Preparation method of soluble blanking plug

Abstract

The invention relates to the technical field of under-pressure operation or other operation temporary plugging in the petroleum industry, and discloses a preparation method of a soluble blanking plug, which comprises the following steps: firstly, respectively preparing a lower joint and an upper joint by using low-carbon alloy steel and nickel-based alloy steel, and then preparing a soluble core matrix by using magnesium alloy; then the surface of the base body is pretreated, then the soluble core base body obtained after surface pretreatment is cleaned and dried, and then the outer surface, except for the dissolving surface, of the soluble core base body is machined to form a corrosion-resistant composite coating; and finally, assembling the prepared soluble core with the corrosion-resistant composite coating with an upper joint, a lower joint and a sealing assembly to form the soluble blanking plug. The corrosion resistance of the magnesium alloy can be greatly improved by adopting the soluble material and the corrosion-resistant coating, the ultrahigh pressure-bearing and temperature-resistant performance of the prepared soluble blanking plug can meet most working conditions, and the soluble blanking plug can be used in high-temperature and high-pressure wells with the pressure of 105 MPa and the temperature of 150 DEG C or above.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure - maintained operation technology in the oil industry or other temporary plugging technologies for operations, and particularly relates to a preparation method of a soluble plugging device. Background Art

[0002] When conducting well completion operations on on - site oil and gas wells, in order to protect formation parameters and reduce the pollution of the formation by external construction, pressure - maintained operation is usually adopted to lower the well completion string. The pressure control in the pressure - maintained tubing is achieved by mechanical plugging or chemical plugging methods to control the leakage of fluid in the tubing. Mechanical plugging includes mechanical setting and anchoring tools such as tubing plugs, cable bridge plugs, wire bridge plugs, check valves, rupture disks, blind plugs, etc. Chemical plugging includes freeze - temporary plugging, liquid bridge plugging, etc.

[0003] When lowering the well completion string under pressure - maintained operation, mechanical plugging of the pressure in the tubing is usually used. A common process is to connect a ceramic rupture disk at the bottom of the well completion string for tubing plugging and sealing. After the well completion string is lowered, set in place, the equipment is removed, and the gas production tree is installed, positive pressure is applied to break through the ceramic rupture disk to communicate the oil - casing annulus and realize the tubing - draining gas - production process; another common process is to connect a blind plug at the bottom of the well completion string for tubing plugging and sealing. After the well completion string is lowered, set in place, the equipment is removed, and the gas production tree is installed, positive pressure is applied to knock out the blind plug to communicate the oil - casing annulus and realize the tubing - draining gas - production process.

[0004] There is currently a constant - pressure plugging device in China. The pressure value is set on the ground through a pin. After the well completion string is lowered into the well and the gas production tree is installed, positive pressure is applied to blow off the plugging joint to communicate the oil - casing annulus. However, there is a problem that foreign objects fall into the well and the foreign objects do not dissolve, bringing unpredictable risks to subsequent downhole operations. In domestic pressure - maintained well completion operations of gas wells, ceramic rupture disks can also be used for tubing plugging. However, all the ceramic rupture disks used in China are imported products, with a long supply cycle, high price, and being restricted by foreign suppliers. The lack of ceramic rupture disk tools on - site will seriously affect on - site production operations and is not conducive to the development of pressure - maintained operations.

[0005] At present, the commonly used tubing plugs mainly include constant pressure plugs, ceramic rupture disks and soluble blind plugs. Among them, the constant pressure plug sets the pressure value on the ground through a pin. After the completion string is lowered into the well and the gas production tree is installed, the plug joint is blown out under positive pressure to communicate the tubing and casing. However, there is a problem that foreign objects fall into the well and the foreign objects do not dissolve, bringing unpredictable risks to subsequent downhole operations. The reverse pressure difference of the ceramic rupture disk can reach 70-105 MPa. However, all the ceramic rupture disks used in China are imported products, with a long supply cycle, high price and being restricted by foreign suppliers. The lack of ceramic rupture disk tools on site will seriously affect on-site production operations and is not conducive to the development of pressure-bearing operations. The soluble blind plugs in the existing technology generally only bear a reverse low pressure difference of 35 MPa. Only by applying positive pressure to communicate the tubing and casing, and after the operation, the string cannot reach full bore, which limits subsequent plugging operations. Moreover, it can only be connected to the bottom of the string and cannot be used to connect the string, with poor versatility and not meeting the pressure rating of the construction well.

