CORRODIBLE DOWNHOLE ARTICLE

Abstract

This invention relates to a corrodible downhole article comprising an aluminium alloy, wherein the aluminium alloy comprises (a) 3-15 wt % Mg, (b) 0.01-5 wt % In, (c) 0-0.25 wt % Ga, and (d) at least 60 wt % Al. The invention also relates to a method of making a corrodible downhole article comprising an aluminium alloy, the method comprising the steps of: (a) melting aluminium, Mg, In, optionally Ga, and Ni, to form a molten aluminium alloy comprising 3-15 wt % Mg, 0.01-5 wt % In, 0-0.25 wt % Ga, and at least 60 wt % Al, (b) mixing the resulting molten aluminium alloy, (c) casting the aluminium alloy or producing an aluminium alloy powder, and (d) forming the aluminium alloy into a corrodible downhole article. In addition, the invention relates to a method of hydraulic fracturing comprising the use of the corrodible downhole article.

Claims

1. A corrodible downhole article comprising an aluminium alloy, wherein the aluminium alloy comprises (a) 3-15 wt % Mg, (b) 0.01-5 wt % In, (c) 0-0.25 wt % Ga, and (d) at least 60 wt % Al.

2. The corrodible downhole article of claim 1, wherein the aluminium alloy comprises 5-11 wt % Mg.

3. The corrodible downhole article of claim 1, wherein the aluminium alloy comprises 0.1-4 wt % In.

4. The corrodible downhole article of claim 1, wherein the aluminium alloy comprises 0-2.5 wt % Fe.

5. The corrodible downhole article of claim 4, wherein the aluminium alloy comprises 0.1-1.50 wt % Fe.

6. The corrodible downhole article of claim 1, wherein the aluminium alloy comprises 0-10 wt % Ni.

7. The corrodible downhole article of claim 6, wherein the aluminium alloy comprises 0.1-6 wt % Ni.

8. The corrodible downhole article of claim 1, wherein the aluminium alloy comprises 0.3-15 wt % Zn.

9. The corrodible downhole article of claim 8, wherein the aluminium alloy comprises 1-13 wt % Zn.

10. The corrodible downhole article of claim 1, wherein the aluminium alloy comprises (a) 5-11 wt % Mg, (b) 0.3-1.2 wt % In, (c) 0-0.25 wt % Ga, (e) 0-1.8 wt % Fe, (f) 0-6 wt % Ni, and (g) 1-13 wt % Zn.

11. The corrodible downhole article of claim 1, wherein the aluminium alloy comprises (a) 5-11 wt % Mg, (b) 0.3-1.2 wt % In, (c) 0-0.25 wt % Ga, (e) 0-1.5 wt % Fe, (f) 0-0.5 wt % Ni, and (g) 0.3-10 wt % Zn.

12. The corrodible downhole article of claim 1, wherein the aluminium alloy comprises at least 70 wt % Al.

13. The corrodible downhole article of claim 1, wherein the corrodible downhole article is a fracking ball.

14. A method of making a corrodible downhole article of claim 1, the method comprising the steps of: (a) melting aluminium, Mg, In and optionally Ga, to form a molten aluminium alloy comprising 3-15 wt % Mg, 0.01-5 wt % In, 0-0.25 wt % Ga, and at least 60 wt % Al, (b) mixing the resulting molten aluminium alloy, (c) casting the aluminium alloy or producing an aluminium alloy powder, and (d) forming the aluminium alloy into a corrodible downhole article.

15. A method of hydraulic fracturing comprising the use of a corrodible downhole article as claimed in claim 1.

Description

[0046] This invention will be further described by reference to the following Figures which are not intended to limit the scope of the invention claimed, in which:

[0047] FIG. 1 shows an example of the typical geometry of a fracking ball on a seat,

[0048] FIG. 2 shows a graph of corrosion rate as a function of In content for three alloy compositions, and

[0049] FIG. 3 shows a graph of the force withstood in load with ball on seat testing as a function of In content for two alloy compositions.

EXAMPLES

[0050] Alloy Preparation

[0051] Aluminium alloy compositions were prepared by combining the components in the amounts listed in Table 1 below (the balance being aluminium and incidental impurities) and then melting them. These components were then melted by heating at a temperature in the range 600° C.-900° C. (dependent upon the alloy components). Each melt was then cast into a billet.

[0052] Corrosion Testing

[0053] In order to simulate the corrosion performance in a well, the material was corrosion tested by measuring weight loss in an aqueous solution of 3 wt % potassium chloride at a constant temperature of 93° C. (200 F). These results are shown in Table 1 below. The results demonstrate that the alloys of the invention achieve the desired corrosion rates.

