Patent Application
20230392235
The present invention relates to a material composition in the oil and gas industry. More particularly, the present invention relates to dissolvable metal alloys to form components of downhole tools. Even more particularly, the present invention relates to a dissolvable magnesium alloy for components in hydraulic fracturing operations.
Downhole tools are commonly used in oil and gas production. A borehole is drilled through a hydrocarbon bearing formation, and downhole tools, such as plugs and sleeves are positioned along and within the borehole. The plugs close and open portions of the borehole so that zones may be selectively isolated. A plug can include at least one dissolvable metallic component. As an assembly, the plug must hold a pressure differential around 7.5 ksi. A sleeve opens and closes to make the fluid connection between the borehole and the formation. The downhole tools work to isolate and connect the zone for various operations to prepare and produce the hydrocarbons from the formation. When the operations are complete in the zone, components of the downhole tool or even the entire downhole tool may require removal. For example, a dissolvable frac ball set in a plug to trigger a seal may be removed by injecting a solvent targeted to the dissolvable frac ball so that the seal is removed. After the fracturing operation, the components dissolve in the wellbore fluid, typically a potassium chloride brine. Alternatively, the entire plug may be removed.
Dissolvable alloys were developed for the manufacture of downhole tool components in the oil and gas industry. There are mainly two types of metallic dissolvable alloys: magnesium and aluminum based alloys. These alloys may be cast and mechanically worked in a variety of manners, including but not limited to vertical direct chill casting, vacuum induction melting, and extrusion.
The disclosure of dissolvable metal alloys, and particularly, dissolvable magnesium alloys are known in the prior art intended for a variety of conditions. US Publication No. 20160168965 published on 16 Jun. 2016 for Marya, U.S. Pat. No. 8,425,651, issued on 23 Apr. 2013 to Xu et al, US Publication No. 20140286810 published on 25 Sep. 2014 for Marya, US Publication No. 20180238133 published on 23 Aug. 2018 for Fripp et al, US Publication No. 20190032173 published on 31 Jan. 2019 for Sherman et al, US Publication No. 20190055810 published on 21 Feb. 2019 for Fripp et al, US Publication No. 20190271061 published on 5 Sep. 2019 for Tang et al, U.S. patent Ser. No. 10/081,853 issued on 25 Sep. 2018 to Wilks et al, U.S. Pat. No. 9,757,796 issued on 12 Sep. 2017 to Sherman et al, and US Publication No. 20160256091 published on 20 Aug. 2019 to Cho et al, disclose dissolvable magnesium alloys.
It is an object of the present invention to provide a dissolvable magnesium alloy.
It is another object of the present invention to provide a dissolvable magnesium alloy for components of a downhole tool.
These and other objectives and advantages of the present invention will become apparent from a reading of the attached specification.
Embodiments of the present invention include a dissolvable alloy for components of a downhole tool. The assembly of a downhole tool with a dissolvable metallic component, which comprises a dissolvable alloy, having from about 0.04 to about 0.4 wt % nickel and the balance of magnesium, holds a pressure differential around 7.5 ksi and dissolves in a wellbore fluid after downhole operation. The alloy is dissolvable in KCl at 2.1% by weight and 95 QC with a dissolving rate in a range of 10-100 mg/cm2/hr, yield strength in a range of 20-40 ksi, ultimate tensile strength in a range of 25-45 ksi, and elongation in a range of 7-40%.
Optionally in any embodiment, the alloy may comprise about 0-20% lithium by weight, about 0-15% gadolinium by weight, about 0-15% yttrium by weight, about 0-2% copper by weight, about 0-2% zirconium by weight, about 0-15% aluminum by weight.
Optionally in any embodiment, the alloy may comprise up to about 10 wt % total of other elements. which comprises one of manganese, neodymium, cerium, calcium, iron, bismuth, indium, or silver.
Optionally in any embodiment, said copper is about 1.4 wt %, said gadolinium is about 3.1 wt %, said nickel is about 0.15 wt %, and said yttrium is about 4.0 wt %.
Optionally in any embodiment, said copper is about 1.47 wt %, said aluminum is about 10.1 wt %, said zinc is about 0.45 wt %, said nickel is about 0.15 wt %, and said manganese is about 0.16 wt %.
Optionally in any embodiment, said copper is about 0.4 wt %, said nickel is about 0.04 wt %, and said aluminum is about 0.5 wt %.
Optionally in any embodiment, said gadolinium is about 3.1 wt %, said copper is about 0.4 wt %, said nickel is about 0.04 wt %, and said aluminum is about 0.5 wt %.
Optionally in any embodiment, said copper is about 0.4 wt %, said nickel is about 1.4 wt %, and said aluminum is about 5.6 wt %.
