Abstract: A method for staging a fracturing treatment in a horizontal wellbore where solidified gel is used as a diverting medium. A desired section of the horizontal wellbore farthest removed from the angle of deviation from vertical of the wellbore is perforated. Via perforations contained in the horizontal section, the desired interval is fractured hydraulically. The gel is displaced with a "wiper plug" and the gel confined to the fractured interval and wellbore area adjacent the fractured interval. Here the gel forms a solid gel in the interval and a gel plug in the wellbore. Afterwards, another section of the horizontal well is perforated. Thereafter, a second desired interval is fractured. After completion of the fracturing process, the gel plug breaks and the "wiper plug" is pumped to the farthest end of the horizontal wellbore.

Abstract: The present invention is a phosphate compound for use in a bacterial nutrient medium. The medium is injected downhole in a petroleum formation along with a bacteria (or its spore) and provides the bacteria with growth nutrients. The nutrient solution contains a phosphate compound which: will not precipitate out of solution under ambient conditions; will chelate alkaline earth, rare earth, transition and heavy metal ions; and provide a nutrient source for the bacteria.

Abstract: A secondary oil recovery process is disclosed involving the injection of a polysaccharide polymer naturally produced by certain bacteria in a solubilized form into the oil sand or horizon. When such polymer is injected, it is solubilized in alkali solution such as sodium hydroxide. Within the formation, the polysaccharide polymer may be precipitated by the later injection of an acid solution or carbon dioxide. The order of injection of the acidic materials and the solubilized polymer is not critical, except with respect to carbon dioxide injection, which must follow the solubilized polymer injection. The gelling or the precipitation of polymer in the formation takes place preferentially in the higher permeability zones, such perhaps already wet with water. By such precipitation, the high permeability zones are selectively blocked off, giving sweep access primarily to the lower permeability zones containing mostly oil. The solubilized polymer may be used as a secondary recovery sweep liquid, per se.

Abstract: A gel-forming composition capable of plugging highly permeable zones in a subterranean formation. The composition comprises water, a water-dispersible polyvinyl alcohol copolymer and a crosslinking agent which is a mixture of an aldehyde and a phenolic component in an amount effective to cause gelation of the aqueous solution of the copolymer. The resultant gel is exceptionally thermally stable and, therefore, can be used as an effective profile control agent in all enhanced oil recovery operations, including steam flooding. Also provided is a process for recovering oil from a subterranean oil-bearing formation.

Abstract: A process for closing pores in a heated steam swept zone of a formation having zones of varying permeabilities where a temperature activated aqueous gellable mixture is utilized following a steam flooding or steam stimulation enhanced oil recovery method. After being placed into the steam swept zone having varying permeabilities, a temperature above 300.degree. F. activates components in the gellable mixture which causes a solid gel to form which closes pores in the steam swept zone. A spacer volume of cold water is pumped into the formation to remove any ungelled mixture. Steam is directed into an unswept zone and hydrocarbonaceous fluids recovered therefrom. Polymers utilized include polyvinyl alcohol and polyacrylamide cross-linked with phenol and an aldehyde producing compound sufficient to form a phenolic resin in situ.

Abstract: A method and composition for altering the permeability of a high temperature subterranean formation are provided. The composition of the invention is comprised of water, at least one water dispersible acrylamide containing polymer, and a water dispersible crosslinker for bringing about the delayed crosslinking of the polymer comprised of the combination of an aldehyde and a salicylic acid derivative.

Abstract: The recovery of oil or gas from underground porous formations bearing such hydrocarbons is enhanced by using an injection fluid containing a viscosifying amount of a poly(vinylamine) formed in-situ by hydrolysis of a high molecular weight poly(N-vinylamide). The hydrolysis conditions are strongly acidic or highly alkaline and include the elevated temperature of the formation.The poly(N-vinylamide), such as poly(N-vinylformamide), can be made by inverse emulsion polymerization and the high solids emulsion mixed directly with the acidic or basic solutions to form the injection fluid.The process is applicable to enhanced oil recovery using fluids for water-flooding, well completion or workover, and acidifying or fracturing.

Abstract: An aqueous polymeric gel-forming composition of improved stability for selectively plugging highly permeable zones in subterranean oil-bearing formations. The composition comprises an aqueous solution of a water-dispersable polymer present in a viscosifying amount, a crosslinking agent present in an amount sufficient to cause gelation and a stabilizing agent in an amount effective to reduce syneresis of the gelled composition.