[0054] In addition, three further alloy compositions were prepared as follows: [0055] (i) 1 wt % Fe, 5 wt % Ni, 5 wt % Zn, 10 wt % Mg, X wt % In, remainder Al, [0056] (ii) 1 wt % Fe, 5 wt % Ni, 10 wt % Zn, 10 wt % Mg, X wt % In, remainder Al, and [0057] (iii) 1 wt % Fe, 3 wt % Ni, 6 wt % Zn, 5 wt % Mg, X wt % In, remainder Al.

[0058] Various alloys were produced where the amount of In (ie the X value) was varied from 0-1.2 wt %. These alloys were then subjected to corrosion testing. The results of this testing are shown in FIG. 2, which demonstrates the effect of In addition on corrosion behaviour.

[0059] “Ball on Seat” Testing

[0060] 23.5 mm diameter balls were manufactured by machining alloy billets. The ball on seat test is shown in FIG. 1 which utilises a steel seat for the ball test. The seat angle was 30° and the overlap between the aluminium alloy ball and the steel ball seat is approximately 1.5%, where % overlap=(1−(Diameter.sub.seat/Diameter.sub.ball))×100). Each ball was then forced through the steel seat using a Zwick universal testing machine, utilising uniaxially applied compressive load, which gives a maximum force in kN. Where a particular alloy was tested, these results are shown in Table 1 below. These results demonstrate that the alloys of the invention achieve the required force values.

[0061] In addition, two further alloy compositions were prepared as follows: [0062] (i) 1 wt % Fe, 4 wt % Ni, 8 wt % Zn, 10 wt % Mg, X wt % In, remainder Al, and [0063] (ii) 1 wt % Fe, 3 wt % Ni, 6 wt % Zn, 5 wt % Mg, X wt % In, remainder Al.

[0064] Various alloys were produced where the amount of In (ie the X value) was varied from 0-1.1 wt %. These alloys were then subjected to ball on seat testing. The results of this testing are shown in FIG. 3, which demonstrates that force can be maintained within the desired range at varying amounts of In.

TABLE-US-00001 TABLE 1 Corr. Rate Ball Weight % additions to aluminium base (mcd) in holding Other Casting 3% KCl, (kN, 1.5% Example No. Fe Ni Zn Mg additions temp. (° C.) 200 F. overlap) Comparative 1.4 2.2 7.1 6.6 740 222 28.1 Example 1 Comparative 1.4 3.9 9.3 7.6 760 240 Example 2 Comparative 1.2 4.2 9.6 8.2 1.5% Cu 760 50 Example 3 Comparative 1.1 4.4 9.3 8.3 7% Cu 760 0 Example 4 Comparative 1.5 5 7 7 1% Mn 760 67 Example 5 Comparative 3.0 10.0 6.0 10.0 800 146 Example 6 Comparative 3.0 10.0 6.0 10.0 0.1% Y 800 169 Example 7 Comparative 3.0 10.0 6.0 10.0 0.5% Y 800 136 Example 8 Comparative 3.0 10.0 6.0 10.0 1% Y 800 119 Example 9 Comparative 1.7 4.6 12.8 — 0.1% In 750 104 Example 10 Comparative 1.0 4.3 12.4 — 0.6% In 750 214 Example 11 Example 1 0.9 3.7 11.0 9.1 0.22% In 750 338 Example 2 0.9 3.9 11.3 9.4 0.4% In 750 3418 Example 3 1.3 4.5 10.1 8.4 0.74% In 750 4912 Example 4 1.0 3.6 6.0 9.8 0.6% In 750 4615 33.6 Example 5 1.0 4.5 6.3 9.8 1.1% In 750 5858 31.3 Example 6 1.8 3.8 6.3 5.3 0.42% In 750 788 29.3 Example 7 1.4 3.2 6.0 5.1 0.73% In 750 1511 26.8 Example 8 1.0 5.0 10.0 10.0 1% In 750 1881 Example 9 1.0 5.0 10.0 10.0 1% In, 750 1804 1% Sn Example 10 0.9 2.1 5.7 5.4 0.50% In 700 1268 30.8 Example 11 1.4 3.2 6.0 5.1 0.73% In 700 1511 26.8 Example 12 — 3.7 0.7 7.7 1.19% In 700 3709 Example 13 — 2.9 0.9 7.7 0.6% In 700 1582 Example 14 — 3.3 — 7.7 0.9% In 700 1540 Example 15 — 3.3 — 7.7 1.1% In 700 699 Example 16 0.6 0.4 1.1 7.8 0.69% In 700 1558 Example 17 1.1 0.3 5.0 6.8 0.75% In 700 1895 26.6 Example 18 0.7 — 1.2 10.1 1.2% In 700 1761 27.7 Example 19 1.5 — 1.2 9.4 0.7% In 700 1470 28.8