Delay toe end sliding sleeve capable of testing pressure for multiple times

Abstract

The invention belongs to the technical field of oil production engineering equipment, and discloses a time-delay toe-end sliding sleeve capable of multiple pressure tests, which comprises an upper joint, a high-strength outer pipe, a sand blasting inner pipe, a rupture disc, an opening control mechanism and a time-delay mechanism. According to the high-temperature and high-pressure delay toe-end sliding sleeve capable of being subjected to multiple pressure tests, the full-drift-diameter structural design is adopted, the inner drift diameter is the same as the size of a sleeve of the same specification, and when cement is returned or a stratum is opened and cannot absorb water, and the accidents cannot be opened, treatment is convenient; when the outer sand blasting hole in the high-strength outer pipe is fully opened, the first-section fracturing large-displacement requirement can be met, the limit position of the sliding sleeve can be adjusted through ground pressing when the sliding sleeve opens the stratum due to the fact that the stratum fracture is too high, and the pressure is conducted to the stratum only through the inner sand blasting hole and the outer sand blasting hole; the stress concentration effect of the inner and outer sand blasting holes is utilized, a crack initiation point is manufactured in the stratum, and conditions are created for fracturing the stratum.

Description

Technical Field

[0001] The invention belongs to the technical field of oil production engineering equipment, and in particular relates to a delayed toe end sliding sleeve capable of multiple pressure tests. Background Art

[0002] Low-grade resources have become the main source of reserve growth for oil companies. Among the newly added proven reserves of oil and natural gas, low-grade resources account for more than 70% and 90% respectively. At the same time, unconventional resources such as shale / tight oil and gas have become the focus of capacity construction. Increasing the effective use of unconventional resources while improving the use of remaining oil has become the primary responsibility of reservoir reconstruction. Improving the efficiency of staged fracturing and reducing operating costs have put forward new requirements for staged fracturing technology and tools.

[0003] As a completion tool for communicating with the first oil and gas layer, the delayed toe sleeve can replace traditional first-stage opening methods such as crawlers and oil transmission perforating. It has the characteristics of short cycle, low cost and low construction risk, and has been applied effectively in staged fracturing of long horizontal wells. With the continuous deepening of the development of unconventional oil and gas resources, such as in the development of medium-deep and deep shale gas, the bottom hole working conditions are typical high temperature and high pressure conditions, which puts higher requirements on the wellbore itself and the performance of the tools lowered into the wellbore. In order to fully verify the integrity of the wellbore, it is often required to carry out full wellbore pressure testing during drilling and well handover and first-stage fracturing. This poses new challenges to the technical performance of the toe sleeve. In terms of opening method: the existing toe sleeve is basically a one-time opening type, which cannot achieve secondary or even multiple pressure tests; both the mechanical spring recovery type and the electric switch type have the problems of limited recovery force, sleeve closure, and low success rate of reopening. They are still in the principle test stage and there are no successful implementation cases. In terms of the delay principle: the throttling toe sleeve achieves the purpose of delay by controlling the flow speed or flow of hydraulic oil. There are contradictions such as too high bursting pressure of the rupture disk and small system safety margin. Since the viscosity of the hydraulic oil is greatly affected by the bottom hole temperature, the delay time is difficult to control. The pulse wireless transmission open toe sleeve receives the pressure pulse signal transmitted from the wellhead through the receiver preset on the sleeve, and then drives the sleeve to move through the downhole power. This method relies on electronic control to achieve delay, and the sleeve can be opened at any time according to ground needs, but the downhole electronic components are prone to failure at high temperatures, resulting in a high risk of failure of the toe sleeve. Summary of the invention

[0004] In order to solve at least one problem in the background technology, the present invention provides a delayed toe end sliding sleeve that can be pressure tested multiple times.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A time-delay toe end sliding sleeve capable of multiple pressure tests, comprising:

[0007] The upper joint is axially connected with a high-strength outer tube;