Optionally in any embodiment, said gadolinium is about 1.56 wt %, said zirconium is about 0.4 wt %, said nickel is about 0.04 wt %, and wherein said zinc is about 3.88 wt %.
Optionally in any embodiment, said lithium is about 11 wt %, said gadolinium is about 1.0 wt %, said yttrium is about 0.6 wt %, said nickel is about 0.4 wt %, said copper is about 0.2 wt %, and wherein said zinc is about 3.3 wt %.
In another embodiment, an alloy may comprise about 0-20% lithium by weight, about 0-15% gadolinium by weight, about 0-15% yttrium by weight, about 0-2% copper by weight, about 0-2% zirconium by weight, about 0-15% aluminum by weight, about 0.04% to about 0.4% nickel by weight; the balance of magnesium (Mg) and inevitable impurities, so as to be dissolvable in KCl at about 2.1% by weight and about 93° C. with a dissolving rate in a range of from about 10 to about 100 mg/cm2/hr, yield strength in a range of from about 25 to about 37 ksi, ultimate tensile strength in a range of from about 35 to about 45 ksi, and elongation in a range of from about 10 to about 19%.
Optionally in any embodiment, the copper to nickel ration is within the range of about 50:1 to about 0.1:1 wt %.
Optionally in any embodiment, said range of aluminum is about 7 to about 12 wt %, particularly when the range of aluminum to copper is in the range of about 3.5:1 to about 60:1 wt %.
Optionally in any embodiment, said range of zinc is about 0.5 to about 3 wt %, particularly when the range of copper to zinc is in the range of about 0.07:1 to about 4:1 wt %.
In further embodiment, an alloy may comprise about 0.04% to about 0.4% nickel by weight; about 0.2% to about 2% copper by weight; and the balance of magnesium (Mg) and inevitable impurities, wherein the alloy yields strength in a range of from about 25 to about 37 ksi, ultimate tensile strength in a range of from about 35 to about 45 ksi, and elongation in a range of from about 10 to about 19%.
Optionally in any embodiment, the alloy yields strength in a range of from about 25 to about 37 ksi, ultimate tensile strength in a range of from about 35 to about 45 ksi, and elongation in a range of from about 10 to about 19%.
Optionally in any embodiment, the alloy may further comprise about 0-20% lithium by weight, about 0-15% gadolinium by weight, about 0-15% yttrium by weight, about 0-2% zirconium by weight, about 0-15% aluminum by weight.
Optionally in any embodiment, the alloy may further comprise up to about wt % total of other elements. which comprises one of manganese, neodymium, cerium, calcium, iron, bismuth, indium, or silver.
Before the description of the embodiment, terminology, methodology, systems, and materials are described; it is to be understood that this disclosure is not limited to the particular terminologies, methodologies, systems, and materials described, as these may vary. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions of embodiments only, and is not intended to limit the scope of embodiments. For example, as used herein, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. In addition, the word “comprising” as used herein is intended to mean “including but not limited to.” Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.
Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as size, weight, reaction conditions and so forth used in the specification and claims are to the understood as being modified in all instances by the term “about”.
Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
As used herein, the term “about” means plus or minus 10% of the numerical value of the number with which it is being used. Therefore, about 50% means in the range of 45%-55%.
Magnesium alloy is an ahoy based on magnesium and some other additional elements. It has the following characteristics: low density (about 1.8 g/cm3), high specific strength, high specific elastic modulus, good heat dissipation, good shock absorption, better impact load resistance than aluminum alloy, and good resistance to organic and alkali corrosion, Magnesium alloy has a wide range of applications in various industrial fields, mainly used in aviation, aerospace, transportation, chemical, rocket, oil and gas industries and other industrial sectors. Magnesium is the lightest metal in the practical applications. The specific gravity of magnesium is about ⅔ that of aluminum and ¼ that of iron, Magnesium alloy has high strength and high rigidity. On the other hand, magnesium alloy is chemically active among existing materials and can be used in industrial fields where structural materials are required to be degradable.
Although the chemical properties of magnesium alloys are relatively active, the reaction rate of magnesium with a medium such as water, aqueous solutions and water-oil mixtures is extremely slow at normal temperature. The main reason is that the magnesium hydroxide formed by the reaction can prevent further reaction between magnesium and the medium. Even if the magnesium alloys are heated to the boiling temperature of water, only a very slow reaction can be observed. Because the reaction rate of conventional magnesium alloy with medium is low within a certain temperature range and the controllable range is narrow, it cannot meet the demands of industrial applications. Thus, for the manufacture of structural and functional integrated components in industries such as oil and gas sector, there is a great need for an improved alloying process that would enhance the rate of chemical reaction between magnesium alloy and the medium, while maintaining the high strength of the magnesium alloy.
