Acid-resistant controllable dissolution coating for soluble alloy, protection method and application

Abstract

The invention provides an acid-resistant controllable dissolution coating for a soluble alloy, relates to the field of oil field oil production engineering, and aims to solve the problem that a soluble alloy material adopted by a soluble bridge plug in a high-temperature and acid environment cannot meet the construction environment requirements of acid fracturing fluid of an unconventional tight reservoir. A micro-arc oxidation coating is arranged on the surface of the soluble alloy; three dissolution starting holes with the depth reaching the surface of the soluble alloy are preset in the surface of the soluble alloy; and spraying a resin coating on the surface of the micro-arc oxidation coating. The acid-resistant controllable dissolution coating is applied to an acid-resistant soluble bridge plug tool body material used in unconventional tight reservoir large-scale fracturing, and the resin coating is sprayed on the surface of the soluble alloy after micro-arc oxidation treatment, so that the dissolution time of the soluble alloy in an acid fracturing fluid is effectively delayed; therefore, the effective pressure bearing time of a soluble bridge plug tool is prolonged, corrosion can be delayed for more than 8 hours in a high-temperature and acid environment, and the requirements of an unconventional tight reservoir acid fracturing fluid construction environment are met.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield production engineering, and in particular to an acid-resistant controllable dissolution coating for soluble alloys, a protection method and an application thereof. Background Art

[0002] The soluble bridge plugs currently used in unconventional tight reservoir development are made from soluble alloys. Spraying resins or butter on the surface can delay dissolution in neutral fracturing fluids for more than eight hours. However, in acidic fracturing fluids (0.2% acetic acid) or those requiring strong acid treatment (such as 10% hydrochloric acid), coupled with the high temperatures of 90-150°C at the wellbore, the resin corrosion-inhibiting coating quickly loses effectiveness, making it difficult to guarantee an effective high-pressure bearing time of more than eight hours. Conventional lightweight alloy surface treatments such as anodizing, electrophoresis, and micro-arc oxidation cannot simultaneously achieve both material strength and rapid dissolution. Summary of the Invention

[0003] The present invention proposes an acid-resistant, controllable dissolution coating for soluble alloys to address the problem that soluble alloy materials used in soluble bridge plugs cannot meet the construction environment requirements of acid fracturing fluids for unconventional tight reservoirs under high-temperature, acidic environments. The acid-resistant, controllable dissolution coating for soluble alloys can effectively delay the dissolution time of the soluble alloy in acid fracturing fluids, thereby increasing the effective pressure-bearing time of the soluble bridge plug tool and achieving rapid dissolution after fracturing. The present invention also provides a method and application for protecting soluble alloys with the acid-resistant, controllable dissolution coating.

[0004] According to one aspect of the present invention, an acid-resistant controllable dissolution coating for a soluble alloy is provided, comprising a soluble alloy as a base material, a micro-arc oxidation coating provided on the surface of the soluble alloy; three electrodes are pre-placed on the surface of the soluble alloy, and after the micro-arc oxidation coating is formed, three dissolution initiation holes are formed on the surface of the soluble alloy block at depths corresponding to the electrodes and reaching the surface of the soluble alloy block; and a resin coating is sprayed on the surface of the micro-arc oxidation coating. According to a second aspect of the present invention, there is provided a method for protecting a soluble alloy with an acid-resistant controlled dissolution coating, comprising the following steps: S1. Selecting a soluble alloy block as the base material; S2. Based on the selected soluble alloy base material, performing micro-arc oxidation treatment on the surface of the soluble alloy base material to form a micro-arc oxidation coating on the surface of the soluble alloy base material; S3. During the micro-arc oxidation coating treatment, three electrodes need to be pre-placed on the surface of the soluble alloy block. Therefore, after the micro-arc oxidation coating is formed, three small holes with a depth reaching the surface of the soluble alloy block are naturally formed on the surface; S4. Electrostatically spray resin powder on the surface of the micro-arc oxidation coating and form a resin coating by high-temperature curing.

