Underwater wellhead annular sealing assembly

Abstract

The utility model discloses an underwater wellhead annular sealing assembly which is arranged in an annular area between a high-pressure wellhead and a casing hanger and comprises a metal sealing body, an inner locking ring and an upper driving ring. The metal sealing body is provided with an outer side sealing point on the upper side and an inner side sealing point on the lower side, and the inner locking ring is arranged on the upper side of the metal sealing body in a sleeving mode and aligned with the outer side sealing point in position. When the metal sealing body is put down, the inner side sealing point firstly makes contact with the casing hanger through interference fit and activates the inner side seal, loads in the seal activation process are dispersed, and only the self weight of the metal sealing body and interference fit are used. The upper drive ring is lowered between the inner lock ring and the metal seal body, and the outer seal is activated by locking the inner lock ring. According to the step-by-step activation mechanism, the large load needed by simultaneous activation of seals on the two sides in a traditional design is avoided, and therefore the overall load in the seal activation process is reduced. The asymmetric structure design of the inner and outer sealing points effectively reduces the axial driving force.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sealing of marine underwater wellhead devices, and particularly relates to a ring-shaped sealing assembly of an underwater wellhead. BACKGROUND

[0002] The sealing system of a marine underwater wellhead device is crucial, which mainly includes wellhead sealing and annular sealing. The annular sealing particularly refers to the sealing structure between the hanger of each casing string in the well and the wellhead. This sealing mechanism builds a solid barrier in the annular area between the wellhead and the casing hanger by carefully designing the sealing surface of the wellhead, the casing hanger and the annular sealing assembly, and using special sealing installation tools, aiming to effectively prevent high-pressure oil and gas in the formation from entering the seabed.

[0003] The reliability of the annular sealing is extremely high, not only requiring the structure to have strong load-carrying capacity, but also needing to strictly control the tolerance capacity. However, in the prior art, in the face of a multiphase flow device containing corrosive medium, most designs use sealing bevels or conical protrusions for sealing. This approach has many shortcomings: (1) When the sealing body is subjected to downward pressure, it needs to be in close contact with the inner diameter of the wellhead and the casing hanger, which results in a significant increase in the load required for sealing activation; (2) The sealing protrusion lacks sufficient support when subjected to extrusion pressure, which can cause significant damage to the metal sealing surface and the sealing protrusion itself; (3) The elastic deformation capacity of the metal seal is insufficient, and when there are scratches in the sealing position caused by underwater substances, the sealing effect will be greatly reduced. Once the precision of the fixed position cannot meet the requirements, the performance of the metal seal will be severely weakened. Therefore, the prior art needs to be further improved and enhanced. CONTENT OF THE UTILITY MODEL

[0004] The utility model provides a ring-shaped sealing assembly of an underwater wellhead, which at least solves or alleviates one or more technical problems in the prior art, or at least provides a beneficial alternative.

[0005] To achieve the above-mentioned purpose, the utility model provides the following technical scheme:

[0006] A ring-shaped sealing assembly of an underwater wellhead is arranged in the annular area between a high-pressure wellhead and a casing hanger, which comprises a metal sealing body, an inner locking ring and an upper driving ring. The metal sealing body is provided with an outer sealing point on the upper side and an inner sealing point on the lower side, and the inner locking ring is sleeved on the upper side of the metal sealing body with the outer sealing point in alignment. The outer sealing point is in contact with the high-pressure wellhead to form an outer seal, and the inner sealing point is in contact with the casing hanger to form an inner seal.

[0007] When the metal sealing body is lowered, the inner sealing point is activated by the interference fit with the contact of the casing hanger, and the upper driving ring is lowered between the inner locking ring and the metal sealing body to lock the inner locking ring and simultaneously activate the outer sealing.

