Soluble metal delayed starting toe end sliding sleeve

Abstract

The invention relates to the technical field of oil and gas well fracturing, and discloses a soluble metal delayed starting toe end sliding sleeve which comprises an outer cylinder and a center pipe coaxial with the outer cylinder, sand blasting holes are formed in the side wall of the outer cylinder and the side wall of the center pipe, and a piston cavity and a reaction cavity are formed between the outer cylinder and the center pipe; the pressure triggering piece is arranged on the side wall of the central pipe and is used for guiding fluid to the reaction chamber when the pressure of the fluid reaches a preset value; and the delay control piece is arranged in the piston chamber and comprises a containing part for containing reactants and a soluble part made of soluble materials, the soluble part initially seals the flow channel, and a fluid passage between the reaction chamber and the piston chamber is established after the soluble part is dissolved by the reaction products. The soluble metal delay start toe end sliding sleeve aims at solving the problem that due to the fact that an existing delay toe end sliding sleeve lacks pressure control and reaction process control, the working reliability and delay precision of a delay mechanism are difficult to guarantee.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well fracturing technology, specifically to a toe sleeve with a soluble metal delayed start-up mechanism. Background Technology

[0002] In horizontal well fracturing operations, the toe sleeve, as the key tool closest to the well bottom, must only be opened after casing pressure testing and the preceding fracturing operations are completed. This is to avoid premature ball-drop fracturing at the toe sleeve, which would affect the overall construction efficiency. To achieve this function, existing technologies generally employ delayed opening of the toe sleeve. This is achieved by setting a delay mechanism inside the sleeve, utilizing the dissolving effect of wellbore fluid on specific materials to realize automatic delayed start-up. Typical delay methods include direct dissolution of soluble metals and structures combining a fracture disc with soluble materials. The working principle is to expose the soluble metal material to the wellbore environment or to contact the wellbore fluid after fracturing by a fracture disc. Once the soluble material dissolves and becomes ineffective, the flow channel is opened, thereby realizing the delayed start-up function of the toe sleeve.

[0003] However, traditional soluble ring designs suffer from uneven dissolution rates at various points within the ring, leading to difficulties in controlling residual strength decay and final fracture time. Furthermore, the large ring volume results in an excessively long dissolution cycle. In contrast, the design using a rupture disc combined with soluble materials suffers from the lack of an effective pressure relief and buffer mechanism. When the rupture disc ruptures under high pressure, the high-pressure fluid directly impacts the soluble metal structure, causing mechanical damage or detachment of the soluble material due to pressure shock. Simultaneously, the direct entry of high-pressure fluid into the reaction zone interferes with the stability of the chemical reaction. This structural design, lacking pressure and reaction process control, makes it difficult to guarantee the reliability and accuracy of the delay mechanism, impacting the applicability and construction safety of the toe sleeve under complex well conditions. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that the reliability and delay accuracy of the delay mechanism are difficult to guarantee due to the lack of pressure control and reaction process control in existing delay toe sleeves, and to propose a toe sleeve with soluble metal delay start.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A toe sleeve for delayed activation of soluble metal includes an outer cylinder and a central tube coaxially arranged with the outer cylinder. Both the outer cylinder and the central tube have sandblasting holes on their side walls. A piston chamber and a reaction chamber are formed between the outer cylinder and the central tube. The sleeve also includes: A pressure trigger is disposed on the side wall of the central tube, which guides the fluid to the reaction chamber when the fluid pressure reaches a preset value; A delay control component is disposed in the piston chamber, including a container for containing reactants and a soluble part made of soluble material. The soluble part initially closes the flow channel, and a fluid passage is established between the reaction chamber and the piston chamber after the reaction product dissolves the soluble part. A drive component is movably disposed within the piston chamber. Initially, the sandblasting orifice is closed. After fluid enters the piston chamber through the fluid passage, it drives the drive component to displace, thereby opening the sandblasting orifice.