Abstract: An aqueous polymeric gel-forming composition which slowly crosslinks to form stable gels for plugging highly permeable zones in subterranean oil-bearing formations. The composition comprises an aqueous solution of a water-dispersible polymer present in a viscosifying amount and a crosslinking agent present in an amount effective to cause gelation of the polymeric solution which comprises a mixture of an aldehyde and a member selected from the group consisting of phenolic ester, naphtholic esters, halogenated phenolic esters and halogenated naphtholic esters.

Abstract: Volumetric sweep efficiency and oil recovery by CO.sub.2 flooding processes may be increased by injecting a surfactant solution into the formation which will form a gel in-situ in the high permeability zones via interaction of the surfactant with formation brine, oil, and CO.sub.2 under formation conditions. Thereafter, improved oil recovery efficiency is realized in displacing oil from the lesser permeability zones. The surfactant solution is selected from phase behavior experiments which show gel precipitation at conditions of temperature, salinity, oil composition, and CO.sub.2 pressure which are expected to exist or may be practically established in the particular oil-containing formation. Preferably, the gel is precipitated at CO.sub.2 pressures above the minimum miscibility pressure for CO.sub.2 miscible flooding, and below the prevailing formation pressure during the CO.sub.2 flooding.

Abstract: Methods and compositions for altering the water permeability of subterranean formations are provided. The compositions are comprised of water, at least one polymer capable of being gelled when contacted with a crosslinking agent, at least one crosslinking agent comprised of polyvalent metal cation, and a cation reactivity retarding chelating agent which provides anion for chelating the polyvalent metal cation selected from substantially water soluble dicarboxylic acids, hydroxy carboxylic acids, ketocarboxylic acids and the corresponding salts thereof.

Abstract: A method for controlling the permeability profile of a subterranean oil-bearing formation utilizing polymeric gel-forming compositions which gel in-situ. The method comprises the steps of determining an amount of polymeric gel required for profile control; introducing a first aqueous gel-forming composition in a non-gelatinous state into the formation in an amount which is a portion of the total gel requirement; and, introducing into the formation in a non-gelatinous state at least a second aqueous composition capable of forming a gel at a rate in excess of the first gel-forming composition wherein the gelation of all compositions proceeds in timed relation such that each solution gels at approximately the same time. The method so described reduces reservoir shut-in time and is especially useful in the treatment of large reservoirs.

Abstract: A process for closing pores in a bottom water zone where steam is directed so as to by-pass a zone of the formation containing hydrocarbonaceous fluids. Once a portion of the bottom water zone has reached a temperature in excess of about 300.degree. F., steam entry is ceased. Afterwards, a temperature activated gellable composition is placed into the bottom water zone. When the composition reaches that portion of the bottom water zone where a temperature in excess of about 300.degree. F. has been reached, the composition activates and forms a rigid gel. Thereafter, a steam flooding method is commenced. Steam is diverted from the bottom water zone and into an upper zone containing hydrocarbonaceous fluids.

Abstract: A process for the selective gelation of a polymer for profile control during carbon dioxide flooding. First, a size selective gel is formed ex-situ. Upon entering a thief zone or a more permeable low pH zone resultant from carbon-dioxide flooding, the gel forms a solid, firm gel. This gel comprises an aqueous composition of a partially and fully alkylated melamine resin and an xanthan polymer. Size selectivity is imparted by the partially alkylated resin and the polymer. Upon contact with the low pH environment, active melamine resin is released from the fully alkylated resin which reacts with the polymer to form a stable, solid gel. Once the solid gel has formed, steam-flooding, water-flooding or a carbon-dioxide oil recovery process is commenced in a zone where a solid gel has not formed.

Abstract: A process for profile control in a high permeability zone of a formation. A water flooding or carbon dioxide stimulation enhanced oil recovery (EOR) process is conducted in an an oil-containing formation having a high permeability zone. After breakthrough occurs, the EOR process is ceased. The high permeability zone is heated to a temperature of 300.degree. F. or higher by steam injection. Subsequently, steam injection is ceased and a temperature activated mixture is injected into the high permeability zone where it forms a solid gel. Thereafter, an EOR process can be used to remove hydrocarbons from a low permeability zone.