[0008] The high-strength outer tube has a plurality of external sandblasting holes on its surface, and the end of the high-strength outer tube away from the upper joint is connected to a lower joint;

[0009] A sandblasting inner tube has a plurality of inner sandblasting holes on its surface, and the sandblasting inner tube is coaxially arranged inside the high-strength outer tube, one end of the sandblasting inner tube is connected to the upper joint, and the other end is connected to the lower joint;

[0010] A rupture disk, a plurality of which are arranged along the circumference of the lower joint;

[0011] The opening control mechanism is located in the annulus between the high-strength outer tube and the sandblasting inner tube and is used to periodically control the opening of the inner sandblasting hole under the well fluid pressure;

[0012] The time delay mechanism is fixedly arranged between the annulus of the high-strength outer tube and the sandblasting inner tube, and is used to prolong the time for the well fluid to reach the flow control mechanism.

[0013] Preferably, the plurality of external sandblasting holes are evenly distributed along the circumference of the high-strength outer tube and penetrate in the radial direction;

[0014] The plurality of inner sandblasting holes are evenly distributed along the circumference of the sandblasting inner tube and penetrate in the radial direction.

[0015] Preferably, four rupture disks are provided.

[0016] Preferably, the opening control mechanism comprises a spring, a positioning pin and a sliding sleeve;

[0017] One end of the spring is fixedly connected to the end of the upper joint, and the other end is fixedly connected to the sliding sleeve;

[0018] The positioning pin is detachably connected to the sandblasting inner tube;

[0019] A limiting ring groove is provided on the surface of the sleeve, and the limiting ring groove slides relative to the positioning pin. When the sleeve rotates circumferentially, the positioning pin slides along the limiting ring groove, and the minimum opening of the inner sandblasting hole first changes from the minimum to the maximum, and then gradually decreases from the maximum to the minimum.

[0020] Preferably, the positioning pin is threadably matched with the sandblasting inner tube.

[0021] Preferably, the limiting ring groove is composed of a plurality of guide grooves connected end to end;

[0022] The guide groove comprises an axial section, a transition section and an inclined section;

[0023] The axial section is arranged along the axial direction of the sandblasting inner tube;

[0024] The transition section is used to connect the axial section and the inclined section;

[0025] The angle A between the projections of the inclined section and the axial section on the same plane is an acute angle;

[0026] The angle B between the transition section and the axial section projected on the same plane is an obtuse angle;

[0027] The angle between the transition section and the inclined section projected on the same plane is an acute angle C;

[0028] The acute angle C is greater than the angle A.

[0029] Preferably, among the plurality of guide grooves, the axial lengths of the first guide groove to the last guide groove gradually increase, and the axial sections are parallel to each other;

[0030] The arc length of the transition section from the first guide groove to the last guide groove gradually increases, and the transition sections are parallel to each other;

[0031] The arc length of the inclined sections from the first guide groove to the last guide groove gradually increases, and the inclined sections are parallel to each other.

[0032] Preferably, the delay mechanism comprises a creep delay ring, a rigid support ring and a slow dissolving delay ring;

[0033] One end of the creep delay ring abuts against the step surface of the sandblasted inner tube, and the other end abuts against the rigid support ring; the end of the rigid support ring away from the creep delay ring abuts against the slow dissolving delay ring; the end of the slow dissolving delay ring away from the rigid support ring abuts against the end of the lower joint.

[0034] Preferably, the creep delay ring, rigid support ring and slow dissolving delay ring are all interference fit with the sandblasted inner tube, and the outer surface of the creep delay ring is interference fit with the high-strength outer tube, and an annular gap is formed between the rigid support ring and the slow dissolving delay ring and the high-strength outer tube.

[0035] Preferably, the rupture disk is threadably matched with the lower joint, and anaerobic adhesive is applied at the matching position.

[0036] Beneficial effects of the present invention:

[0037] 1. The invention can test the high temperature and high pressure delayed toe end sliding sleeve for many times, and adopts a full-diameter structure design. The inner diameter is the same as the casing size of the same specification. It is easy to handle when accidents such as cement backflow or the formation does not absorb water or cannot be opened occur.