[0008] By adopting the underwater wellhead annular sealing assembly of the present application, the asymmetric design of the inner and outer sealing points makes the inner sealing point first activated by the interference fit with the contact of the casing hanger when the metal sealing body is lowered, and the load during the sealing activation process is dispersed, because the activation of the inner sealing does not require additional external force, but only relies on the self-weight of the metal sealing body and the interference fit. Subsequently, the upper driving ring is lowered between the inner locking ring and the metal sealing body to simultaneously activate the outer sealing by locking the inner locking ring. This step-by-step activation mechanism avoids the large load required for the simultaneous activation of the two-sided sealing in the traditional design, thereby reducing the overall load during the sealing activation process. The asymmetric structure design of the inner and outer sealing points optimizes the activation sequence and mode of the inner and outer sealing points, thereby effectively reducing the axial driving force.

[0009] In the preferred implementation, the outer sealing point includes two circular-arc-shaped protrusions on the outer side of the metal sealing body and an outer rubber ring between the two circular-arc-shaped protrusions, and the inner sealing point includes two circular-arc-shaped protrusions on the inner side of the metal sealing body and an inner rubber ring between the two circular-arc-shaped protrusions.

[0010] The strength and rigidity of the metal material enable the sealing structure to withstand large axial and radial loads and prevent sealing failure caused by pressure changes. The rubber ring is located between the metal sealing protrusions and plays a flexible compensation role. The rubber material has good elasticity and sealing performance, which can fill the small gaps caused by scratches on the sealing surface, size deviation or sand intrusion, and ensure the tightness of the sealing.

[0011] In the preferred implementation, the outer rubber ring and the inner rubber ring are arranged in the groove provided on the metal sealing body, and the circular-arc-shaped protrusions are inclinedly arranged towards the groove direction, so that the outer rubber ring and the inner rubber ring can support the circular-arc-shaped protrusions and enhance the sealing effect.

[0012] The rubber ring is located between the protrusions and the groove, providing additional support for the protrusions. This support effectively prevents the circular-arc-shaped protrusions from being damaged due to excessive bending during the extrusion process, thereby maintaining their original strength and sealing performance.

[0013] In the preferred implementation, the inner locking ring has a notch to allow the ring to elastically deform when subjected to external force.

[0014] In the preferred implementation, the casing hanger is provided with a locking ring groove, the shape of the locking ring groove is adapted to the outer contour of the inner locking ring, and the upper driving ring extrudes the inner locking ring into the locking ring groove to fix the inner locking ring.

[0015] In the preferred implementation, the inner locking ring is provided with a first inclined surface on the side facing the metal sealing body, and the upper driving ring is provided with a first opening inclined surface on the side facing the casing hanger.

[0016] In the preferred implementation, the metal sealing body is provided with a second inclined surface on the side facing the inner locking ring, and the upper driving ring is provided with a second opening inclined surface on the side facing the high-pressure wellhead.

[0017] When the upper driving ring is lowered and contacts the inner locking ring and the metal sealing body, the first opening inclined surface and the second opening inclined surface on the upper driving ring respectively contact the first inclined surface of the inner locking ring and the second inclined surface of the metal sealing body. Due to the presence of the inclined surfaces, a component perpendicular to the inclined surface is generated on the contact surface, which produces a translation effect along the direction of the inclined surface to simultaneously activate the outer seal and the locking of the inner locking ring.

[0018] In the preferred implementation, the inner locking ring is provided with a first vertical guide surface on the side facing the high-pressure wellhead, and the first vertical guide surface is located above the first inclined surface. The metal sealing body is provided with a second vertical guide surface on the side facing the inner locking ring, and the second vertical guide surface is located above the second inclined surface to vertically guide the upper driving ring.

[0019] In the preferred implementation, the metal sealing body is narrow on the top side and wide on the bottom side, and a stepped surface is formed between the top side and the bottom side. The inner locking ring is located above the stepped surface.

[0020] In the preferred implementation, the casing hanger is provided with a first bearing shoulder and a second bearing shoulder. The first bearing shoulder abuts the bottom end of the metal sealing body, and the second bearing shoulder contacts the outer wall of the inner locking ring to reduce the load on the metal sealing body.

[0021] The above scheme has the following beneficial effects:

[0022] 1. The sealing system has a small activation force, the outer seal point and the inner locking ring position are aligned, the complicated design of the driving ring is simplified, and the locking of the inner locking ring and the outer seal can be simultaneously activated.

