Air-tight seal screwed joint with pressure compensation self-balancing function

Abstract

A self-balancing airtight seal threaded connector with pressure compensation comprises a male connector and a female connector. An external thread part and an external sealing part are arranged on the male joint; an internal thread part and an internal sealing part are arranged on the female joint; the external thread part and the internal thread part are screwed and matched to realize threaded connection, and the external sealing part and the internal sealing part are abutted and matched to realize sealing; an annular external thread cavity is formed in the external thread sealing part of the male connector in the circumferential direction, and the external thread cavity communicates with the exterior of the male connector through a plurality of first communicating channels. An annular internal thread cavity is formed in the internal thread sealing part of the female connector in the circumferential direction, and the internal thread cavity is communicated with the interior of the female connector through a plurality of second communication channels. According to the invention, when the joint bears internal pressure or external pressure load action, a sealing part can obtain pressure compensation support of corresponding internal pressure or external pressure, so that the propping effect of medium pressure on a sealing surface is balanced, and the sealing capability of the joint is improved.

Description

Technical Field

[0001] The invention relates to the technical field of threaded joints, and in particular to an air-tight threaded joint with pressure compensation and self-balancing. Background Art

[0002] In oil and gas production, it is necessary to connect underground reservoirs and surface oil and gas collection equipment through oil well pipes to achieve the purpose of production. In order to facilitate the reuse of pipes, oil well pipes are often connected through threaded joints. At present, the main form of threaded joints is API standard thread. This thread form has a simple structure and strong versatility, but its bearing capacity is weak. In order to meet the bearing capacity requirements of pipes under complex working conditions, various steel pipe manufacturers have successively developed various new types of threaded joints, namely special threaded joints for oil casing. Among them, the high-performance oil casing gas-sealed threaded joint is a joint product specially used for gas well production and development. Its high gas-sealing performance ensures the production and development of high-pressure gas wells.

[0003] In the process of oil and gas field development, the integrity of the tubing is a crucial link. Once the tubing fails due to leakage, the annular pressure will cause operational risks and reduce the recovery rate of the oil and gas wells. In severe cases, it will cause serious leakage accidents such as fire, explosion, etc., which will lead to the scrapping of the oil and gas wells.

[0004] The sealing performance of the oil casing threaded joint will directly affect the integrity of the pipe string. The joint with good sealing performance can have excellent sealing performance under various load conditions, thus avoiding the failure of the pipe string integrity.

[0005] However, threaded joints are subjected to a variety of load conditions underground, including tension, compression, bending, torsion, etc. Major oil well pipe manufacturers have carried out a large number of excellent threaded joint structure designs in order to meet the high air sealing performance of the joints under complex load conditions.

[0006] Chinese patent CN201910289791.7 discloses an end face sealing ring structure of an external threaded joint for oil well pipes. When the steel pipe manufacturing factory connects the internal thread of the coupling to the external thread of the pipe body, by limiting the thickness of the sealing ring, the end face of the coupling is at the base of the first triangle or between the base and the vertex of the triangle. When the casing is lowered into the well, the other end face of the internal thread of the coupling is always located at the base of the triangle or between the base and the vertex of the triangle, meeting the API standard for the connection of oil pipes or casings. In this invention, the sealing ring is tightly matched with the inner surface of the middle part of the coupling to prevent the sealing ring from rotating when the field end thread is buckled, causing the factory end external thread to buckle. This invention method improves the axial compressive strength of API standard oil pipes or casings and reduces manufacturing costs. This invention achieves the sealing effect of the joint through an end face sealing ring structure of an external threaded joint for oil well pipes.

[0007] Chinese Patent CN201310335237.0 discloses a non-coupling multi-sealing variable tooth width wedge-shaped threaded oil well pipe structure, which includes an external threaded section of the pipe body, an internal threaded section of the pipe body, an oil well pipe body, a left internal threaded sealing section, a right external threaded sealing section, a right internal threaded sealing section and a left external threaded sealing section; the external threaded section of the pipe body is connected to the right end of the oil well pipe body, and a left external threaded sealing section is provided between the external threaded section of the pipe body and the oil well pipe body. A right external threaded sealing section is provided at the right end of the external threaded section of the pipe body. The internal threaded section of the pipe body is connected to the left end of the oil well pipe body. A right internal threaded sealing section is provided between the internal threaded section of the pipe body and the oil well pipe body. A left internal threaded sealing section is provided at the left end of the internal threaded section of the pipe body. The invention can significantly and effectively improve the high sealing performance, bending resistance, compressive load resistance and high anti-torque performance of the threaded joint connection.