Abstract: An aqueous gel composition is formed from xanthan gum crosslinked with ions of a transitional metal, resorcinol, and formaldehyde. The gel which initially forms is injected into a formation where it selectively enters pores in a more permeable zone. Once in the more permeable zone, the gel reheals and forms a shear and thermally stable gel. This gel can be used in high temperature formations in addition to those formations having a pH of from about 3.0 to about 10. After the shear and thermally stable gel has formed, a steam-flooding, water-flooding, or a carbon dioxide oil recovery process is commenced in a zone of lesser permeability.

Abstract: A method for selectively closing pores in a formation's zone of greater permeability. A rehealable Xanthan or Alcaligenes biopolymer in an aqueous medium is combined with an organic or transition metal cross-linker which forms a first stage selective ex-situ gel. Second stage non-selective gel precursors are also included. The second stage gel comprises a polymer cross-linked with organic cross-linkers so as to form an in-situ gel more able to withstand formation conditions. The combination is injected into a formation after the first stage gel forms where it selectively enters a zone of greater permeability carrying therewith said non-selective gel. Once in the formation's zone of greater permeability, the gel reheals and forms a rigid gel having the desirable characteristics of the non-selective gel.

Abstract: A method for minimizing blockage in a zone of lesser permeability when injecting gels into a formation during profile control. A solidifiable gel which comprises a hydroxyproyl guar gum containing a gel breaker is injected into the formation where it enters a zone of lesser and a zone of greater permeability. Said gel blocks pores in the zone of lesser permeability. A second solidifiable gel formed from a melamine formaldehyde resin, a crosslinkable polymer, and lacking a gel breaker is injected into the zone of greater permeability where it subsequently solidifies. Said gel contained in the zone of lesser permeability liquefies thereby unblocking this zone. Afterwards, a water-flooding enhanced oil recovery method is directed into the zone of lesser permeability.

Abstract: A novel cross-linked polymer is obtained by cross-linking polyvinyl alcohol with a cross-linking agent which is a mixture of a phenolic component and an aldehyde or a mixture of a naphtholic component and an aldehyde. The resulting polymer is exceptionally thermally stable and, therefore, can be used as an effective permeability control agent in all enhanced oil recovery operations, including steam flooding.

Abstract: An active combustion zone is established in situ within a permeable hydrocarbon formation. The permeable formation is periodically charged with a combustible gas, and is thereafter subjected to a high pressure pulse produced by detonation of the combustible gas within an injection well. The periodic pressure pulses drive the combustible gas into the in situ combustion zone. Combustion is sustained by injection of an oxidant. The injection of oxidant is terminated periodically, and the injection well along with the surrounding formation is pressurized and saturated with the combustible gas mixture. The combustible gas mixture is displaced through the permeable formation in advance of the combustion flame front in response to a high pressure pulse produced by detonation of the pressurized combustible gas within the injection well. In the preferred embodiment, the combustible injection gas is a mixture of hydrogen gas and chlorine gas.

Abstract: The effectiveness of a water injection oil recovery process is increased by incorporating a viscosifying amount of a hydrophilic polymer in the injection fluid, together with from 0.005 to 2.0 percent by weight of an alkalinity agent, preferably sodium hydroxide, and from 0.01 to 5.0 percent by weight of an alkalinity stabilizing agent, preferably sodium carbonate. The hot alkaline polymer water flood is especially effective when applied after a steam flood to recover oil bypassed by the steam.

Abstract: Polymers and gels useful for permeability control in subterranean formations, said polymers having structural forms of ABA triblocks and (AB).sub.n multiblock are disclosed.

Abstract: A method of removing polymeric material from injection and producing wells in which an aqueous medium containing, chlorine dioxide or sodium chlorite is introduced into the well and maintained in contact with the polymeric material for a period of time sufficient to degrade the polymeric material to a desired degree and allow enhanced injectivity of polymer flooding medium into the injection well or enhanced production from a producing well.

Abstract: Viscous oil in a geological formation is recovered by producing hydrogen peroxide near the formation, injecting hydrogen peroxide into the formation to effect its decomposition and reaction of oxygen with resident hydrocarbon, and recovering oil in response to injection of hydrogen peroxide.

Abstract: In cosurfactant enhanced alkaline flooding of a formation containing anhydrite, the pH of the flooding material is maintained at a high lvel by the addition of an alkali metal sulfate or ammonium sulfate.

