Method for preventing scale formation in the presence of dissolved iron
The present invention relates to a method of using threshold scale inhibitors of the formula: wherein n is 2 or 3 and M is hydrogen or an alkali metal cation, for preventing calcium carbonate, iron carbonate, and calcium sulfate scale formation in oilwell brines containing dissolved iron.
1. A method of treating an oil or gas well comprising:
(a) placing into a subterranean formation, which has been penetrated by a wellbore and contains an oilfield brine with a concentration of greater than 5 ppm of dissolved iron, a polyamino polyether methylene phosphonate of the formula:
wherein n is 2 or 3 and M is a hydrogen or an alkali metal cation; and
(b) inhibiting or controlling the deposition in the well and the subterranean formation of scales selected from the group consisting of calcium carbonate, iron carbonate, calcium sulfate or a mixture thereof.
2. The method of claim 1 , wherein the subterranean formation contains an oilfield brine having a concentration of between about 15 ppm and about 3000 ppm of dissolved iron.
3. The method of claim 1 , wherein the polyamino polyether methylene phosphonate is dissolved in an aqueous treatment fluid in a concentration between about 5 ppm to about 30 ppm based on the weight of the aqueous treatment fluid.
4. The method of claim 1 , wherein the polyamino polyether methylene phosphonate is dissolved in an aqueous treatment fluid in a concentration between about 25 ppm to about 100 ppm based on the weight of the aqueous treatment fluid.
5. The method of claim 1 , wherein the polyamino polyether methylene phosphonate is in a solid composite of well treatment agents.
6. The method of claim 1 , wherein the scales are calcium carbonate scales.
7. The method of claim 6 , wherein the polyamino polyether methylene phosphonate is dissolved in an aqueous treatment fluid in a concentration between about 10 ppm to about 50 ppm based on the weight of the aqueous treatment fluid.
8. The method of claim 1 , wherein the scales are calcium sulfate scales.
9. The method of claim 8 , wherein the polyamino polyether methylene phosphonate is dissolved in an aqueous treatment fluid in a concentration between about 5 ppm to about 30 ppm based on the weight of the aqueous treatment fluid.
10. The method of claim 1 , wherein the scales are iron carbonate scales.
11. The method of claim 10 , wherein the polyamino polyether methylene is dissolved in an aqueous treatment fluid in a concentration between about 10 ppm to about 50 ppm based on the weight of the aqueous treatment fluid.
12. The method of claim 1 , wherein citric acid is placed in the subterranean formation with the polyamino polyether methylene phosphonate in a ratio of about 2:1 by weight of the polyamino polyether methylene phosphonate to citric acid, respectively.
13. A method of treating an oil or gas production system comprising:
(a) placing into the production system, which contains an aqueous fluid with a concentration greater than 5 ppm of dissolved iron, a polyamino polyether methylene phosphonate of the formula:
wherein n is 2 or 3 and M is a hydrogen or an alkali metal cation; and
(b) inhibiting or controlling the deposition in the production system of scales selected from the group consisting of calcium carbonate, iron carbonate, calcium sulfate or a mixture thereof.
14. The method of claim 13 , wherein the production system contains an aqueous fluid having a concentration between about 15 ppm and about 3000 ppm of dissolved iron.
15. The method of claim 13 , wherein the aqueous fluid is an oilfield brine.
16. The method of claim 13 , wherein the polyamino polyether methylene phosphonate is dissolved in an aqueous treatment fluid in a concentration between about 5 ppm to about 30 ppm based on the weight of the aqueous treatment fluid.
17. The method of claim 13 , wherein the polyamino polyether methylene phosphonate is dissolved in an aqueous treatment fluid in a concentration of about 25 to about 100 ppm based on the weight of the aqueous treatment fluid.
18. The method of claim 13 , wherein the polyamino polyether methylene phosphonate is in a solid composite of production system treatment agents.
19. The method of claim 13 , wherein the oil or gas production system is an injection well or a disposal well.
20. The method of claim 13 , wherein the scales are calcium carbonate scales.
21. The method of claim 20 , wherein the polyamino polyether methylene phosphonate is dissolved in an aqueous treatment fluid in a concentration between about 10 ppm to about 50 ppm based on the weight of the aqueous treatment fluid.
22. The method of claim 13 , wherein the scales are calcium sulfate scales.
23. The method of claim 22 , wherein the polyamino polyether methylene phosphonate is dissolved in an aqueous treatment fluid in a concentration between about 5 ppm to about 30 ppm based on the weight of the aqueous treatment fluid.
24. The method of claim 13 , wherein the scales are iron carbonate scales.
25. The method of claim 24 , wherein the polyamino polyether methylene phosphonate is dissolved in an aqueous treatment fluid in a concentration between about 10 ppm to about 50 ppm based on the weight of the aqueous treatment fluid.
26. The method of claim 13 , wherein citric acid is placed in the oil or gas production system with the polyamino polyether methylene phosphonate in a ratio of about 2:1 by weight of the polyamino polyether methylene phosphonate to citric acid, respectively.