Toe end sliding sleeve with time-delay opening function

Abstract

This invention provides a toe sleeve with a delayed opening function, relating to the field of downhole tools for oil and gas wells. It includes an outer cylinder, an inner sleeve inside the outer cylinder, a ball seat inside the inner sleeve, and a soluble ball plug inside the ball seat. A plurality of fracturing holes are formed around the surface of the outer cylinder. Threaded grooves are formed at both ends of the outer cylinder, and limit seats are threadedly installed inside the threaded grooves at both ends. A soft metal ring is installed between one of the limit seats and an adjacent threaded groove. The soft metal ring is located on the moving path of the inner sleeve. In this application, when the inner sleeve is compressed and moves to squeeze the soft metal ring, the soft metal ring gradually deforms. This not only overcomes the defect of a sudden pressure drop caused by the instantaneous rupture of a fragile disc, but also provides a sufficient "pressure storage stage" for the fluid inside the pipe during the deformation period. This ensures sufficient hydraulic pressure to meet the fracturing requirements when the fracturing holes are fully opened subsequently, thus achieving controllable delay and sufficient pressure storage.

Description

Technical Field

[0001] This invention relates to the field of downhole tools for oil and gas wells, and more specifically, to a toe sleeve with a delayed opening function. Background Technology

[0002] In staged fracturing operations in oil and gas wells, existing delayed-opening toe sleeves, such as the one described in patent publication number CN117266789B, include: a hollow tube with its lower end configured as a lower connector and having a first connecting hole; a sealing sleeve and a connecting sleeve fitted onto the hollow tube, with a first annular space and a second annular space formed between the sealing sleeve and the connecting sleeve and the hollow tube, respectively, and the connecting sleeve having a second connecting hole aligned with the first connecting hole; a pressure-transmitting sleeve disposed between the sealing sleeve and the connecting sleeve, the pressure-transmitting sleeve having a pressure-transmitting hole; a delayed medium and a sleeve arranged in the second annular space; and a rupture disc assembly disposed in the side wall of the lower connector.

[0003] The delay control mechanism often has flaws. Currently, the industry widely uses a "fragile disc" structure to achieve delayed and constant-pressure opening. However, the delay characteristics of the fragile disc structure are highly uncontrollable, and the fracturing of the fragile disc often occurs instantaneously. This instantaneous opening causes a sharp drop in hydraulic pressure within the tubing string, making it impossible to maintain sufficient formation fracturing pressure in the initial stage of fracturing hole opening, resulting in insufficient fluid pressure buildup. This, in turn, severely affects the subsequent fracturing effect, leading to incomplete fracturing of the toe formation and reducing the final production of the oil and gas well. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a toe sleeve with a delayed opening function, which solves the problem that insufficient liquid pressure affects the fracturing effect when opening the fracturing hole in existing toe sleeves.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A toe sleeve with a delayed opening function includes an outer cylinder, an inner sleeve inside the outer cylinder, a ball seat inside the inner sleeve, a soluble ball plug inside the ball seat, a plurality of fracturing holes around the surface of the outer cylinder, and threaded grooves at both ends of the outer cylinder. Limiting end seats are threadedly installed inside the threaded grooves at both ends. A soft metal ring is installed between the limiting end seat at one end and the adjacent threaded groove. The soft metal ring is located on the moving path of the inner sleeve. The soft metal ring is used to be squeezed when the inner sleeve is compressed and moves, so that the inner sleeve breaks through the resistance and opens the plurality of fracturing holes to achieve delayed opening.

[0007] Preferably, the ball seat has a conveying through hole in the middle, and a number of extension rods are provided on one side of the ball seat. Each extension rod has a swing groove inside. An elastic reinforcing rib is fixedly installed on one side of the inner wall of the swing groove. A swing plate is integrally provided on one side of the elastic reinforcing rib. A number of matching brackets are provided on the outer side of the swing plate.

[0008] Preferably, the inner sleeve has an assembly groove on one side, an installation ring is fixedly installed inside the assembly groove, and the installation ring has several matching slots inside, the grooves of the matching slots matching the protrusions of the corresponding matching seats.