Abstract: A novel cross-linked polymer is obtained by cross-linking polyvinyl alcohol with a cross-linking agent which is a mixture of a phenolic component and an aldehyde or a mixture of a naphtholic component and an aldehyde. The resulting polymer is exceptionally thermally stable and, therefore, can be used as an effective permeability control agent in all enhanced oil recovery operations, including steam flooding.

Abstract: A method for selectively closing pores in a zone of greater permeability in a formation for profile control. A rehealable Xanthan biopolymer is combined with a crosslinked non-selective polyacrylamide polymer gel. The combined gel system is injected into a formation where the Xanthan biopolymer gel selectively enters a zone of greater permeability carrying therewith said non-slective gel. Once in the formation's zone of greater permeability, the gel reheals and forms a rigid gel with substantially better temperature stability.

Abstract: A caustic waterflooding process for enhanced oil recovery from a production well is disclosed comprising injection of an aqueous solution under pressure to sweep oil to the production well. That aqueous solution comprises a caustic and a polymer that has an intrinsic viscosity that is at least twice as high in its hydrolyzed form than in its unhydrolyzed form, wherein the polymer is injected with less than 15% of polymer being hydrolyzed. The aqueous solution contains from 100 to 5,000 ppm of polymer and 100 to 50,000 ppm of caustic. Such solutions have improved injectivity and good efficiency in recovering oil from underground formations.Preferably, the polymer is injected with from 5% to 10% of polymer being hydrolyzed. That polymer is preferably a polyacrylamide (such as a polyacrylamide homopolymer, a polymethylacrylamide homopolymer, or a copolymer of acrylamide and monomers selected from the group consisting of methylacrylamide, N-alkyl-substituted acrylamides, alkylacrylates, and acrylic acids).

Abstract: A composition of matter wherein amino resins such as melamine formaldehyde ("MF") resins modify polysaccharide polymers thereby forming gels with transitional metal ions useful for profile control where said polymers have amine, amide, hydroxyl and thiol functionalities. Said gels are thermally stable, brine tolerant and rehealable. Said resin modified polysaccharide polymers can be used in their liquid or ungelled state as a mobility control agent in a reservoir during the removal of hydrocarbonaceous fluids therefrom.

Abstract: A method for minimizing blockage in a zone of lesser permeability when injecting gels into a formation during profile control. A solidifiable gel containing a gel breaker is injected into the formation where it enters a zone of lesser and a zone of greater permeability. Said gel blocks pores in the zone of lesser permeability. Another solidifiable gel lacking a gel breaker is injected into the zone of greater permeability where it subsequently solidifies. Said gel contained in the zone of lesser permeability liquefies thereby unblocking this zone. Afterwards, a water-flooding enhanced oil recovery method is directed into the zone of lesser permeability.

Abstract: A method for reducing the permeability in a desired area of a formation wherein a solid foam is formed in situ by injecting a one phase solution into the formation. Said solution comprises an alkali metal silicate, a chemical surfactant, and an alkali metal salt of azodicarboxylic acid in an amount sufficient to produce a foam. The azodicarboxylic acid salt decomposes when the pH is reduced to less than about 12 and generates gas in an amount sufficient to form a foam which subsequently hardens. When hardened the foam reduces the permeability in a desired area.

Abstract: A process for recovering hydrocarbons from a subterranean hydrocarbon-bearing reservoir comprising:contacting the reservoir with at least one metal component selected from the group consisting of vanadium components in which vanadium is present in the 5+ oxidation state in an amount effective to promote the chemical modification of at least one component of the hydrocarbons in the reservoir, iron components in which iron is present in the 3+ oxidation state in an amount effective to promote the chemical modification of at least one component of the hydrocarbons is the reservoir, manganese components in which manganese is present in the 3+ oxidation state in an amount effective to promote the chemical modification of at least one component of the hydrocarbons in the reservoir and mixtures thereof, and at least one oxygen transfer agent in an amount effective to do at least one of the following: maintain at least partially the promoting activity of the metal component; produce at least a portion of metal compon

Abstract: A process for treating a region in a high-temperature hydrocarbon-bearing formation with a gel for hydrocarbon recovery applications. The gel is prepared by mixing a single aqueous gelation system at the surface comprising a solution of a polyvalent metal crosslinking agent and an unhydrolyzed acrylamide polymer. The system is injected into a desired treatment region of the high-temperature formation wherein the polymer is hydrolyzed in situ. The gelation system is then gelled to completion in the treatment region.