[0023] 2. By combining the advantages of metal and non-metal seals, the non-metal seal can effectively assist the metal seal at low pressure to improve the overall sealing effect. At high pressure, the metal seal plays a leading role to ensure the reliability and stability of the seal. The sealing performance of the annulus between the high-pressure wellhead and the casing hanger is significantly improved.

[0024] 3. The inner side of the metal seal will have frictional contact with the casing hanger during lowering, but due to its small structural stiffness, the friction force is very limited, avoiding excessive lowering force and unnecessary friction damage, prolonging the service life of the metal seal.

[0025] 4. The high-pressure wellhead sealing surface and the casing hanger sealing surface corresponding to the metal sealing point are vertical surfaces, and the length of the sealing surface is much greater than the effective contact length of the circular-arc protrusion, so that the sealing position has good fault tolerance in up-down deviation.

[0026] 5. The metal sealing body is made of corrosion-resistant metal material. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings, which are included to provide a further understanding of the present application and are incorporated in and constitute a part of this application, illustrate embodiments of the present application and serve to explain the principles of the present application. In the drawings:

[0028] Figure 1 a schematic diagram of an exemplary implementation state of the underwater wellhead annular sealing assembly of the present application is shown;

[0029] Explanation of reference signs:

[0030] 1. high-pressure wellhead; 2. casing hanger; 20. locking ring groove; 21. first bearing shoulder; 22. second bearing shoulder; 3. metal sealing body; 30. circular-arc protrusion; 31. outer rubber ring; 32. inner rubber ring; 33. groove; 34. second inclined surface; 35. stepped surface; 36. second vertical guide surface; 4. inner locking ring; 40. first inclined surface; 41. first vertical guide surface; 5. upper driving ring. DETAILED DESCRIPTION

[0031] Hereinafter, only certain exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit and scope of the present application. Therefore, the drawings and the description are considered to be exemplary in nature rather than limiting.

[0032] In the description of the present application, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through an intermediate medium.

[0033] In the utility model, unless another definite provision and limitation, the terms "mount", "link", "connect", "fix" and so on should do the broad sense understanding, for example, can be fixed connection, also can be detachable connection, or be integrated;Can be direct connection, also can pass through the indirect connection of intermediate medium, can be the communication of two element internals or the interaction of two element.But note direct connection, it is explained that the two main bodies between the connection do not pass through the construction connection relationship of excessive structure, only through the connection structure is connected to form a whole.For the ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific situation.

[0034] In the utility model, the description such as "first", "second" is only used for the purpose of description, and can not be understood as indicating or implying the relative importance of the relative importance or implicitly indicating the number of the indicated technical features.Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one feature.

[0035] The utility model will be described below in conjunction with the drawings of the specification.

[0036] The specific scheme adopted is:

[0037] As shown in Figure 1 The utility model provides a kind of underwater wellhead annular sealing assembly, it is located between the annular region of high-pressure wellhead 1 and casing hanger 2, including metal sealing body 3, inner locking ring 4 and upper drive ring 5;Upper outside sealing point and lower inside sealing point are equipped in metal sealing body 3, inner locking ring 4 is sleeved on the upper side of metal sealing body 3 and outside sealing point position alignment;Outside sealing point and high-pressure wellhead 1 contact form outside seal, inside sealing point and casing hanger 2 contact form inside seal;

[0038] When metal sealing body 3 is placed, its inside sealing point is contacted with casing hanger 2 by interference fit and activates inside seal;Upper drive ring 5 is placed between inner locking ring 4 and metal sealing body 3, so that inner locking ring 4 is locked and outside seal is activated simultaneously, to reduce sealing activation load.