[0005] Furthermore, the method of performing micro-arc oxidation treatment on the surface of the soluble alloy matrix material in step S2 is specifically as follows: First, the surface of the soluble alloy to be processed must be pretreated; After the pretreatment is completed, the micro-arc oxidation process begins; After micro-arc oxidation of soluble alloys, post-processing is required.

[0006] Furthermore, the specific process of the micro-arc oxidation process is as follows: The specific process of micro-arc oxidation is: The soluble alloy block is placed in an oxidation tank, and a standard three-electrode system is used with an external voltage of 600V. The oxides attached to the surface are peeled off within 15 minutes, releasing active ions and free radicals. After ionization reaction, the reaction products of the active ions, i.e. oxides, are adsorbed on the surface of the soluble alloy in a gel state, forming a fine, dense, and high-hardness oxide layer.

[0007] The oxidation tank contains a mixed solution of 10 g / L K2ZrF6 and 10 g / L NH4HF2, and the pH value of the mixed solution is adjusted to 12 with NaOH; The standard three-electrode system is: a soluble alloy as a working electrode, a platinum electrode mounted on the surface of the soluble alloy as an auxiliary electrode, and a saturated calomel electrode mounted on the surface of the soluble alloy as a reference electrode.

[0008] Furthermore, the pretreatment process of the soluble alloy surface to be processed is: First, the surface of the soluble alloy to be processed must be cleaned and degreased to ensure that the surface is clean and free of contamination; After the cleaning work is completed, chemical treatment and electrolytic polishing processes are carried out to eliminate minor surface defects and improve the surface finish of the soluble alloy.

[0009] Furthermore, after the micro-arc oxidation of the soluble alloy, the post-treatment method includes: Cleaning, drying and sealing are carried out; cleaning is to remove the residues on the surface, drying is to use air flow or drying method to dry the oxidized soluble alloy surface, and sealing is to seal the soluble alloy surface treated by micro-arc oxidation to protect its surface.

[0010] Furthermore, the resin coating is formed by electrostatically spraying resin powder on the surface of the micro-arc oxidation coating 2 and curing at high temperature. The specific method includes: Resin powder is electrostatically sprayed on the surface of the soluble alloy after micro-arc oxidation treatment, and then heated to 130-150℃ and cooled and solidified in air to fill the pores of the micro-arc oxidation coating and further enhance the corrosion resistance.

[0011] Furthermore, the resin powder is Aksu resin powder.

[0012] Furthermore, in step S4, electrostatic spraying of resin powder is performed on the surface of the micro-arc oxidation coating 2. When the resin coating is formed by high-temperature curing, three dissolution start holes corresponding to the electrodes are formed on the surface of the micro-arc oxidation coating 2, and the depth reaches the surface of the soluble alloy block. Before spraying the resin powder, placeholder materials are installed at the positions of the three dissolution start holes to prevent the resin powder from fully covering the surface. The placeholder material is polyimide or polyetheretherketone.

[0013] According to a third aspect of the present invention, an application of an acid-resistant controllable dissolution coating for soluble alloys is provided. The acid-resistant controllable dissolution coating of the soluble alloy can be applied to the acid-resistant soluble bridge plug tool body material used in large-scale fracturing of unconventional tight reservoirs.

[0014] The present invention has at least the following beneficial effects: The present invention proposes an acid-resistant, controllable dissolution coating for soluble alloys. Micro-arc oxidation coatings and resin coatings are applied to the surface of the soluble alloy. This method can effectively delay the dissolution of the soluble alloy in acidic fracturing fluids, thereby increasing the effective pressure-bearing time of the soluble bridge plug tool. Furthermore, dissolution initiation holes are provided in the coating to achieve rapid dissolution after fracturing.

[0015] Without affecting the strength of the soluble alloy material and its rapid dissolution performance after fracturing construction, the corrosion can be delayed for more than 8 hours in acidic fracturing fluid or strong acid treatment process, ensuring that the material strength within 8 hours meets the fracturing construction requirements of soluble bridge plug tools, and at the same time, it can be quickly dissolved within 20 days after fracturing construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings herein are incorporated into and constitute a part of the specification. These drawings illustrate embodiments consistent with the present invention and, together with the specification, are used to explain the technical solutions of the present invention.