[0006] The invention patent with the publication number CN110952013A discloses a degradable magnesium alloy downhole tool bridge plug material and its preparation method. The soluble bridge plug prepared by this patent does not have the effect of corrosion resistance and cannot withstand pressure stably and continuously, and cannot meet the pressure-bearing operations of high-temperature and high-pressure wells of 70 Mpa and above. Summary of the Invention

[0007] The invention provides a preparation method of a soluble plug, which on the one hand solves the problems that the current supply mainly depends on imported ceramic rupture disks with a long supply cycle, being restricted by foreign suppliers, affecting on-site production operations and the development of pressure-bearing operations; on the other hand, it also solves the problems that the existing domestic constant pressure plugs drop the plug joint to the bottom of the well and do not dissolve after operation, and the existing domestic soluble plugs have a pressure-bearing capacity lower than 35 MPa and are not suitable for the high-pressure downhole environment of 70 Mpa.

[0008] In order to achieve the above invention purpose, the technical solution of the invention is as follows: A preparation method of a soluble plug, the preparation method mainly includes the following steps: Step S1. Use low-carbon alloy steel and nickel-based alloy steel to prepare a lower joint and an upper joint respectively; Step S2. Use magnesium alloy to prepare a soluble core matrix; Step S3. Perform surface pretreatment on the matrix, and then clean and dry the soluble core matrix after surface pretreatment; Step S4. Process a corrosion-resistant composite coating on the outer surface of the soluble core matrix except the dissolution surface to finally prepare a soluble core with a corrosion-resistant composite coating; Step S5. Assemble the prepared soluble core with a corrosion-resistant composite coating, the upper joint, the lower joint and the sealing component to form a soluble plug.

[0009] Preferably, in the present invention, the outer circumferential surface of the prepared soluble core has a first wedge surface, and the inner circumferential surface of the upper joint is machined with a second wedge surface that cooperates with the first wedge surface.

[0010] Preferably, in the present invention, the corrosion-resistant composite coating sequentially includes a transition layer, a corrosion-resistant layer, and a stable layer from the inside to the outside.

[0011] Preferably, in the present invention, the transition layer is an Al x Mg 1-x inner layer, the corrosion-resistant layer is an Al x Mg 1-x / Al y Ti 1-y nanomultilayer, and the stable layer is an Al y Ti 1-y O amorphous layer; wherein, x is the mass ratio of aluminum element to the total amount of aluminum and magnesium elements in Al x Mg 1-x y is the mass ratio of aluminum element to the total amount of aluminum and magnesium elements in Al y Ti 1-y or Al y Ti 1-y O.

[0012] Preferably, in the present invention, the Al x Mg 1-x inner layer, Al x Mg 1-x / Al y Ti 1-y nanomultilayer, and Al y Ti 1- y O amorphous layer are formed by magnetron sputtering on the surface of the magnesium alloy.

[0013] Preferably, in the present invention, 0.3 ≤ x ≤ 0.7 and 0.5 ≤ y ≤ 0.95.

[0014] Preferably, in the present invention, the Al x Mg 1-x inner layer has a thickness of 0.15 - 0.5 μm.

[0015] Preferably, in the present invention, the Al x Mg 1-x / Al y Ti 1-y nanomultilayer has a thickness of 2 - 10 μm.

[0016] Preferably, in the present invention, the Al y Ti1-y The thickness of the O amorphous layer is 0.5 - 2 μm.

[0017] Preferably, in the present invention, the pretreatment includes: putting the soluble core substrate into a sandblasting machine for dry sandblasting to remove contaminants and oxide layers on the surface of the substrate; the cleaning and drying of the soluble core after surface pretreatment include: putting the substrate into absolute ethanol for cleaning and finally putting it into a drying oven for drying.

[0018] Advantages of the present invention: The preparation method of the soluble plug used in the present invention has a low possibility of galvanic corrosion effect after deposition on the magnesium alloy surface; the two-phase metal compound in the transition layer makes the coating firmly bonded to the substrate; the multi-element nano aluminum-titanium layer structure in the intermediate layer prevents liquid from entering the interatomic pores; the outermost stable layer uses ceramic ion physical vapor deposition technology with high hardness, wear resistance, and corrosion resistance, preventing liquid from contacting the metal and preventing electrochemical corrosion. The present invention solves the problem of the falling object into the well after the shear pin of the constant pressure plug is cut. By using the method of soluble material and corrosion-resistant coating, the corrosion resistance of magnesium alloy can be greatly improved. The ultra-high pressure-bearing and high-temperature resistance performance of the soluble plug of the present invention meets most working conditions and can be used in high-temperature and high-pressure wells above 105 MPa and 150 °C at most, filling the technical gap in this field. Description of the drawings

[0019] The foregoing and following specific descriptions of the present invention become clearer when read in conjunction with the following drawings, in which: Figure 1 is a flow chart of the preparation method of the soluble plug of the present invention; Figure 2 is a schematic diagram of the structure of the corrosion-resistant composite coating of the present invention; Figure 3 is a schematic diagram of the structure of the soluble core of the present invention; Figure 4 is a schematic diagram of the structure of the soluble plug of the present invention.

