An underwater wellhead cap

Abstract

This invention discloses a subsea wellhead corrosion-resistant cap, comprising a protective cap for being fitted onto the subsea wellhead, a liquid storage cylinder installed inside the protective cap, and a mandrel penetrating the liquid storage cylinder. The liquid storage cylinder has a liquid storage chamber, and the bottom of the liquid storage cylinder has a liquid outlet hole communicating with the liquid storage chamber. The top end of the mandrel protrudes from the protective cap, and the bottom end of the mandrel is located in the liquid outlet hole. The mandrel is slidable relative to the liquid storage cylinder to open and close the liquid outlet hole. This subsea wellhead corrosion-resistant cap is lowered to the top of the wellhead on the seabed using a delivery tool connected to the drill string until the protective cap is fitted onto the top of the wellhead. A portion of the liquid storage cylinder located inside the protective cap enters the subsea wellhead. At this point, only internal pressurization of the drill string is needed to drive the mandrel downward relative to the liquid storage cylinder, thereby opening the liquid outlet hole. This allows the corrosion-resistant liquid in the liquid storage chamber to be injected into the wellhead through the liquid outlet hole, completing the operation of adding corrosion-resistant liquid into the wellhead. This method eliminates the need for an underwater robot, is time-efficient, and has high timeliness and economy.

Description

Technical Field

[0001] This invention relates to the field of offshore oil drilling technology, and more particularly to a subsea wellhead anti-corrosion cap. Background Technology

[0002] In offshore oil and gas exploration and production using subsea wellhead systems, when temporary well abandonment is required, wellhead corrosion caps are necessary to protect the wellhead from damage caused by foreign objects dragging it, seawater corrosion, and contamination by rock cuttings and marine organisms. These caps typically also require corrosion-resistant fluid injection capabilities. Existing wellhead corrosion caps are usually inserted via wire rope. After reaching the operating water depth, an underwater robot is needed for installation and unlocking, a cumbersome and time-consuming process. When injecting corrosion-resistant fluid into the wellhead, an underwater robot carrying the injection pack must be used. Due to the limitations of underwater robots, this is particularly difficult when dealing with complex ocean currents and severe weather conditions. Therefore, developing a wellhead corrosion cap suitable for drill string insertion is essential. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a corrosion-resistant cap for underwater wellheads that facilitates the injection of corrosion-resistant liquid.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a subsea wellhead anti-corrosion cap, comprising a protective cap for being fitted onto the subsea wellhead, a liquid storage cylinder installed inside the protective cap, and a core rod disposed through the liquid storage cylinder; the liquid storage cylinder has a liquid storage cavity, and the bottom of the liquid storage cylinder is provided with a liquid outlet hole communicating with the liquid storage cavity; the top end of the core rod is exposed outside the protective cap, the bottom end of the core rod is disposed in the liquid outlet hole, and the core rod is slidable relative to the liquid storage cylinder to open and close the liquid outlet hole.

[0005] The beneficial effects of this invention are as follows: This subsea wellhead anti-corrosion cap is lowered to the top of the wellhead on the seabed by a delivery tool connected to the drill string until the cap is fitted onto the top of the wellhead. A portion of the liquid storage cylinder located inside the cap enters the subsea wellhead. At this point, it is only necessary to pressurize the drill string to drive the mandrel downward relative to the liquid storage cylinder, thereby opening the liquid outlet. The anti-corrosion liquid in the liquid storage chamber can then be injected into the wellhead through the liquid outlet, completing the operation of adding anti-corrosion liquid into the wellhead. This eliminates the need for an underwater robot, is time-efficient, and has high timeliness and economy. Attached Figure Description

[0006] Figure 1 This is a schematic diagram of the overall structure of the underwater wellhead anti-corrosion cap according to Embodiment 1 of the present invention;

[0007] Figure 2 This is a cross-sectional view of the anti-corrosion cap for the underwater wellhead according to Embodiment 1 of the present invention. Figure 1 ;

[0008] Figure 3 for Figure 2 Enlarged detail of section A in the middle;

[0009] Figure 4 This is a cross-sectional view of the anti-corrosion cap for the underwater wellhead according to Embodiment 1 of the present invention. Figure 2 (Work status);

[0010] Figure 5 This is a schematic diagram of the liquid storage cylinder in the anti-corrosion cap of the underwater wellhead according to Embodiment 1 of the present invention;

[0011] Figure 6 This is a partial exploded view of the anti-corrosion cap for the underwater wellhead according to Embodiment 1 of the present invention.