[0017] Figure 1 This is a flow chart of the acid-resistant controlled dissolution coating protection method for soluble alloys of the present invention; Figure 2 This is an axonometric view of a sample of a soluble alloy with an acid-resistant controllable dissolution coating according to the present invention (one corner of which is partially cut away); Figure 3 for Figure 2 Cross-sectional view of .

[0018] In the figure, 1-soluble alloy block, 2-micro-arc oxidation coating, 3-resin coating, 4-dissolution starting hole. DETAILED DESCRIPTION

[0019] like Figure 2-3 As shown, an acid-resistant controllable dissolution coating for a soluble alloy comprises a soluble alloy block 1 as a base material, a micro-arc oxidation coating provided on the surface of the soluble alloy; three electrodes are pre-set on three different surfaces of the soluble alloy, and after the micro-arc oxidation coating is formed, three dissolution start holes 4 are formed on the surface of the soluble alloy block at depths corresponding to the electrodes and reaching the surface of the soluble alloy block; Spraying a resin coating 3 on the surface of the micro-arc oxidation coating; The present invention also provides a method for protecting a soluble alloy with an acid-resistant controllable dissolution coating, comprising the following steps: S1. Selecting a soluble alloy block as the base material; S2. Based on the selected soluble alloy block substrate material, performing micro-arc oxidation treatment on the surface of the soluble alloy block substrate material to form a micro-arc oxidation coating on the surface of the soluble alloy block substrate material; The specific method of micro-arc oxidation treatment on the surface of soluble alloy matrix material is as follows: First, the surface of the soluble alloy to be processed must be pretreated; After the pretreatment is completed, the micro-arc oxidation process begins; After micro-arc oxidation of soluble alloys, post-processing is required.

[0020] S3. During the micro-arc oxidation coating treatment, three electrodes need to be pre-placed on the surface of the soluble alloy. Therefore, after the micro-arc oxidation coating is formed, three small holes with a depth reaching the surface of the soluble alloy are naturally formed on the surface. S4. Electrostatically spray resin powder on the surface of the micro-arc oxidation coating and form the resin coating by high-temperature curing. Since there are three small holes on the surface of the micro-arc oxidation coating, booth materials are installed at these three locations before spraying the resin powder, so that the resin powder cannot fully cover the entire surface, forming three dissolution start holes.

[0021] The acid-resistant controllable dissolution coating of the soluble alloy of the present invention can be applied to the acid-resistant soluble bridge plug tool body material used in large-scale fracturing of unconventional tight reservoirs, and can effectively delay the dissolution time of the soluble alloy in the acid fracturing fluid, thereby increasing the effective pressure-bearing time of the soluble bridge plug tool. At the same time, it can also achieve rapid dissolution after fracturing. Example

[0022] Figure 2 Axonometric view of a sample of a soluble alloy with an acid-resistant controlled dissolution coating according to the present invention (one corner of which is partially cut away); Figure 3 yes Figure 2 Cross-sectional view of .

[0023] like Figure 2-3As shown, an acid-resistant controllable dissolution coating for a soluble alloy comprises a soluble alloy block 1 as a base material, a micro-arc oxidation coating provided on the surface of the soluble alloy; three electrodes are pre-set on three different surfaces of the soluble alloy, and after the micro-arc oxidation coating is formed, three dissolution initiation holes 4 are naturally formed on the surface, the depth of which reaches the surface of the soluble alloy block; A resin coating 3 is sprayed on the surface of the micro-arc oxidation coating 2.

[0024] like Figure 1 As shown, a method for protecting a soluble alloy with an acid-resistant controlled dissolution coating comprises the following steps: S1. Selecting a soluble alloy 1 as a matrix material; the soluble alloy is a soluble magnesium alloy; S2. Based on the selected soluble alloy 1 matrix material, a micro-arc oxidation treatment is performed on the surface of the soluble alloy matrix material to form a micro-arc oxidation coating on the surface of the soluble alloy matrix material; the micro-arc thickness is 15 microns; the specific method includes: First, the surface of the soluble alloy to be processed must be pretreated by cleaning and degreasing to ensure that the surface is clean and free of pollution.