[0008] Chinese Patent CN201510013286.1 discloses a threaded joint for extremely thick-walled oil well pipes, which can balance the ensuring of sealing performance and the prevention of wear under the condition of high external pressure in addition to high compressive force. By requiring the thickness ts of the pin seal and the ratio of shape parameters in the structure, the gas sealing performance requirements of the joint under high compressive load are met.

[0009] Chinese Patent CN98252196.0 discloses a special threaded over-torque protection joint for oil well pipes, which includes two parts: a pipe end and a pipe coupling. The threaded connection part includes a pitch shoulder, a metal sealing surface and a connecting thread. There is an over-torque protection shoulder lower than the thickness of the metal sealing surface between the torque shoulder and the metal sealing surface. When the thread bears over-torque and compressive load, the energy at the metal sealing part overflows through the over-torque protection shoulder before the metal sealing surface reaches the elastic limit, and no plastic deformation occurs at the metal sealing part, ensuring sealing.

[0010] Chinese Patent CN202121364839.5 discloses an oil casing joint for thermal recovery wells, including a coupling, a middle surface and a pipe body. The coupling and the pipe body are threadedly connected. The coupling and the pipe body have a common axis. The coupling is symmetrically arranged with respect to the middle surface. The inner wall of the coupling is provided with an internal thread, an internal shoulder and a sealing structure, an internal thread tooth top line, an internal thread pitch diameter line and an internal thread tooth bottom line. The internal thread is located between the internal thread tooth top line and the internal thread tooth bottom line; there are gaps between the tooth bottom and tooth top of the thread, which can store a certain amount of thread grease, and the lubrication effect between the threads is better, making the threads less likely to stick and fail; a metal-metal sealing structure is provided. This structural design uses an improved partial trapezoidal thread. During the repeated pulling and pressing of the joint, the load-bearing surfaces and guiding surfaces of the internal and external threads can maintain contact at the same time, improving the ability of the thread to resist repeated stretching and compression.

[0011] Chinese Patent CN202110715022.6 provides an oil casing joint and an oil casing assembly. The oil casing joint includes: an external thread joint; an internal thread joint threadedly connected to the external thread joint; wherein, along the direction parallel to the axis of the oil casing joint, a thread structure, a first groove, a sealing structure, a second groove and a shoulder structure are sequentially arranged between the external thread joint and the internal thread joint. The sealing structure includes a first sealing cone surface and a second sealing cone surface that is sealingly mated with a part of the first sealing cone surface. The first sealing cone surface is arranged on a part of the outer wall surface of the external thread joint, and the second sealing cone surface is arranged on a part of the inner wall surface of the internal thread joint. In the technical solution of this invention, the oil casing joint has excellent robust sealing performance and anti-compression performance under the action of combined loads.

[0012] In the above joint design, the structural optimization is mainly carried out in two aspects: enhancing the strength of the joint shoulder part and adopting a complex sealing structure, and a better sealing effect can be achieved.

[0013] However, as oil and gas production goes deeper and the pressure gets higher, the requirements for the sealing performance of threaded joints are also getting higher and higher. Therefore, it is necessary to continuously develop threaded joints with better sealing performance. Summary of the Invention

[0014] The purpose of the present invention is to provide a gas-tight threaded joint with pressure compensation and self-balancing, which has better sealing performance through the pressure compensation structure, so as to meet the gas-tight performance requirements under ultra-deep well and ultra-high pressure conditions.

[0015] To achieve the above object, the technical solution of the present invention is:

[0016] In the structural design of conventional oil casing threaded joints, a metal-to-metal sealing structure is usually adopted to ensure the sealing integrity of the joints. The metal-to-metal sealing structure realizes a certain contact pressure through the interference fit between the sealing contact surfaces, and prevents the leakage of the medium through this contact pressure, so as to achieve the sealing effect.

[0017] The metal-to-metal sealing structure has the advantages of large contact pressure, stable contact, high temperature resistance, and not easy to deform. However, affected by the strength of the metal material, the contact stress it can generate is limited. When the contact pressure is too large, the sealing contact surface will be stuck or plastically deformed during make-up, thus affecting the sealing effect of the joint.

[0018] However, with the development of current deep wells and ultra-deep wells, the formation medium pressure is getting higher and higher, and the requirements for the sealing performance of the joints are also getting higher and higher. The risk of sealing failure of the conventional sealing structure under ultra-high pressure conditions is also getting higher and higher.