[0006] Based on the above technical solution, the present invention can be further improved as follows.

[0007] Furthermore, the pressure trigger includes a rupture portion and a pressure relief portion; The rupture section is located on the side wall of the central tube and ruptures when the fluid pressure reaches a preset threshold to establish a fluid passage. The pressure reducing section is located between the rupture section and the reaction chamber, and is used to throttle and reduce the pressure of the fluid entering after the rupture, and guide the depressurized fluid to the reaction chamber.

[0008] Furthermore, the fracture portion includes: A protective cap is threaded through the side wall of the central tube, and a flow hole and a mounting hole are sequentially opened from the outside to the inside at the radial center position of the protective cap; A rupture disc is disposed in the mounting hole of the protective cap. When the fluid pressure reaches a specific threshold, the rupture disc ruptures, and the fluid enters the reaction chamber through the mounting hole and the flow hole.

[0009] Furthermore, the pressure-reducing section includes: A pressure-reducing ring is threadedly connected to the side wall of the central tube. The pressure-reducing ring and the central tube are threaded together to form a threaded clearance, which constitutes a throttling channel. An O-ring is embedded on the outside of the pressure-reducing ring and located in the throttling channel. Fluid enters the reaction chamber through the throttling channel, thereby achieving controlled pressure reduction and fluid introduction.

[0010] Furthermore, the accommodating portion includes: A valve seat mounting sleeve is coaxially sleeved on the outside of the central tube, and its axial central region is provided with a receiving area and a flow area; A C-shaped ring is embedded on the outside of the central tube and abuts against the end of the valve seat mounting cylinder to limit the axial displacement of the valve seat mounting cylinder. A piston rod is inserted into the receiving area, with one end of the piston rod extending to the outside of the receiving area.

[0011] Furthermore, the soluble portion includes: A soluble nut is threadedly connected to the end of the piston rod that extends to the outside of the receiving area. The end face of the soluble nut abuts against the end face of the valve seat mounting cylinder. The number of soluble nuts is set to several and they are evenly distributed along the circumferential direction of the end face of the valve seat mounting cylinder. In the initial state, each soluble nut corresponds to and blocks each of the flow areas. A solid acid is pre-placed in the reaction chamber. When the solid acid mixes with the incoming fluid, an acidic solution is generated. The acidic solution simultaneously corrodes and dissolves the soluble caps. When any one of the soluble caps dissolves to the point of failure, the corresponding piston rod loses its axial constraint, and the flow area opens to establish a fluid passage.

[0012] Furthermore, a retaining ring is also embedded on the outer side of the central tube. The retaining ring is located between the valve seat mounting cylinder and the driving component. One end face of the valve seat mounting cylinder and one end face of the driving component respectively abut against the retaining ring. The retaining ring is used to limit the relative position of the valve seat mounting cylinder and the driving component and to axially limit both of them.

[0013] Furthermore, the sandblasting holes on the outer cylinder are external through holes, while the sandblasting holes on the central tube are internal through holes; In the initial state, the driving component blocks the outer and inner through holes to prevent them from communicating; when the driving component undergoes axial displacement, the outer and inner through holes communicate with each other, forming a fracturing channel that runs through the outer cylinder and the central tube.

[0014] Furthermore, a support sleeve is provided on the side wall of the central tube, and the outer cylinder is connected to the support sleeve by threads. The annular space formed by the support sleeve, the central tube, and the outer cylinder forms the piston chamber, and the annular space formed by the valve seat mounting cylinder, the central tube, and the outer cylinder forms the reaction chamber.

[0015] Furthermore, the driving component is a piston cylinder structure, which is coaxially sleeved between the central tube and the outer cylinder. The inner wall of the piston cylinder is fitted with a first sealing member that contacts and cooperates with the outer wall of the central tube, and the outer wall of the piston cylinder is fitted with a second sealing member that contacts and cooperates with the inner wall of the outer cylinder. The first sealing member and the second sealing member are used to ensure the sealing of the piston chamber.

