Disclosed are methods and compositions for coagulating and clarifying produced waters for use as boiler feed waters, for example for the generation of steam. The methods and compositions are especially useful for treatment of produced waters from steam-injection methods of tertiary oil recovery such as steam-assisted gravitational drainage. Disclosed are compositions comprising a first copolymer having a high molecular weight and bearing a low molar cationic charge and a second copolymer having a lower molecular weight and bearing a high molar cationic charge. The compositions are suitable for addition as coagulants to produced waters that have been treated by warm lime softening. Also disclosed are methods of treating produced waters from steam-injection oil recovery for use as boiler feed waters to generate steam in such steam injection methods.