Abstract: High viscosity well treating fluids having low friction pressure loss when pumped through tubular goods and methods of treating wells using such treating fluids are provided. The treating fluids basically comprise an aqueous fluid, a graft copolymer of hydroxyalkylcellulose and vinyl phosphonic acid, a salt containing a divalent cation and a basic compound for crosslinking the graft copolymer and causing the resulting crosslinked aqueous gel to undergo syneresis.

Abstract: The present invention relates to a method of preparing an encapsulated enzyme breaker and method of use in treating a subterranean formation. An encapsulated breaker is prepared by coating an enzyme on a cellulose substrate. A micron-sized particulate is admixed with the enzyme solution to prevent undesired agglomeration of the substrate. The enzyme solution coated substrate is covered with a membrane comprising a partially hydrolyzed acrylic crosslinked with either an aziridine prepolymer or a carbodiimide. The membrane contains imperfections through which an aqueous fluid may pass into the breaker to contact the enzyme and diffuse the enzyme outward from the breaker particle.

Abstract: The present invention provides a method of gravel packing a subterranean formation using a gel of a graft copolymer of a hydroxyalkyl cellulose prepared by a redox reaction with vinyl phosphonic acid. The gel is formed by hydrating the graft copolymer in an aqueous liquid. The gel in crosslinked by the addition of a crosslink initiator comprising a Lewis base or Bronsted-Lowry base, which is substantially free of polyvalent metal ions, to the gel in an amount sufficient to effect crosslinking of the graft copolymer. The viscosity of the crosslinked gel is reduced by contacting the gel with an acidic fluid whereby the pH of the gel is caused to decrease. The reduction in gel viscosity facilitates formation of the gravel pack.

Abstract: The present invention provides a method of cleaning a pipeline using a gel pig of a graft copolymer of a hydroxyalkyl cellulose prepared by a redox reaction with vinyl phosphonic acid. The gel pig is formed by hydrating the graft copolymer in an aqueous liquid. The gel pig is crosslinked by the addition of a Lewis base or Bronsted-Lowry base, to the gel in an amount sufficient to initiate crosslinking of the graft copolymer. Contaminants entrained in the crosslinked gel pig during the cleaning process may be separated by the addition of a pH reducing agent to the pig whereby the viscosity of the gel is caused to decrease. The gel may be used for further cleaning after contaminant separation by addition of an additional quantity of the Lewis base or Bronsted-Lowry base.

Abstract: The present invention provides a method of treating of subterranean formation using a gel of a graft copolymer of a hydroxyalkyl cellulose, guar or hydroxypropyl guar prepared by a redox reaction with vinyl phosphonic acid. The gel is formed by hydrating the graft copolymer in an aqueous liquid containing at least a trace amount of at least one divalent cation. The gel is crosslinked by the addition of a Lewis base or Bronsted-Lowry base, which is substantially free of polyvalent metal ions, to the gel in an amount sufficient to effect crosslinking of the graft copolymer.

Abstract: Novel treating fluid compositions containing crosslinkable non-ionic cellulose derivatives and methods of use in petroleum recovery operations are disclosed. The treating fluid polymers are prepared by reacting vinyl monomers having a crosslinkable substituent with a cellulose derivative using a redox system comprising the reaction product of hydrogen peroxide with ferrous salt. The polymers readily crosslink with polyvalent metal ions, such as zirconium and titanium, to form temperature-stable gels useful in petroleum recovery operations.

Abstract: Novel treating fluid compositions containing crosslinkable non-ionic cellulose derivatives and methods of use in petroleum recovery operations are disclosed. The treating fluid polymers are prepared by reacting vinyl monomers having a crosslinkable substituent with a cellulose derivative using a redox system comprising the reaction product of hydrogen peroxide with ferrous salt. The polymers readily crosslink with polyvalent metal ions, such as zirconium and titianium, to form temperature-stable gels useful in petroleum recovery operations.

