A method for inhibiting gas hydrate formation in a fluid comprising a hydrocarbon and water, the method comprising adding to the fluid an effective amount of an inhibitor composition to inhibit gas hydrate formation in the fluid, the inhibitor composition comprising a gas hydrate inhibitor agent and a polyamine derived from reaction of a first amine and a second amine; the second amine being a diamine, a triamine, or a polyamine; and the first amine being a tertiary amine having a structure of formula 1 or a quaternary amine having a structure of formula 2 wherein the tertiary amine of formula 1 is obtainable by reacting an amine having the structure of H 2 N-R 5 -Z with an acrylate or acrylic acid having the structure of H 2 C=C -Z' where Z' is -C OR 6; the quaternary amine of formula 2 is obtainable by reacting the tertiary amine of formula 1 with an alkylating group; R 1 R 2, and R 3 are each independently -R 5 -Z; R 4 is alkyl; R 5 is C 1 to C 20 alkylene, substituted C 1 to C 20 alkylene, arylene or aralkylene; R 6 is independently hydrogen or alkyl; and Z is -OH, -C OR 6, or -C NHR 6; and wherein the gas hydrate inhibitor agent is a polyvinylcaprolactone; a polyvinylpyrrolidone; a copolymer of a vinylcaprolactone and a vinylpyrrolidone; poly(N-alkyl(alkyl)acrylamide), a copolymer of N-alkyl(alkyl)acrylamide and alkyl chloride quaternary salts of N,N-dialkylaminoalkyl(meth)acrylates, a copolymer of N-alkyl(alkyl)acrylamide and alkyl chloride quaternary salts of N,N-dialkylaminoalkyl(meth)acrylamides, a terpolymer of a vinylcaprolactone, a vinylpyrrolidone, and a vinyl acetate; a dendrimeric polyesteramide derived from hexahydrophthalic anhydride; diisopropanol amine, and N,N-bis(3-dimethylaminopropyl)amine; a substituted polyethyleneimines; a polyoxyalkylenediamine; a dicarboxylic acid-polyol polyester; a polycyclicpolyether polyol; a hyperbranched polyester polyol having hydroxyl end groups; a hyperbranched polyester polyamine; a hyperbranched polyamidoamine; a linear polyester polyamine; or a combination thereof. the tertiary amine of formula 1 is obtainable by reacting an amine having the structure of H 2 N-R 5 -Z with an acrylate or acrylic acid having the structure of H 2 C=C -Z' where Z' is -C OR 6; the quaternary amine of formula 2 is obtainable by reacting the tertiary amine of formula 1 with an alkylating group; R 1 R 2, and R 3 are each independently -R 5 -Z; R 4 is alkyl; R 5 is C 1 to C 20 alkylene, substituted C 1 to C 20 alkylene, arylene or aralkylene; R 6 is independently hydrogen or alkyl; and Z is -OH, -C OR 6, or -C NHR 6; and wherein the gas hydrate inhibitor agent is a polyvinylcaprolactone; a polyvinylpyrrolidone; a copolymer of a vinylcaprolactone and a vinylpyrrolidone; poly(N-alkyl(alkyl)acrylamide), a copolymer of N-alkyl(alkyl)acrylamide and alkyl chloride quaternary salts of N,N-dialkylaminoalkyl(meth)acrylates, a copolymer of N-alkyl(alkyl)acrylamide and alkyl chloride quaternary salts of N,N-dialkylaminoalkyl(meth)acrylamides, a terpolymer of a vinylcaprolactone, a vinylpyrrolidone, and a vinyl acetate; a dendrimeric polyesteramide derived from hexahydrophthalic anhydride; diisopropanol amine, and N,N-bis(3-dimethylaminopropyl)amine; a substituted polyethyleneimines; a polyoxyalkylenediamine; a dicarboxylic acid-polyol polyester; a polycyclicpolyether polyol; a hyperbranched polyester polyol having hydroxyl end groups; a hyperbranched polyester polyamine; a hyperbranched polyamidoamine; a linear polyester polyamine; or a combination thereof.