[0016] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: The pressure trigger of this invention guides the fluid to the reaction chamber when the fluid pressure reaches a preset value, rather than directly impacting the soluble material. This design fundamentally avoids the mechanical damage or detachment of the soluble material caused by the instantaneous impact of high-pressure fluid. Simultaneously, the independent reaction chamber provides a stable environment for the chemical reaction. The pre-placed reactants and the introduced fluid are fully mixed and reacted within the reaction chamber to generate reaction products with precise dissolving capabilities. These reaction products controllably dissolve the soluble portion. Compared to the uneven dissolution method of traditional soluble rings directly exposed to wellbore fluid, this invention achieves controllability and uniformity of the dissolution process through a chemical reaction mechanism. Furthermore, the use of a small-sized soluble portion combined with the dissolution of chemical reaction products significantly shortens the delay period and improves operational efficiency compared to bulky soluble ring solutions. By adjusting the amount of solid reactants or the dissolution cross-sectional area of ​​the soluble portion, the delay time can be flexibly controlled, enhancing the adaptability of the solution. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall connection structure of the present invention; Figure 2 For the present invention Figure 1 Enlarged view of point A in the middle; Figure 3 For the present invention Figure 1 Enlarged view of section B in the middle.

[0018] In the diagram: 1. Outer cylinder; 2. Central tube; 3. Sandblasting hole; 31. External through hole; 32. Internal through hole; 4. Pressure trigger element; 41. Rupture part; 411. Protective cap; 412. Rupture disc; 42. Pressure reducing part; 421. Pressure reducing ring; 422. O-ring; 5. Delay control element; 51. Receiving part; 511. Valve seat mounting cylinder; 512. Receiving area; 513. Flow area; 514. C-ring; 515. Piston rod; 52. Soluble part; 521. Soluble nut; 522. Solid acid; 6. Drive element; 7. Retaining ring; 8. Support sleeve. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figures 1 to 3As shown, this invention provides a toe sleeve for delayed start-up of soluble metal, including an outer cylinder 1 and a central tube 2 coaxially arranged with the outer cylinder 1. Both the outer cylinder 1 and the central tube 2 have sandblasting holes 3 on their side walls. Specifically, the sandblasting holes 3 on the outer cylinder 1 are external through holes 31, and the sandblasting holes 3 on the central tube 2 are internal through holes 32. In the initial state, the driving component 6 blocks the external through holes 31 and the internal through holes 32, preventing them from communicating. Under specific operating conditions, they communicate with each other to form a through-type fracturing channel. That is, when the driving component 6 undergoes axial displacement, the external through holes 31 and the internal through holes 32 communicate with each other, forming a fracturing channel penetrating the outer cylinder 1 and the central tube 2. The outer cylinder 1 and the central tube 2 are made of conventional tubing material, which should have sufficient compressive strength and corrosion resistance.

[0021] like Figure 1 and Figure 2 As shown, a support sleeve 8 is fitted over the side wall of the central tube 2. The outer cylinder 1 is connected to the support sleeve 8 by threads. The annular space formed by the support sleeve 8, the central tube 2, and the outer cylinder 1 forms a piston chamber. The annular space formed by the valve seat mounting cylinder 511, the central tube 2, and the outer cylinder 1 forms a reaction chamber. The support sleeve 8 not only achieves coaxial fixation between the outer cylinder 1 and the central tube 2, but also rationally divides the annular space into functional areas, providing a reference surface and load-bearing structure for the subsequent installation of various functional components. The support sleeve 8 is connected to the outer cylinder 1 by threads, facilitating overall assembly and maintenance. A sealing ring is also embedded on the outer side of the support sleeve 8 to ensure the sealing between the support sleeve 8 and the outer cylinder 1. The same sealing ring is also provided on the outer wall of the central tube 2 to ensure the sealing performance between the central tube 2 and the support sleeve 8. An upper connector is connected to the upstream end of the central tube 2 by a set pin.