Abstract: A chemical blowing agent is incorporated into a polymer formulation to provide delayed foaming in a subterranean reservoir when, via catalysis through reservoir temperature or minerals present, the reservoir itself initiates or accelerates decomposition of the chemical. The resultant gelled foam expands and stiffens thereby closing pores in a more permeable zone of said reservoir. Once foaming is completed, a carbon-dioxide or water-flooding oil recovery process can be used to recover hydrocarbonaceous fluids from a zone of lesser permeability.

Abstract: A composition of matter wherein amino resins such as melamine formaldehyde ("MF") resins co-gel and crosslink with polymers useful for profile control where said polymers have amine, amide, hydroxyl and thiol functionalities. Resulting gels are useful as profile control agents for high temperature reservoirs during a water-flooding operation.

Abstract: A method for reducing the permeability in a desired area of a formation wherein a foamed gel is formed in-situ by injecting a solution into said formation. Said solution comprises a gellable composition including water; a cross linkable polysaccharide biopolymer; an aminoplast resin which reinforces said biopolymer; and sufficient transitional metal ions to form a gel of the desired size and strength. The gelled solution is foamed by including therein a chemical surfactant, and a chemical blowing agent. Once in the formation to the desired depth, the chemical blowing agent decomposes and generates a gas sufficient to foam the gelled solution. The gelled foam stiffens and reduces the permeability in a desired area.

Abstract: Aqueous gel-forming compositions are prepared by reacting for 1-10 hours at 50.degree.-95.degree. C., melamine, formaldehyde and a sulfurous acid salt with the optional addition of a gel-modifying agent and/or a gelling agent which is added to the composition immediately prior to use.

Abstract: Improved sweep efficiency is obtained in an oil recovery process wherein oil is recovered from a subterranean, viscous oil containing formation having relatively highly permeable zones and relatively low permeability zones penetrated by at least one injection well and at least one spaced apart production well in fluid communication with a substantial portion of the formation. First, a predetermined amount of gel solution is injected into the formation at high pressure to deeply penetrate and plug the fracture face and highly permeable zones of the formation. Thereafter, a breaker material such as hydrochloric acid is injected into the formation at a low pressure to break the gel and displace it from the fracture face and highly permeable zones in the vicinity of the injection well thereby reestablishing injectivity into the formation in the vicinity of the injection well.

Abstract: A process for generating gas in-situ where a decomposable chemical blowing agent is utilized in combination with an aqueous medium. When a slug of the aqueous medium containing said blowing agent is injected into the formation, heat from the formation, coinjected activators, reservoir fluids, or formation mineralogy causes said blowing agent to decompose thereby generating a gas. This gas forms bubbles which close pores in a more permeable zone of a formation which causes a drive fluid to be diverted into a less permeable zone for removal of hydrocarbonaceous fluids therefrom. Bubbles can also be formed by incorporating a water thickening amount of a water soluble polymer or gel into an aqueous medium containing a decomposable chemical blowing agent. A foam can be made in-situ by placing into an aqueous medium, a surfactant and a decomposable chemical blowing agent. In-situ generated bubbles or foam can be used to divert a drive fluid into a formation's less permeable zone.

Abstract: An aqueous liquid medium having increased low shear viscosity and utility as a mobility control agent in enhanced oil recovery is provided by dispersing into the aqueous medium (1) a hydrophilic/hydrophobic polymer having hydrophobic groups, e.g., an acrylamide/dodecyl methacrylate copolymer, and (2) a water-dispersible surfactant, e.g., dodecyl polyethyleneoxy glycol monoether.

Abstract: High permeable thermally fluid swept zones in an oil containing formation are selectively plugged by a high temperature selective gel-forming solution without plugging the less permeable unswept portion of the formation. Ungelled solution in the less permeable unswept portion of the formation in the vicinity of the injection well is removed and a thermal fluid is injected into the formation that sweeps oil from the less permeable, unswept portion of the formation, thereby resulting in more complete displacement of oil from the formation.

