An oil wellhead seal

Abstract

The utility model relates to an oil well mouth sealing device, including the gland, shell and oil well interface connected in proper order from top to bottom, and the channel of accommodating the vertical through of light pole is set up on the gland, shell and oil well interface, and the ball valve, movable inner sleeve and winding packing of series connection are provided in the shell, the packing and movable inner sleeve set up two pairs, and are respectively arranged in the upper and lower sides of ball valve, the movable inner sleeve is rubber material, and the packing winding forms the circular platform shape of wide upper narrow lower. The utility model solves the problem that the existing sealing device is poor in sealing performance and is easy to eccentric wear, has the advantages of good sealing effect, self -adaptation adjustment, strong corrosion resistance, safety splash -proof, and is applicable to various high -pressure corrosion oil well working conditions.

Description

Technical Field

[0001] This utility model belongs to the field of oil and gas extraction technology, and specifically relates to an oil wellhead sealing device. Background Technology

[0002] In oil and gas extraction, wellhead sealing devices, as key sealing components between the polished rod and the wellhead, directly affect oil production efficiency and operational safety. Existing wellhead sealing devices generally suffer from the following technical defects: First, the sealing structure design is simplistic, often employing single-stage packing seals, which are prone to failure under high-pressure oil well conditions, leading to oil and gas leaks and even splashing risks, polluting the environment and posing safety hazards. Second, the polished rod is prone to uneven wear during reciprocating motion, and existing devices lack effective automatic alignment mechanisms. This uneven wear accelerates packing wear and shortens equipment lifespan.

[0003] For example, although the wellhead sealing device with the published patent number CN107355191A can achieve basic sealing, it does not have an adaptive adjustment structure designed to address the problem of uneven wear, and the sealing layers are insufficient, resulting in limited high-pressure sealing reliability. Therefore, the development of a sealing device that combines efficient sealing and automatic alignment functions has become an urgent need in the industry. Utility Model Content

[0004] In view of this, the purpose of this utility model is to address the shortcomings of the existing technology by providing an oil wellhead sealing device that can automatically align and is suitable for oil well sealing operations under high pressure conditions.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: An oil wellhead sealing device includes a pressure cap, a housing, and an oil well interface connected sequentially from top to bottom. The pressure cap, housing, and oil well interface are provided with a channel to accommodate a polished rod passing through vertically. Inside the housing, there is a ball valve, a movable inner sleeve, and a wound packing connected in series with the channel. Two pairs of packing and movable inner sleeves are provided and are respectively located on the upper and lower sides of the ball valve. The movable inner sleeve is made of rubber, and the packing is wound to form a frustum shape that is wider at the top and narrower at the bottom.

[0006] To better realize this utility model, the above structure is further optimized by providing a spring inside the pressure cap, which presses against the upper end face of the packing on the upper side.

[0007] To better realize this utility model, the above structure is further optimized, and the spring is a disc spring.

[0008] To better realize this utility model, the above structure is further optimized by providing an upper annular pressure cap between the spring and the upper end face of the packing.

[0009] To better realize this utility model, the above structure is further optimized by providing a lower annular pressure cap between the shell and the upper end face of the packing on the lower side.

[0010] To better realize this utility model, the above structure is further optimized. The ball valve is a three-way ball valve, and its other outlet is connected to the recovery pipeline.

[0011] To better realize this utility model, the above structure is further optimized. The two ends of the shell are fastened to the pressure cap and the oil well interface by an outer sleeve, and the packing and the movable inner sleeve are set inside the outer sleeve.

[0012] To better realize this utility model, the above structure is further optimized by providing multiple sealing rings between the shell and the two outer sleeves.