[0020] In the figure: 1, upper joint; 2, soluble core; 3, first sealing assembly; 4, lower joint; 5, second sealing assembly. Detailed implementation manners

[0021] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will further illustrate the technical solutions for achieving the purpose of the present invention through several specific embodiments. It should be noted that the technical solutions claimed by the present invention include but are not limited to the following embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] At present, the commonly used tubing plugs mainly include constant-pressure plugs, ceramic rupture disks, and soluble blind plugs. Among them, for the constant-pressure plug, the pressure value is set on the ground through a pin. After the completion string is lowered into the well and the production tree is installed, the plug joint is blown out under positive pressure to communicate the tubing and casing. However, there is a problem that foreign objects may fall into the well and the foreign objects do not dissolve, bringing unpredictable risks to subsequent downhole operations. The reverse pressure difference of the ceramic rupture disk can reach 70 - 105 MPa. However, all the ceramic rupture disks used in China are imported products, with a long supply cycle, high price, and being restricted by foreign suppliers. The lack of ceramic rupture disk tools on site will seriously affect on-site production operations and is not conducive to the development of pressure-bearing operations. The soluble blind plugs in the existing technology generally can only withstand a reverse low pressure difference of 35 MPa, and can only communicate the tubing and casing by applying positive pressure. Moreover, after the operation, the string cannot reach full bore, which limits subsequent plugging operations, etc. It can only be connected to the bottom of the string and cannot be used to connect the string, with poor versatility and not meeting the pressure rating of the construction well.

[0023] Based on this, an embodiment of the present invention proposes a preparation method for a soluble plug. The soluble plug prepared by the present invention solves, on the one hand, the problems that the current mainly relies on imported ceramic rupture disks with a long supply cycle, being restricted by foreign suppliers, affecting on-site production operations and the development of pressure-bearing operations; and on the other hand, it also solves the problems that the existing constant-pressure plugs in China have the plug joint falling into the bottom of the well and not dissolving after operation, and the existing soluble plugs in China have a pressure-bearing capacity lower than 35 MPa and are not suitable for high-pressure downhole environments of 70 MPa and above.

[0024] Embodiment 1 This embodiment discloses a preparation method for a soluble plug. As shown in the attached drawings of the specification, the preparation process mainly includes the following steps: Figure 1 The preparation process mainly includes the following steps: Step S1. Using low-carbon alloy steel as the raw material, the lower joint of the soluble plug is prepared by machining with an ordinary lathe; using nickel-based alloy steel as the raw material, the upper joint of the soluble plug is prepared by numerical control machining through processes such as turning, milling, and precision grinding.

[0025] Step S2. Using magnesium alloy as the raw material, the soluble core matrix is prepared by one-time processing and forming.

[0026] Step S3. The surface of the prepared soluble core matrix is pretreated, and then the pretreated soluble core matrix is cleaned and dried.

[0027] In the present invention, the pretreatment refers to putting the soluble core matrix into a sandblasting machine for dry sandblasting to remove the contaminants and oxide layers on the surface of the magnesium alloy. Further, the cleaning and drying refer to putting the pretreated core matrix into absolute ethanol for cleaning, and finally putting it into a drying oven for drying.

[0028] Step S4. A corrosion-resistant composite coating is processed and formed on the outer surface of the soluble core matrix except for the dissolution surface, and finally a soluble core with a corrosion-resistant composite coating on its surface is prepared.

[0029] The soluble core prepared by the present invention comprises two parts, a matrix made of magnesium alloy and a corrosion-resistant composite coating wrapped on the outer surface of the matrix. Among them, the overall outer surface profile of the soluble core matrix is composed of a circumferential surface, an upper end surface and a lower end surface; among them, the upper end surface is also called the dissolution surface, the lower end surface is also called the pressure-bearing surface, and the circumferential surface is the sealing surface; when the soluble plug enters the well, brine can be poured into the direct eye of the tubing, the brine contacts the upper end surface (dissolution surface), the soluble core gradually dissolves, the oil casing is communicated to realize gas production, and the natural gas well produces normally; the lower end surface (pressure-bearing surface) is used for reverse pressure-bearing. Therefore, when processing the composite coating of the soluble core, a corrosion-resistant composite coating is processed on the outer surface of the matrix except for the dissolution surface, that is, a corrosion-resistant composite coating is processed on the lower end surface and the circumferential surface, and no coating is processed on the upper end surface, and the magnesium alloy matrix of the upper end surface is exposed, which not only ensures the corrosion resistance and continuous stable pressure-bearing capacity of the soluble core, but also during the production process, the magnesium alloy matrix of the dissolution surface exposed to the outside contacts with liquids such as brine, so that the soluble core gradually dissolves completely and the natural gas well produces normally.