[0022] The pressure trigger 4 is disposed on the side wall of the central tube 2, and guides the fluid to the reaction chamber when the fluid pressure reaches a preset value. The pressure trigger 4 includes a dual structure design of a rupture part 41 and a pressure reducing part 42.

[0023] like Figure 1 and Figure 3 As shown, the rupture section 41 is disposed on the side wall of the central tube 2. When the fluid pressure reaches a preset threshold, it ruptures to establish a fluid passage. The rupture section 41 includes a protective cap 411 and a rupture disc 412. The protective cap 411 is threaded through the side wall of the central tube 2, and a flow hole and a mounting hole are sequentially formed from the outside to the inside at the radial center position of the protective cap 411. The protective cap 411 is made of high-strength alloy steel, and its external thread mates with the pre-drilled threaded hole in the central tube 2 for reliable fixation. The diameter of the flow hole is preferably 8-12 mm, and the diameter of the mounting hole is designed to match the size of the rupture disc.

[0024] The rupture disc 412 is installed within the mounting hole of the protective cap 411. When the fluid pressure reaches a specific threshold, the rupture disc 412 ruptures, allowing fluid to enter through the mounting hole and the flow hole. The rupture disc 412 is preferably made of aluminum alloy or stainless steel with a thickness of 0.3-0.8 mm, and precise calculations ensure accurate rupture under actual operating conditions of 70-100 MPa. The protective cap 411 protects the rupture disc 412 from external damage during installation and pressure testing, improving the tool's reliability. It should also be noted that the protective cap 411 and the rupture disc 412 are fastened together by threads, and a sealing ring is provided between the protective cap 411 and the pre-drilled threaded hole in the central tube 2 to ensure overall sealing during installation.

[0025] A pressure-reducing section 42 is disposed between the rupture section 41 and the reaction chamber, and is used to throttle and reduce the pressure of the fluid entering after rupture, and guide the reduced-pressure fluid to the reaction chamber. Specifically, the fluid flow path is as follows: Figure 1 As shown, the fluid flows in the direction indicated by the arrow. The pressure-reducing section 42 includes a pressure-reducing ring 421 and an O-ring 422. The pressure-reducing ring 421 is threadedly connected to the side wall of the central tube 2, forming a threaded gap that constitutes a throttling channel. The inner wall of the pressure-reducing ring 421 has internal threads, and the outer wall of the central tube 2 has external threads. The pressure-reducing ring 421 is connected to the central tube 2 via a threaded connection. The O-ring 422 is embedded outside the pressure-reducing ring 421 and located within the throttling channel. The O-ring 422 only serves a throttling function and does not completely seal the flow. The fluid enters the reaction chamber through the throttling channel, achieving controlled pressure reduction and fluid introduction. The O-ring 422 can be made of hydrogenated nitrile rubber, with its compression controlled at 10%-15%, ensuring both throttling effect and preventing complete blockage of the throttling channel. Through this pressure reduction mechanism, the high-pressure fluid (e.g., 70 MPa) after the rupture disc ruptures is reduced to 40-50 MPa through the throttling channel before entering the reaction chamber, thus avoiding impact damage to the subsequent chemical reaction structure. At the same time, the narrow threaded gap also plays a role in unidirectional flow restriction, preventing the backflow of liquid in the chamber, thereby providing a continuous and stable reaction environment for solid acid 522.

[0026] Meanwhile, the throttling channel of the pressure reducing section 42 can also adopt a multi-stage pressure reducing design, that is, several sets of spiral grooves (not shown in the figure) are opened on the pressure reducing ring 421 to form a multi-stage throttling path, making the pressure reducing process more stable and further reducing the impact on the reaction chamber.

