Oil and gas wellhead rotary sealing device suitable for workover treatment

Abstract

The invention relates to the technical field of oil and gas wellhead sealing equipment in the field of petroleum engineering, and discloses an oil and gas wellhead rotary sealing device suitable for workover treatment. The device consists of a bottom flange, a self-sealing middle body, a central pipe, a rotor upper body, a thrust bearing, a tapered roller bearing, a deep groove ball bearing, a lower rubber ring, an upper rubber ring, an upper rubber ring compression ring, a lower rubber ring compression ring, a gland and a positioning pin, is simple in structure, small in size and light in weight, adopts an integrated design, reduces redundant parts, is compact in overall structure, is convenient to mount and carry on site, and is convenient to maintain and maintain. The load burden of a wellhead is reduced; the sealing pressure is small, the sealing performance is good, reliable sealing can be achieved under the low pre-tightening pressure through the synergistic effect of mechanical pre-sealing and hydraulic sealing, and the sealing stability under the high-pressure working condition is effectively improved through the double-sealing mode; due to the design of the three-bearing structure and the detachable central pipe, the operation stability of the device under the complex working conditions of rotation, drilling and the like is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas wellhead sealing equipment technology in the petroleum engineering field, specifically a rotary sealing device for oil and gas wellheads suitable for well workover operations. Background Technology

[0002] Currently, rotary sealing devices for oil and gas wellheads are mainly suitable for drilling operations, but not for well workover operations. Specifically: (1) Current rotary sealing devices for oil and gas wellheads have complex structures, are large and heavy, and have limited lifting capacity for workover rigs. They cannot meet the weight requirements for lifting at the workover site. (2) Drilling operations typically use multiple mud pumps to provide sealing pressure to the rotary sealing device, usually above 20 MPa. Workover operations typically use a single pump truck to provide sealing pressure, usually below 15 MPa. Insufficient sealing pressure results in poor sealing performance, and current rotary sealing devices cannot meet the sealing pressure requirements at the workover site. Therefore, it is urgent to design a rotary sealing device for oil and gas wellheads that is simple in structure, small in size and weight, has low sealing pressure, and good sealing performance, suitable for workover operations. Summary of the Invention

[0003] In view of the above situation and to overcome the defects of the prior art, the present invention provides a rotary sealing device for oil and gas wellheads suitable for well workover operations, which effectively solves the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a rotary sealing device for oil and gas wellheads suitable for well workover operations, comprising a bottom flange, a self-sealing middle body, a central tube, an upper rotor body, a thrust bearing, a tapered roller bearing, a deep groove ball bearing, a lower rubber ring, an upper rubber ring, an upper rubber ring pressure ring, a lower rubber ring pressure ring, a pressure cap, and a positioning pin; The bottom flange is fixedly connected to the self-sealing middle body by bolts. The center tube is installed inside the self-sealing middle body. The upper end of the center tube is positioned with the upper rotor body by the positioning pin. The upper rotor body is fixed to the pressure cap by bolts. The deep groove ball bearing, the tapered roller bearing, and the thrust bearing are installed sequentially from top to bottom on the outside of the center tube. The upper rubber ring is fixed to the inner side of the upper part of the self-sealing middle body by the upper rubber ring pressure ring. The lower rubber ring is fixed to the inner side of the lower part of the bottom flange by the lower rubber ring pressure ring. The bottom flange consists of an upper flange connection surface, a stepped transition section, and a lower flange connection surface. The upper flange connection surface is connected to the self-sealing body, and the lower rubber ring and the lower rubber ring pressure ring are located within the stepped transition section.

[0005] Preferably, both the upper and lower rubber rings are annular structures, and are fixed to the self-sealing body and the inner wall of the bottom flange via grooves.

[0006] Preferably, the upper rubber ring and the lower rubber ring are annular rubber parts, respectively fitted on the outside of the central tube and axially limited by the corresponding pressure ring.