[0030] Step S5. The soluble core with a corrosion-resistant composite coating prepared is assembled with an upper joint, a lower joint and a sealing assembly to form a soluble plug.

[0031] It should be noted that the outer circumferential surface of the soluble core prepared by the present invention has a first wedge surface, the inner circumferential surface of the upper joint is processed and formed with a second wedge surface that cooperates with the first wedge surface, and a step surface that cooperates with the upper end surface of the soluble core is provided. When assembling the plug, first, a first sealing assembly is installed circumferentially on the circumferential surface of the prepared soluble core, and then the soluble core is inserted into the upper joint from below the upper joint, so that the upper end surface of the soluble core abuts against the step surface inside the upper joint. Then, a second sealing assembly is installed circumferentially on the outer wall of the lower joint, and the lower joint is connected to the upper joint by threads. Finally, the soluble plug is assembled.

[0032] According to the requirements of the construction period, after timed pressure-bearing, liquids such as brine can be poured into the direct eye of the tubing to dissolve the soluble core in the plug, the production channel is opened, and the natural gas well enters the normal production process.

[0033] In the present invention, the lower end face and the outer circumferential face of the prepared soluble core are coated with a corrosion-resistant composite coating, which greatly improves the downhole pressure-bearing and temperature-resistant properties of the magnesium alloy material, enables the soluble plug to achieve the function of timed pressure-bearing, and the soluble core can withstand the ultra-high pressure and high temperature downhole environment of 105 MPa and 150 °C. Moreover, the circumferential sealing face of the soluble core is in wedge-shaped fit with the inner circumferential face of the upper joint inner wall. Under the impact of the fluid pressure in the pipe, the soluble core continuously presses upwards along the wedge-shaped face, achieving the self-sealing effect of the conical surface and having a good sealing effect.

[0034] Furthermore, the corrosion-resistant composite coating processed on the circumferential face of the soluble core actually also serves as a kind of filling seal, closely fits with the inner wall of the upper joint, and together with the sealing components arranged on the circumferential face of the soluble core, realizes combined sealing. Together with the self-sealing of the soluble core, it achieves a triple sealing effect, enabling the soluble core to withstand the ultra-high pressure and high temperature downhole environment of 105 MPa and 150 °C.

[0035] Example 2 This example discloses a preparation method of a soluble plug. On the basis of Example 1, the corrosion-resistant composite coating formed on the outer surface of the soluble core from the inside to the outside is successively a transition layer, a corrosion-resistant layer, and a stable layer; the transition layer is an Al x Mg 1-x inner layer, the corrosion-resistant layer is an Al x Mg 1-x / Al y Ti 1-y nanomultilayer, and the stable layer is an Al y Ti 1-y O amorphous layer; wherein, Al x Mg 1-x The inner layer is adjacent to the magnesium alloy, x is the mass ratio of aluminum element to the total amount of aluminum and magnesium elements in Al x Mg 1-x , y is the mass ratio of aluminum element to the total amount of aluminum and magnesium elements in Al y Ti 1-y or Al y Ti 1-y O.

[0036] In some embodiments of the present invention, the Al x Mg 1-x inner layer, the Al x Mg 1-x / Al y Ti 1-y nanomultilayer, and the Al y Ti 1-y O amorphous layer are deposited on the magnesium alloy surface by magnetron sputtering method.

[0037] In some embodiments of the present invention, 0.3 ≤ x ≤ 0.7 and 0.5 ≤ y ≤ 0.95. For example, x = 0.3, 0.4, 0.5, 0.6 or 0.7, and y = 0.5, 0.6, 0.7, 0.8, 0.9 or 0.95.

[0038] In some embodiments of the present invention, the Al x Mg 1-x The thickness of the inner layer is 0.15 - 0.5 μm, such as 0.15 μm, 0.2 μm, 0.3 μm, 0.4 μm or 0.5 μm.

[0039] In some embodiments of the present invention, the Al x Mg 1-x / Al y Ti 1-y The thickness of the Al / Mg / Ti nano - multilayer is 2 - 10 μm, such as 2 μm, 4 μm, 6 μm, 8 μm or 10 μm.

[0040] In some embodiments of the present invention, the Al y Ti 1-y The thickness of the Al - Ti - O amorphous layer is 0.5 - 2 μm, such as 0.5 μm, 1 μm, 1.5 μm or 2 μm.