[0009] Preferably, a rotating shaft is rotatably installed on the other side of the inner wall of the swing groove, and an embedded claw is fixedly installed on the shaft body. The inner wall of the inner sleeve has a circumferential embedded claw groove, and the embedded claw groove and the embedded claw are interlocked.

[0010] Preferably, an adapter rod is fixedly installed at one end of the swing plate, and an adapter groove is provided on one side of the embedded claw, the adapter groove being rotatably connected to the adapter rod.

[0011] Preferably, the outer cylinder surface is provided with a plurality of mounting holes, and a shear pin is installed inside each mounting hole.

[0012] Preferably, the outer surface of the inner sleeve is provided with several limiting grooves, the bottom of the shear pin extends into the corresponding limiting groove, and a reinforcing block is fixedly installed on one side of the inner wall of each limiting groove. The reinforcing block is used to collide with the shear pin so that the shear pin is sheared under a predetermined pressure.

[0013] Preferably, one of the limiting end seats has a mating thread on its outer side, and the other limiting end seat has a mating sleeve installed on its inner thread, the mating sleeve being threadedly connected to the adjacent mating thread.

[0014] Preferably, a positioning pin is provided inside the threaded groove on one side, and a mounting bracket is integrally provided at one end of the soft metal ring.

[0015] Preferably, the mounting bracket is engaged with the positioning pin for limiting, with one end of the limiting end seat pressing against the mounting bracket.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. This invention uses a soft metal ring as the delay medium, utilizing the creep property of zinc-aluminum alloy under downhole ambient temperature. When the inner sliding sleeve is compressed and moves to squeeze the soft metal ring, the soft metal ring gradually deforms. This not only overcomes the defect of instantaneous rupture of the fragile disc leading to a sudden drop in pressure, but also provides a sufficient "pressure storage phase" for the fluid inside the pipe during the deformation period. This ensures that there is sufficient hydraulic pressure to meet the fracturing requirements when the fracturing hole is fully opened later, thereby achieving controllable delay and sufficient pressure storage.

[0018] 2. This invention combines a shear pin and a soft metal ring. By pre-positioning the shear pin, false triggering due to hydraulic fluctuations during liquid delivery is avoided. Simultaneously, the soft metal ring is prevented from being squeezed and deformed from the outset, ensuring system stability and thus providing an anti-false triggering mechanism.

[0019] 3. The mounting ring and matching slot installed inside the assembly slot can match the matching slot on the outside of the ball seat. The groove inside the matching slot gradually increases in size from deep to shallow, which can realize the precise insertion of ball seats of different specifications, and realize the precise control and modular design of downhole multi-stage fracturing.

[0020] 4. Once the ball seat is in place, the elastic reinforcing rib releases its elasticity, causing the inserting claw to unfold and insert into the inserting claw groove. Under continuous hydraulic pressure, the connection between the inner sliding sleeve and the ball seat is further strengthened, ensuring stable advancement of the inner sliding sleeve. Attached Figure Description

[0021] Figure 1 This is a three-dimensional structural schematic diagram of the present invention;

[0022] Figure 2 This is a top view of the structure of the present invention;

[0023] Figure 3 yes Figure 2 Schematic diagram of the cross-sectional structure at point AA;

[0024] Figure 4 yes Figure 3 Enlarged structural diagram at point a;

[0025] Figure 5 yes Figure 3 Enlarged structural diagram at point b;

[0026] Figure 6 yes Figure 3 Enlarged structural diagram at point c;

[0027] Figure 7 yes Figure 3 Enlarged structural diagram at point d;

[0028] Figure 8 This is a three-dimensional structural diagram of the ball seat;

[0029] Figure 9 This is a three-dimensional structural diagram of the spherical base from another perspective;

[0030] Figure 10 This is a side view of the ball seat structure.

[0031] Figure 11 yes Figure 10 Schematic diagram of the cross-sectional structure at point BB;

[0032] Figure 12 This is a three-dimensional structural diagram of the outer cylinder;

[0033] Figure 13 This is a top view of the outer cylinder structure;

[0034] Figure 14 yes Figure 13 Schematic diagram of the cross-sectional structure at point CC.

