A method of secondary oil recovery is disclosed wherein from 0.1 to 100 000 ppm of a medium soluble aminoalkylene phosphonic acid amine salt are used wherein both the aminoalkylene phosphonic acid moiety and the amine moiety are selected from a specifically defined class of compounds. The substantially medium soluble aminoalkylene amine phosphonates exhibit a significantly improved compatibility with the recovery medium and thus can propagate fairly freely into the medium and consequently cover a largely extended rock surface before being subject to precipitation in the form of a medium insoluble scale inhibitor. The amine compound is represented by combinations of structurally different compounds.