A two-stage pressure-retaining ball seat assembly

Abstract

This invention provides a two-stage pressure-retaining ball seat assembly, comprising a ball seat shell, a primary ball seat that seals with a sealing ball during primary pressure-retaining, a secondary ball seat that seals with the primary ball seat during secondary pressure-retaining, a primary ball seat body for mounting the primary ball seat, and a secondary ball seat body for mounting the secondary ball seat. The primary ball seat body is housed within the ball seat shell, and the secondary ball seat body is connected to the lower end of the primary ball seat body. The secondary ball seat body has a throttling through-hole that connects the internal and external spaces of the body. This invention offers advantages such as preventing formation breakdown and improving cementing success rate.

Description

Technical Field

[0001] This invention relates to the field of cementing operations, and more particularly to a two-stage pressure-reducing ball seat assembly. Background Technology

[0002] In recent years, with the rapid development of my country's oil and gas industries, the demand for cementing tools has increased significantly, and the number of wells in complex formations has also increased dramatically, leading to a substantial rise in cementing accidents where the ball seat penetrates the formation. Existing ball seats shear off the shear studs when pressure is built up to a certain level during ball placement. The ball seat, carrying its initial kinetic energy, falls to the bottom of the tailpipe, where it is highly susceptible to penetrating the formation, causing cement loss and ultimately leading to cementing failure. To address these technical problems, the current approach is to use a two-stage pressure buildup method to reduce the initial pressure when the ball seat detaches. While this can reduce the probability of the ball seat penetrating the formation to some extent, the risk of the initial pressure of the ball seat penetrating the formation during the secondary pressure buildup remains. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a two-stage pressure-retaining ball seat assembly that prevents formation penetration and improves cementing success rate.

[0004] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0005] A two-stage pressure-retaining ball seat assembly includes a ball seat shell, a primary ball seat that seals with a sealing ball during primary pressure-retaining, a secondary ball seat that seals with the primary ball seat during secondary pressure-retaining, a primary ball seat body for mounting the primary ball seat, and a secondary ball seat body for mounting the secondary ball seat. The primary ball seat body is installed inside the ball seat shell, and the secondary ball seat body is connected to the lower end of the primary ball seat body. The secondary ball seat body has a throttling through section that connects the inner and outer spaces of the body.

[0006] As a further improvement to the above technical solution:

[0007] The throttling passage includes multiple throttling grooves arranged circumferentially along the secondary ball seat body, and each throttling groove is arranged axially along the secondary ball seat body.

[0008] The throttling passage includes multiple throttling holes, which are arranged in an array on the secondary ball seat body.

[0009] The primary ball seat is installed in the primary ball seat body by a primary shear pin, and the secondary ball seat body is installed at the lower end of the primary ball seat body by a secondary shear pin. The strength of the secondary shear pin is less than that of the primary shear pin.

[0010] A first sealing ring is provided between the primary ball seat and the primary ball seat body, and along the cement grout injection direction, the first sealing ring is located above the primary shear pin.

[0011] A second sealing ring is provided between the primary ball seat body and the ball seat shell.

[0012] The bottom surface of the primary ball seat is a conical sealing surface, and the upper surface of the secondary ball seat is a sealing mating surface adapted to the conical sealing surface.

[0013] The upper surface of the primary ball seat is provided with a tapered mating surface that seals with the sealing ball.

[0014] The sealing ball includes a body and a sealing rubber layer, the sealing rubber layer being vulcanized on the outer surface of the body.

[0015] The primary ball seat body and the ball seat shell are connected by threads, as are the secondary ball seat body and the secondary ball seat.

[0016] Compared with the prior art, the advantages of the present invention are as follows:

[0017] This invention features a two-stage pressure-retaining structure, with a throttling and connecting section on the second-stage ball seat body. During the second-stage pressure-retaining descent, this section connects the inner and outer spaces of the second-stage ball seat body. This creates a backflow of liquid within the second-stage ball seat body, generating a throttling effect that continuously reduces the descent speed of the second-stage ball seat and its body. This minimizes the kinetic energy generated during the ball seat's descent, ensuring that the kinetic energy is insufficient to penetrate the formation when the ball seat reaches the bottom of the well, preventing cement loss and effectively improving cementing success rate. Furthermore, the first-stage ball seat body is housed within a ball seat shell, and the second-stage ball seat body is connected to the lower end of the first-stage ball seat body, resulting in a simple structure and convenient operation. Attached Figure Description

[0018] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0019] Figure 1 This is a schematic diagram of the structure (initial state) of the two-stage pressure-retaining ball seat assembly of the present invention.

[0020] Figure 2 This is a schematic diagram of the structure of the two-stage pressure-retaining ball seat assembly of the present invention (first-stage shear pin cutting).

[0021] Figure 3 This is a schematic diagram of the structure of the two-stage pressure-retaining ball seat assembly of the present invention (two-stage shear pin cutting).