[0027] like Figure 1 and Figure 2As shown, the delay control component 5 is disposed in the piston chamber, including a containing part 51 for containing reactants and a soluble part 52 made of a soluble material. The soluble part 52 initially closes the flow channel, and after the reaction product dissolves in the soluble part 52, a fluid passage is established between the reaction chamber and the piston chamber. The receiving portion 51 includes a valve seat mounting sleeve 511, a C-ring 514, and a piston rod 515. The valve seat mounting sleeve 511 is coaxially sleeved on the outside of the central tube 2, and its axial central region has a receiving area 512 and a flow area 513. The valve seat mounting sleeve 511 is made of corrosion-resistant stainless steel. The receiving area 512 and the flow area 513 are interconnected. The C-ring 514 is embedded on the outside of the central tube 2 and abuts against the end of the valve seat mounting sleeve 511 to limit the axial displacement of the valve seat mounting sleeve 511. The C-ring 514 is made of spring steel and is embedded in an annular groove on the outer wall of the central tube 2. The C-ring 514 only serves as a limiting element during assembly and does not function under high pressure; its purpose is to ensure that the axial position of the valve seat mounting sleeve is fixed during assembly. The piston rod 515 passes through the flow area 513, with one end of the piston rod 515 extending outside the receiving area 512. The piston rod 515 is made of stainless steel, with an outer diameter slightly smaller than the inner diameter of the flow area 513. The gap between the two is controlled at 0.05-0.1mm, ensuring fluid passage while maintaining a certain guiding effect. A sealing ring is also provided on the outer wall of the valve seat mounting cylinder 511 and the outer wall of the central tube 2. This sealing ring ensures the sealing performance between the central tube 2, the valve seat mounting cylinder 511, and the outer cylinder 1. At the same time, a sealing ring is also embedded on the outer wall of the piston rod 515 to ensure the sealing performance between the piston rod 515 and the valve seat mounting cylinder 511. The dimensions between the piston rod 515 and the flow area 513 are carefully preset so that when the preset liquid pressure pushes the piston rod 515 to move, it will not obstruct the flow effect of the flow area 513.

[0028] The soluble section 52 includes a soluble nut 521 and a solid acid 522. The soluble nut 521 is threadedly connected to the end of the piston rod 515 extending to the outside of the receiving area 512. A high-strength threaded connection is used, providing excellent mechanical connection strength while maintaining a compact structure. The end face of the soluble nut 521 abuts against the end face of the valve seat mounting cylinder 511. Several soluble nuts 521 are evenly distributed along the circumference of the end face of the valve seat mounting cylinder 511. In the initial state, each soluble nut 521 corresponds to and blocks each of the flow areas 513. The soluble nut 521 is preferably made of soluble magnesium-aluminum alloy, with an outer diameter of approximately 10 mm, larger than the inner diameter of the flow area 513, forming a mechanical constraint. The nut thickness is 3-5 mm, and the dissolution cross-sectional area is designed according to the delay requirements. When solid acid 522 mixes with the incoming fluid to form an acid solution, the soluble nut 521 begins to dissolve, and its outer diameter is continuously corroded and gradually shrinks. Only when its outer diameter decreases to match the inner diameter of the flow channel and loses its end-face constraint can the preset liquid pressure drive the piston rod 515 to move, thereby precisely opening the fluid channel. This dual control mechanism of "size constraint + chemical dissolution" ensures the accuracy and reliability of the delay.

[0029] Solid acid 522 is pre-placed in the reaction chamber. When solid acid 522 mixes with the incoming fluid, it generates an acidic solution, which simultaneously corrodes and dissolves the soluble cap 521. Solid acid 522 is preferably either solid hydrochloric acid or potassium chloride. These substances react rapidly with the fracturing fluid to generate an acidic solution with a pH of 2-4, providing a controllable dissolution rate for soluble magnesium-aluminum alloys. The amount of solid acid 522 used is determined based on the required delay time, typically 50-200g. When any soluble cap 521 dissolves to the point of failure, the corresponding piston rod 515 loses its axial constraint, and the flow area 513 opens, establishing a fluid passage.

