 or more. The higher viscosity fracturing fluid is displaced from the well into the formation in the course of the fracturing process. The energizing phase is provided by incorporating a substantial amount of liquid carbon dioxide into the aqueous fracturing fluid.

Abstract: The method for the enhanced recovery of hydrocarbons from a hydrocarbon bearing reservoir during gas injunction into the reservoir comprises the at least periodic injection of steam and a foam-forming mixture into the reservoir from a known depth interval in a well source to provide a foam in the presence of residual oil and high gas permeable channels of the reservoir. The mixture comprises water, an effective foam forming amount of an alkyl aromatic sulfate component having an average molecular weight from about 400 to about 600 and at least one alkyl group comprising 18 to 24 carbon atoms and a viscosity control agent. The viscosity control agent comprises a surfactant which is present in an amount effective to prevent gelling of the mixture during storage. The reservoir fluids are contacted with the resulting foam so as to assist movement of the hydrocarbons toward a producing interval and the hydrocarbons are recovered from the producing interval.

Abstract: Method for fracturing coal seams to improve the production (e.g. methane and/or water) therefrom. A water-based fracturing fluid is injected into the coal seam under pressure wherein the fracturing fluid contains both a wetting agent and a dispersant. The wetting agent contacts the fines which are formed during the fracturing of the coal and converts them from "hydrophobic" to "hydrophilic" while the dispersant serves to disperse and suspend the fines within the fracturing fluid. This prevents early screen-out of the fines from the fracturing fluid which allows the fluid to propagate fractures of longer lengths into a coal seam before the fines settle out to block further flow through a fracture.

Abstract: A method to enhance steam flooding where at least two horizontal wellbores are utilized. Carbon dioxide is injected into a lower perforated horizontal wellbore. Once sufficient carbon dioxide has been injected into the formation, steam is injected through the lower horizontal wellbore. The steam displaces the carbon dioxide into the formation where it contacts and mixes with hydrocarbonaceous fluids. Steam causes the carbon dioxide to expand, thereby providing for a better sweep of the formation. Steam injection is ceased and liquid carbon dioxide injection again is commenced. Afterwards, steam is injected again into the formation. This sequence is continued until it becomes uneconomical to produce hydrocarbonaceous fluids from an upper horizontal wellbore. Hydrocarbon displacement efficiencies are enhanced when hydrocarbons are produced into the upper horizontal wellbore due to viscosity and density differences.

Abstract: A method of enhanced oil recovery using foam to improve the effectiveness of steam to mobilize viscous crude, either for steam stimulation in a single well or for steam drive between wells. The new surfactant composition used comprises alkyl aromatic sulfonates having an average molecular weight of from about 400 to about 600 and comprising at least 2 alkyl groups wherein one alkyl group is linear and has from 3 to about 30 carbon atoms and one alkyl group is a branched chain and has from 5 to about 25 carbon atoms as the effective agent for the steam foamer. The dialkyl aromatic sulfonates having linear and branched chain substitutes provide significant economic advantages over alkyl aromatic sulfonates having only branched chain substituted and provide significant performance advantages over alkyl aromatic sulfonates which do not contain branched chain alkyl groups.

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 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 of preparing either foamed or nonfoamed fracturing fluids which maintain an at least substantially constant viscosity during the introduction of varying concentrations of proppant. The at least substantially constant viscosity fluids of the present invention provide a substantially constant friction pressure, which provides improved on-site, real-time analysis and to a better evaluation of the fracture treatment.

Abstract: A reservoir-engineering method wherein horizontal barriers against flow of undesired reservoir fluids into an oil well are formed by density-controlled injection of a barrier-forming fluid mixture having a large penetration depth into the reservoir. A barrier-forming injection fluid may be placed at the fluid contacts in the reservoir independent on whether it is injected at these, in that it has an intermediate density in relation to the reservoir fluids between which it is desired to be placed. Particularly suitable barrier-forming injection fluids are foam-forming chemicals which in several ways may be converted into mobility reducing barriers in situ.

Abstract: Thread leaks, small holes, and leaks around packers in well casings and production tubing are repaired by applying a compressed foam mixture which includes discrete solid particles of various sizes for forcing the suspended particles into the opening to provide a high friction seal. The foam mixture is moved along the inside of the conduit sandwiched between fluid bodies for maintaining the foam mixture intact. Back pressure is applied to the foam mixture for aiding the mixture to be forced through the openings.

Abstract: A gas flooding process for displacing oil within a reservoir is improved by injections of a surfactant having a composition and concentration correlated with those of the brine used to remain substantially within the water phase of the injected fluid at a concentration below the critical micelle concentration of the surfactant.