Methods of treating flowback water

A method of treating flowback water from a subterranean formation penetrated by a well bore for reuse as a fracturing fluid, comprising:

• (a) providing flowback water having a ferrous iron (Fe+2) ion concentration of less than about 100 milligrams of ferrous iron ion per liter of flowback water, a barium ion (Ba +2) concentration of less than about 500 milligrams of barium ion per liter of flowback water, and a calcium ion (Ca+) concentration of at least about 1,000 milligrams of calcium ion per liter of flowback water;
• and
• (b) treating the flowback water with a fluid treatment system comprising:
• (i) at least one friction reducing agent comprising a water-in-oil emulsion composition comprising:
• (1) 5 % to 99% by weight of a water-in-oil emulsion polymer comprising one or more repeat units according to Formula I:
• wherein each occurrence of R1 is independently selected from H, methyl and ethyl;
• n is an integer from 10 to 10,000,000 ;
• Z is selected from —O —and —NR2—;
• and each occurrence of R2 is independently selected from the group consisting of H, C1-C22 linear, branched or cyclic alkyl, aryl, alkaryl, aralkyl or alkenyl group,—R3—NR22—R3—N+R23 X, and —R3—SO3 Y, wherein R2 is as previously defined;
• R3 is a divalent linking group selected from the group consisting of C1-C22 linear, branched or cyclic alkylene, arylene, alkarylene, aralkylene or alkenylene, poly(ethyleneoxide) and poly(propyleneoxide);
• Y is H or an alkali metal ion;
• and X is a halide or methylsulfate, wherein the polyacrylamide has a molecular weight of 1,000,000 to 50,000,000grams per mole;
• (2) 0.1 % to 10 % by weight of one or more inorganic microparticles;
• (3) 0.5% to 90 % by weight of a carrier solvent;
• and
• (4) 0 to 90 % by weight of a fluidizing agent.;
• and
• (ii) at least one scale formation inhibiting agent comprising 2-phosphono-1,2,4-tricarboxybutane, polyacrylic acid and a reaction product prepared from acrylic acid and 2-acrylamido-2-methylpropyl sulfonic acid, and
• (iii) at least one iron control agent comprising () at least one carboxylic acid functional group and (2) at least one sulfur-containing group selected from the group consisting of sulfonyl functional groups, sulfonate functional groups, and mixtures thereof, wherein the material (a) has a weight average molecular weight ranging from about 500 to about 1,000,000 grams per mole to provide a treated flowback water;
• and
• (3) introducing the treated flowback water into a subterranean formation as an aqueous fracturing fluid for hydraulic fracturing of the formation.