Sulfate scale inhibition in high pressure and high temperature applications

A method of inhibiting scale formation in an oil or gas production system comprising adding to said system a scale inhibiting treatment comprising:

• (A) a water soluble or dispersible polymer having the formula I
• wherein E is the repeat unit remaining after polymerization of an ethylenically unsaturated compound;
• R1 is H or lower alkyl (C1-C4);
• or CH2—CH2—CH2;
• f is an integer of about 1-100, preferably from about 1-20, X and A are independently selected and are an anionic group selected from OSO3, SO3, PO3, OPO3, or COO;
• G and Z are independently selected and are chosen from H or a cationic group such as Na, K, or NH4;
• R3 is H or lower alkyl (C1-C4), and R4 is a hydroxyl substituted alkylene radical having from 1 to about 6 carbon atoms;
• subscripts c, d, and e represent the molar amounts of the monomer repeat units in the polymer and wherein c is present in an amount of 1-80, d is present in an amount of 0-30, and e is present in an amount of 0-30, with the proviso that at least one of d and e must be present and the sum of c+d+e=100;
• and
• (B) phosphonate.