[0039] The above structure adopts an asymmetric design of the inner and outer sealing points, so that when the metal sealing body 3 is lowered, the inner sealing point first contacts the sleeve hanger 2 through interference fit and activates the inner sealing, dispersing the load during the sealing activation process. Since the activation of the inner sealing does not require additional external force, it only relies on the self-weight and interference fit of the metal sealing body 3. Subsequently, the upper driving ring 5 is lowered between the inner locking ring 4 and the metal sealing body 3, and the outer sealing is activated by locking the inner locking ring 4. This step-by-step activation mechanism avoids the large load required for simultaneous activation of the two-sided sealing in traditional designs, thereby reducing the overall load during the sealing activation process. The asymmetric structure design of the inner and outer sealing points optimizes the activation sequence and method of the inner and outer sealing points, thereby effectively reducing the axial driving force.

[0040] The alignment of the outer sealing point and the inner locking ring 4 simplifies the structure of the driving ring. In traditional designs, a complex driving mechanism is required to activate both sides of the sealing simultaneously. In the present design, the driving ring only needs to be simply lowered to the specified position to achieve the locking of the inner locking ring 4 and the activation of the outer sealing.

[0041] As a preferred embodiment of the present application, the outer sealing point includes two circular arc-shaped protrusions 30 on the outer side of the metal sealing body 3 and an outer rubber ring 31 between the two circular arc-shaped protrusions, and the inner sealing point includes two circular arc protrusions on the inner side of the metal sealing body 3 and an inner rubber ring 32 between the two circular arc-shaped protrusions 30.

[0042] The circular arc-shaped protrusions 30 on the metal sealing body 3 provide a solid support for the sealing structure, ensuring the stability of the sealing point in a high-pressure environment. The strength and rigidity of the metal material enable the sealing structure to withstand large axial and radial loads, preventing sealing failure due to pressure changes. The rubber ring is located between the metal sealing protrusions, serving as a flexible compensation. The rubber material has good elasticity and sealing properties, which can fill the small gaps caused by scratches on the sealing surface, size deviation or sand intrusion, ensuring the tightness of the sealing. In addition, the corrosion resistance of rubber also helps to prolong the service life of the sealing. The composite sealing design combines the rigidity of metal sealing and the flexibility of rubber sealing, effectively reducing the risk of sealing failure due to the deficiency of a single sealing material.

[0043] As a preferred embodiment of the present application, the outer rubber ring 31 and the inner rubber ring are arranged in the groove 33 provided on the metal sealing body 3, and the circular arc-shaped protrusions 30 are inclined towards the groove 33. The outer rubber ring 31 and the inner rubber ring can support the circular arc-shaped protrusions 30, enhancing the sealing effect.

[0044] During the pressing process under seal, the arc-shaped protrusion 30 inclines towards the direction of the groove 33, while the rubber ring is located between the protrusion and the groove 33, providing additional support for the protrusion. This support effectively prevents the arc-shaped protrusion 30 from being damaged due to excessive bending during the pressing process, thus maintaining its original strength and sealing performance. Due to the elasticity of the rubber ring, it can form better contact with the wellhead and casing hanger 2 during the sealing process. The arc-shaped protrusion 30 on the metal sealing body 3, combined with the rubber ring, forms multiple sealing guarantees. Even if the metal sealing surface is worn or aged due to long-term use, the rubber ring can still continue to provide effective sealing, thereby extending the service life of the sealing system.

[0045] As a preferred embodiment of the present application, the inner locking ring 4 has a notch to allow the ring to elastically deform when subjected to external force. When the upper driving ring 5 is placed between the inner locking ring 4 and the upper side of the metal seal and pressure is applied, the inner locking ring 4 can move and deform as necessary through its notch to accommodate and stabilize this pressing process.

[0046] Further, the casing hanger 2 is specially designed with a locking ring groove 20, which precisely matches the outer contour of the inner locking ring 4. When the upper driving ring 5 applies pressure to the inner locking ring 4, the inner locking ring 4 will be precisely pressed and embedded into the locking ring groove 20, thereby achieving stable fixation of the inner locking ring 4. This design ensures the tight connection between the inner locking ring 4 and the casing hanger 2, further enhancing the stability and reliability of the sealing system.

