Corrodible downhole article and method of removing the article from downhole environment

1. A method of removing a corrodible downhole article having a core and a surface coating disposed on the core, the method comprising:

eroding the surface coating by physical abrasion, chemical etching, or a combination of physical abrasion and chemical etching,

wherein the surface coating comprises:

a metallic layer resistant to corrosion by a corrosive material,

the metallic layer comprising tungsten, cobalt, copper, iron, nickel, aluminum, nickel alloy, aluminum alloy, or a combination comprising at least one of nickel, aluminum, nickel alloy, or aluminum alloy; and

wherein the core comprises magnesium alloy having greater than zero but less than 1 weight percent of nickel.

2. The method of claim 1 , wherein the corrodible core comprises magnesium alloy having greater than zero but less than or equal to about 0.5 weight percent of nickel.

3. The method of claim 1 , wherein eroding is by physical abrasion alone.

4. The method of claim 1 , wherein eroding comprises flowing a slurry of a proppant over the surface coating of the corrodible downhole article.

5. The method of claim 4 , wherein the proppant includes sand, aluminum pellets, glass beads, ceramic beads, and combinations comprising at least one of the foregoing.

6. The method of claim 1 , further comprising corroding the downhole article in the corrosive material after eroding.

7. The method of claim 6 , wherein the corrosive material is water, brine, an acid, hydrogen sulfide, or a combination comprising at least one of the foregoing.

8. The method of claim 1 , wherein the metallic layer has a thickness of less than or equal to about 1,000 micrometers.

9. The method of claim 1 , wherein the metallic layer is formed by an electroless plating process, or by an electrodeposition process in the presence of an anhydrous ionic solvent.

10. The method of claim 1 , wherein the corrodible downhole article is a ball, ball seat or frac plug.

11. The method of claim 1 , wherein the metallic layer has a thickness of about 50 to about 750 micrometers.

12. The method of claim 1 , wherein the core comprises magnesium alloyed with about 0.25 wt% of Ni.

13. The method of claim 1 , wherein the core comprises about 0.25 to about 1 wt% of Ni.

14. A method of forming a reversible seal with a corrodible downhole article, comprising

seating a ball or plug in the corrodible downhole article having a shaped surface which accommodates a surface shape of the ball or plug, the corrodible downhole article comprising:

a magnesium alloy core comprising greater than zero but less than or equal to about 1 wt% of nickel, and

a metallic layer covering the magnesium alloy core, the metallic layer being resistant to corrosion by a corrosive material and comprising tungsten, cobalt, copper, iron, nickel, nickel alloy, aluminum, aluminum alloy, or a combination comprising at least one of nickel, nickel alloy, aluminum, or aluminum alloy;

wherein the corrodible downhole article prevents fluid flow when the ball or plug is seated.

15. The method of claim 14 , wherein seating comprises placing the ball or plug in a downhole environment and applying pressure to the downhole environment.

16. The method of claim 15 , further comprising removing the metallic layer of the corrodible downhole article, prior to seating, by injecting a slurry of a proppant into the downhole environment at a pressure greater than that of the downhole environment.

17. The method of claim 16 , wherein the proppant slurry flows past the article and erodes the metallic layer to expose the magnesium alloy core.

18. The method of claim 17 , further comprising corroding the exposed magnesium alloy core in a corrosive material.

19. The method of claim 15 , further comprising unseating the ball or the plug seated in the corrodible downhole article by reducing the pressure applied to the downhole environment to a pressure below that of an ambient downhole pressure.

20. A method of removing a corrodible downhole article comprising:

a core, and

a metallic layer covering the core,

the method comprising eroding the metallic layer by physical abrasion, chemical etching, or a combination of physical abrasion and chemical etching, and

corroding the corrodible downhole article in a corrosive material after eroding,

wherein the core of the corrodible downhole article comprises magnesium alloy and greater than zero but less than or equal to about 1 wt% of nickel; and

the metallic layer of the downhole article comprises tungsten, cobalt, copper, iron, nickel, nickel alloy, aluminum, aluminum alloy, or a combination comprising at least one of nickel, nickel alloy, aluminum, or aluminum alloy.