The present invention presents a magnesium alloy which would destroy the continuity of magnesium hydroxide formed during the reaction between magnesium and a medium, thereby accelerating the reaction between magnesium and the medium. The medium could be aqueous solutions such as fresh water, pond water, lake water, salt water, brine water, produced water or flow back water and their mixture with crude oil etc. In one embodiment, the chemical reaction can be: Mg+2H2O→Mg(OH)2+H2 (gas)
By adjusting the proportion of each element in the magnesium alloy, the reaction rate of the magnesium alloy with the medium can be regulated, resulting in a relatively wider controllable range, and the magnesium alloy material is flexible, so that the magnesium alloy meets the application requirements of the industrial sector such as oil and gas industry.
The mechanical properties such as tensile strength and yield strength of magnesium alloy are improved by adding gadolinium and yttrium to the magnesium alloy. Tensile strength is the resistance of a material to breakage under tension and it is usually obtained by the stress-strain curve. The unit is usually in MPa or KSI etc. Elongation is the amount of extension of an object under stress upon breakage, usually expressed as a percentage of the original length. In the application in oil and gas industries, such as frac balls, frac plugs or frac seats, not only has the magnesium alloys to be dissolved in a medium, but also the alloys need to have higher mechanical strength to withstand the high pressure and high temperature scenario.
It is desirable to alloy iron, copper, and nickel to the baseline to accelerate corrosion. Nickel, copper, iron, or a combination of the three may be added to achieve a specific dissolution rate by intra-granular or intergranular galvanic corrosion. Copper alone will not have a sufficient corrosion rate for many conditions. Nickel and iron may drop out of solution if an improper amount is added. Tuning the corrosion rate without a detrimental impact to mechanical properties often requires a combination of two elements in a particular amount.
The present invention disclosure shows the dissolvable magnesium alloy compatible for the conditions associated with downhole operations, such as hydraulic fracturing operations. When the dissolvable magnesium alloy is formed in a component of a downhole tool, the component must have the same functionality as the conventional non-dissolving component. The component must be sufficiently strong to hold a pressure differential around 7.5 ksi as assembled in the downhole tool. There may be other components of the dissolvable magnesium alloy in the downhole tool as well. The component must also dissolve in a wellbore fluid, such as a potassium chloride brine, after the downhole operation is completed. The alloy remains strong, and ductile to be formed into a component and functional as a downhole tool. The dissolvability is controlled within a range for a potassium chloride brine. Additionally, the yield strength, ultimate tensile strength, and elongation of the present invention are sufficient to function as component of a downhole tool, despite the additives in grains of the magnesium to affect overall strength.
In one embodiment, gadolinium and yttrium in magnesium alloys are used to improve the mechanical properties (tensile strength and yield strength) of magnesium alloys. Elements of copper, nickel, gallium and indium are used to improve the solubility of various other metal elements. Moreover, copper, nickel, gallium, indium and silicon in magnesium alloys increase the reaction rate of magnesium alloys with a medium. Other elements in magnesium alloys, such as aluminum, zinc, zirconium, rhenium, iron, beryllium and calcium, may serve to catalyze the improvement of the mechanical properties of magnesium alloys.
As shown in
The
The yield and UTS of Alloy 3 fits in the window close to AZ31, but the ductility unexpected exceeded the base and modified chemistries. Then, again improving on Alloy 1, Alloy 4 was created by adding 3.1 wt % gadolinium with 0.5 wt % Al, 1.4 wt %) Cu, and 0.15 wt % Ni, achieving a remarkable increase in the yield strength to 37 ksi, a 100% increase, with ductility staying constant. Alloy 4 sees an unexpected increase in mechanical properties compared to alloy 1 after an addition of gadolinium.
Alloy 5 was created by removing the aluminum from alloy 4, with a formulation of 3.1 wt % Gd, 1.4 wt % Cu, and 0.15 wt % Ni having the startling effect of a dramatic increase in ductility to 16%, a 50% improvement over Alloy 4. The yield strength fell relative to alloy 4 to 23.8 ksi. The ductility for alloy 5 unexpectedly is increased while the yield and UTS is essentially unchanged from alloy 1 after the removal of aluminum and addition of gadolinium equal to alloy 4. Alloy 6 results in the increase of all properties with the addition of yttrium to alloy 5.
More specifically, alloy 6 improves upon Alloy 5 with the addition of 4 wt % Y, with 3.1 wt % Gd, 1.4 wt % Cu, and 0.15 wt % Ni. Again, the yield strength experienced a dramatic increase to 32.4 ksi, a 40% increase, while increasing the ductility to 17.5%. Yttrium unexpectedly optimized both mechanical strength and ductility in alloy 6.
In another embodiment, alloy 7 is made with 3.3 wt % Al, 1 wt % Gd, 0.6 wt % Y, 11 wt % Li, 0.4 wt % Ni, and 0.2 wt % Cu. The lithium addition is to increase the ductility, as one skilled in the art would know. Unexpectedly, the ductility increased more than what a skilled practitioner would expect.