[0007] Preferably, the positioning pin is a cylindrical structure, evenly arranged circumferentially at the junction of the rotor body and the central tube to achieve circumferential positioning of the two.

[0008] Preferably, the thrust bearing, the tapered roller bearing, and the deep groove ball bearing are installed separately, with the thrust bearing located at the bottom, the tapered roller bearing located in the middle, and the deep groove ball bearing located at the top, together supporting the central tube; The thrust bearing is located within the stepped transition section, the tapered roller bearing is located within the self-sealing body, and the deep groove ball bearing is located within the self-sealing body.

[0009] Preferably, the upper rubber ring is axially positioned by the upper rubber ring pressure ring, and the lower rubber ring is axially positioned by the lower rubber ring pressure ring. When the bolts of the pressure cover and the upper body of the rotor are tightened, the pressure ring applies axial pre-pressure to the rubber ring, causing the rubber ring to undergo radial deformation to achieve mechanical pre-sealing. High-pressure oil enters the sealing cavity outside the rubber ring through the bottom flange, causing the rubber ring to further contract radially to achieve hydraulic sealing, thus forming an overall dual-sealing mode of mechanical pre-sealing and hydraulic sealing.

[0010] Preferably, the gland is connected to the rotor body by bolts, and the preload can be adjusted axially by tightening or loosening the bolts; The bottom flange adopts a stepped cross-section transition to withstand the axial pressure and radial load from the self-sealing body, while providing positioning support for the pressure ring and pressure ring to ensure sealing stability.

[0011] Preferably, the thrust bearing, the tapered roller bearing, and the deep groove ball bearing form a three-bearing structure. The upper part is the deep groove ball bearing, which supports the radial load of the central tube and ensures smooth rotation; the middle part is the tapered roller bearing, which can withstand bidirectional radial loads and assist in alignment, ensuring the coaxiality of the central tube and the self-sealing body; the lower part is the thrust bearing, which is specifically designed to withstand the axial thrust generated during drilling operations. The three bearings work together to meet the functional requirements of device rotation, bearing axial thrust, and alignment.

[0012] Preferably, the inner surface of the central tube adopts a three-step structure. The first step is a scraping step, with an annular scraping groove on its inner wall, which can scrape away mud, sand and impurities from the drill bit surface. The second step is a sealing step, which cooperates with the rubber ring to form a sealing surface. The third step is a flow guiding step, with a spiral flow guiding groove on its inner wall, which can guide the well washing fluid to flow along the inner surface of the central tube during well washing operations, clean residual impurities, and realize the functions of layered scraping, sealing and online cleaning. A threaded connection section is machined on the outer side of the top of the central tube, and the threaded connection section is threadedly connected to a threaded groove located inside the lower side of the rotor body.

[0013] Preferably, the central tube and the upper body of the rotor are circumferentially positioned by the positioning pin and axially pressed and fixed by the pressure cap; During drilling operations, the pressure cap and the positioning pin can be removed to take out the entire central tube, avoiding frequent contact and friction between the drill bit and the inner surface of the central tube, thereby reducing wear on the central tube and extending its service life.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a rotary sealing device for oil and gas wellheads suitable for well workover operations. It has a simple structure and small size and weight. The device adopts an integrated design, which reduces redundant parts. The overall structure is compact, which is convenient for on-site installation and transportation, and reduces the load on the wellhead. 2. This invention provides a rotary sealing device for oil and gas wellheads suitable for well workover operations, which has low sealing pressure and good sealing performance: through the synergistic effect of mechanical pre-sealing and hydraulic sealing, reliable sealing can be achieved under low pre-tightening pressure, and the dual sealing mode effectively improves the sealing stability under high pressure conditions; 3. This invention provides a rotary sealing device for oil and gas wellheads suitable for well workover operations, which is stable and reliable: the three-bearing structure and the design of the detachable central tube ensure the stability of the device under complex working conditions such as rotation and drilling, reduce component wear and failure risk, and improve the overall service life. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0016] In the attached diagram: Figure 1 This is a full sectional view of a rotary sealing device for oil and gas wellheads suitable for well workover operations, provided by the present invention.