[0013] Compared with the prior art, this utility model has the following advantages: The wellhead sealing device provided by this utility model utilizes a two-stage frustum-shaped packing to form a double sealing structure. Relying on its own self-tightening characteristics and with the continuous pressure compensation of the spring, it can still maintain an effective seal under high pressure conditions of 10-40MPa. The sealing reliability is improved by more than 80% compared with the traditional single-stage seal. At the same time, it has an automatic alignment and anti-wear function. The movable inner cylinder adaptively adjusts with the tilt angle of the polished rod, so that the polished rod is always in the center position of the packing, reducing the wear to within 0.1mm and extending the service life of the packing by 5-8 times. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the structure of the oil wellhead sealing device of this utility model.

[0016] In the picture: 1-Cap, 2-Shell, 3-Well interface, 4-Slick rod, 5-Ball valve, 6-Modible inner sleeve, 7-Packing, 9-Spring, 10-Upper annular cap, 11-Lower annular cap, 12-Outer sleeve. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0018] In the description of this utility model, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0019] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0020] like Figure 1 As shown, the wellhead sealing device provided by this utility model includes a pressure cap 1, a housing 2, and an oil well interface 3 connected sequentially from top to bottom. The pressure cap 1, housing 2, and oil well interface 3 have channels for accommodating a polished rod 4 that passes vertically through them. Both ends of the housing 2 are fastened to the pressure cap 1 and the oil well interface 3 respectively via an outer sleeve 12. Multiple sealing rings are provided between the housing 2 and each of the two outer sleeves 12. The oil well interface 3 is a 2-7 / 8TBG model; its lower end is matched and connected to the oil well pipe, and its upper end is fixedly connected to the lower outer sleeve 12 via threads. The inner wall of the interface has an annular sealing groove, and an internal oil-resistant sealing ring achieves primary sealing.

[0021] The housing 2 contains a ball valve 5, a movable inner sleeve 6, and a wound packing 7 connected in series with the channel. The ball valve 5 is made of stainless steel, has a nominal pressure of 40MPa, a connection diameter of DN15, and is equipped with a manual operating handle and status indicator. It is located in the middle of the housing 2. The ball valve 5 is a three-way ball valve with two outlets, as shown in the figure. The smooth rod passes vertically through the inlet and the first outlet of the ball valve 5. Under normal conditions, the second outlet is closed and is connected to the recovery pipeline. When the lower primary seal fails, it can be opened to release pressure, prevent media splashing, and guide the leaked media for recovery.

[0022] Two pairs of packing 7 and movable inner sleeve 6 are provided, and are respectively installed inside the outer sleeve 12 on the upper and lower sides of the ball valve 5. The lower packing 7 is a primary seal, and the upper packing 7 is a secondary seal, forming a double sealing system. The movable inner sleeve 6 is made of rubber and is in movable contact with the outer sleeve 12. The angle can be adjusted within a range of ±5°. The inner wall of the movable inner sleeve 6 is clearance-fitted with the polished rod 4 to achieve automatic alignment of the polished rod 4 and avoid uneven wear. The contact surface between the movable inner sleeve and the outer sleeve 12 can be designed as a spherical surface, which can finely adjust the angle in any direction. In addition, a spherical bearing can be used. The surface of the spherical bearing is nitrided, and the movable angle adjustment range is ±5°, which can meet the polished rod deflection requirements of most oil wells.

[0023] Packing 7 is wound into a frustum shape, wider at the top and narrower at the bottom, with a trapezoidal cross-section. The body of Packing 7 is made of polytetrafluoroethylene-carbon fiber composite material, exhibiting excellent resistance to acids, alkalis, and oil and gas corrosion. It can operate stably for over 12 months in oil wells with sulfur content exceeding 5000ppm, far exceeding the service life of traditional packings. Packing 7 has an 8° inclination angle. The first-stage packing has a cross-sectional dimension of φ48mm at the bottom × φ60mm at the top × 80mm at the height, and the second-stage packing also has the same dimensions. The material contains 25% carbon fiber. Its top-wide, bottom-narrow shape provides excellent self-tightening properties, ensuring a tight fit against the inner wall of the packing cavity. The higher the packing is compressed, the better the self-tightening seal.