[0022] Figure 4 This is a schematic diagram of the structure of the secondary ball seat body of the present invention.

[0023] Figure 5 This is another structural schematic diagram of the secondary ball seat body of the present invention.

[0024] The labels in the diagram represent:

[0025] 1. Ball seat shell; 2. Primary ball seat; 21. Conical sealing surface; 22. Conical mating surface; 3. Secondary ball seat; 31. Sealing mating surface; 4. Primary ball seat body; 5. Secondary ball seat body; 51. Throttling through part; 511. Throttling groove; 512. Throttling orifice; 6. Primary shear pin; 7. Secondary shear pin; 8. First sealing ring; 9. Second sealing ring; 10. Sealing ball. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, but this does not limit the scope of protection of the present invention.

[0027] like Figures 1 to 3 As shown, the two-stage pressure-retaining ball seat assembly of this embodiment includes a ball seat shell 1, a primary ball seat 2, a secondary ball seat 3, a primary ball seat body 4, and a secondary ball seat body 5. The primary ball seat 2 is installed inside the primary ball seat body 4, and during the first pressure-retaining operation, it seals against the sealing ball 10. The primary ball seat body 4 is installed inside the ball seat shell 1. The secondary ball seat 3 is installed inside the secondary ball seat body 5, and during the second pressure-retaining operation, it seals against the primary ball seat 2. The secondary ball seat body 5 is connected to the lower end of the primary ball seat body 4. The secondary ball seat body 5 is provided with a throttling through-hole 51 to connect the inner and outer spaces of the secondary ball seat body 5.

[0028] This invention features a two-stage pressure-retaining structure, with a throttling and connecting section 51 on the secondary ball seat body 5. During the secondary pressure-retaining descent of the secondary ball seat body 5 and secondary ball seat 3, the throttling and connecting section 51 connects the inner and outer spaces of the secondary ball seat body 5. At this time, the liquid inside and outside the secondary ball seat body 5 forms a backflow, generating a throttling effect. This continuously reduces the velocity of the secondary ball seat 3 and secondary ball seat body 5 during the descent, resulting in low kinetic energy of the components. This ensures that the kinetic energy of the falling components is insufficient to penetrate the formation when they reach the bottom of the well, preventing cement loss and effectively improving the cementing success rate. Simultaneously, the primary ball seat body 4 is installed inside the ball seat shell 1, and the secondary ball seat body 5 is connected to the lower end of the primary ball seat body 4. Its structure is simple and easy to operate.

[0029] like Figure 4 As shown, the throttling and connecting section 51 includes multiple throttling orifices 512, which are arranged in an array on the secondary ball seat body 5. While ensuring sufficient pressure to shear the secondary shear pin 7, it also effectively creates a throttling effect, allowing for the backflow of liquid inside and outside the secondary ball seat body 5 during its descent, thus ensuring that the kinetic energy of the falling component when it reaches the bottom of the well is insufficient to penetrate the formation. Figure 5As shown, in other embodiments, the throttling through section 51 may also be configured as a plurality of throttling grooves 511, with the plurality of throttling grooves 511 arranged along the circumference of the secondary ball seat body 5, and a single throttling groove 511 arranged along the axial direction of the secondary ball seat body 5.

[0030] Furthermore, the primary ball seat 2 is installed inside the primary ball seat body 4 via a primary shear pin 6, and the secondary ball seat body 5 is installed at the lower end of the primary ball seat body 4 via a secondary shear pin 7. The strength of the secondary shear pin 7 is less than that of the primary shear pin 6. This results in the initial pressure value of the secondary ball seat 3 being lower than that of a conventional ball seat, reducing the initial kinetic energy of the secondary ball seat 3 and the secondary ball seat body 5 during their descent, further ensuring that the kinetic energy of the falling components when they reach the bottom of the well is insufficient to penetrate the formation.

[0031] like Figure 1 As shown, the bottom surface of the primary ball seat 2 is a conical sealing surface 21; the upper surface of the secondary ball seat 3 is a sealing mating surface 31, which is adapted to the conical sealing surface 21 to form a contact seal and ensure the pressure-locking effect. At the same time, the upper surface of the primary ball seat 2 is provided with a conical mating surface 22 to form an effective sealing fit with the sealing ball 10.

[0032] Furthermore, the sealing ball 10 includes a body and a sealing rubber layer, the sealing rubber layer being vulcanized on the outer surface of the body. The sealing rubber layer allows the sealing ball 10 to effectively fit and seal with the conical mating surface 22 of the primary ball seat 2, ensuring a pressure-sealing effect.

