Friction reducers

1. A friction reducer formulation comprising:

a water-in-oil emulsion having an oil phase (O) and an aqueous phase (A), wherein the oil phase (O) comprises an inert hydrophobic liquid, and the aqueous phase (A) comprises water, a friction reducing polymer, and a first surfactant;

a diluting formulation comprising an oil, a surfactant with a hydrophilic-lipophilic balance (HLB) value<10, and a formate salt; and

a second surfactant;

wherein the first surfactant has a hydrophilic-lipophilic balance (HLB) value less than a HLB value of the second surfactant; and

wherein the friction reducer formulation is freeze thaw stable.

2. The friction reducer formulation of claim 1 , wherein the formate salt comprises potassium formate, sodium formate, or a combination thereof.

3. The friction reducer formulation of claim 1 , wherein the friction reducing polymer comprises an anionic polymer, a cationic polymer, or an amphoteric polymer.

4. The friction reducer formulation of claim 3 , wherein the cationic polymer comprises one or more monomers selected from the group consisting of (meth)acrylamidopropyltrimethyl ammonium halides, (meth)acryloyloxyethyltrimethyl ammonium halides, (meth)acryloyloxyethyltrimethyl ammonium methyl sulfate, diallyl dimethyl ammonium halides, diallylamine, methyldiallylamine, dimethylaminoethylmethacrylate, and dimethylaminopropylmethacrylamide.

5. The friction reducer formulation of claim 3 , wherein the anionic polymer comprises one or more monomers selected from the group consisting of acrylic acid, sodium acrylate, ammonium acrylate, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), vinyl sulfonic acid, styrene sulfonic acid, maleic acid, sulfopropyl acrylate, methacrylate, olymerisable carboxylic or sulphonic acids, sulfomethylated acrylamide, allyl sulfonate, itaconic acid, acrylamidomethylbutanoic acid, fumaric acid, vinylphosphonic acid, allylphosphonic acid, and phosphonomethylated acrylamide.

6. The friction reducer formulation of claim 3 , wherein the amphoteric polymer comprises:

i) one or more cationic monomers selected from the group consisting of (meth)acrylamidopropyltrimethyl ammonium halides, (meth)acryloyloxyethyltrimethyl ammonium halides, (meth)acryloyloxyethyltrimethyl ammonium methyl sulfate, diallyl dimethyl ammonium halides, diallylamine methyldiallylamine, dimethaminoethylmethacrylate, and dimethylaminopropylmethacrylamide; and

ii) one or more anionic monomers selected from the group consisting of acrylic acid, sodium acrylate, ammonium acrylate, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), vinyl sulfonic acid, styrene sulfonic acid, maleic acid, sulfopropyl acrylate, methacrylate, olymerisable carboxylic or sulphonic acids, sulfomethylated acrylamide, allyl sulfonate, itaconic acid, acrylamidomethylbutanoic acid, fumaric acid, vinylphosphonic acid, allylphosphonic acid, and phosphonomethylated acrylamide.

7. The friction reducer formulation of claim 3 , wherein the friction reducing polymer has a molecular weight in the range of from about 1,000,000 to about 20,000,000.

8. The friction reducer formulation of claim 1 , wherein the first surfactant comprises one or more of fatty acid esters of mono-, di- and polyglycerols, fatty amines, and fatty acid alkyloxylates.

9. The friction reducer formulation of claim 1 , wherein the second surfactant comprises one or more selected from the group consisting of ethoxylate of branched alkyl alcohol; polyoxyethyylene alkyl phenol; polyoxyethylene (10 mole) cetyl ether; polyoxyethylene alkyl-aryl ether; quaternary ammonium derivatives; potassium oleate; N-cetyl-N-ethyl morpholinium ethosulfate; sodium lauryl sulfate; condensation products of fatty alcohols with ethylene oxide; condensation products of alkylphenols and ethylene oxide; condensation products of fatty acid amines with five, or more, ethylene oxide units; ethylene oxide condensation products of polyhydric alcohol partial fatty esters, and their inner anhydrides.

10. The friction reducer formulation of claim 1 , wherein the inert hydrophobic liquid comprises paraffinic hydrocarbons, naphthenic hydrocarbons, or a mixture thereof.