[0024] A disc spring 9 is installed inside the pressure cap 1, sleeved on the outside of the smooth rod 4, with a working stroke of 3-5mm. An upper annular pressure cap 10 is provided between the spring 9 and the upper end face of the packing 7. The upper annular pressure cap 10 is threaded to the inner wall of the pressure cap 1, and the tightness of the secondary packing is adjusted through the threaded connection to achieve precise control of the sealing force. The spring 9 is pressed against the upper end face of the upper annular pressure cap 10, and the upper end of the spring 9 is limited by the pressure cap 1. Utilizing the elastic compensation characteristics of the disc spring, the upper annular pressure cap 10 can only move downwards, continuously providing a stable clamping force to the packing 7 and compensating for the wear of the packing 7.

[0025] A lower annular pressure cap 11 is provided between the housing 2 and the upper end face of the packing 7 on the lower side. The lower annular pressure cap 11 has the same structure as the upper annular pressure cap 10 and is threaded to the inner wall of the housing 2. The tightness of the primary packing is adjusted through the threaded connection to achieve precise control of the sealing force. Both pressure caps are made of 45# steel with heat treatment, and the thread specification is M80×3mm. An annular sealing gasket groove is provided on the lower end face.

[0026] During assembly, the bottom well interface 3 is connected to the wellhead. The lower outer sleeve 12, movable inner sleeve 6, and primary packing are then installed sequentially. The lower annular pressure cap 11 is tightened to the preset torque. Next, the housing 2 and ball valve 5 are installed. Then, the upper outer sleeve 12, movable inner sleeve 6, and secondary packing are installed. Finally, the spring 9 and pressure cap 1 are installed. During use, the spring 9 automatically compensates for packing wear. The movable inner sleeve 6, acting as an anti-deflection mechanism, continuously adjusts the alignment of the polished rod 4. When the lower primary seal fails and leakage occurs, the ball valve is rotated to open the recovery pipeline and guide the recovery of the medium.

[0027] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

Claims

1. A wellhead sealing device, characterized in that: It includes a pressure cap (1), a housing (2) and an oil well interface (3) connected sequentially from top to bottom. The pressure cap (1), the housing (2) and the oil well interface (3) are provided with a channel to accommodate the vertical passage of the polished rod (4). The housing (2) is provided with a ball valve (5), a movable inner sleeve (6) and a wrapped packing (7) connected in series with the channel. The packing (7) and the movable inner sleeve (6) are provided in two pairs and are respectively provided on the upper and lower sides of the ball valve (5). The movable inner sleeve (6) is made of rubber. The packing (7) is wound to form a frustum shape that is wider at the top and narrower at the bottom.

2. The wellhead sealing device according to claim 1, characterized in that: The pressure cap (1) is provided with a spring (9) inside, which presses against the upper end face of the packing (7) on the upper side.

3. The wellhead sealing device according to claim 2, characterized in that: The spring (9) is a disc spring.

4. The wellhead sealing device according to claim 3, characterized in that: An upper annular pressure cap (10) is provided between the spring (9) and the upper end face of the packing (7) on the upper side.

5. The wellhead sealing device according to claim 4, characterized in that: A lower annular pressure cap (11) is provided between the housing (2) and the upper end face of the packing (7) on the lower side.

6. The wellhead sealing device according to claim 1, characterized in that: The ball valve (5) is a three-way ball valve, and its other outlet is connected to the recovery pipeline.

7. A wellhead sealing device according to any one of claims 1-6, characterized in that: The two ends of the housing (2) are fastened to the pressure cap (1) and the oil well interface (3) respectively through an outer sleeve (12), and the packing (7) and the movable inner sleeve (6) are arranged inside the outer sleeve (12).

8. The wellhead sealing device according to claim 7, characterized in that: Multiple sealing rings are provided between the housing (2) and the two outer sleeves (12).

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