[0030] It should be noted that the delayed start-up time can be flexibly controlled by adjusting the dissolution cross-sectional area of ​​the soluble nut 521 or the amount of solid acid 522: the larger the dissolution cross-sectional area of ​​the soluble nut 521 or the more solid acid 522 is used, the higher the concentration of the generated acidic solution or the faster the dissolution rate, and the shorter the delay time; conversely, the delay time is longer. This adjustability allows the present invention to adapt to different construction needs, and the delay range can be controlled between 30 minutes and 4 hours.

[0031] The delay control element 5 is set to a number of units, preferably four sets in total. The multiple sets of delay control elements 5 are evenly distributed along the circumference of the valve seat mounting cylinder 511. The flow channel can be opened when any set of soluble nuts 521 dissolves and fails. This redundant design aims to solve the problem of uneven reaction rates of valves caused by processing and assembly deviations or reaction environment factors. In actual operation, it is not required that all valves react synchronously. As long as any set completes dissolution first and opens its corresponding flow channel, the opening condition can be met. This greatly reduces the risk of the entire valve failing due to the failure of a single unit and multiplies the reliability and risk resistance of the system.

[0032] Meanwhile, solid acid 522 can also be a mixture of citric acid and sodium bisulfate in a mass ratio of 1:2. This combination can achieve a staged reaction, first rapidly generating an initial acidic environment, and then continuously releasing acidic substances, making the dissolution process more uniform.

[0033] Furthermore, the soluble nut 521 can be made of magnesium-aluminum alloy or magnesium-zinc alloy. By adjusting the alloy ratio, the dissolution rate can be controlled. Compared with pure magnesium material, the dissolution process of alloy material is more stable, and the delay accuracy can be improved by 15%-20%.

[0034] like Figure 1 and Figure 2 As shown, the driving component 6 is movably disposed within the piston chamber, initially sealing the sandblasting hole 3. After fluid enters the piston chamber through the fluid passage, it drives the driving component 6 to displace, opening the sandblasting hole 3. The driving component 6 is a piston cylinder structure, coaxially sleeved between the central tube 2 and the outer cylinder 1. The inner wall of the piston cylinder is fitted with a first sealing member that contacts and engages with the outer wall of the central tube 2, and the outer wall of the piston cylinder is fitted with a second sealing member that contacts and engages with the inner wall of the outer cylinder 1. The first and second sealing members ensure the sealing of the piston chamber. The first and second sealing members are preferably high-temperature and corrosion-resistant hydrogenated nitrile rubber O-rings or Glyd rings, embedded in the annular grooves of the outer and inner walls of the piston cylinder. Initially, the driving component 6 blocks the outer through hole 31 and the inner through hole 32, preventing them from communicating. When the driving component 6 undergoes axial displacement, the outer through hole 31 and the inner through hole 32 communicate with each other, forming a fracturing channel penetrating the outer cylinder 1 and the central tube 2. The axial length design of the piston cylinder ensures that it completely covers the inner and outer through holes in the initial position, and the displacement stroke is generally around 150mm.

[0035] A retaining ring 7 is also embedded on the outer side of the central tube 2. The retaining ring 7 is located between the valve seat mounting cylinder 511 and the driving component 6. One end face of the valve seat mounting cylinder 511 and one end face of the driving component 6 respectively abut against the retaining ring 7. The retaining ring 7 is used to limit the relative position of the valve seat mounting cylinder 511 and the driving component 6 and to axially limit both of them. The retaining ring 7 is made of high-strength alloy steel and is embedded in the annular groove on the outer wall of the central tube 2. Its thickness is 6-8mm. It serves both as a stroke limiter for the driving component 6 and as a preventer from axially moving the valve seat mounting cylinder 511 under pressure.