[0041] Example 3 This example discloses a preparation method of a soluble plugging device. On the basis of Example 2, this example further discloses the preparation process of the corrosion - resistant composite coating, and the specific process is as follows: Heat and etch the cleaned and dried soluble core substrate. Deposit the Al - Mg inner layer on the surface of the heat - etched soluble core substrate. x Mg 1-x Inner layer; Perform thermal diffusion treatment on the soluble core substrate after depositing the Al - Mg inner layer. x Mg 1-x Perform Al - Mg / Al - Ti nano - multilayer deposition on the soluble core substrate after thermal diffusion treatment. x Mg 1-x / Al y Ti 1-y Perform Al - Ti - O amorphous layer deposition on the soluble core substrate after Al - Mg / Al - Ti nano - multilayer deposition. x Mg 1-x / Al y Ti 1-y y Ti 1-y

[0042] In the present invention, it is worth mentioning that the corrosion-resistant composite coating prepared by machining the surface of the soluble core matrix is a coating rich in Al from the inside to the outside. The purpose is to give full play to the excellent corrosion resistance of Al, and moreover, the potential of Al is close to that of the magnesium alloy, and the galvanic corrosion effect is small. Adjacent to the magnesium alloy matrix is Al x Mg 1-x inner layer. Al and Mg can form intermetallic compounds. Using Al as the inner layer can enhance the overall bonding performance of the coating; the middle is a nanomultilayer structure of Al x Mg 1-x / Al y Ti 1-y layer. The nanomultilayer structure can break the columnar growth of the coating, eliminate the fast atomic diffusion channels formed by the gaps between the columnar crystals of the coating, improve the density of the coating, and block the penetration of atomic diffusion; the outermost layer is an amorphous structure of Al y Ti 1-y O layer. On the one hand, the amorphous structure coating has no fast atomic diffusion channels and can better resist the inward diffusion of corrosive medium atoms. On the other hand, oxide ceramics have relatively poor conductivity compared to metals or alloys. Even if the corrosive solution reaches the magnesium alloy matrix, the galvanic corrosion effect can also be weakened. In addition, before depositing the composite coating on the surface of the magnesium alloy matrix in the present invention, the magnesium alloy matrix is subjected to surface pretreatment, argon ion etching, and aluminum ion etching. The purpose is to remove the oxide layer and contamination on the surface of the magnesium alloy matrix, expose the fresh surface of the magnesium alloy, and facilitate the bonding between the coating and the magnesium alloy.

[0043] In some embodiments of the present invention, the heated and etched substrate after cleaning and drying includes: Heating the magnesium alloy substrate using a magnetron sputtering coating device; Etching the heated substrate with ions generated by argon plasma discharge; Further etching the magnesium alloy substrate etched with argon with aluminum metal ions.

[0044] In some embodiments of the present invention, when heating the magnesium alloy substrate using a magnetron sputtering coating device, the heating temperature is controlled to be 100 - 120 °C, and the heating time is 30 - 60 minutes.

[0045] In some embodiments of the present invention, when etching the heated magnesium alloy substrate with ions generated by argon plasma discharge, the etching bias voltage is controlled to be -80 - 200 V, the etching time is 15 - 20 minutes, and the pressure is 1 - 2×10 -1 Pa.

[0046] In some embodiments of the present invention, when further etching the magnesium alloy substrate etched with argon with aluminum metal ions, the current magnitude of the aluminum target is set to 4 - 5 A, and the etching time is 10 - 20 minutes.

[0047] In some embodiments of the present invention, Al is deposited on the surface of the magnesium alloy substrate after heating and etching. x Mg 1-x Inner layer, including: When depositing Al x Mg 1-x inner layer, adjust the pressure of the magnetron sputtering coating equipment to 3 - 4×10 -1 Pa, adjust the temperature to 200 - 250 °C, adjust the bias voltage of the bias power supply to -150 - -200 V, set the current of the aluminum target to 3 - 4 A, and the deposition time is 10 - 20 minutes. During the deposition process, reduce the bias voltage at a rate of 6 - 10 V / minute. When depositing Al x Mg 1-x At the beginning stage of the inner layer, a larger bias voltage can be used to make aluminum ions enter the surface of the magnesium alloy substrate, improving the bonding performance of the coating.

[0048] In some embodiments of the present invention, the magnesium alloy substrate deposited with Al x Mg 1-x inner layer is subjected to thermal diffusion treatment, including: Heat the magnesium alloy substrate deposited with Al x Mg 1-x inner layer to 300 - 350 °C and keep it warm for 10 - 20 minutes. At a higher temperature, it can accelerate the diffusion of Al atoms in the Al x Mg 1-x inner layer into the magnesium alloy to ensure that more Mg 17 Al2 intermetallic compounds are formed near the layer / substrate interface, and the metallurgical bonding interface is beneficial to improving the bonding strength between the coating and the substrate.

