Methods for decreasing calcium sulfate precipitation in produced water

A method comprising:

• providing a first produced water comprising dissolved sulfate anions;
• treating the first produced water with a metal salt capable of forming an insoluble metal sulfate, thereby forming a metal sulfate precipitate and a treated produced water;
• separating the metal sulfate precipitate from the treated produced water;
• and
• after separating the metal sulfate precipitate, mixing the treated produced water with at least one second produced water to obtain a mixed produced water, the at least one second produced water containing dissolved calcium ions, and the mixed produced water having a saturation ratio for calcium sulfate of less than 1;
• wherein the first produced water and the at least one second produced water are obtained from separate subterranean reservoirs.

A method comprising:

• providing a first produced water comprising dissolved sulfate anions and having a pH of about 5 to about 8;
• treating the first produced water with a metal salt dissolved in an aqueous solution, thereby forming a metal sulfate precipitate and a treated produced water;
• separating the metal sulfate precipitate from the treated produced water;
• and
• after separating the metal sulfate precipitate, mixing the treated produced water with at least one second produced water in a common pipeline to obtain a mixed produced water, the at least one second produced water containing dissolved calcium ions, and the mixed produced water having a saturation ratio for calcium sulfate of less than 1 in the common pipeline.