[0019] See Figure 1, which shows the principle of the metal-to-metal sealing structure. After the connection is made up, due to the existence of interference, contact pressure will be formed between the metal sealing surfaces, and this contact pressure prevents the medium from passing through, thus achieving sealing. When the medium penetrates, the medium pressure acts on the metal sealing surfaces, canceling part of the contact pressure and making the sealing surfaces tend to separate. When the contact pressure is not sufficient to resist the medium pressure, the connection leaks and fails, as Figure 2 shown. Limited by factors such as the characteristics of the metal structure and material strength, there is also an upper limit to the contact stress between the metal sealing surfaces. When the contact stress exceeds the yield strength of the material, the metal material itself will undergo failure deformation.

[0020] However, with the increasingly harsh oilfield working conditions and the ever-increasing oil and gas production pressure, the existing metal-to-metal sealing structure has an increasingly high risk of failure when facing high-pressure media.

[0021] A gas-tight threaded connection with pressure compensation and self-balancing designed in the present invention includes a male connection and a female connection; an external thread portion and an external sealing portion are provided on the male connection; an internal thread portion and an internal sealing portion are provided on the female connection; the external thread portion and the internal thread portion are screwed together to achieve threaded connection, and the external sealing portion and the internal sealing portion are pressed tightly together to achieve sealing; wherein,

[0022] An annular external thread chamber is circumferentially provided inside the external thread sealing portion of the male connection, and the external thread chamber is communicated with the outside of the male connection through a plurality of first communication channels;

[0023] An annular internal thread chamber is circumferentially provided inside the internal thread sealing portion of the female connection, and the internal thread chamber is communicated with the inside of the female connection through a plurality of second communication channels.

[0024] Furthermore, the width of the internal thread chamber of the female connection and the external thread chamber of the male connection in the direction along the contact length of the sealing surface ≥ 1 / 2 of the contact length of the sealing surface.

[0025] Even further, the cross-sectional area of the first communication channel of the male connection and / or the second communication channel of the female connection ≤ 5% of the minimum cross-sectional area of the connection.

[0026] When the connection bears pressure:

[0027] 1. When the connection only bears internal pressure, there is pressure inside the pipe body and no pressure outside. The external thread sealing portion is in direct contact with the medium and is supported by the medium pressure; the internal thread chamber has the same pressure under the connection effect, thus providing additional support for the metal contact pressure and improving the sealing performance of the connection.

[0028] 2. When the joint only bears external pressure, there is pressure on the outer side of the pipe body but no pressure on the inner side. The inner thread sealing part can be supported by the medium pressure; the outer thread chamber has the same pressure under the connection effect, thereby providing additional support for the metal contact pressure and improving the sealing performance of the joint.

[0029] 3. When the joint receives both internal pressure and external pressure, the internal and external thread chambers act simultaneously, improving the sealing effect of the joint.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] By providing external and internal thread chambers that communicate with the outside of the male joint or the inside of the female joint inside the external and internal thread sealing parts of the male and female joints, the present invention enables the sealing part to obtain corresponding internal pressure or external pressure compensation support when bearing internal pressure or external pressure loads, thereby balancing the opening effect of the medium pressure on the sealing surface and improving the sealing ability of the joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the principle of the metal-to-metal sealing structure Figure 1 ;

[0033] Figure 2 is the principle of the metal-to-metal sealing structure Figure 2 ;

[0034] Figure 3 is the structural schematic diagram of the embodiment of the present invention;

[0035] Figure 4 is the exploded schematic diagram of the embodiment of the present invention;

[0036] Figure 5 is the enlarged schematic diagram of the mating and sealing structure of the male and female joints in the embodiment of the present invention;

[0037] Figure 6 is the sealing effect diagram when the joint is under internal pressure;

[0038] Figure 7 is the sealing effect diagram when the joint is under external pressure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] Referring to Figure 3 , Figure 4 , Figure 5 , the gas-tight threaded joint with pressure compensation and self-balancing of the present invention includes a male joint 1 and a female joint 2; an external thread part 11 and an external sealing part 12 are provided on the male joint 1; an internal thread part 21 and an internal sealing part 22 are provided on the female joint 2; the external thread part 11 is screwed and fitted with the internal thread part 21 to achieve threaded connection, and the external sealing part 12 and the internal sealing part 22 are pressed and fitted to achieve sealing; wherein,

[0040] An annular external thread chamber 13 is circumferentially provided inside the external sealing portion 12 of the male joint 1, and the external thread chamber 13 is communicated with the outside of the male joint 1 through a plurality of first communication channels 14;

[0041] An annular internal thread chamber 23 is circumferentially provided inside the internal sealing portion 22 of the female joint 2, and the internal thread chamber 23 is communicated with the inside of the female joint 2 through a plurality of second communication channels 24.