[0012] Label Explanation:

[0013] 1. Protective cap; 11. Assembly part; 111. Anti-rotation pin; 12. Protective sleeve; 121. Window; 122. Mounting slot;

[0014] 2. Liquid storage cylinder; 21. Mounting part; 211. J-shaped groove; 212. Limiting ring; 213. Anti-rotation groove; 22. Liquid storage part; 221. Liquid storage chamber; 222. Liquid outlet; 223. Filling hole; 224. Plug; 23. Flanged edge; 24. Shear pin;

[0015] 3. Mandrel; 31. Shear ring; 32. Sealing boss; 33. Third sealing ring; 34. First limiting boss;

[0016] 4. Locking claw; 41. Bending part; 42. Connecting part; 43. Locking part; 44. Rotating shaft;

[0017] 5. Elastic components;

[0018] 6. Seal the cap. Detailed Implementation

[0019] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0020] Please refer to Figures 1 to 6 A corrosion-resistant cap for a submersible wellhead includes a protective cap 1 for being fitted onto the submersible wellhead, a liquid storage cylinder 2 installed inside the protective cap 1, and a core rod 3 penetrating the liquid storage cylinder 2; the liquid storage cylinder 2 has a liquid storage cavity 221, and the bottom of the liquid storage cylinder 2 is provided with a liquid outlet hole 222 communicating with the liquid storage cavity 221; the top end of the core rod 3 is exposed outside the protective cap 1, and the bottom end of the core rod 3 is located in the liquid outlet hole 222, and the core rod 3 is slidable relative to the liquid storage cylinder 2 to open and close the liquid outlet hole 222.

[0021] As can be seen from the above description, the beneficial effects of the present invention are as follows: The subsea wellhead anti-corrosion cap is lowered to the top of the wellhead on the seabed by a delivery tool connected to the drill string until the cap 1 is fitted onto the top of the wellhead. A portion of the liquid storage cylinder 2 located inside the cap 1 enters the subsea wellhead. At this time, it is only necessary to pressurize the drill string to drive the mandrel 3 to move downward relative to the liquid storage cylinder 2, thereby opening the liquid outlet 222. The anti-corrosion liquid in the liquid storage chamber 221 can be injected into the wellhead through the liquid outlet 222, thus completing the operation of adding anti-corrosion liquid into the wellhead. There is no need to use an underwater robot, the time consumption is short, and it has high efficiency and economy.

[0022] Furthermore, the liquid storage cylinder 2 includes a mounting part 21 and a liquid storage part 22 connected below the mounting part 21. The liquid storage part 22 has a liquid storage cavity 221 and a liquid outlet 222. One end of the mounting part 21 away from the liquid storage part 22 is exposed on the protective cap 1. J-shaped grooves 211 are respectively opened on the outer peripheral surfaces of the mounting part 21 and the protective cap 1.

[0023] As described above, the anti-corrosion cap for this subsea wellhead can be connected to the feed tool on the drill string via the J-shaped groove 211.

[0024] Furthermore, a limiting ring 212 is fitted onto one end of the mounting part 21 that is exposed on the cap 1.

[0025] As described above, the limiting ring 212 is used to limit the relative position of the liquid storage cylinder 2 and the protective cap 1, and to prevent the liquid storage cylinder 2 and the protective cap 1 from separating.

[0026] Furthermore, the mounting part 21 and the protective cap 1 are respectively provided with anti-rotation pins 111 and anti-rotation slots 213 that cooperate with the anti-rotation pins 111.

[0027] As described above, the anti-rotation pin 111, when inserted into the anti-rotation slot 213, can prevent the liquid storage cylinder 2 and the protective cap 1 from rotating relative to each other, ensuring that the installation structure of each component of the underwater wellhead anti-corrosion cap remains stable, and providing sufficient torsional torque for the operating tools during operation.

[0028] Furthermore, the top of the liquid storage section 22 is provided with a filling hole 223 that communicates with the liquid storage chamber 221 and a plug 224 for sealing the filling hole 223.

[0029] As described above, by using the plug 224 to open the filling hole 223, the anticorrosive liquid can be injected into the liquid storage chamber 221 through the filling hole 223. Then, the plug 224 is used to close the filling hole 223, thus completing the anticorrosive liquid filling operation of the liquid storage cylinder 2.

[0030] Furthermore, the inner circumferential surface of the cap 1 is provided with a locking claw 4. The locking claw 4 includes a bent portion 41, a connecting portion 42 and a locking portion 43 connected sequentially from top to bottom. The connecting portion 42 is rotatably connected to the cap 1. The bent portion 41 bends and extends inward. The bent portion 41 is used to abut against the underwater wellhead to drive the locking portion 43 to rotate inward.