[0017] Figure 2 The present invention provides a structural diagram of a rotary sealing device for oil and gas wellheads suitable for well workover operations.

[0018] Figure 3 This invention provides an internal structural diagram of a rotary sealing device for oil and gas wellheads suitable for well workover operations.

[0019] Figure 4 A top view of an oil and gas wellhead rotary sealing device suitable for well workover operations provided by the present invention.

[0020] Figure 5 The present invention provides a structural diagram of the central tube of a rotary sealing device for oil and gas wellheads suitable for well workover operations.

[0021] Figure 6 The present invention provides a structural diagram of a self-sealing base for a rotary sealing device for oil and gas wellheads suitable for well workover operations.

[0022] In the diagram: 1. Bottom flange; 2. Self-sealing middle body; 3. Central tube; 4. Rotor upper body; 5. Thrust bearing; 6. Tapered roller bearing; 7. Deep groove ball bearing; 8. Lower rubber ring; 9. Upper rubber ring; 10. Upper rubber ring pressure ring; 11. Lower rubber ring pressure ring; 12. Gland; 14. Locating pin; 3.1 Threaded connection section; 3.2 Scraping step; 3.3 Sealing step; 3.4 Guide step; 1.1 Upper flange connection face; 1.2 Lower flange connection face; 1.3 Step transition section. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] like Figure 1-6 As shown, the present invention provides a rotary sealing device for oil and gas wellheads suitable for well workover operations, which consists of a bottom flange 1, a self-sealing middle body 2, a central tube 3, a rotor upper body 4, a thrust bearing 5, a tapered roller bearing 6, a deep groove ball bearing 7, a lower rubber ring 8, an upper rubber ring 9, an upper rubber ring pressure ring 10, a lower rubber ring pressure ring 11, a pressure cap 12, and a positioning pin 14. The bottom flange 1 is fixedly connected to the self-sealing middle body 2 by bolts. The center tube 3 is installed inside the self-sealing middle body 2. The upper end of the center tube 3 is positioned with the rotor upper body 4 by the positioning pin 14. The rotor upper body 4 is fixed to the pressure cover 12 by bolts. The deep groove ball bearing 7, the tapered roller bearing 6, and the thrust bearing 5 are installed sequentially from top to bottom on the outside of the center tube 3. The upper rubber ring 9 is fixed to the upper inner side of the self-sealing middle body 2 by the upper rubber ring pressure ring 10. The lower rubber ring 8 is fixed to the lower inner side of the bottom flange 1 by the lower rubber ring pressure ring 11. The bottom flange 1 consists of an upper flange connection surface 1.1, a stepped transition section 1.3, and a lower flange connection surface 1.2. The upper flange connection surface 1.1 is connected to the self-sealing body 2, and the lower rubber ring 8 and the lower rubber ring pressure ring 11 are located within the stepped transition section 1.3.

[0025] Advantageously, both the upper rubber ring 10 and the lower rubber ring 11 are annular structures, and are fixed to the self-sealing body and the inner wall of the bottom flange through a groove.

[0026] Advantageously, the upper rubber ring 9 and the lower rubber ring 8 are annular rubber parts, respectively fitted on the outside of the central tube 3 and axially limited by the corresponding pressure ring.

[0027] Advantageously, the positioning pin 14 is a cylindrical structure and is evenly arranged circumferentially at the junction of the rotor upper body 4 and the central tube 3 to achieve circumferential positioning between the two.

[0028] Advantageously, the thrust bearing 5, the tapered roller bearing 6, and the deep groove ball bearing 7 are installed separately, with the thrust bearing 5 located at the bottom, the tapered roller bearing 6 located in the middle, and the deep groove ball bearing 7 located at the top, together supporting the central tube 3; The thrust bearing 5 is located within the stepped transition section 1.3, the tapered roller bearing 6 is located within the self-sealing body 2, and the deep groove ball bearing 7 is located within the self-sealing body 2.