[0049] In some embodiments of the present invention, Al x Mg 1-x / Al y Ti 1-y nanomultilayer deposition is carried out on the magnesium alloy after thermal diffusion treatment, including: Set the current of the aluminum - titanium target of the magnetron sputtering coating equipment to 4 - 6 A, adjust the current of the aluminum target to 4 - 6 A, adjust the substrate bias voltage to -30 - -60 V, and periodically deposit Al x Mg 1-x layers and Al y Ti 1-y layers on the magnesium alloy to obtain 2 - 10 μm of Al x Mg 1-x / Al y Ti 1-yNanomultilayers. The nanomultilayer structure can break the columnar growth of the coating, eliminate the fast atomic diffusion channels formed by the gaps between columnar crystals in the coating, improve the densification of the coating, and block the penetration of atomic diffusion.

[0050] In some embodiments of the present invention, after depositing the Al x Mg 1-x / Al y Ti 1-y nanomultilayer on the magnesium alloy, Al y Ti 1-y O amorphous layer deposition is carried out, including: After carrying out the Al x Mg 1-x / Al y Ti 1-y nanomultilayer deposition, turn off the power supply of the aluminum target and stop introducing argon gas, introduce oxygen into the magnetron sputtering coating equipment, adjust the pressure to 2 - 3.5×10 -1 Pa, adjust the substrate bias voltage to -50~-100V, and control the thickness of the Al y Ti 1-y O amorphous layer to be 0.5~2μm by adjusting the deposition time. The amorphous structure coating has no channels for rapid atomic diffusion and can better resist the inward diffusion of corrosive medium atoms. On the other hand, compared with metals or alloys, oxide ceramics have poor conductivity. Even if the corrosive solution reaches the magnesium alloy substrate, the galvanic corrosion effect can be weakened.

[0051] To better illustrate the present solution, the present invention further provides the following examples and comparative examples.

[0052] Example 4 (1) Use a magnesium alloy to fabricate a soluble core substrate by one-time processing, and then place the soluble core substrate in a sandblaster for dry sandblasting treatment to remove contaminants and oxide layers on the substrate surface.

[0053] (2) Place the substrate after dry sandblasting treatment in absolute ethanol for 10 minutes of cleaning, and immediately place the substrate in a vacuum drying oven for 10 minutes of drying after cleaning.

[0054] (3) Place the dried substrate in a magnetron sputtering coating equipment, turn on the auxiliary heating system to heat the substrate to 120°C for 60 minutes of heating. Then, introduce argon gas into the vacuum chamber, control the pressure of the vacuum chamber to be 1.5×10 -1 Pa, use the ions generated by argon plasma discharge to etch the magnesium alloy substrate, apply a bias voltage of -100V to the substrate, and etch for 20 minutes. Then, turn on the magnetron sputtering target power supply, set the current of the aluminum target to 5A, and further etch the magnesium alloy on the substrate surface with aluminum metal ions for 20 minutes.

[0055] (4) Adjust the argon flow rate to make the working pressure of the vacuum chamber 3.5×10 -1 Pa. Set the target temperature for heating the magnesium alloy substrate to 250 °C. After the actual temperature of the substrate reaches the target temperature, adjust the bias voltage of the bias power supply to -200 V. At the same time, set the current of the aluminum target to 4 A, the deposition time to 10 minutes, and the deposition thickness to 0.15 μm. During the deposition process, reduce the bias voltage at a rate of 10 V per minute.

[0056] (5) Heat the core after the deposition treatment in step (4) to 350 °C and hold for 15 minutes to accelerate the diffusion of Al atoms in the inner layer to the substrate at a higher temperature, so as to ensure the formation of more Mg 17 Al2 intermetallic compounds at positions near the layer / substrate interface. The metallurgical bonding interface is beneficial to improving the bonding strength between the coating and the substrate.

[0057] (6) Turn on the power supply of the aluminum-titanium target, set the current of the aluminum-titanium target to 5 A, adjust the current of the aluminum target to 5 A, and adjust the substrate bias voltage to -60 V. The substrate rotates in the vacuum chamber and alternately passes through the sputtering areas of the Al target and the AlTi target to achieve periodic deposition of a 10-μm-thick Al 0.3 Mg 0.7 layer and an Al 0.5 Ti 0.5 layer. The deposition time is 120 minutes to obtain a 2-μm-thick Al 0.3 Mg 0.7 / Al 0.5 Ti 0.5 nanomultilayer.