[0035] In the diagram: 1. Outer cylinder; 101. Mounting hole; 102. Shear pin; 103. Threaded groove; 104. Locating pin; 2. Fracturing hole; 3. Limiting end seat; 301. Butt thread; 4. Butt sleeve; 5. Soft metal ring; 501. Mounting bracket; 6. Inner sliding sleeve; 601. Limiting groove; 602. Reinforcing block; 603. Embedded claw groove; 604. Assembly groove; 605. Mounting ring; 6051. Matching slot; 7. Ball seat; 701. Extension rod; 702. Swing groove; 703. Rotating shaft; 7031. Embedded claw; 7032. Adapter groove; 704. Elastic reinforcing rib; 7041. Swing plate; 7042. Matching bracket; 7043. Adapter rod; 705. Conveying through hole; 8. Soluble ball plug. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] like Figures 1 to 3 As shown, a toe sleeve with a delayed opening function includes an outer cylinder 1, an inner sleeve 6 inside the outer cylinder 1, a ball seat 7 inside the inner sleeve 6, a soluble ball plug 8 inside the ball seat 7, a plurality of fracturing holes 2 around the surface of the outer cylinder 1, and threaded grooves 103 at both ends of the outer cylinder 1. Limiting end seats 3 are threadedly installed inside the threaded grooves 103 at both ends, and a soft metal ring 5 is installed between one of the limiting end seats 3 and the adjacent threaded groove 103.

[0039] Before fracturing, the outer cylinder 1 is pre-transported to the required fracturing position by the equipment, and then the ball seat 7 is transported. The soluble ball plug 8 installed inside the ball seat 7 blocks the delivery through hole 705, and hydraulic fluid is then transported between the inner sliding sleeve 6 and the ball seat 7. As the hydraulic pressure gradually increases, the ball seat 7 drives the inner sliding sleeve 6 to move. Under the movement of the inner sliding sleeve 6, several blocked fracturing holes 2 are opened, so that the fracturing fluid inside can be sprayed out from several fracturing holes 2, thereby realizing the fracturing operation. The position and number of fracturing holes 2 can be adjusted according to the fracturing needs to meet the required fracturing requirements.

[0040] It should be noted that the soft metal ring 5 is made of zinc-aluminum alloy. The zinc-aluminum alloy allows creep to occur when working deep underground due to the ambient temperature. This allows the inner sliding sleeve 6 to squeeze the soft metal ring 5 as it moves, enabling the inner sliding sleeve 6 to overcome the resistance of the soft metal ring 5 and open several fracturing holes 2. The soft metal ring 5 can be used to achieve delayed opening operation, avoiding hydraulic instability during fluid transportation. In case of hydraulic fluctuations, relying solely on the shear pin 102 to limit the opening of the fracturing holes 2 may mistakenly trigger the opening of the fracturing holes 2, resulting in insufficient internal hydraulic pressure and affecting the subsequent fracturing effect.

[0041] Example 2

[0042] like Figures 3 to 11 As shown, a conveying through hole 705 is provided in the middle of the ball seat 7, and several extension rods 701 are provided on one side of the ball seat 7. Each extension rod 701 has a swing groove 702 inside. An elastic reinforcing rib 704 is fixedly installed on one side of the inner wall of the swing groove 702. A swing plate 7041 is integrally provided on one side of the elastic reinforcing rib 704. Several matching card seats 7042 are provided on the outer side of the swing plate 7041.

[0043] Among them, the elastic reinforcing rib 704 is an elastic deformation component to ensure that the swing plate 7041 can swing within a certain range of angles. When the ball seat 7 is placed inside the inner sliding sleeve 6, the inner wall of the inner sliding sleeve 6 will restrict the matching card seat 7042, so that the swing plate 7041 is pressed inward by the inner wall of the inner sliding sleeve 6. At this time, the embedded claw 7031 is in a contracted state.