[0038] 2. The present invention can perform multiple pressure tests on the high-temperature and high-pressure delayed toe-end sliding sleeve. When the external sandblasting holes on the high-strength outer tube are fully opened, the large-volume requirement of the first stage of fracturing can be met. When the formation fracture is too high and the sliding sleeve opens but the formation does not crack, the sliding sleeve limit position can be adjusted by ground pressure. The pressure is only transmitted to the formation through the internal and external sandblasting holes. The stress concentration effect of the internal and external sandblasting holes is used to create a cracking point in the formation, creating conditions for pressing the formation open.

[0039] 3. The present invention can perform multiple pressure tests on the high-temperature and high-pressure delayed toe sleeve. The surfaces of all parts in contact with cement slurry are sprayed with an anti-cement deposition coating, which can effectively prevent cement from being deposited on the toe sleeve during the cementing process, and even block the rupture disk pressure guide port, resulting in the rupture disk being unable to blast smoothly.

[0040] 4. The present invention can perform multiple pressure tests on the high-temperature and high-pressure delayed toe sleeve. The creep delay ring and the slow-dissolving delay element are less affected by the well temperature and pressure, and the delay time can be precisely controlled.

[0041] 5. The present invention can perform pressure tests on the delayed toe sleeve at high temperature and high pressure for multiple times. The opening control mechanism can realize repeated opening and closing of the sleeve on the ground by pressurizing the wellhead on the ground. The process is simple and repeatable. The opening control mechanism can realize delayed pressure testing during the fracturing process. In the subsequent production process, the opening of the sandblasting port of the sleeve can be adjusted, including complete closing and repeated opening, to achieve dynamic production adjustment of the position of the sleeve.

[0042] 6. The present invention provides a limit ring groove on the sleeve. Under the combined effect of hydraulic force and energy-gathering spring restoring force, the sleeve can achieve extreme position changes of different phases, thereby adjusting the opening of the inner sandblasting hole.

[0043] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 A schematic structural diagram of a delayed toe end sliding sleeve capable of multiple pressure tests according to the present invention when the opening degree is the smallest;

[0046] Figure 2 An enlarged view of the time delay mechanism is shown;

[0047] Figure 3 A schematic structural diagram of a time-delay toe-end sliding sleeve capable of multiple pressure tests according to the present invention when the opening degree is the maximum;

[0048] Figure 4 A display diagram of the limiting ring groove of the present invention is shown;

[0049] Figure 5 The structural diagram of the guide groove in the limiting ring groove is shown;

[0050] Figure 6 The distribution diagram of the maximum opening point and the minimum opening point in the limit ring groove is shown.

[0051] In the figure: 1. upper joint; 2. high-strength outer tube; 3. spring; 4. sandblasted inner tube; 5. positioning pin; 6. sliding sleeve; 601. limit ring groove; 6011. maximum opening point; 6012. minimum opening point; 6013. axial section; 6014. transition section; 6015. inclined section; 7. creep delay ring; 8. rigid support ring; 9. slow dissolution delay ring; 10. rupture disk; 11. lower joint. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] A time-delayed toe end sliding sleeve capable of multiple pressure tests, such as Figure 1 As shown, it includes an upper joint 1, a high-strength outer tube 2, a sandblasting inner tube 4, a rupture disk 10, an opening control mechanism and a delay mechanism. The upper joint 1 is connected to the high-strength outer tube 2 by threads along the axial direction. A plurality of external sandblasting holes are opened on the surface of the high-strength outer tube 2, and the end of the high-strength outer tube 2 away from the upper joint 1 is threadedly connected to the lower joint 11. A plurality of internal sandblasting holes are opened on the surface of the sandblasting inner tube 4, and the sandblasting inner tube 4 is coaxially arranged inside the high-strength outer tube 2, one end is connected to the upper joint 1, and the other end is connected to the lower joint 11. A plurality of rupture disks 10 are arranged along the circumference of the lower joint 11, and the rupture disks 10 and the lower joint 11 are threadedly matched, and anaerobic glue is applied at the matching position. The opening control mechanism is located in the annulus between the high-strength outer tube 2 and the sandblasting inner tube 4, and is used to periodically control the opening of the internal sandblasting holes under the well fluid pressure; the delay mechanism is fixedly arranged between the annulus between the high-strength outer tube 2 and the sandblasting inner tube 4, and is used to prolong the time for the well fluid to reach the flow control mechanism.

