Scale inhibiting well treatment

1. A method for inhibiting scale formation within a hydrocarbon producing system, said method comprising performing a squeeze treatment comprising contacting said system with a copolymer formed from a diallyl ammonium salt of formula (I)

wherein R 1 and R 2 are each independently hydrogen or unsubstituted organic radicals having from 1 to 20 carbon atoms;

wherein each R is independently selected from hydrogen or organic radicals having from 1 to 20 carbon atoms; and

X is a counterion;

and at least one anionic monomer of formula (II):

wherein R 3 is —CO 2 Z, —SO 3 Z, —PO 3 Z 2 or an alkyl or aryl group -substituted with at least one —CO 2 Z, —SO 3 Z or —PO 3 Z 2 group in which Z is a hydrogen atom or a univalent metal atom; and

wherein R 4 , R 5 and R 6 are each independently hydrogen, an optionally substituted alkyl or aryl group having from 1 to 6 carbon atoms, —CO 2 Z, —SO 3 Z, —PO 3 Z 2 or an alkyl or aryl group substituted with at least one —CO 2 Z, —SO 3 Z or —PO 3 Z 2 group in which Z is a hydrogen atom or a univalent metal atom, wherein said copolymer does not comprise acrylamide monomers and said copolymer comprises at least 5 wt % of said diallyl ammonium salt relative to the total weight of monomers, such that scale formation within the hydrocarbon producing system is inhibited by said squeeze treatment, and wherein the copolymer comprises at least one inorganic end group selected from —SO 4 H 2 , —SO 3 H, —H 2 PO 3 , or —H 2 PO 4 , or salts thereof.

2. A method as claimed in claim 1 , wherein said copolymer comprises 5 to 20 wt % of said diallyl ammonium salt relative to the total weight of monomers.

3. A method as claimed in claim 1 , wherein said copolymer is formed from diallyl dimethyl ammonium chloride.

4. A method as claimed in claim 1 , wherein R 3 is a —CO 2 Z, —SO 3 Z, or —PO 3 Z 2 group.

5. A method as claimed in claim 1 , wherein said anionic monomer is selected from acrylic acid, methacrylic acid, vinyl sulfonic acid, vinyl phosphonic acid, maleic anhydride, itaconic acid, maleic acid or styrene sulfonic acid.

6. A method as claimed in claim 1 , wherein said anionic monomer is selected from acrylic acid, vinyl sulfonic acid or vinyl phosphonic acid.

7. A method as claimed in claim 1 , wherein said copolymer is formed from anionic monomers of formula (II) providing at least two different anionic groups.

8. A method as claimed in claim 1 , wherein said copolymer does not comprise non-ionic monomer.

9. A method as claimed in claim 1 , wherein said copolymer comprises repeating units represented by formula (III) and/or formula (IV)

wherein R 1 and R 2 are each independently hydrogen or unsubstituted organic radicals having from 1 to 20 carbon atoms;

wherein each R is independently selected from hydrogen or organic radicals having from 1 to 20 carbon atoms;

wherein X is a counterion;

wherein R 3 is —CO 2 Z, —SO 3 Z, —PO 3 Z 2 or an alkyl or aryl group substituted with at least one —CO 2 Z, —SO 3 Z or —PO 3 Z 2 group in which Z is a hydrogen atom or a univalent metal atom;

wherein R 4 , R 5 and R 6 are each independently hydrogen, an optionally substituted alkyl or aryl group having from 1 to 6 carbon atoms, —CO 2 Z, —SO 3 Z, —PO 3 Z 2 or an alkyl or aryl group substituted with at least one —CO 2 Z, —SO 3 Z or —PO 3 Z 2 group in which Z is a hydrogen atom or a univalent metal atom;

wherein n is 1 to 50; and

wherein m is 10 to 200.

10. A method as claimed in claim 1 , wherein the weight average molecular weight of said copolymer is in the range of 800 to 500,000.

11. A method as claimed in claim 1 , wherein said copolymer is applied as a dispersion or solution in a liquid carrier.

12. A method as claimed in claim 11 , wherein said copolymer is present in said liquid carrier at a concentration of 6-50% wt.

13. A method as claimed in claim 1 , wherein R 1 and R 2 in formula (I) are both methyl.

14. A method as claimed in claim 4 , wherein R 3 is a —CO 2 Z or a —PO 3 Z 2 group.

15. A method as claimed in claim 14 , wherein R 3 is a —PO 3 Z 2 group.

16. A method as claimed in claim 6 , wherein said anionic monomer is selected from acrylic acid or vinyl phosphonic acid.

17. A method as claimed in claim 16 , wherein said anionic monomer is vinyl phosphonic acid.

18. A method as claimed in claim 10 , wherein the weight average molecular weight of said copolymer is in the range 1,000 to 100,000.