Abstract: The present invention relates to novel crosslinkable interpolymers and methods of use in treating subterranean formations. The novel interpolymers comprise a water soluble monomer, a hydrophobe monomer, and vicinal diol monomer polymerized to form high molecular weight polymers which viscosify aqueous liquids. The solution viscosity may be enhanced by the addition of a surfactant having an HLB value of about 10 or less. The interpolymers are readily crosslinkable with polyvalent metal ions, such as titanium and zirconium to form thermally stable viscoelastic gels. The gels provide viscosity and solids transport characteristics that are useful in stimulating, gravel packing and polymer flooding operations.

Abstract: Novel treating fluid compositions containing crosslinkable non-ionic cellulose derivatives and methods of use in petroleum recovery operations are disclosed. The treating fluid polymers are prepared by reacting vinyl or allyl monomers having a crosslinkable substitutent with a cellulose derivative using a ceric ion redox system. Treatment of a non-ionic cellulose derivative with a ceric ion redox system also yields a crosslinkable polymer. The polymers readily crosslink with polyvalent metal ions, such as zirconium and titanium, to form temperature-stable gels useful in petroleum recovery operations.

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: A method and composition for stimulating high temperature subterranean formations. The composition comprises a novel crosslinkable polymer containing anionic and cationic functional groups (a polyampholyte). The polyampholyte comprises a mixture of at least one from each of the following groups:Group I acrylamide, partially hydrolyzed acrylamide, N,N-dimethylacrylamide, N-substituted-(N'-dialkylaminoalkyl) acrylamides, aminoalkylacrylates, dialkylaminoalkylacrylates or mixtures thereof;Group II 2-acrylamido-2-methylpropane sulfonic acid, sodium salt, vinylphosphonic acid, partially hydrolyzed acrylamide or mixtures thereof; andGroup III methacrylamidopropyldimethyl-2,3-dihydroxypropylammonium sulfate having the formula ##STR1## In the performance of the method, the polyampholyte is inverted into an aqueous liquid to form a viscous liquid which is buffered to about 4 to 6.5 and admixed with a crosslinking agent capable of crosslinking dihydroxypropyl functionalities.

Abstract: The present invention relates to a method and composition for viscosifying hydrocarbon liquids utilizing a viscosifying agent. The viscosifying agent comprises: (i) a copolymer of N,N-dimethylacrylamide and dimethylaminopropyl methacrylamide, (ii) a monocarboxylic acid and (iii) a selected amine having an ethanolamine structure admixed in a hydrocarbon liquid. The viscosifying agent constituents are admixed with the liquid hydrocarbon in an amount sufficient to effect viscosification of the hydrocarbon.

Abstract: A method of fracturing a subterranean formation with a stabilized foamed fracturing fluid comprising from about 30 percent to in excess of about 95 percent by volume of carbon dioxide with the remainder comprising a substantially anhydrous liquid and a selected surfactant. The foam is formed in situ by injection of a stabilized liquid-liquid emulsion containing liquid carbon dioxide into a well bore penetrating the formation. The temperature and pressure of the emulsion is controlled to maintain the carbon dioxide in the liquid phase during injection into the well bore. Thereafter, the carbon dioxide is heated by the subterranean formation to a temperature above about 88.degree. F. at which time the stabilized emulsion spontaneously forms a high quality stabilized foam.

Abstract: A method of fracturing a subterranean formation with a stabilized foamed fracturing fluid comprising from about 30 percent to in excess of about 95 percent by volume of carbon dioxide with the remainder comprising a substantially anhydrous liquid and a selected surfactant. The foam is formed in situ by injection of a stabilized liquid-liquid emulsion containing liquid carbon dioxide into a well bore penetrating the formation. The temperature and pressure of the emulsion is controlled to maintain the carbon dioxide in the liquid phase during injection into the well bore. Thereafter, the carbon dioxide is heated by the subterranean formation to a temperature above about 88.degree. F. at which time the stabilized emulsion spontaneously forms a high quality stabilized foam.