[0054] It should be noted that from Figure 1It can be seen that the delayed toe end sliding sleeve of the present invention that can be pressure tested multiple times is a rotating body structure, wherein the sandblasted inner tube 4 can be positioned on the upper joint 1 and the lower joint 11 by fastening screws, and the connection between the upper joint 1 and the high-strength outer tube 2, the connection between the lower joint 11 and the high-strength outer tube 2, and the connection between the sandblasted inner tube 4 and the upper joint 1 and the lower joint 11 can all be coated with sealant or use rubber sealing rings to improve the sealing performance. The invention can test the delayed toe end sliding sleeve 6 of high temperature and high pressure multiple times, and the upper and lower joints can be customized according to the on-site casing connection buckle type. At the same time, because the toe end sliding sleeve 6 body meets the airtightness requirements, it has good process adaptability.

[0055] Furthermore, a plurality of outer sandblasting holes are evenly distributed along the circumference of the high-strength outer tube 2 and penetrate in the radial direction; a plurality of inner sandblasting holes are evenly distributed along the circumference of the sandblasting inner tube 4 and penetrate in the radial direction.

[0056] It should be noted that the outer sandblasting holes and the inner sandblasting holes are blocked by the sliding sleeve 6 in the opening control mechanism in the initial state. When the sliding sleeve 6 is removed, the outer sandblasting holes and the inner sandblasting holes can be connected, and the well fluid or other liquid can enter the inner side of the sandblasting inner tube 4 and the annulus of the high-strength outer tube 2 and the sandblasting inner tube 4 from the outside of the high-strength outer tube 2.

[0057] Furthermore, four rupture disks 10 are provided.

[0058] It should be noted that four rupture disks 10 are evenly distributed along the circumference of the lower joint 11, ensuring that in the horizontal section, no matter what phase the sleeve 6 is in (i.e., according to the Figure 1 At least two rupture disks 10 are placed in the upper half of the circumference. When the wellhead is pressurized, the rupture disk 10 cannot be exploded due to the blockage of the pressure guide port of the rupture disk 10 in the lower half of the circumference. At the same time, high temperature resistant grease is set inside the rupture disk 10 to prevent the impurities in the liquid from mechanically piercing the diaphragm of the rupture disk 10 during pressure, causing the rupture disk 10 precision distortion problem. The design starting pressure of the rupture disk 10 is more than 15% lower than the compressive strength of the casing 6, and the success rate of the sliding sleeve 6 opening is high.

[0059] Furthermore, if Figure 1 and Figure 3 As shown, the opening control mechanism includes a spring 3, a positioning pin 5 and a sleeve 6; one end of the spring 3 is fixedly connected to the end of the upper joint 1, and the other end is fixedly connected to the sleeve 6; the positioning pin 5 is detachably connected to the sandblasting inner tube 4, specifically by threaded engagement; a limiting annular groove 601 is provided on the surface of the sleeve 6, and the limiting annular groove 601 slides relative to the positioning pin 5, so that the positioning pin 5 can achieve axial and circumferential relative movement with the sleeve 6 under the combined action of the spring 3 and the bottom hole fluid force. When the sleeve 6 rotates in the circumferential direction, the positioning pin 5 slides along the limiting annular groove 601, and the minimum opening of the inner sandblasting hole first changes from the minimum to the maximum, and then gradually decreases from the maximum to the minimum.