[0031] As described above, when the cap 1 is fitted onto the underwater wellhead, the peripheral wall of the wellhead will abut against the bent portion 41 of the locking claw 4, thereby driving the locking portion 43 to rotate inward until it fits against the locking groove on the outer peripheral surface of the wellhead, thereby locking the relative position of the underwater wellhead anti-corrosion cap and the wellhead, ensuring that the underwater wellhead anti-corrosion cap is aligned with the wellhead, and preventing the underwater wellhead anti-corrosion cap from loosening and falling off.

[0032] Furthermore, the liquid storage cylinder 2 is adjustable relative to the protective cap 1, and a protruding flange 23 is provided on the outer peripheral surface of the liquid storage cylinder 2. The bent portion 41 abuts against the bottom of the flange 23, and the bent portion 41 is rotatable relative to the protective cap 1 so that the bent portion 41 is separated from the flange 23.

[0033] As described above, during the insertion process, the bent portion 41 of the locking claw 4 is used to limit the relative height between the liquid storage cylinder 2 and the protective cap 1. When the protective cap 1 is fitted onto the underwater wellhead, the peripheral wall of the wellhead will abut against the bent portion 41 of the locking claw 4, thereby driving the locking portion 43 to rotate inward until it fits against the locking groove on the outer peripheral surface of the wellhead. At this time, the bent portion 41 separates from the flange 23, and the liquid storage cylinder 2 will sink relative to the protective cap 1 and penetrate into the wellhead until the flange 23 abuts against the peripheral wall of the wellhead. The outer side of the flange 23 abuts against the bent portion 41, preventing the locking portion 43 of the locking claw 4 from rotating away from the wellhead and causing the wellhead to unlock.

[0034] Furthermore, it also includes an elastic element 5, the two ends of which respectively abut against the liquid storage cylinder 2 and the protective cap 1, so that the liquid storage cylinder 2 moves downward relative to the protective cap 1.

[0035] As can be seen from the above description, when the liquid storage cylinder 2 loses the support of the bending part 41, the elastic member 5 will apply a downward elastic force to the liquid storage cylinder 2 to help the liquid storage cylinder 2 descend into place.

[0036] Furthermore, it also includes a cover 6 and a pivot 44. A window 121 is provided on the peripheral wall of the cap 1. The two sides of the opening of the window 121 on the outer peripheral surface of the cap 1 are respectively recessed to form mounting grooves 122. The pivot 44 passes through the connecting part 42, and the two ends of the pivot 44 are respectively provided in the two mounting grooves 122. The cover 6 is fixedly connected to the cap 1 to close the opening of the window 121 on the outer peripheral surface of the cap 1.

[0037] As can be seen from the above description, the installation structure of the locking claw 4 is simple, easy to disassemble and assemble, and convenient for later maintenance or replacement.

[0038] Furthermore, a shearing ring 31 is fitted onto the core rod 3, and a protruding shearing pin 24 is provided on the inner wall surface of the liquid storage cylinder 2, with the shearing pin 24 abutting against the bottom of the shearing ring 31.

[0039] As described above, the shear ring 31 and shear pin 24 work together to apply an upward supporting force to the mandrel 3, so as to prevent the mandrel 3 from being accidentally subjected to force and falling relative to the liquid storage cylinder 2 during the feeding process, and effectively avoid the accidental leakage of the anti-corrosion liquid caused by the opening of the liquid outlet 222.

[0040] Please refer to Figures 1 to 6 Embodiment 1 of the present invention is: a submersible wellhead anti-corrosion cap, used to be fitted onto the submersible wellhead for protection and to inject anti-corrosion liquid into the wellhead.

[0041] The underwater wellhead corrosion protection cap includes a protective cap 1 for being fitted onto the underwater wellhead, a liquid storage cylinder 2 installed inside the protective cap 1, and a core rod 3 that penetrates the liquid storage cylinder 2; the liquid storage cylinder 2 has a liquid storage chamber 221, and the bottom of the liquid storage cylinder 2 is provided with a liquid outlet hole 222 communicating with the liquid storage chamber 221; the top end of the core rod 3 is exposed outside the protective cap 1, and the bottom end of the core rod 3 is located in the liquid outlet hole 222, and the core rod 3 can slide relative to the liquid storage cylinder 2 to open and close the liquid outlet hole 222.

[0042] Specifically, such as Figure 1 and Figure 2 As shown, the cap 1 includes a casing 12 and an assembly part 11 connected to the top of the casing 12. Both the casing 12 and the assembly part 11 are cylindrical, and their axial directions are vertical and coaxially arranged. The diameter of the casing 12 is larger than the diameter of the assembly part 11. The bottom of the casing 12 extends downward to form a ring edge, and the diameter of the ring edge gradually increases from the top to the bottom. It is easy to understand that the ring edge can serve as a guide to facilitate the cap 1 being fitted onto the wellhead.

