Dispersion polymers for oil field water clarification

A method of removing emulsified oil from a oil field produced water, the method comprising the step of treating the oil-containing water with an effective amount of a dispersion of a water-soluble cationic polymer, said dispersion of the water-soluble cationic polymer being prepared by polymerizing a water-soluble monomer mixture containing a least 5 mole % of a cationic or methacrylamide in an aqueous solution of a polyvalent anionic salt, said polymerization is carried out in an aqueous solution including from about 1 to about 10 percent by weight based on the total weight of the monomers a dispersant polymer, said dispersant polymer being a water-soluble cationic polymer which is soluble in said aqueous solution of the polyvalent anionic salt and which contains at least 20 mole % of cationic monomer units represented by a general formula (II):

• ##STR4## wherein R.sub.1 and R.sub.4 are each H or CH.sub.3 ;
• R.sub.2, R.sub.3, R.sub.5 and R.sub.6 are each an alkyl group having 1 to 2 carbon atoms;
• R.sub.7 is a hydrogen atom or an alkyl group having 1 to 2 carbon atoms;
• A.sub.1 and A.sub.2 are each an oxygen atom or NH;
• B.sub.1 and B.sub.2 are each 2 to 4 carbon atoms or a hydroxypropyl group and X.sub.1 - and X.sub.2 - are each a counter anion once treated, the emulsified oil flocculates;
• and removing the flocculated emulsified oil from the treated oil field produced water.