[0029] Advantageously, the upper rubber ring 9 is axially positioned by the upper rubber ring pressure ring 10, and the lower rubber ring 8 is axially positioned by the lower rubber ring pressure ring 11. When the bolts of the pressure cover 12 and the upper rotor body 4 are tightened, the pressure ring applies axial pre-pressure to the rubber ring, causing the rubber ring to undergo radial deformation to achieve mechanical pre-sealing. High-pressure oil enters the sealing cavity outside the rubber ring through the bottom flange, causing the rubber ring to further contract radially to achieve hydraulic sealing, thus forming an overall dual-sealing mode of mechanical pre-sealing and hydraulic sealing.

[0030] Advantageously, the pressure cap 12 is connected to the rotor upper body 4 by bolts, and the preload can be adjusted axially by tightening or loosening the bolts; The bottom flange 1 adopts a stepped cross-section transition to withstand the axial pressure and radial load from the self-sealing body 2, while providing positioning support for the pressure ring and pressure ring to ensure sealing stability.

[0031] Advantageously, the thrust bearing 5, the tapered roller bearing 6, and the deep groove ball bearing 7 form a three-bearing structure. The upper part is the deep groove ball bearing 7, which supports the radial load of the central tube 3 and ensures smooth rotation; the middle part is the tapered roller bearing 6, which can withstand bidirectional radial loads and assist in alignment, ensuring the coaxiality of the central tube 3 and the self-sealing body 2; the lower part is the thrust bearing 5, which is specifically designed to withstand the axial thrust generated during drilling operations. The three bearings work together to meet the functional requirements of device rotation, bearing axial thrust, and alignment.

[0032] Advantageously, the inner surface of the central tube 3 adopts a three-step structure. The first step is a scraping step 3.2, with an annular scraping groove on its inner wall, which can scrape away mud, sand and impurities from the drill bit surface. The second step is a sealing step 3.3, which cooperates with the rubber ring to form a sealing surface. The third step is a flow guiding step 3.4, with a spiral flow guiding groove on its inner wall, which can guide the well washing fluid to flow along the inner surface of the central tube during well washing operations, clean residual impurities, and realize the functions of layered scraping, sealing and online cleaning. The outer side of the top of the central tube 3 is machined with a threaded connection section 3.1, which is threadedly connected to a threaded groove located inside the lower side of the rotor upper body 4.

[0033] Advantageously, the central tube 3 and the rotor upper body 4 are circumferentially positioned by the positioning pin 14 and axially pressed and fixed by the pressure cap 12; During drilling operations, the pressure cap 12 and the positioning pin 14 can be removed to take out the central tube 3 as a whole, avoiding frequent contact and friction between the drill bit and the inner surface of the central tube 3, thereby reducing wear on the central tube and extending its service life.

[0034] The specific working process of the rotary sealing device for oil and gas wellheads, which is suitable for well workover operations, provided by this invention is as follows: First, clean the bottom flange 1. After hoisting the rotary blowout preventer into place, tighten the diagonal flange bolts to complete the housing installation. The diagonal flange bolts connect to the lower flange connection surface 1.2. Then, remove the gland 12, place the upper rubber ring 9 and lower rubber ring 8 into the inner cavity, apply grease, and reinstall the gland 12. Pre-tighten the bolts to apply initial axial pressure to the rubber rings using the upper rubber ring pressure ring 10 and lower rubber ring pressure ring 11. The drill string, relying on its own weight and rotating motion, penetrates the inner hole of the central tube 3 until it is tightly connected to the drill string in the well. During the rotation of the drill string, it automatically aligns and centers. Tighten the bolts of the gland 12. Adjust the gland 12 to ensure there is no leakage from the upper rubber ring 9 and lower rubber ring 8. The axial pressure of the upper rubber ring pressure ring 10 and lower rubber ring pressure ring 11 causes radial deformation of the rubber rings, achieving mechanical pre-sealing.