[0036] The workflow of this invention is as follows: Pressure triggering stage: When the fluid pressure inside the wellbore reaches a preset threshold, the rupture disc 412 ruptures, and the fluid enters through the flow hole and installation hole of the cap 411; Pressure reduction introduction stage: The fluid is depressurized through the threaded gap throttling channel formed by the pressure reducing ring 421 and the central tube 2. After the pressure drops from 70MPa to 40-50MPa, it enters the reaction chamber. The O-ring 422 assists in throttling control. Chemical reaction stage: The depressurized fluid mixes thoroughly with the solid acid 522 in the reaction chamber to generate an acidic solution with a pH of 2-4; Delayed dissolution stage: The acidic solution continuously corrodes and dissolves the soluble nut 521, and the outer diameter of the nut gradually decreases. This process lasts from 30 minutes to 4 hours (depending on the parameter settings). Constraint release stage: When the outer diameter of the soluble nut 521 decreases to be equivalent to the inner diameter of the flow area 513, the end face constraint fails, and the piston rod 515 loses its constraint under the action of pressure difference. During the flow channel opening stage: the fluid enters the piston chamber through the flow area 513, and the driving component 6 undergoes axial displacement under the action of pressure difference; Fracturing channel formation: After the drive component 6 is displaced, the outer through hole 31 and the inner through hole 32 are connected to form a fracturing channel that runs through the outer cylinder 1 and the central tube 2, and the toe end sliding sleeve is opened.

[0037] This invention achieves reliable delayed start-up of the toe sleeve through the coordinated cooperation of the dual structure of rupture-decompression of the pressure trigger, the isolation and protection of the independent reaction chamber, the precise delay control driven by chemical reaction, and the size constraint mechanism, effectively solving the problems of insufficient delay accuracy and poor working reliability in the prior art.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A toe sleeve with a soluble metal delayed start, comprising an outer cylinder (1) and a central tube (2) coaxially arranged with the outer cylinder (1), wherein sandblasting holes (3) are provided on the side walls of both the outer cylinder (1) and the central tube (2), characterized in that, A piston chamber and a reaction chamber are formed between the outer cylinder (1) and the central tube (2); it also includes: A pressure trigger (4) is disposed on the side wall of the central tube (2) and guides the fluid to the reaction chamber when the fluid pressure reaches a preset value. The delay control component (5) is disposed in the piston chamber and includes a container (51) for containing the reactants and a soluble part (52) made of soluble material. The soluble part (52) initially closes the flow channel, and when the reaction product dissolves the soluble part (52), a fluid passage is established between the reaction chamber and the piston chamber. The driving component (6) is movably disposed in the piston chamber. Initially, it closes the sandblasting hole (3). After the fluid enters the piston chamber through the fluid passage, it drives the driving component (6) to move, thereby opening the sandblasting hole (3).

2. The toe sleeve with soluble metal delayed start according to claim 1, characterized in that, The pressure trigger (4) includes a rupture part (41) and a pressure relief part (42). The rupture section (41) is disposed on the side wall of the central tube (2), and ruptures when the fluid pressure reaches a preset threshold to establish a fluid passage; The pressure reducing section (42) is disposed between the rupture section (41) and the reaction chamber, and is used to throttle and depressurize the fluid that enters after rupture, and guide the depressurized fluid to the reaction chamber.

3. The toe sleeve with soluble metal delayed start according to claim 2, characterized in that, The fracture portion (41) includes: The protective cap (411) is threaded through the side wall of the central tube (2), and the radial center of the protective cap (411) is provided with a flow hole and a mounting hole from the outside to the inside. A rupture disc (412) is disposed in the mounting hole of the cap (411). When the fluid pressure reaches a specific threshold, the rupture disc (412) ruptures, and the fluid enters the reaction chamber through the mounting hole and the flow hole.