[0044] In this embodiment, an assembly groove 604 is provided on one side of the inner sliding sleeve 6. An installation ring 605 is fixedly installed inside the assembly groove 604. The installation ring 605 has several matching slots 6051 inside, and the grooves of the matching slots 6051 match the protrusions of the corresponding matching seats 7042. The installation ring 605 and the assembly groove 604 are connected in combination, so that the installation ring 605 with the required specification matching slot 6051 can be installed into the assembly groove 604 as needed to achieve modular design.

[0045] When the ball seat 7 is moved by pressure, the matching card seat 7042 will pass through the corresponding matching card slot 6051 and be locked inside the matching card slot 6051. At this time, the compression force inside the elastic reinforcing rib 704 is released, causing the swing plate 7041 to lift upward, realizing the automatic triggering operation of the unfolding of the embedded claw 7031. The multiple matching card slots 6051 and the matching card seat 7042 have different specifications, so that each ball seat 7 can be accurately locked into the corresponding inner sleeve 6.

[0046] In practice, the internal groove of the matching slot 6051 gradually increases from deep to shallow. When the ball seat 7 is conveyed in sequence, the matching slot 7042 is matched with the internal groove of the corresponding matching slot 6051, so that the ball seat 7 can be accurately inserted into the corresponding inner sleeve 6, thereby achieving precise crack control of the current toe sleeve.

[0047] It should be noted that a rotating shaft 703 is rotatably installed on the other side of the inner wall of the swing groove 702. An embedded claw 7031 is fixedly installed on the shaft of the rotating shaft 703. A circumferential embedded claw groove 603 is opened on the inner wall of the inner sliding sleeve 6. The embedded claw groove 603 and the embedded claw 7031 are interleaved.

[0048] One end of the swing plate 7041 is fixedly installed with an adapter rod 7043, and an adapter groove 7032 is opened on one side of the embedded claw 7031. The adapter groove 7032 is rotatably connected to the adapter rod 7043.

[0049] The adapter groove 7032 is rotatably connected to the adapter rod 7043, so that when the swing plate 7041 moves, it will drive the embedded claw 7031 to swing. The embedded claw 7031 is rotatably mounted on the other side of the inner wall of the swing groove 702 by the rotating shaft 703, so that when the swing plate 7041 is pressed down, the embedded claw 7031 will retract into the swing groove 702. When the elastic reinforcing rib 704 releases its elasticity, the swing plate 7041 will drive the embedded claw 7031 to unfold outward, thereby realizing the automatic triggering of the unfolding operation of the embedded claw 7031.

[0050] When the inserting claw 7031 unfolds, the inner wall of the inner sliding sleeve 6 has a circumferential inserting claw groove 603, which allows several inserting claws 7031 to be inserted into the inserting claw groove 603. Since both the inserting claw groove 603 and the inserting claw 7031 are inclined, the inner sliding sleeve 6 will be pushed to one side when the ball seat 7 is continuously pushed under hydraulic drive. Based on the cooperation of the matching card seat 7042 and the matching groove 6051, the connection between the inner sliding sleeve 6 and the ball seat 7 is further enhanced, ensuring that the inner sliding sleeve 6 can be pushed forward stably.

[0051] Example 3

[0052] like Figures 1 to 5 , Figures 9 to 11As shown, the outer cylinder 1 has several mounting holes 101 on its surface, and each mounting hole 101 has a shear pin 102 installed inside it.

[0053] In this embodiment, the outer surface of the inner sliding sleeve 6 is provided with a plurality of limiting grooves 601, the bottom of the shear pin 102 extends into the corresponding limiting groove 601, and a reinforcing block 602 is fixedly installed on one side of the inner wall of each limiting groove 601. The reinforcing block 602 is used to collide with the shear pin 102 so that the shear pin 102 is sheared under a predetermined pressure.

[0054] To ensure that the initial position of the inner sleeve 6 can block several fracturing holes 2, several shear pins 102 are installed around the outer cylinder 1, and the shear pins 102 extend into the limiting groove 601 on the outer side of the inner sleeve 6 to limit the initial position of the inner sleeve 6, ensuring that the fracturing holes 2 will not leak liquid and ensuring the stability of subsequent fracturing.

