Method of controlling corrosion rate in downhole article, and downhole article having controlled corrosion rate
View Patent ↗A method of removing a downhole assembly comprises contacting, in the presence of an electrolyte, a first article comprising a first material and acting as an anode, and a second article comprising a second material having a lower reactivity than the first material and acting as a cathode, the downhole assembly comprising the first article in electrical contact with the second article, wherein at least a portion of the first article is corroded in the electrolyte.
1. A method of removing a downhole assembly, comprising
contacting, in the presence of an electrolyte,
a first article comprising a first material and acting as an anode, and
a second article comprising a second material having a lower reactivity than the first material and acting as a cathode,
the downhole assembly comprising the first article in electrical contact with the second article,
wherein at least a portion of the first article is corroded in the electrolyte; and
wherein the first material comprises a magnesium alloy having less than or equal to about 0.5 weight percent of nickel.
2. The method of claim 1 , wherein the first article has a non-metallic coating on a surface thereof.
3. The method of claim 2 , wherein the coating comprises a soluble glass, a soluble polymer, or a metal oxide or hydroxide coating.
4. The method of claim 2 , wherein the non-metallic coating is magnesium hydroxide.
5. The method of claim 2 , wherein the non-metallic coating is removed by application of an electric potential to establish electrical contact between the first and second articles.
6. The method of claim 1 , wherein the second material comprises steel, tungsten, chromium, nickel, cobalt, copper, iron, aluminum, zinc, alloys thereof, or a combination comprising at least one of the foregoing.
7. The method of claim 1 , wherein the first article is a controlled electrolytic material (CEM) ball or fracture plug.
8. The method of claim 1 , wherein the second article is a ball seat.
9. The method of claim 1 , wherein the first article comprises:
a corrodible core comprising the first material and at least partially penetrating the first article, and
a non-corrodible surrounding structure comprising the second material,
wherein only the core is corroded.
10. The method of claim 1 , wherein the first article comprises:
a non-corrodible core comprising the second material and at least partially penetrating the first article, and
a corrodible surrounding structure comprising the first material,
wherein only the surrounding structure is corroded.
11. The method of claim 1 , wherein the electrolyte is water, brine, acid, or a combination comprising at least one of the foregoing.
12. The method of claim 1 , wherein the first material and the second material are selected such that the first material has a corrosion rate of about 0.1 to about 150 mg/cm 2 /hour using aqueous 3 wt % KCl at 200° F.
13. The method of claim 1 , wherein the magnesium alloy in the first material further comprises one or more of the following: Al; Cd; Ca; Co; Cu; Fe; Mn; Si; Ag; Sr; Th; Zn; or Zr.
14. A method of producing an electrical potential in a downhole assembly, comprising
contacting, with an electrolyte,
a first article, the first article comprising a first material and acting as an anode, and
a second article, the second article comprising a second material having a lower reactivity than the material of the first article and acting as a cathode,
with a conductive element to form a circuit;
wherein the first material comprises a magnesium alloy having less than or equal to about 0.5 weight percent of nickel.
15. The method of claim 14 , wherein the electrolyte is water, brine, an acid, or a combination comprising at least one of the foregoing.
16. The method of claim 14 , wherein the second material comprises steel, tungsten, chromium, nickel, cobalt, copper, iron, aluminum, zinc, alloys thereof, or a combination comprising at least one of the foregoing.
17. The method of claim 14 , further comprising corroding the first article in the electrolyte.
18. A downhole assembly, comprising:
a first article comprising a first material and acting as an anode, and
a second article comprising a second material having a lower reactivity than the first material and acting as a cathode,
the first and second articles being electrically connected by a conductive element to form a circuit,
wherein in the presence of an electrolyte, the downhole assembly produces an electrical potential, and at least a portion of the first article is corroded; and
wherein the first material comprises a magnesium alloy having less than or equal to about 0.5 weight percent of nickel.
19. The article of claim 18 , wherein the second material comprises steel, tungsten, chromium, nickel, cobalt copper, iron, aluminum, zinc, alloys thereof, or a combination comprising at least one of the foregoing.
20. The article of claim 18 , wherein the first article is a ball, and the second article is a ball seat.
21. A method of removing a downhole assembly, comprising:
contacting, in the presence of an electrolyte,
a first article comprising a first material and acting as an anode, and
a second article comprising a second material having a lower reactivity than the first material and acting as a cathode,
the downhole assembly comprising the first article in electrical contact with the second article,
wherein at least a portion of the first article is corroded in the electrolyte; and
wherein the first article has a non-metallic coating comprising magnesium hydroxide on a surface thereof.