Abstract: A gelable composition is provided which can be injected into a well prior to steam treatment of the well. The composition comprises water, a water-dispersible polymer, a water-dispersible first crosslinker and a water-dispersible second crosslinker, wherein the first and second crosslinkers have differing temperature responsive crosslinking characteristics over the temperature range of about 70.degree. F. to about 400.degree. F. so as to enable crosslinking of the polymer and gelation of the composition over substantially the entire temperature range. Injection of the composition into a "cold" well followed by steam treatment of the well causes the polymer to undergo a two stage crosslinking reaction which produces a particularly effective and stable gel in diverting steam from "thief zones" in the formation surrounding the well.

Abstract: A gel-forming composition is provided comprising a first substance selected from the group consisting of a polyvinyl alcohol, a polyvinyl alcohol copolymer, and mixtures thereof, glutaraldehyde, and water, and which does not require a separately provided acidic catalyst to crosslink and form a gel. The gel-forming composition is useful for retarding the flow of fluids in subterranean formations. For example, a method is provided for retarding the flow of water in high permeability channels in an oil reservoir. Such method is particularly useful in waterflood operations to increase the sweep efficiency of the oil recovery process. Since these gels have very good stability at elevated temperature they can be used in reservoirs having an average in situ temperature of 80.degree. C. or higher.

Abstract: An oil recovery process in which oil is displaced by a viscous alkaline aqueous solution is improved by using such an aqueous alkaline solution containing a water-thickening polymer partially hydrolyzed polyacrylamide polymer and a stabilizer consisting essentially of a 2-mercaptobenzothiazole in the presence of a sulfur-containing oxygen scavenger. A readily oxidizable alcohol or glycol may also be included.

Abstract: The invention is a method for recovering hydrocarbons from an underground hydrocarbon reservoir penetrated by at least one injection well and at least one production well, which comprises injecting into the reservoir through an injection well an aqueous caustic solution comprising greater than 0.1% and less than 1.0% lignosulfonate by weight to shift the optimal salinity for enhanced oil recovery of the caustic solution to a relatively higher salinity, and producing hydrocarbons and other fluids through a production well.

Abstract: A process for recovering hydrocarbonaceous fluids from a formation having a substantially low pH where a rehealable gel prepared ex-situ is used to close off a zone of greater permeability. Said gel is obtained by mixing into an aqueous medium sufficient biopolymer amounts of a Xanthan or Alcaligene polysaccharide. This mixture is maintained at a pH of about 5.5 while an aminoplast resin in excess of 4,000 ppm is added thereto which causes said gel to form in about 0.5 to 6 hours. The resultant gel is suitable for use in a carbon-dioxide flood process. Said gels are very stable at a pH of less than about 5.5.

Abstract: An improved process for forming improved gels where biopolymers and synthetic polymers are cross-linked with melamine/formaldehyde and other amino resins at an optimal range of ratios of amine to aldehyde in the amino resins. This optimal range of ratios can vary from about 1:6 to about 1:30 amine to aldehyde. Resins utilized in said optimal range are most effective for producing improved firm, stable gels. The resultant gels are useful in waterflooding and carbon dioxide flooding operations during the recovery of hydrocarboneaceous fluids.

Abstract: The permeability of subterranean oil-bearing formations is controlled by injection of an organic polysilicate ester. The ester may be derived from simple, monohydroxylic alcohols such as methanol, ethanol, propanol or butanol, from diols such as ethylene glycol, from polyols such as glycerol and alkylene oxide polymerization products and from other organic compounds containing functional hydroxy groups, for example, partial ethers and esters of glycols and polyols. The polysilicates are injected into a formation through injection wells, suitably in an amount from 10 to 100% of the pore volume of the zone to be treated. In the formation, the polysilicate esters form gels which selectively decrease the permeability of the high permeability regions of the formation, to divert the flow of flooding liquid used in flooding operations to the less permeable regions of the formation.

Abstract: A process for minimizing gravity override via carbon dioxide combined with a sized gel. A polysaccharide gel of a size sufficiently greater than the pores contained in a more permeable formation area is prepared ex situ in the presence of sodium hydroxide. Said gel is then pumped into said formation causing pores in the more permeable formation area to be blocked off. Thereafter, carbon dioxide flooding is commenced and said flood is directed into the less permeable formation area causing hydrocarbonaceous fluids to be produced therefrom.

Abstract: Aqueous gel-forming compositions useful for improving oil recovery from subterranean hydrocarbon-containing reservoirs are prepared by reacting an aminoalkylated polyacrylamide with an aldehyde, dialdehyde or derivative thereof in aqueous medium. These compositions are particularly effective in reducing excessive water encroachment at producer wells.