[0025] After the cleaning work is completed, chemical treatment and electrolytic polishing processes are carried out to eliminate minor surface defects and improve the surface finish of the soluble alloy.

[0026] After the pretreatment is completed, the micro-arc oxidation process begins; the specific process is: The soluble alloy was placed in an oxidation tank containing K2ZrF6 (10 g / L) and NH4HF2 (10 g / L) solutions (the pH value was adjusted to 12 with NaOH). A standard three-electrode system was used (the soluble alloy served as the working electrode, a platinum electrode installed on the surface of the soluble alloy served as the auxiliary electrode, and a saturated calomel electrode (Ag / AgCl) installed on the surface of the soluble alloy served as the reference electrode). An external voltage of 600 V was applied, and within 15 minutes, the oxides attached to the surface were stripped off, releasing active ions and free radicals. After ionization reaction, the reaction products of the active ions, i.e., oxides, were adsorbed on the surface of the soluble alloy in a gel state, forming a fine, dense, and high-hardness oxide scale.

[0027] After micro-arc oxidation of soluble alloys, post-processing is required, which mainly includes cleaning, drying, sealing, etc. to remove residues on the surface. Drying is to use air flow or drying to dry the oxidized soluble alloy surface. Sealing is to seal the soluble alloy surface treated by micro-arc oxidation to protect its surface.

[0028] S3. During the micro-arc oxidation coating treatment, three electrodes need to be pre-placed on three different surfaces of the soluble alloy block 1. Therefore, after the micro-arc oxidation coating 2 is formed, three small holes with a depth reaching the surface of the soluble alloy block are naturally formed on the surface; S4, electrostatically spraying resin powder on the surface of the micro-arc oxidation coating 2, and forming a resin coating 3 by high-temperature curing, with a resin thickness of 30 microns; Electrostatic spraying of resin powder is performed on the surface of the micro-arc oxidation coating 2, and the resin coating is formed by high-temperature curing. The specific method includes: Resin powder is electrostatically sprayed on the surface of the soluble alloy after micro-arc oxidation treatment, and then heated to 130-150℃ and cooled and solidified in air to fill the pores of the micro-arc oxidation coating and further enhance the corrosion resistance.

[0029] When forming a resin coating on the surface of the micro-arc oxidation coating 2, before spraying the resin powder, placeholder materials in the form of blocks or rods are installed at the three small holes on the surface of the micro-arc oxidation coating 2 to prevent the resin powder from completely covering the three holes, thereby forming three dissolution initiation holes 4. The placeholder material is specifically polyimide or polyetheretherketone. Test Case

[0030] Prepare a mixed solution: a mixture of 0.2% acetic acid and 0.1% potassium chloride; A soluble alloy sample treated according to this embodiment was placed in a container containing a mixed solution of 0.2% by mass acetic acid and 0.1% by mass potassium chloride, heated to 90 degrees Celsius and maintained at a constant temperature. The test coating was found to be able to delay corrosion of the soluble alloy for more than 14 hours and completely dissolve into powder within the next 8-12 days.

[0031] Tests have confirmed that the method of the present invention can effectively delay the dissolution time of soluble alloys in acidic fracturing fluid by ≥14 hours, thereby increasing the effective pressure-bearing time of the soluble bridge plug tool. At the same time, it can also achieve rapid dissolution 8-12 days after fracturing.

[0032] While various embodiments of the present invention have been described above, the above descriptions are intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technological improvements in the marketplace, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An acid-resistant controllable dissolution coating of a soluble alloy, comprising a soluble alloy block (1), characterized in that: A micro-arc oxidation coating (2) is provided on the surface of the soluble alloy block (1); three electrodes are pre-set on three different surfaces of the soluble alloy block (1); after the micro-arc oxidation coating (2) is formed, three dissolution starting holes (4) corresponding to the electrodes are formed on the surface of the soluble alloy block at depths reaching the surface of the soluble alloy block; and a resin coating (3) is sprayed on the surface of the micro-arc oxidation coating (2).