[0047] Referring to Figure 1 , the inner locking ring 4 is provided with a first inclined surface 40 on the side facing the metal sealing body 3, and the upper driving ring 5 is provided with a first opening inclined surface on the side facing the casing hanger 2, which is matched with the first inclined surface 40. The metal sealing body 3 is provided with a second inclined surface 34 on the side facing the inner locking ring 4, and the upper driving ring 5 is provided with a second opening inclined surface on the side facing the high-pressure wellhead 1, which is matched with the second inclined surface 34.

[0048] When the upper driving ring 5 is lowered and contacts the inner locking ring 4 and the metal sealing body 3, the first opening inclined surface and the second opening inclined surface on the upper driving ring 5 respectively form contact with the first inclined surface 40 of the inner locking ring 4 and the second inclined surface 34 of the metal sealing body 3. Due to the presence of the inclined surface, a component perpendicular to the inclined surface will be generated on the contact surface, which will produce a translation effect along the direction of the inclined surface.

[0049] The first inclined surface 40 contacts the first opening inclined surface: when the first opening inclined surface of the upper driving ring 5 contacts the first inclined surface 40 of the inner locking ring 4, the inner locking ring 4 will be subjected to a pushing force in the direction of the locking ring groove 20 due to the principle of force translation. This pushing force will cause the elastic deformation of the inner locking ring 4 and gradually be pressed into the locking ring groove 20 of the casing hanger 2, thereby realizing the fixation of the inner locking ring 4. At the same time, when the second opening inclined surface of the upper driving ring 5 contacts the second inclined surface 34 of the metal sealing body 3, the same force translation effect will occur. This force will cause the metal sealing body 3 to be subjected to a pushing force in the direction of the high-pressure wellhead 1, thereby realizing the tightness of the outer seal.

[0050] Further, the first vertical guide surface 41 is arranged on the side of the inner locking ring 4 facing the high-pressure wellhead 1, and the second vertical guide surface 36 is arranged on the side of the metal sealing body 3 facing the inner locking ring 4, thereby vertically guiding the upper driving ring 5.

[0051] The first vertical guide surface 41 on the inner locking ring 4 and the second vertical guide surface 36 on the metal sealing body 3 provide precise vertical guidance for the upper driving ring 5. When the upper driving ring 5 is lowered, it will first contact these two vertical guide surfaces, thereby ensuring its stable movement in the vertical direction. The design of the vertical guide surface can effectively prevent the upper driving ring 5 from tilting or deviating from the vertical direction during movement. After precise guidance by the vertical guide surface, the upper driving ring 5 will smoothly enter the inclined support stage. At this time, the first opening inclined surface and the second opening inclined surface on the upper driving ring 5 will respectively contact the first inclined surface 40 of the inner locking ring 4 and the second inclined surface 34 of the metal sealing body 3, and produce force translation effect, thereby reducing the operation difficulty and cost.

[0052] Referring to Figure 1 , the metal sealing body 3 is narrow on the upper side and wide on the lower side, and a stepped surface 35 is formed between the upper and lower sides, and the inner locking ring 4 is arranged on the upper side of the stepped surface 35. The stepped surface 35 is designed to be horizontal, thereby providing a stable support surface for the inner locking ring 4. When the upper driving ring 5 applies a pushing force to the inner locking ring 4, the inner locking ring 4 will move along the stepped surface 35 until it is fixed in the locking ring groove 20 of the casing hanger 2. This design simplifies the translation process of the inner locking ring 4 and improves the convenience of operation.

[0053] As a preferred embodiment of the present application, the casing hanger 2 is provided with a first load bearing shoulder 21 and a second load bearing shoulder 22. The first load bearing shoulder 21 abuts against the bottom end of the metal sealing body 3, and the second load bearing shoulder 22 contacts the outer wall of the inner locking ring 4 to reduce the load on the metal sealing body 3. The first load bearing shoulder 21 abuts against the bottom end of the metal sealing body 3, forming a stable support point. When the metal sealing body 3 is subjected to downward pressure, this pressure will be effectively transmitted to the first load bearing shoulder 21. This design ensures that the metal sealing body 3 will not be damaged by overloading when subjected to pressure, and also improves its stability. The second load bearing shoulder 22 contacts the outer wall of the inner locking ring 4, providing an additional support point for the inner locking ring 4. During the process of the inner locking ring 4 being pressed by the upper driving ring 5 and fixed in the locking ring groove 20 of the casing hanger 2, the second load bearing shoulder 22 can share part of the load. Through the design of the first load bearing shoulder 21 and the second load bearing shoulder 22, the load is effectively dispersed to the casing hanger 2, thereby reducing the load on the metal sealing body 3 and the inner locking ring 4. This helps to prolong the service life of the equipment and improve its reliability.