[0055] When the hydraulic pressure reaches a certain threshold, the reinforcing block 602 inside the limiting groove 601 will squeeze and collide with the shear pin 102, causing the shear pin 102 to break, so that the inner sliding sleeve 6 can perform the subsequent operation of squeezing the soft metal ring 5 and start the delayed opening operation. The pre-positioning of the shear pin 102 can prevent the soft metal ring 5 from being squeezed and deformed at the beginning.

[0056] Example 4

[0057] like Figures 3 to 7 , Figure 14 As shown, one of the limiting end seats 3 has a mating thread 301 on its outer side, and the other limiting end seat 3 has a mating sleeve 4 installed inside its internal thread. The mating sleeve 4 is threadedly connected to the adjacent mating thread 301.

[0058] To connect multiple toe sleeves, one end of the mating sleeve 4 is connected to the internal thread of the limiting end seat 3, and the other end is connected to the external mating thread 301, thereby realizing the series connection of multiple toe sleeves and enabling multi-point fracturing operations.

[0059] In this embodiment, a positioning pin 104 is provided inside the threaded groove 103 on one side, and a mounting bracket 501 is integrally provided at one end of the soft metal ring 5.

[0060] In the specific setup, the mounting bracket 501 and the positioning pin 104 are matched for limiting, with one end of the limiting end seat 3 pressing against the mounting bracket 501.

[0061] To prevent accidental opening of the fracturing hole 2 due to fluid instability, after the shear pin 102 cuts off, the inner sliding sleeve 6, along with the ball seat 7, is pushed to one side. One end of the inner sliding sleeve 6 begins to compress the soft metal ring 5. At this time, the hydraulic pressure is in the accumulating stage to ensure that the hydraulic pressure is sufficient to meet the fracturing requirements when the fracturing hole 2 is opened later. The set delay stage is then entered, during which different specifications of soft metal ring 5 can be used according to the delay requirements. Subsequently, the soft metal ring 5 is completely squeezed through, causing the resistance to disappear. The inner sliding sleeve 6 instantly slides into place, and the fracturing hole 2 of the outer cylinder 1 is fully opened, allowing fracturing to be carried out.

[0062] To facilitate assembly, the soft metal ring 5 is installed in the threaded groove 103 on one side using the mounting bracket 501 and is pressed and fixed by the limiting end seat 3 on one side, which is beneficial for the fixation and assembly of the soft metal ring 5.

[0063] The working principle of this toe sleeve with delayed opening function:

[0064] Initial delivery stage: Before fracturing, the outer cylinder 1 is first pre-delivered to the required fracturing position using equipment. At this time, the inner sleeve 6 is in its initial position, blocking several fracturing holes 2 on the outer cylinder 1. The shear pins 102 on the outer cylinder 1 extend into the limiting grooves 601 of the inner sleeve 6 to initially position the inner sleeve 6 and prevent liquid leakage.

[0065] Ball seat placement and pressure build-up stage: Ball seat 7 is inserted into the pipe, and the matching retainer 7042 on ball seat 7 precisely engages with the matching slot 6051 of the corresponding inner sliding sleeve 6. Simultaneously, the embedding claw 7031 automatically unfolds and inserts into the embedding claw groove 603, achieving a secure lock between ball seat 7 and inner sliding sleeve 6. Subsequently, the soluble ball plug 8 is inserted, blocking the delivery through hole 705, and the fluid hydraulic pressure begins to gradually increase between the inner sliding sleeve 6 and ball seat 7.

[0066] Shear pin breakage stage: When the hydraulic pressure reaches a certain threshold, the reinforcing block 602 inside the limiting groove 601 will squeeze and collide with the shear pin 102, causing it to be sheared under a predetermined pressure.

[0067] Delay and full pressurization phase: After shearing, the inner sliding sleeve 6 begins to move to one side under hydraulic pressure, and its end begins to squeeze the soft metal ring 5. Because the soft metal ring 5, such as a zinc-aluminum alloy, provides creep resistance, the movement of the sliding sleeve slows down, entering the set delay phase. During this period, the fluid inside the pipe is fully pressurized.