[0060] It should be noted that the opening control mechanism is mainly to control the position of the sleeve 6 so that the sleeve 6 completely or partially blocks the opening size of the inner sandblasting hole, wherein the spring 3 can be adjusted under the action of the well fluid pressure. Figure 1 The left side of the middle part contracts, and then the liquid outside the high-strength outer tube 2 enters the sandblasting inner tube 4 and the annulus, so that the well fluid pressure is released, and the spring 3 rebounds to move the sleeve 6 to the right. At this time, due to the characteristics of the limiting ring groove 601, the inner sandblasting hole will not be completely blocked by the sleeve 6, but the minimum opening will first change from the minimum to the maximum, and then gradually decrease from the maximum to the minimum. In addition, when the ground is pressed, the pressure pushes the end face of the sleeve 6 to move axially, but because of the matching relationship between the positioning pin 5 and the limiting ring groove 601, the sleeve 6 will rotate along the circumference while moving axially, which is equivalent to an irregular spiral motion.

[0061] It should be further explained that the spring 3 can adopt a focused gas spring, which has the technical characteristics of long stroke, quick response, large gas compression ratio, high reliability, etc. It can provide a strong restoring force for the axial movement of the sleeve 6. At the same time, since the focused gas spring is preset with a certain amount of compression, during the lowering process of the sleeve 6, the internal sandblasting hole can be prevented from accidentally opening in advance; compared with the common shear pins, the pins are easy to get stuck and prevent the movement of the sleeve 6 after being sheared off. The use of focused gas springs can effectively avoid such risks.

[0062] Furthermore, if Figure 4 As shown, in order to achieve the minimum opening of the inner sandblasting hole to change from the minimum to the maximum first, and then gradually decrease from the maximum to the minimum, the limiting ring groove 601 needs to be composed of a plurality of guide grooves connected end to end. Figure 5 It can be seen that the guide groove includes an axial section 6013, a transition section 6014 and an inclined section 6015; the axial section 6013 is arranged axially along the sandblasting inner tube 4; the transition section 6014 is used to connect the axial section 6013 and the inclined section 6015; the angle A between the inclined section 6015 and the axial section 6013 projected on the same plane is an acute angle; the angle B between the transition section 6014 and the axial section 6013 projected on the same plane is an obtuse angle; the angle between the transition section 6014 and the inclined section 6015 projected on the same plane is an acute angle C; the angle of the acute angle C is greater than the angle of the angle A.

[0063] It should be noted that if Figure 5 As shown, each guide groove has a maximum opening point 6011 and a minimum opening point 6012, wherein the maximum opening point 6011 is located at the rightmost side of the guide groove (the side close to the lower joint 11), and the minimum opening point 6012 is located at the leftmost side (the side away from the lower joint 11). When the positioning pin 5 moves to the maximum opening point 6011, the inner sandblasting hole is fully opened, and when the positioning pin 5 moves to the minimum opening point 6012, the inner sandblasting hole is partially opened or completely closed.

[0064] like Figure 6 As shown in the figure, a, c, e, g, i, k are the minimum opening points 6012 corresponding to each guide groove, and b, d, f, h, j and l are the maximum opening points 6011 corresponding to each guide groove. In the initial state, the positioning pin 5 is located at Figure 6 At point a, the inner sandblasting hole is completely blocked by the sliding sleeve 6, corresponding to Figure 1 Then the sleeve 6 moves under the action of the well fluid pressure. Figure 1 The positioning pin 5 will slide along the inclined section 6015 until it moves to point b. At this time, the sliding sleeve 6 is away from the inner sandblasting hole, so that the inner sandblasting hole is fully opened, corresponding to Figure 3 The state of the middle sliding sleeve 6 and the inner sandblasting hole; then the positioning pin 5 slides along the axial section 6013 and the transition section 6014 until it moves to point c, at which time the inner sandblasting hole is partially opened, and the minimum opening of the inner sandblasting hole reaches the maximum, and then the positioning pin 5 moves to point d, at which time the inner sandblasting hole is fully opened, and then the positioning pin 5 will continue to move to points e, g, i, k, etc. During this process, the minimum opening of the inner sandblasting hole will gradually decrease, and finally reach the minimum when it reaches point a. This process can be cyclically carried out for the pressure change of the well fluid.