[0054] The parts not described in the present application can be realized by using or referring to the existing technology.

[0055] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any skilled person in the art can easily think of various changes or substitutions within the technical scope disclosed by the present application, and these should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An underwater wellhead annular seal assembly, provided in the annulus area between the high-pressure wellhead and the casing hanger, characterized in that: It includes a metal sealing body, an inner locking ring and an upper driving ring; the metal sealing body is provided with an outer sealing point on the upper side and an inner sealing point on the lower side; the inner locking ring is arranged on the upper side of the metal sealing body and aligned with the outer sealing point; the outer sealing point contacts the high-pressure wellhead to form an outer seal, and the inner sealing point contacts the casing hanger to form an inner seal; When the metal seal body is lowered, its inner sealing point contacts the sleeve hanger through interference fit to activate the inner seal; the upper drive ring is lowered between the inner locking ring and the metal seal body, so that the inner locking ring is locked and the outer seal is activated at the same time to reduce the seal activation load.

2. The underwater wellhead annular seal assembly according to claim 1, characterized in that: The outer sealing point includes two arc-shaped protrusions on the outer side of the metal sealing body and an outer rubber ring between the two circular arc-shaped protrusions; the inner sealing point includes two arc-shaped protrusions on the inner side of the metal sealing body and an inner rubber ring between the two circular arc-shaped protrusions.

3. The underwater wellhead annular seal assembly according to claim 1, characterized in that: The outer rubber ring and the inner rubber ring are arranged in the groove set in the metal sealing body, and the arc-shaped protrusion is arranged inclined toward the groove. The outer rubber ring and the inner rubber ring can support the arc-shaped protrusion to enhance the sealing effect.

4. The underwater wellhead annular seal assembly according to claim 1, characterized in that: The inner locking ring has a notch to allow the ring to be elastically deformed when subjected to external force.

5. The underwater wellhead annular seal assembly according to claim 1, characterized in that: The sleeve is hung with a locking ring groove, the shape of which is adapted to the outer contour of the inner locking ring, and the upper driving ring squeezes the inner locking ring into the locking ring groove to fix the inner locking ring.

6. The underwater wellhead annular seal assembly according to claim 1, characterized in that: The inner lock ring is provided with a first inclined surface on a side facing the metal sealing body, and the upper drive ring is provided with a first expansion inclined surface matching the first inclined surface on a side facing the casing hanger.

7. The underwater wellhead annular seal assembly according to claim 6, characterized in that: The metal sealing body is provided with a second inclined surface on a side facing the inner lock ring, and the upper driving ring is provided with a second expansion inclined surface matched with the second inclined surface on a side facing the high-pressure wellhead.

8. The underwater wellhead annular seal assembly according to claim 7, characterized in that: The inner locking ring is provided with a first vertical guide surface facing the high-pressure wellhead surface, and the first vertical guide surface is located above the first inclined surface. The upper side of the metal sealing body is provided with a second vertical guide surface facing the inner locking ring surface, and the second vertical guide surface is located above the second inclined surface to vertically guide the upper drive ring.

9. The underwater wellhead annular seal assembly according to claim 1, characterized in that: The metal sealing body is narrow on the upper side and wide on the lower side, and a step surface is formed between the upper and lower sides. The inner locking ring is arranged on the upper side of the step surface.

10. The underwater wellhead annular seal assembly according to claim 1, characterized in that: The sleeve is hung with a first bearing shoulder and a second bearing shoulder, the first bearing shoulder abuts against the bottom end of the metal sealing body, and the second bearing shoulder contacts the outer wall of the inner locking ring to reduce the load on the metal sealing body.

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