4. The toe sleeve with soluble metal delayed start according to claim 3, characterized in that, The pressure relief section (42) includes: The pressure reducing ring (421) is threadedly connected to the side wall of the central tube (2). The pressure reducing ring (421) and the central tube (2) are threaded together to form a threaded gap, which constitutes a throttling channel. An O-ring (422) is embedded on the outside of the pressure-reducing ring (421) and located in the throttling channel. Fluid enters the reaction chamber through the throttling channel, thereby achieving controlled pressure reduction and fluid introduction.

5. The toe sleeve with soluble metal delayed start according to claim 1, characterized in that, The receiving portion (51) includes: The valve seat mounting sleeve (511) is coaxially sleeved on the outside of the central tube (2), and its axial central area is provided with a receiving area (512) and a flow area (513). A C-ring (514) is embedded on the outside of the central tube (2) and abuts against the end of the valve seat mounting cylinder (511) to limit the axial displacement of the valve seat mounting cylinder (511). A piston rod (515) is inserted into the receiving area (512), with one end of the piston rod (515) extending to the outside of the receiving area (512).

6. The toe sleeve with soluble metal delayed start according to claim 5, characterized in that, The soluble portion (52) includes: A soluble nut (521) is threaded to the end of the piston rod (515) extending to the outside of the receiving area (512). The end face of the soluble nut (521) abuts against the end face of the valve seat mounting cylinder (511). The number of soluble nuts is set to several and they are evenly distributed along the circumferential direction of the end face of the valve seat mounting cylinder (511). In the initial state, each soluble nut (521) corresponds to sealing each of the flow areas (513). Solid acid (522) is pre-placed in the reaction chamber. When the solid acid (522) is mixed with the incoming fluid, an acidic solution is generated. The acidic solution simultaneously corrodes and dissolves the soluble cap (521). When any one of the soluble caps (521) is dissolved to failure, the corresponding piston rod (515) loses its axial constraint, and the flow area (513) is opened to establish a fluid passage.

7. The toe sleeve with soluble metal delayed start according to claim 5, characterized in that, A retaining ring (7) is also embedded on the outside of the central tube (2). The retaining ring (7) is located between the valve seat mounting cylinder (511) and the driving member (6). One end face of the valve seat mounting cylinder (511) and one end face of the driving member (6) respectively abut against the retaining ring (7). The retaining ring (7) is used to limit the relative position of the valve seat mounting cylinder (511) and the driving member (6) and to axially limit the two.

8. The toe sleeve with soluble metal delayed start according to claim 1, characterized in that, The sandblasting hole (3) on the outer cylinder (1) is an external through hole (31), and the sandblasting hole (3) on the central tube (2) is an internal through hole (32). In the initial state, the driving member (6) blocks the outer through hole (31) and the inner through hole (32) so that they are not connected; when the driving member (6) undergoes axial displacement, the outer through hole (31) and the inner through hole (32) are connected to each other, forming a fracturing channel that runs through the outer cylinder (1) and the central tube (2).

9. The toe sleeve with soluble metal delayed start according to claim 5, characterized in that, The side wall of the central tube (2) is fitted with a support sleeve (8). The outer cylinder (1) is connected to the support sleeve (8) by a thread. The annular space formed by the support sleeve (8), the central tube (2) and the outer cylinder (1) forms the piston chamber. The annular space formed by the valve seat mounting cylinder (511), the central tube (2) and the outer cylinder (1) forms the reaction chamber.

10. The toe sleeve with soluble metal delayed start according to claim 1, characterized in that, The driving component (6) is a piston cylinder structure. The piston cylinder is coaxially sleeved between the central tube (2) and the outer cylinder (1). The inner wall of the piston cylinder is fitted with a first sealing member that contacts and cooperates with the outer wall of the central tube (2). The outer wall of the piston cylinder is fitted with a second sealing member that contacts and cooperates with the inner wall of the outer cylinder (1). The first sealing member and the second sealing member are used to ensure the sealing of the piston chamber.

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