[0042] As Figure 5 shown, when the joints are screwed together, contact stress is generated between the external sealing portion 12 and the internal sealing portion 22 under interference fit to achieve joint sealing.

[0043] When the joint bears pressure:

[0044] 1. When the joint only bears internal pressure, as Figure 6 shown, there is pressure (arrows a, b, c) on the inner side of the pipe body and no pressure on the outer side. The external sealing portion 12 is in direct contact with the inner medium and is supported by the medium pressure (arrow a); It can be seen from Figure 3 that the internal thread chamber 23 is connected to the inner side of the pipe body through the second communication channel 24. Therefore, under the connection action, the internal thread chamber 23 has the same pressure as the inner side of the pipe body, thus providing further support for the metal contact pressure (arrow d), and this pressure is in the opposite direction to the leakage pressure (arrow c) and can be supplemented and balanced, thereby improving the joint sealing performance.

[0045] 2. When the joint only bears external pressure, as Figure 7 shown, there is pressure on the outer side of the pipe body and no pressure on the inner side. The internal sealing portion 22 is in direct contact with the outer medium and is supported by the outer medium pressure (arrow e); It can be seen from Figure 4 that the external thread chamber 13 is connected to the outer side of the pipe body through the first communication channel 14. Therefore, under the connection action, the external thread chamber 13 has the same pressure as the outer side of the pipe body, thus providing further support for the metal contact pressure (arrow f), and this pressure (arrow f) is in the opposite direction to the leakage pressure (arrow g) and can be supplemented and balanced, thereby improving the joint sealing performance.

[0046] Embodiment 1

[0047] The Φ339.7mm×12.09mm P110 specification is designed according to the solution of the present invention, adopting 4TPI threads, double-thread design, pitch 6.35mm, thread lead 12.70mm, taper 1:12, male and female thread tooth height 2.0mm, male and female thread guiding side tooth profile angle 30°, and load-bearing side tooth profile angle -3°. An external thread chamber is provided at the external thread sealing part and is connected to the outside of the pipe body through a communication channel; an internal thread chamber is provided at the internal thread sealing part and is connected to the inside of the pipe body through a communication channel. The contact length of the joint sealing surface is 6mm, and the minimum cross-sectional area of the joint is 12444mm 2 , the widths of the external thread chamber and the internal thread chamber along the contact length direction of the sealing surface are 3.5mm, and the cross-sectional areas of the first communication channel 14 and the second communication channel 24 are 450mm 2 .

[0048] Example 2

[0049] The Φ177.80mm×10.36mm P110 specification is designed according to the solution of the present invention, adopting 5TPI threads, double-thread design, pitch 5.08mm, thread lead 10.16mm, taper 1:12, male and female thread tooth height 1.60mm, male and female thread guiding side tooth profile angle 40°, and load-bearing side tooth profile angle 2°. An external thread chamber is provided at the external thread sealing part and is connected to the outside of the pipe body through a communication channel; an internal thread chamber is provided at the internal thread sealing part and is connected to the inside of the pipe body through a communication channel.

[0050] The contact length of the joint sealing surface is 4mm, and the minimum cross-sectional area of the joint is 5450mm 2 , the widths of the external thread chamber and the internal thread chamber along the contact length direction of the sealing surface are 2.5mm, and the cross-sectional areas of the first communication channel 14 and the second communication channel 24 are 190mm 2 .

Claims

1. A gas-tight threaded joint with pressure compensation and self-balancing, comprising a male joint and a female joint; an external thread portion and an external sealing portion are provided on the male joint; an internal thread portion and an internal sealing portion are provided on the female joint; the external thread portion is screwed with the internal thread portion to achieve threaded connection, and the external sealing portion and the internal sealing portion are pressed against each other to achieve sealing; characterized in that, An annular external thread chamber is circumferentially provided inside the external thread sealing portion of the male joint, and the external thread chamber is communicated with the outside of the male joint through a plurality of first communication channels; An annular internal thread chamber is circumferentially provided inside the internal thread sealing portion of the female joint, and the internal thread chamber is communicated with the inside of the female joint through a plurality of second communication channels.

2. The gas-tight threaded joint with pressure compensation and self-balancing according to claim 1, characterized in that, The width of the internal thread chamber of the female joint and the external thread chamber of the male joint in the length direction of the sealing surface contact is ≥ 1 / 2 of the sealing surface contact length.

3. The gas-sealed threaded joint with pressure compensation and self-balancing according to claim 1 or 2, characterized in that, The cross-sectional area of the first communication channel of the male joint and / or the second communication channel of the female joint is ≤ 5% of the minimum cross-sectional area of the joint.

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