Still in
The strength of an alloy is contingent upon the ease with which dislocations move. Opposing dislocation motion increases mechanical strength. The addition of rare earth acts as a grain refiner in magnesium, as smaller grains hinder dislocation motion. Dislocations may be pinned due to stress field interactions with other dislocations and solute particles, creating physical barriers from second phase precipitates forming along grain boundaries. Further, rare earth depresses the corrosion rate. It is expected that corrosion will decrease significantly; the elongation would be similar, with a modest increase in yield and UTS.
The addition of 3.1 wt % gadolinium to 1.4 wt % copper, 0.6 wt % aluminum, and 0.15 wt % nickel (alloy 4) results in the formation of LPSO structures, specifically 14H. A yield strength of 37 ksi and UTS of 40 ksi is achieved with an elongation of 9%. Two important deviations from expectations occur. First, the yield doubled and secondly, the corrosion rate stays high (55 mg/cm2/hr in 2.1 weight % KCl). A modest increase in the UTS (40 ksi) of 33% is observed.
The combination of aluminum and gadolinium are known to act as a corrosion inhibitor. However, in this alloy, the corrosion rate increased from 45 to 55 mg/cm2/hr compared to embodiment without gadolinium.
Increasing the aluminum content and adding zinc (alloy 2) results in a dissolution rate of 57 mg/cm2/hr. Removing zinc and lowering aluminum to 5.6 weight % (Alloy 3) results in a dissolution rate of 45 mg/cm2/hr. Then, by adding 3.1 gadolinium, a dissolution rate of 55 mg/cm2/hr is measured in 2.1% KCl at 95° C. By removing aluminum, a dissolution rate of 13 mg/cm2/hr is measured in 2.1% KCl at 95° C.
In a final embodiment, aluminum is removed and 0.4 weight % zirconium is added with the expectation of a lower yield and UTS due to fewer phases generated, a modest increases in ductility, and a moderate decrease in dissolution rate. As expected, the yield decreased to 24 ksi, with UTS decreasing to 33 ksi. Surprisingly, the elongation is more than doubled to 19%, very similar to the 5.6 wt % Al alloy. No similar phases are formed between these two alloys, as seen in
As shown in
Alloy 1 has fewer secondary phases than alloy 2. Alloy 3 had fewer secondary phases than Alloy 2, but a higher ductility. Alloy 5 has more secondary phases than alloy 3, with slightly lower ductility. The cuboidal features in the alloys formed from the copper and nickel addition act to increase the corrosion rate.
All known dissolvable magnesium alloys start from a chemistry in the range of 0-20 wt % lithium, 0-15 wt % gadolinium, 0-15 wt % yttrium, 0-2 wt % copper, 0-2 wt %) nickel, 0-2 wt % zirconium, 0-15 wt % aluminum, and up to 10% total of other elements including but not limited to manganese, neodymium, cerium, calcium, iron, bismuth, indium, and silver with the balance magnesium. With all zero, plain elemental magnesium is the starting point.
From the testing Mg-3Gd-4Y-1.4Cu in alloy 6 is at least one embodiment of the dissolvable magnesium alloy of the present invention. The strength (tensile yield strength, ultimate tensile strength) and performance (elongation and dissolution rate) are compatible with components of a downhole tool. More specifically, one chemistry of Mg-3Gd-4Y-1.4Cu alloy has the form of 3.1 wt % gadolinium, 4 wt % yttrium, 1.4 wt % copper, wt % nickel, and 0.4 wt % zirconium with magnesium as the balance. This embodiment of the present invention achieves 32.4 ksi yield, 46.6 ksi UTS, 17.5% elongation, and a dissolution rate of 25 mg/cm2/hr in 95° C. 2.1 wt % KCl. Removing the copper and nickel from this chemistry may also form a corrosion resistant alloy for long duration applications.
In one embodiment, magnesium alloy of the present invention comprises wt Al, 1.4% wt Cu, 0.15% wt Ni, 97.95 wt % Mg. In one embodiment, the production process is as follows:
Weighing raw materials such as magnesium, aluminum, copper, nickel, and pretreating magnesium, aluminum, copper, and nickel at 100 C for 5 h; mixing the raw materials, and then smelting them in a crucible electric resistance furnace, covering them with a covering agent, and refining them with a refining agent, thus the components are uniformly mixed, removing the inclusions, and casting the materials at 670 C to form an ingot; subjecting the ingot to a homogenization heat treatment at 450 C for a treatment time of 8 h; subjecting the ingot to a forging processing at 350 C so as to obtain a forged piece; subjecting the forged piece to an aging heat treatment at room temperature for a treatment time of 20 h.
The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated structures, construction and method can be made without departing from the true spirit of the invention.