[0065] Furthermore, among several guide grooves, the length of the axial section 6013 from the first guide groove to the last guide groove gradually increases, and the axial sections 6013 are parallel to each other; the arc length of the transition section 6014 from the first guide groove to the last guide groove gradually increases, and the transition sections 6014 are parallel to each other; the arc length of the inclined section 6015 from the first guide groove to the last guide groove gradually increases, and the inclined sections 6015 are parallel to each other.

[0066] Furthermore, if Figure 2 As shown, the delay mechanism includes a creep delay ring 7, a rigid support ring 8 and a slow-dissolving delay ring 9; one end of the creep delay ring 7 abuts against the step surface of the sandblasted inner tube 4, and the other end is fixedly connected to the rigid support ring 8; the end of the rigid support ring 8 away from the creep delay ring 7 is fixedly connected to the slow-dissolving delay ring 9; the end of the slow-dissolving delay ring 9 away from the rigid support ring 8 abuts against the end of the lower joint 11. In addition, the creep delay ring 7, the rigid support ring 8 and the slow-dissolving delay ring 9 are all interference fit with the sandblasted inner tube 4, and the outer surface of the creep delay ring 7 is interference fit with the high-strength outer tube 2, and an annular gap is formed between the rigid support ring 8 and the slow-dissolving delay ring 9 and the high-strength outer tube 2.

[0067] It should be noted that when the pressure in the sandblasting inner tube 4 increases, the rupture disk 10 ruptures under the action of the well fluid pressure, and then the well fluid enters the right end of the annulus between the high-strength outer tube 2 and the sandblasting inner tube 4 from the rupture disk 10, and then the well fluid pressure squeezes the creep delay ring 7, and then the creep delay ring 7 gradually deforms, and then the well fluid passes through the delay mechanism, squeezing Figure 1 The right end of the middle sliding sleeve 6 makes the sliding sleeve 6 Figure 1 If the creep delay ring 7 deforms too slowly, the slow-dissolving delay ring 9 will gradually dissolve, and then the creep delay ring 7 loses support, and the area of ​​the liquid pressure changes. After the dissolution, the load generated by the liquid pressure increases greatly, which is conducive to pushing the creep delay ring 7 to creep to the left and deform, thereby achieving liquid flow conduction.

[0068] It should be further explained that both the creep delay ring 7 and the slow dissolving delay ring 9 can be made of magnesium alloy, wherein the creep delay ring 7 has a room temperature elongation of 60% and a strength of 200-250 MPa, and the slow dissolving delay ring 9 has a room temperature elongation of 8% and a strength of 450 MPa. In addition, the elongation will further increase with increasing temperature.

[0069] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A delayed toe end sliding sleeve capable of multiple pressure tests, characterized in that: include: An upper joint (1) is axially connected to a high-strength outer tube (2); The high-strength outer tube (2) has a plurality of external sandblasting holes on its surface, and the end of the high-strength outer tube (2) away from the upper joint (1) is connected to a lower joint (11); A sandblasting inner tube (4) is provided with a plurality of inner sandblasting holes on its surface, and the sandblasting inner tube (4) is coaxially arranged inside the high-strength outer tube (2), one end of the sandblasting inner tube is connected to the upper joint (1), and the other end is connected to the lower joint (11); A plurality of rupture disks (10) are arranged along the circumference of the lower joint (11); An opening control mechanism is located in the annulus between the high-strength outer tube (2) and the sandblasting inner tube (4) and is used to periodically control the opening of the inner sandblasting hole under well fluid pressure; The time delay mechanism is fixedly arranged between the annulus of the high-strength outer tube (2) and the sandblasting inner tube (4) and is used to prolong the time for the well fluid to reach the flow control mechanism.