[0035] Then, as the drill bit rotates, it drives the central tube 3 to rotate synchronously. The rubber ring adheres to the outer wall of the drill bit along with the central tube 3, maintaining a dynamic seal. The three bearing structures work together: the deep groove ball bearing 7 supports the radial load of the central tube 3, the tapered roller bearing 6 bears the bidirectional radial load and assists in alignment, and the thrust bearing 5 bears the axial thrust during drilling, ensuring stable operation of the device. The three-step structure on the inner surface of the central tube 3 scrapes away mud and sand impurities from its surface when the drill bit rotates. Finally, after the drilling and milling operation is completed, the pressure cap 12 should be removed when pulling the drill string out. The rubber ring should be pulled out along with the drill string, placed on the drill string, and stood upright on the drill table for later use to reduce wear on the rubber ring. After the drill string is completely pulled out, check the condition of the upper rubber ring 9, lower rubber ring 8, and bearings, and replace or maintain them if necessary. Then reset the device to prepare for the next operation.

[0036] The working principle of this invention is that the oil and gas wellhead rotary sealing device is installed on the wellhead during the workover. During the tripping and rotation of the downhole tubing, the sealing rubber core shrinks and deforms due to the self-sealing effect and the liquid pressure inside the downhole casing, gripping the drill string and sealing the annulus. At the same time, the rubber core and the central tube can rotate together with the drill string to seal the wellhead. Under low pressure, the pre-tightening force of the rubber core is used to achieve pre-sealing of the drill string.

[0037] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A rotary sealing device for oil and gas wellheads suitable for well workover operations, characterized in that: It consists of a bottom flange (1), a self-sealing middle body (2), a central tube (3), a rotor upper body (4), a thrust bearing (5), a tapered roller bearing (6), a deep groove ball bearing (7), a lower rubber ring (8), an upper rubber ring (9), an upper rubber ring pressure ring (10), a lower rubber ring pressure ring (11), a pressure cap (12), and a locating pin (14). The bottom flange (1) is fixedly connected to the self-sealing middle body (2) by bolts. The center tube (3) is installed inside the self-sealing middle body (2). The upper end of the center tube (3) is positioned with the rotor upper body (4) by the positioning pin (14). The rotor upper body (4) is fixed with the pressure cap (12) by bolts. The deep groove ball bearing (7), the tapered roller bearing (6), and the thrust bearing (5) are installed sequentially from top to bottom on the outside of the center tube (3). The upper rubber ring (9) is fixed to the upper inner side of the self-sealing middle body (2) by the upper rubber ring pressure ring (10). The lower rubber ring (8) is fixed to the lower inner side of the bottom flange (1) by the lower rubber ring pressure ring (11). The bottom flange (1) consists of an upper flange connection surface (1.1), a stepped transition section (1.3), and a lower flange connection surface (1.2). The upper flange connection surface (1.1) is connected to the self-sealing body (2), and the lower rubber ring (8) and the lower rubber ring pressure ring (11) are located within the stepped transition section (1.3).

2. The rotary sealing device for oil and gas wellheads suitable for well workover operations according to claim 1, characterized in that: Both the upper rubber ring pressure ring (10) and the lower rubber ring pressure ring (11) are annular structures, and are fixed to the self-sealing middle body and the inner wall of the bottom flange through the groove.

3. A rotary sealing device for oil and gas wellheads suitable for well workover operations according to claim 2, characterized in that: The upper rubber ring (9) and the lower rubber ring (8) are annular rubber parts, respectively fitted on the outside of the central tube (3) and axially limited by the corresponding pressure ring.

4. A rotary sealing device for oil and gas wellheads suitable for well workover operations according to claim 3, characterized in that: The positioning pin (14) is a cylindrical structure and is evenly arranged circumferentially at the junction of the rotor upper body (4) and the central tube (3) to achieve circumferential positioning of the two.