[0058] (7) Introduce oxygen into the vacuum chamber, and at the same time turn off the power supply of the aluminum target and the argon valve to make the working pressure of the vacuum chamber 3.5×10 -1 Pa. Adjust the substrate bias voltage to -75 V, and the deposition time is 60 minutes to obtain an Al 0.5 Ti 0.5 O amorphous layer with a thickness of 0.5 μm, and finally prepare a soluble core with a corrosion-resistant composite coating.

[0059] Perform performance testing on the corrosion-resistant composite coating on the surface of the soluble core. The measured bonding strength grade of the corrosion-resistant composite coating is HF2, and no corrosion spots appear on the surface after 168 h of neutral salt spray corrosion.

[0060] Further, assemble the prepared soluble core into a soluble plug tool. The upper and lower joints are connected by threads, and a sealing component is added. Place the tool in a test fixture and keep it stable for 7 days in an environment with a temperature of 150 °C, a reverse pressure of 105 MPa, and a backflow liquid. Then add a 5% NaCl solution for dissolution, and the soluble core is successfully dissolved after 5 days under the condition of a constant temperature of 95 °C.

[0061] Example 5 (1) The soluble core substrate is prepared by one - step processing of magnesium alloy. Then, the soluble core substrate is placed in a sandblasting machine for dry sandblasting to remove contaminants and oxide layers on the substrate surface.

[0062] (2) The substrate after dry sandblasting is placed in absolute ethanol for 10 minutes of cleaning. Immediately after cleaning, the substrate is placed in a vacuum drying oven for 10 minutes of drying.

[0063] (3) The dried substrate is placed in a magnetron sputtering coating device. The magnesium alloy block is heated to 100 °C by turning on the auxiliary heating system, and the heating time is 45 minutes. Then, argon is introduced into the vacuum chamber, and the pressure of the vacuum chamber is controlled to be 1.8×10 -1 Pa. The magnesium alloy substrate is etched by ions generated by argon plasma discharge. The bias voltage applied to the magnesium alloy substrate is - 150 V, and the etching time is 15 minutes. Then, the magnetron sputtering target power supply is turned on, the current of the aluminum target is set to 4 A, and the magnesium alloy substrate is further etched by aluminum metal ions for 10 minutes.

[0064] (4) The argon flow rate is adjusted to make the working pressure of the vacuum chamber 3.8×10 -1 Pa. The target temperature for heating the magnesium alloy substrate is set to 200 °C. After the actual temperature of the substrate reaches the target temperature, the bias voltage of the bias voltage power supply is adjusted to - 150 V. At the same time, the current of the aluminum target is set to 3 A, the deposition time is 20 minutes, and the deposition thickness is 0.5 μm. During the deposition process, the bias voltage is reduced at a rate of 6 V / minute.

[0065] (5) The magnesium alloy substrate processed in step (4) is heated to 300 °C and kept warm for 10 minutes to accelerate the diffusion of Al atoms in the inner layer to the magnesium alloy substrate at a higher temperature, so as to ensure the formation of more Mg 17 Al2 intermetallic compounds near the layer / substrate interface, and the metallurgical bonding interface is beneficial to improving the bonding strength between the coating and the substrate.

[0066] (6) The aluminum - titanium target power supply is turned on, the current of the aluminum - titanium target is set to 4 A, the current of the aluminum target is adjusted to 4 A, and the substrate bias voltage is adjusted to - 30 V. The magnesium alloy substrate rotates in the vacuum chamber and alternately passes through the sputtering areas of the Al target and the AlTi target to achieve periodic deposition of a 50 - nm - thick Al 0.7 Mg 0.3 layer and an Al 0.95 Ti 0.05 layer. The deposition time is 180 minutes to obtain a 10 - μm - thick Al 0.7 Mg 0.3 / Al 0.95 Ti 0.05 nano - multilayer.

[0067] (7) Oxygen is introduced into the vacuum chamber, while the power supply of the aluminum target and the argon valve are closed, so that the working pressure of the vacuum chamber is 3.3×10 -1 Pa, the substrate bias voltage is adjusted to -50V, and the deposition time is 80 minutes. The obtained thickness of the Al 0.95 Ti 0.05 O amorphous layer is 2μm, and finally a soluble core with a corrosion-resistant composite coating is prepared.

[0068] The performance of the corrosion-resistant composite coating on the surface of the soluble core is detected. The bonding strength grade of the corrosion-resistant coating is measured as HF2, and no corrosion spots appear on the surface after 168h of neutral salt spray corrosion.

[0069] Comparative Example 1 (1) A soluble core substrate is prepared by one-time processing of magnesium alloy, and then the soluble core substrate is placed in a sandblasting machine for dry sandblasting treatment to remove pollutants and oxide layers on the substrate surface.