[0033] Furthermore, a first sealing ring 8 is provided between the primary ball seat 2 and the primary ball seat body 4, and the first sealing ring 8 is located above the primary shear pin 6 along the cement grout injection direction. At the same time, a second sealing ring 9 is provided between the primary ball seat body 4 and the ball seat shell 1. Both the first sealing ring 8 and the second sealing ring 9 are O-rings to effectively prevent cement grout leakage and ensure the pressure-holding effect.

[0034] In this embodiment, the primary ball seat body 4 and the ball seat shell 1, as well as the secondary ball seat body 5 and the secondary ball seat 3, are connected by threads. This design is simple in structure and easy to install and disassemble.

[0035] In this embodiment, the operation process of the dual-stage pressure-retaining ball seat assembly is as follows: During cementing, the sealing ball 10 is inserted and falls to form a seal with the primary ball seat 2; when the primary ball seat 2 is pressurized to a certain extent, the primary shear pin 6 is sheared, and the primary ball seat 2 falls to contact and cooperate with the secondary ball seat 3, forming a seal; because the secondary ball seat body 5 has a small diameter throttling orifice 512, the pressure cannot be completely released, causing the secondary shear pin 7 to be sheared when the pressure is reached to a certain extent. The secondary ball seat 3 and the secondary ball seat body 5 will detach from the primary ball seat body 4. Since the strength of the secondary shear pin 7 is less than that of the primary ball seat body 4, the pressure will be released. The strength of the primary shear stud 6 ensures that the kinetic energy of the secondary ball seat 3 and the secondary ball seat body 5 is less than that of the primary ball seat 2, thereby reducing the initial kinetic energy of the secondary ball seat 3 and the secondary ball seat body 5 during their descent. During the descent, the throttling orifice 512 of the secondary ball seat body 5 creates a throttling effect inside and outside the secondary ball seat body 5, which reduces the pressure difference between the inside and outside of the secondary ball seat body 5, thus reducing the descent kinetic energy of the secondary ball seat 3 and the secondary ball seat body 5. Ultimately, this ensures that the kinetic energy of the secondary ball seat 3 and the secondary ball seat body 5 is insufficient to penetrate the formation when they fall to the bottom of the well, thereby effectively improving the cementing success rate.

[0036] Although the invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A two-stage pressure-retaining ball seat assembly, characterized in that, The device includes a ball seat shell, a primary ball seat that seals with a sealing ball during primary pressure build-up, a secondary ball seat that seals with the primary ball seat during secondary pressure build-up, a primary ball seat body for mounting the primary ball seat, and a secondary ball seat body for mounting the secondary ball seat. The primary ball seat body is housed within the ball seat shell, and the secondary ball seat body is connected to the lower end of the primary ball seat body. The secondary ball seat body has a throttling through-hole connecting the inner and outer spaces of the body. The primary ball seat is mounted to the primary ball seat body via a primary shear pin, and the secondary ball seat body is mounted to the lower end of the primary ball seat body via a secondary shear pin. The primary ball seat body and the ball seat shell, as well as the secondary ball seat body and the secondary ball seat, are connected by threads. The throttling passage is configured to ensure that the pressure required to cut the secondary shear pin is sufficient, while simultaneously allowing the secondary ball seat and the secondary ball seat body to circulate the liquid inside and outside the secondary ball seat body during descent, thus generating a throttling effect.

2. The dual-stage pressure-retaining ball seat assembly according to claim 1, characterized in that, The throttling passage includes a plurality of throttling grooves arranged circumferentially along the secondary ball seat body, and each of the throttling grooves is arranged axially along the secondary ball seat body.

3. The dual-stage pressure-retaining ball seat assembly according to claim 1, characterized in that, The throttling passage includes multiple throttling holes, which are arranged in an array on the secondary ball seat body.

4. The dual-stage pressure-retaining ball seat assembly according to any one of claims 1 to 3, characterized in that, The strength of the secondary shear stud is less than that of the primary shear stud.

5. The dual-stage pressure-retaining ball seat assembly according to claim 4, characterized in that, A first sealing ring is provided between the primary ball seat and the primary ball seat body, and along the cement grout injection direction, the first sealing ring is located above the primary shear pin.

6. The dual-stage pressure-retaining ball seat assembly according to claim 5, characterized in that, A second sealing ring is provided between the primary ball seat body and the ball seat shell.

7. The dual-stage pressure-retaining ball seat assembly according to any one of claims 1 to 3, characterized in that, The bottom surface of the primary ball seat is a conical sealing surface, and the upper surface of the secondary ball seat is a sealing mating surface adapted to the conical sealing surface.

8. The dual-stage pressure-retaining ball seat assembly according to claim 7, characterized in that, The upper surface of the primary ball seat is provided with a tapered mating surface that seals with the sealing ball.

9. The two-stage pressure-retaining ball seat assembly according to any one of claims 1 to 3, characterized in that, The sealing ball includes a body and a sealing rubber layer, the sealing rubber layer being vulcanized on the outer surface of the body.

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