The present invention provides a composition useful as a sulfide scale inhibitor for application in oilfield operations, comprising 1.) at least one copolymer that comprises as monomers a) 0.1 to 10 mol-%, of structural units derived from vinylphosphonic acid and/or of a salt thereof, b) 40 to 80 mol-% of structural units derived from compounds of the formula (1 ) c) 1 to 50 mol-% of structural units derived from compounds of the formula (2) in which X is OH or NR3R4, and R3 and R4, independently of one another, are H or C1-C4-alkyl, 2.) at least one of tris (hydroxymethyl) phosphine or a tetrakis(hydroxymethyl)phosphonium salt, 3. ) at least one surfactant, 4. ) at least one amine or ammonium salt.