[0070] (2) The substrate after dry sandblasting treatment is placed in absolute ethanol for cleaning for 5 minutes, and immediately after cleaning, the substrate is placed in a vacuum drying oven for drying for 5 minutes.

[0071] (3) The dried magnesium alloy substrate is placed in a magnetron sputtering coating device, and the auxiliary heating system is turned on to heat the magnesium alloy to 120°C for 60 minutes. Then, argon is introduced into the vacuum chamber, and the pressure of the vacuum chamber is controlled to be 1.9×10 - 1 Pa, and the surface of the magnesium alloy substrate is etched by ions generated by argon plasma discharge. The bias voltage applied to the magnesium alloy is -150V, and the etching time is 15 minutes.

[0072] (4) The argon flow rate is adjusted so that the working pressure of the vacuum chamber is 3.6×10 -1 Pa. The target temperature for heating the magnesium alloy substrate is set to 250°C. After the actual temperature of the substrate reaches the target temperature, the bias voltage of the bias voltage power supply is adjusted to -50V. At the same time, the current of the aluminum target is set to 5A, and the deposition time is 180 minutes.

[0073] The performance of the Al coating prepared on the surface of the soluble core is detected. The bonding strength grade of the Al coating is measured as HF3, and corrosion spots appear on the surface after 24h of neutral salt spray corrosion.

[0074] The above are only the preferred embodiments of the present invention, and do not constitute any form of obstruction to the present invention. Any simple modification and equivalent change made to the above embodiments based on the technical essence of the present invention all fall within the protection scope of the present invention.

Claims

1. A preparation method of a soluble plugging device, characterized in that, The preparation method includes the following steps: Step S1. Prepare a lower joint and an upper joint respectively using low-carbon alloy steel and nickel-based alloy steel; Step S2. Prepare a soluble core matrix using magnesium alloy; Step S3. Pretreat the surface of the matrix, and then clean and dry the soluble core matrix after surface pretreatment; Step S4. Process a corrosion-resistant composite coating on the outer surface of the soluble core matrix except for the dissolution surface, and finally prepare a soluble core with a corrosion-resistant composite coating; Step S5. Assemble the prepared soluble core with the corrosion-resistant composite coating, the upper joint, the lower joint and the sealing component to form a soluble plug; 2. The preparation method of a soluble plugging device according to claim 1, characterized in that The outer circumferential surface of the prepared soluble core has a first wedge surface, and the inner circumferential surface of the upper joint is machined with a second wedge surface that cooperates with the first wedge surface; 3. The preparation method of a soluble plugging device according to claim 1, characterized in that, The corrosion-resistant composite coating sequentially includes a transition layer, a corrosion-resistant layer and a stable layer from the inside to the outside; 4. The preparation method of a soluble plugging device according to claim 3, characterized in that, The transition layer is Al x Mg 1-x The inner layer, and the corrosion-resistant layer is Al x Mg 1-x / Al y Ti 1-y nanomultilayer, and the stable layer is Al y Ti 1-y O amorphous layer; Among them, x is Al x Mg 1-x The mass ratio of aluminum element to the total amount of aluminum and magnesium elements, y is Al y Ti 1-y or Al y Ti 1-y The mass ratio of aluminum element to the total amount of aluminum and magnesium elements in Al 5. The preparation method of a soluble plugging device according to claim 4, characterized in that, The Al x Mg 1-x inner layer, Al x Mg 1-x / Al y Ti 1-y nanomultilayer and Al y Ti 1-y The amorphous layer of TiO is formed by magnetron sputtering on the surface of the magnesium alloy.

6. The preparation method of a soluble plugging device according to claim 4, characterized in that Where 0.3 ≤ x ≤ 0.7 and 0.5 ≤ y ≤ 0.95; 7. The preparation method of a soluble plugging device according to claim 4, characterized in that, The said Al x Mg 1-x The thickness of the inner layer is 0.15 to 0.5 μm.

8. The preparation method of a soluble plugging device according to claim 4, characterized in that, The Al x Mg 1-x / Al y Ti 1-y The thickness of the nano-multilayer is 2 to 10 μm.

9. The preparation method of a soluble plugging device according to claim 4, characterized in that, The Al y Ti 1-y The thickness of the amorphous layer is 0.5 to 2 μm.

10. The preparation method of a soluble plugging device according to claim 1, characterized in that, The pretreatment includes: putting the soluble core matrix into a sandblasting machine for dry sandblasting to remove pollutants and oxide layers on the surface of the matrix; the cleaning and drying of the soluble core after surface pretreatment includes: putting the matrix into absolute ethanol for cleaning and finally putting it into a drying oven for drying.

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