5. A rotary sealing device for oil and gas wellheads suitable for well workover operations according to claim 4, characterized in that: The thrust bearing (5), the tapered roller bearing (6), and the deep groove ball bearing (7) are installed separately. The thrust bearing (5) is located at the bottom, the tapered roller bearing (6) is located in the middle, and the deep groove ball bearing (7) is located at the top, together supporting the central tube (3). The thrust bearing (5) is located within the stepped transition section (1.3), the tapered roller bearing (6) is located within the self-sealing body (2), and the deep groove ball bearing (7) is located within the self-sealing body (2).

6. A rotary sealing device for oil and gas wellheads suitable for well workover operations according to claim 5, characterized in that: The upper rubber ring (9) is axially positioned by the upper rubber ring pressure ring (10), and the lower rubber ring (8) is axially positioned by the lower rubber ring pressure ring (11). When the bolts of the pressure cover (12) and the upper body of the rotor (4) are tightened, the pressure ring applies axial pre-pressure to the rubber ring, causing the rubber ring to undergo radial deformation to achieve mechanical pre-sealing. High-pressure oil enters the sealing cavity outside the rubber ring through the bottom flange, causing the rubber ring to further contract radially to achieve hydraulic sealing, thus forming an overall dual-sealing mode of mechanical pre-sealing and hydraulic sealing.

7. A rotary sealing device for oil and gas wellheads suitable for well workover operations according to claim 6, characterized in that: The pressure cap (12) is connected to the rotor upper body (4) by bolts, and the preload can be adjusted axially by tightening or loosening the bolts; The bottom flange (1) adopts a stepped cross-section transition to withstand the axial pressure and radial load from the self-sealing body (2), while providing positioning support for the pressure ring and pressure ring to ensure sealing stability.

8. A rotary sealing device for oil and gas wellheads suitable for well workover operations according to claim 7, characterized in that: The thrust bearing (5), the tapered roller bearing (6), and the deep groove ball bearing (7) form a three-bearing structure. The upper part is the deep groove ball bearing (7), which is used to support the radial load of the central tube (3) and ensure smooth rotation. The middle part is the tapered roller bearing (6), which can withstand bidirectional radial loads and assist in alignment, ensuring the coaxiality of the central tube (3) and the self-sealing body (2). The lower part is the thrust bearing (5), which is specifically designed to withstand the axial thrust generated during drilling operations. The three bearings work together to meet the functional requirements of device rotation, bearing axial thrust, and alignment.

9. A rotary sealing device for oil and gas wellheads suitable for well workover operations according to claim 8, characterized in that: The inner surface of the central tube (3) adopts a three-step structure. The first step is a scraping step (3.2), and its inner wall is provided with an annular scraping groove, which can scrape away mud, sand and impurities on the surface of the drill bit; the second step is a sealing step (3.3), which cooperates with the rubber ring to form a sealing surface; the third step is a flow guiding step (3.4), and its inner wall is provided with a spiral flow guiding groove, which can guide the well washing fluid to flow along the inner surface of the central tube during well washing operations, clean the residual impurities, and realize the functions of layered scraping, sealing and online cleaning. The top outer side of the central tube (3) is machined with a threaded connection section (3.1), which is threadedly connected to a threaded groove located inside the lower side of the rotor body (4).

10. A rotary sealing device for oil and gas wellheads suitable for well workover operations according to claim 9, characterized in that: The central tube (3) and the upper rotor body (4) are circumferentially positioned by the positioning pin (14) and axially pressed and fixed by the pressure cap (12); When working with the drill pipe, the pressure cap (12) and the positioning pin (14) can be removed to take out the central tube (3) as a whole, so as to avoid frequent contact and friction between the drill bit and the inner surface of the central tube (3), thereby reducing the wear of the central tube and extending its service life.

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