[0068] Fully open stage: As pressure continues and time passes, the soft metal ring 5 is completely squeezed and deformed, and the resistance disappears instantly. The inner sliding sleeve 6 slides into place instantly, at which point the fracturing holes 2 on the surface of the outer cylinder 1 are fully open, and high-pressure fluid is ejected to carry out efficient formation fracturing.

[0069] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A toe sleeve with a delayed opening function, comprising an outer cylinder (1), an inner sleeve (6) disposed inside the outer cylinder (1), a ball seat (7) disposed inside the inner sleeve (6), and a soluble ball plug (8) disposed inside the ball seat (7), characterized in that: The outer cylinder (1) has several fracturing holes (2) around its surface. The outer cylinder (1) has threaded grooves (103) at both ends. Limiting end seats (3) are threadedly installed inside the threaded grooves (103) at both ends. A soft metal ring (5) is installed between the limiting end seat (3) at one end and the adjacent threaded groove (103). The soft metal ring (5) is located on the moving path of the inner sliding sleeve (6). The soft metal ring (5) is used to be squeezed when the inner sliding sleeve (6) is pressed and moved, so that the inner sliding sleeve (6) opens several fracturing holes (2) after breaking through the resistance to achieve delayed opening.

2. A toe sleeve with a delayed opening function according to claim 1, characterized in that: The ball seat (7) has a conveying through hole (705) in the middle. Several extension rods (701) are provided on one side of the ball seat (7). Each extension rod (701) has a swing groove (702) inside. An elastic reinforcing rib (704) is fixedly installed on one side of the inner wall of the swing groove (702). A swing plate (7041) is integrally provided on one side of the elastic reinforcing rib (704). Several matching card seats (7042) are provided on the outer side of the swing plate (7041).

3. A toe sleeve with a delayed opening function according to claim 2, characterized in that: The inner sleeve (6) has an assembly groove (604) on one side. An installation ring (605) is fixedly installed inside the assembly groove (604). The installation ring (605) has several matching slots (6051) inside. The grooves of the matching slots (6051) match the protrusions of the corresponding matching seats (7042).

4. A toe sleeve with a delayed opening function according to claim 2, characterized in that: A rotating shaft (703) is rotatably installed on the other side of the inner wall of the swing groove (702). An embedded claw (7031) is fixedly installed on the shaft body of the rotating shaft (703). A circumferential embedded claw groove (603) is opened on the inner wall of the inner sleeve (6). The embedded claw groove (603) and the embedded claw (7031) are interlocked.

5. A toe sleeve with a delayed opening function according to claim 4, characterized in that: One end of the swing plate (7041) is fixedly installed with an adapter rod (7043), and an adapter groove (7032) is provided on one side of the embedded claw (7031). The adapter groove (7032) is rotatably connected to the adapter rod (7043).

6. A toe sleeve with a delayed opening function according to claim 1, characterized in that: The outer cylinder (1) has several mounting holes (101) on its surface, and each mounting hole (101) is fitted with a shear pin (102).

7. A toe sleeve with a delayed opening function according to claim 6, characterized in that: The outer surface of the inner sleeve (6) is provided with several limiting grooves (601). The bottom of the shear pin (102) extends into the corresponding limiting groove (601). A reinforcing block (602) is fixedly installed on one side of the inner wall of each limiting groove (601). The reinforcing block (602) is used to collide with the shear pin (102) so that the shear pin (102) is sheared under a predetermined pressure.

8. A toe sleeve with a delayed opening function according to claim 1, characterized in that: One of the limiting end seats (3) is provided with a mating thread (301) on the outside, and the other limiting end seat (3) is provided with a mating sleeve (4) installed inside the thread, and the mating sleeve (4) is threadedly connected to the adjacent mating thread (301).

9. A toe sleeve with a delayed opening function according to claim 1, characterized in that: A positioning pin (104) is provided inside the threaded groove (103) on one side, and a mounting bracket (501) is integrally provided at one end of the soft metal ring (5).

10. A toe sleeve with a delayed opening function according to claim 9, characterized in that: The mounting bracket (501) is limited by the positioning pin (104), and one end of the limiting end seat (3) presses against the mounting bracket (501).

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