2. A time-delay toe end sliding sleeve capable of multiple pressure tests according to claim 1, characterized in that: The plurality of external sandblasting holes are evenly distributed along the circumference of the high-strength outer tube (2) and penetrate in the radial direction; The plurality of inner sandblasting holes are evenly distributed along the circumference of the sandblasting inner tube (4) and penetrate in the radial direction.

3. The delayed toe end sliding sleeve capable of multiple pressure tests according to claim 1, characterized in that: Four rupture disks (10) are provided.

4. The delayed toe end sliding sleeve capable of multiple pressure tests according to claim 1, characterized in that: The opening control mechanism comprises a spring (3), a positioning pin (5) and a sliding sleeve (6); One end of the spring (3) is fixedly connected to the end of the upper joint (1), and the other end is fixedly connected to the sliding sleeve (6); The positioning pin (5) is detachably connected to the sandblasting inner tube (4); A limiting annular groove (601) is provided on the surface of the sliding sleeve (6), and the limiting annular groove (601) slides relative to the positioning pin (5). When the sliding sleeve (6) rotates in the circumferential direction, the positioning pin (5) slides along the limiting annular groove (601), and the minimum opening of the inner sandblasting hole first changes from the minimum to the maximum, and then gradually decreases from the maximum to the minimum.

5. The delayed toe end sliding sleeve capable of multiple pressure tests according to claim 4, characterized in that: The positioning pin (5) is threadably matched with the sandblasting inner tube (4).

6. The delayed toe end sliding sleeve capable of multiple pressure tests according to claim 4, characterized in that: The limiting ring groove (601) is composed of a plurality of guide grooves connected end to end; The guide groove comprises an axial section (6013), a transition section (6014) and an inclined section (6015); The axial section (6013) is arranged axially along the sandblasting inner tube (4); The transition section (6014) is used to connect the axial section (6013) and the inclined section (6015); The angle A between the inclined section (6015) and the axial section (6013) projected on the same plane is an acute angle; The angle B between the transition section (6014) and the axial section (6013) projected on the same plane is an obtuse angle; The included angle between the transition section (6014) and the inclined section (6015) projected on the same plane is an acute angle C; The acute angle C is greater than the angle A.

7. The delayed toe end sliding sleeve capable of multiple pressure tests according to claim 6, characterized in that: Among the plurality of guide grooves, the length of the axial section (6013) from the first guide groove to the last guide groove gradually increases, and the axial sections (6013) are parallel to each other; The arc length of the transition section (6014) from the first guide groove to the last guide groove gradually increases, and the transition sections (6014) are parallel to each other; The arc length of the inclined sections (6015) from the first guide groove to the last guide groove gradually increases, and the inclined sections (6015) are parallel to each other.

8. The delayed toe end sliding sleeve capable of multiple pressure tests according to claim 1, characterized in that: The time delay mechanism comprises a creep time delay ring (7), a rigid support ring (8) and a slow dissolving time delay ring (9); One end of the creep delay ring (7) abuts against the step surface of the sandblasted inner tube (4), and the other end abuts against the rigid support ring (8); the end of the rigid support ring (8) away from the creep delay ring (7) abuts against the slow dissolving delay ring (9); the end of the slow dissolving delay ring (9) away from the rigid support ring (8) abuts against the end of the lower joint (11).

9. The delayed toe end sliding sleeve capable of multiple pressure tests according to claim 8, characterized in that: The creep delay ring (7), the rigid support ring (8) and the slow dissolving delay ring (9) are all interference fit with the sandblasted inner tube (4), and the outer surface of the creep delay ring (7) is interference fit with the high-strength outer tube (2), and an annular gap is formed between the rigid support ring (8) and the slow dissolving delay ring (9) and the high-strength outer tube (2).

10. A time-delay toe end sliding sleeve capable of multiple pressure tests according to any one of claims 1 to 9, characterized in that: The rupture disk (10) is threadably matched with the lower joint (11), and anaerobic adhesive is applied to the matching position.

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