A method for oil recovery by injecting into marine oil wells an aqueous solution of an aminoacid phosphonic acid scale inhibitor in a level of from 0.1 to 100000 ppm, where the scale inhibitor is selected from the group of: i. aminoacid alkylphosphonic acids having the formula A 1 - x wherein A 1 has the formula HOOC-A-NH 2 wherein A is independently selected from C 2 -C 20 linear, branched, cyclic or aromatic hydrocarbon chains, optionally substituted by C 1 -C 12 linear, branched, cyclic or aromatic hydrocarbon groups, optionally substituted by OH, COOH and/or NH 2 moieties, and B is an alkylphosphonic acid moiety having from 1 to 6 carbon atoms in the alkyl group and x is an integer of from 1 to 10, and ii. aminoacid alkylphosphonic acids having the formula A 2 -B y wherein A 2 is selected from D,L-alanine wherein y is 2, L-alanine wherein y is 2, L-lysine wherein y is in the range of from 2 to 4, L-phenylalanine wherein y is 2, L-threonine wherein y is 2, L-methionine wherein y is 2, and L-cysteine wherein y is 2, B is an alkylphosphonic acid moiety having from 1 to 6 carbon atoms in the alkyl group, said amino acid phosphonate scale inhibitor being used singly, or as a mixture of more than one (i) species or a mixture of more than one (ii) species or as a mixture of (i) and (ii) species, one individual inhibitor constituting, on a ponderal basis, at least 50 % of said mixture, with the proviso that when: A 2 is L-lysine, at least one L-lysine amino radical carries 2 (two) alkyl phosphonic acid moieties; and the L-lysine alkylene phosphonate is represented by a mixture of L-lysine di(alkylene phosphonic acid) and L-lysine tetra(alkylene phosphonic acid) whereby the weight ratio of L-lysine tetra(alkylene phosphonic acid) to L-lysine di(alkylene phosphonic acid) is in the range of from 9: 1 to 1: 1. i. aminoacid alkylphosphonic acids having the formula A 1 - x wherein A 1 has the formula HOOC-A-NH 2 wherein A is independently selected from C 2 -C 20 linear, branched, cyclic or aromatic hydrocarbon chains, optionally substituted by C 1 -C 12 linear, branched, cyclic or aromatic hydrocarbon groups, optionally substituted by OH, COOH and/or NH 2 moieties, and B is an alkylphosphonic acid moiety having from 1 to 6 carbon atoms in the alkyl group and x is an integer of from 1 to 10, and ii. aminoacid alkylphosphonic acids having the formula A 2 -B y wherein A 2 is selected from D,L-alanine wherein y is 2, L-alanine wherein y is 2, L-lysine wherein y is in the range of from 2 to 4, L-phenylalanine wherein y is 2, L-threonine wherein y is 2, L-methionine wherein y is 2, and L-cysteine wherein y is 2, B is an alkylphosphonic acid moiety having from 1 to 6 carbon atoms in the alkyl group, said amino acid phosphonate scale inhibitor being used singly, or as a mixture of more than one (i) species or a mixture of more than one (ii) species or as a mixture of (i) and (ii) species, one individual inhibitor constituting, on a ponderal basis, at least 50 % of said mixture, with the proviso that when: A 2 is L-lysine, at least one L-lysine amino radical carries 2 (two) alkyl phosphonic acid moieties; and the L-lysine alkylene phosphonate is represented by a mixture of L-lysine di(alkylene phosphonic acid) and L-lysine tetra(alkylene phosphonic acid) whereby the weight ratio of L-lysine tetra(alkylene phosphonic acid) to L-lysine di(alkylene phosphonic acid) is in the range of from 9: 1 to 1: 1.