11. A method of manufacturing a friction reducer according to claim 1 , comprising:

polymerizing one or more monomers in a water-in-oil emulsion to form a friction reducing polymer wherein the water-in-oil emulsion comprises an oil (O) and an aqueous phase (A), the oil phase (O) comprises an inert hydrophobic liquid, and the aqueous phase (A) comprises water, a friction reducing polymer, and a first surfactant,

diluting the friction reducing polymer by adding a formulation comprising an oil, a surfactant with a hydrophilic-lipophilic balance (HLB) value<10, and a formate salt;

and

adding a second surfactant,

wherein the first surfactant has a hydrophilic-lipophilic balance (HLB) value less than a HLB value of the second surfactant; and

wherein the friction reducer formulation is freeze thaw stable.

12. The method of claim 11 , wherein the formate salt comprises potassium formate, or a combination thereof.

13. The method of claim 11 , wherein the friction reducing polymer comprises an anionic polymer, a cationic polymer, or an amphoteric polymer.

14. The method of claim 13 , wherein the cationic polymer comprises one or more monomers selected from the group consisting of (meth)acrylamidopropyltrimethyl ammonium halides, (meth)acryloyloxyethyltrimethyl ammonium halides, (meth)acryloyloxyethyltrimethyl ammonium methyl sulfate, diallyl dimethyl ammonium halides, diallylamine, methyldiallylamine, dimethylaminoethylmethacrylate, and dimethylaminopropylmethacrylamide.

15. The method of claim 13 , wherein the anionic polymer comprises one or more selected from the group consisting of acrylic acid, sodium acrylate, ammonium acrylate, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), vinyl sulfonic acid, styrene sulfonic acid, maleic acid, sulfopropyl acrylate, methacrylate, olymerisable carboxylic or sulphonic acids, sulfomethylated acrylamide, allyl sulfonate, itaconic acid, acrylamidomethylbutanoic acid, fumaric acid, vinylphosphonic acid, allylphosphonic acid, and phosphonomethylated acrylamide.

16. The method of claim 13 , wherein the amphoteric polymer comprises:

i) one or more cationic monomers selected from the group consisting of (meth)acrylamidopropyltrimethyl ammonium halides, (meth)acryloyloxyethyltrimethyl ammonium halides, (meth)acryloyloxyethyltrimethyl ammonium methyl sulfate, diallyl dimethyl ammonium halides, diallylamine, methyldiallylamine, dimethylaminoethylmethacrylate, and dimethylaminopropylmethacrylamide; and

ii) one or more anionic monomers selected from the group consisting of acrylic acid, sodium acrylate, ammonium acrylate, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), vinyl sulfonic acid, styrene sulfonic acid, maleic acid, sulfopropyl acrylate, methacrylate, olymerisable carboxylic or sulphonic acids, sulfomethylated acrylamide, allyl sulfonate, itaconic acid, acrylamidomethylbutanoic acid, fumaric acid, vinylphosphonic acid, allylphosphonic acid, and phosphonomethylated acrylamide.

17. The method of claim 11 , wherein the first surfactant comprises one or more of fatty acid esters of mono-, di- and polyglycerols, fatty amines, and fatty acid alkyloxylates.

18. The method of claim 11 , wherein the second surfactant comprises one or more selected from the group consisting of ethoxylate of branched alkyl alcohol; polyoxyethylene alkyl phenol; polyoxyethylene (10 mole) cetyl ether; polyoxyethylene alkyl-aryl ether; quaternary ammonium derivatives; potassium oleate; N-cetyl-N-ethyl morpholinium ethosulfate; sodium lauryl sulfate; condensation products of higher fatty alcohols with ethylene oxide; condensation products of alkylphenols and ethylene oxide; condensation products of higher fatty acid amines with five, or more, ethylene oxide units; ethylene oxide condensation products of polyhydric alcohol partial higher fatty esters, and their inner anhydrides.

19. The method of claim 11 , wherein the inert hydrophobic liquid comprises paraffinic hydrocarbons, naphthenic hydrocarbons, or a mixture thereof.

20. A method of treating a portion of a subterranean formation comprising:

introducing a friction reducing formulation of claim 1 into a portion of the subterranean formation.

21. The friction reducer formulation of claim 1 , wherein the friction reducer formulation has a pour point between −30° C. and −37° C.

22. The friction reducer formulation of claim 1 , wherein the water-in-oil emulsion contains the formate salt in an amount ranging from about 0.5 to about 2.0% by weight of the emulsion.