2. A method for protecting the acid-resistant controlled dissolution coating of the soluble alloy according to claim 1, characterized in that: The following steps are involved: S1. Selecting a soluble alloy block as a soluble alloy matrix material; S2. Based on the selected soluble alloy base material, performing micro-arc oxidation treatment on the surface of the soluble alloy base material to form a micro-arc oxidation coating on the surface of the soluble alloy base material; S3. During the micro-arc oxidation coating treatment, three electrodes need to be pre-placed on the surface of the soluble alloy block. Therefore, after the micro-arc oxidation coating is formed, three small holes with a depth reaching the surface of the soluble alloy are naturally formed on the surface. S4. Electrostatically spray resin powder on the surface of the micro-arc oxidation coating and form a resin coating by high-temperature curing.

3. The method for protecting an acid-resistant controlled dissolution coating for a soluble alloy according to claim 2, wherein: The method of performing micro-arc oxidation treatment on the surface of the soluble alloy matrix material in step S2 specifically includes: First, the surface of the soluble alloy block to be processed must be pretreated; After the pretreatment is completed, the micro-arc oxidation process begins; After the soluble alloy block is micro-arc oxidized, the oxide scale formed by the micro-arc oxidation is post-treated.

4. The method for protecting an acid-resistant controlled dissolution coating for a soluble alloy according to claim 3, wherein: The specific process of micro-arc oxidation is: The soluble alloy block is placed in an oxidation tank. A standard three-electrode system is used with an applied voltage of 600V. The oxides attached to the surface are peeled off within 15 minutes, releasing active ions and free radicals. After ionization reaction, the reaction products of the active ions, i.e., oxides, are adsorbed on the surface of the soluble alloy in a gel state, forming a fine, dense, and hard oxide skin. The oxidation tank is filled with a mixed solution of 10 g / L K2ZrF6 and 10 g / L NH4HF2, and the pH value of the mixed solution is adjusted to 12 with NaOH; The standard three-electrode system comprises: a soluble alloy block as a working electrode, a platinum electrode mounted on the surface of the soluble alloy block as an auxiliary electrode, and a saturated calomel electrode mounted on the surface of the soluble alloy block as a reference electrode.

5. The method for protecting an acid-resistant controlled dissolution coating for a soluble alloy according to claim 3, wherein: The pretreatment process of the surface of the soluble alloy block to be processed is as follows: First, the surface of the soluble alloy block to be processed must be cleaned and degreased; After the cleaning work is completed, chemical treatment and electrolytic polishing processes are carried out to eliminate minor surface defects; After the soluble alloy is micro-arc oxidized, the method for post-processing the oxide scale formed by the micro-arc oxidation includes: cleaning, drying and sealing the oxide scale formed by the micro-arc oxidation.

6. The method for protecting an acid-resistant controlled dissolution coating for a soluble alloy according to claim 2, wherein: The soluble alloy is a soluble magnesium alloy.

7. The method for protecting an acid-resistant controlled dissolution coating for a soluble alloy according to claim 2, wherein: Electrostatic spraying of resin powder is used on the surface of the micro-arc oxidation coating, and the resin coating is formed by high-temperature curing. The specific method includes: Resin powder is electrostatically sprayed on the surface of the soluble alloy block after micro-arc oxidation treatment, and then heated to 130-150°C and cooled and solidified in the air to fill the pores of the coating after micro-arc oxidation treatment.

8. The method for protecting a soluble alloy with an acid-resistant controlled dissolution coating according to claim 7, wherein: The resin powder is Aksu resin powder.

9. The method for protecting an acid-resistant controlled dissolution coating for a soluble alloy according to claim 2, wherein: In step S4, when electrostatically spraying resin powder on the surface of the micro-arc oxidation coating and curing the resin coating at high temperature, three dissolution start holes corresponding to the electrodes are formed on the surface of the micro-arc oxidation coating, and the depth reaches the surface of the soluble alloy block. Before spraying the resin powder, placeholder materials are installed at the positions of the three dissolution start holes to prevent the resin powder from fully covering the surface. The placeholder material is polyimide or polyetheretherketone.

10. An acid-resistant controlled dissolution coating of a soluble alloy according to claim 1, used as an acid-resistant soluble bridge plug tool body material for large-scale fracturing of unconventional tight reservoirs.

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