[0043] like Figure 2 and Figure 5As shown, the liquid storage cylinder 2 includes a mounting part 21 and a liquid storage part 22 connected below the mounting part 21. The liquid storage part 22 has a liquid storage cavity 221 and a liquid outlet 222. Specifically, the mounting part 21 is cylindrical, and the liquid storage part 22 is a hollow cylinder. The top wall of the liquid storage part 22 has a through hole communicating with the inner cavity of the mounting part 21, and the bottom wall of the liquid storage part 22 has the liquid outlet 222. The liquid outlet 222 is circular and is coaxially arranged with the liquid storage part 22. The mounting part 21 is located inside the assembly part 11, and the end of the mounting part 21 away from the liquid storage part 22 is exposed outside the cap 1. At least one first sealing ring is provided between the mounting part 21 and the assembly part 11. The liquid storage part 22 is located inside the casing 12, and the difference between the maximum radius of the liquid storage part 22 and the minimum radius of the casing 12 is greater than or equal to the thickness of the peripheral wall of the wellhead. The mandrel 3 passes through the liquid storage section 22 and the mounting section 21, and at least one second sealing ring is provided between the mandrel 3 and the assembly section 11. The mandrel 3 is cylindrical, and the mandrel 3, the mounting section 21, and the liquid storage section 22 are coaxially arranged. The bottom end of the mandrel 3 is provided with an annular sealing boss 32, the diameter of which is less than or equal to the diameter of the liquid outlet 222. An annular first groove is provided on the outer circumferential surface of the sealing boss 32, and a third sealing ring 33 is provided in the first groove. The sealing boss 32 and the sealing ring are used to seal the liquid outlet 222. In other embodiments, in order to enhance the sealing performance of the liquid storage cylinder 2, it is also feasible to provide multiple first grooves on the outer circumferential surface of the sealing boss 32 to assemble multiple third sealing rings 33. The mandrel 3 has an annular first limiting protrusion 34 in the middle. The first limiting protrusion 34 is located in the liquid storage cavity 221 of the liquid storage part 22, and the diameter of the first limiting protrusion 34 is larger than the diameter of the through hole at the connection between the liquid storage part 22 and the mounting part 21. The first limiting protrusion 34 abuts against the top surface of the liquid storage cavity 221, which can limit the relative height between the mandrel 3 and the liquid storage cylinder 2, and prevent the mandrel 3 from moving upward relative to the liquid storage cylinder 2 and accidentally opening the liquid outlet 222.

[0044] like Figure 1 As shown, J-shaped grooves 211 are respectively provided on the outer peripheral surface of the end of the mounting part 21 exposed on the cap 1 and on the outer peripheral surface of the assembly part 11 of the cap 1. Specifically, the top ends of the J-shaped grooves 211 on the mounting part 21 and the assembly part 11 are respectively connected to the top surface of the mounting part 21, i.e., the assembly part 11. The top opening of the J-shaped groove 211 is funnel-shaped, which can play a guiding role during the engagement with the feeding tool. There are multiple J-shaped grooves 211, which are evenly distributed around the circumference of the mounting part 21 or the cap 1. In this embodiment, the mounting part 21 and the assembly part 11 of the cap 1 are each provided with two J-shaped grooves 211. In other embodiments, the mounting part 21 and the assembly part 11 may be provided with two, three or more J-shaped grooves 211.

[0045] Preferred, such as Figure 1 and Figure 3As shown, a limiting ring 212 is fitted onto the end of the mounting part 21 that is exposed outside the cap 1. A second limiting boss and a second locking groove cooperating with the second limiting boss are respectively provided on the contact surface between the limiting ring 212 and the mounting part 21. The second limiting boss and the second locking groove are located below the J-shaped groove 211 of the mounting part 21. In this embodiment, an annular second limiting boss is provided on the inner circumferential surface of the limiting ring 212, and an annular second locking groove cooperating with the second limiting boss is provided on the outer circumferential surface of the mounting part 21. In other embodiments, it is also feasible to provide the second limiting boss on the outer circumferential surface of the mounting part 21 and the second locking groove on the inner circumferential surface of the limiting ring 212.

[0046] Preferred, such as Figure 1 and Figure 3 As shown, the contact surfaces between the mounting part 21 and the protective cap 1 are respectively provided with anti-rotation pins 111 and anti-rotation grooves 213 that cooperate with the anti-rotation pins 111. Specifically, the anti-rotation pins 111 are preferably screws, and the mounting part 11 of the protective cap 1 is provided with threaded through holes through which the anti-rotation pins 111 pass, with the axial direction of the threaded through holes perpendicular to the axial direction of the mounting part 11. The anti-rotation grooves 213 are oblong, and the length direction of the anti-rotation grooves 213 is vertically arranged so that the liquid storage cylinder 2 can rise or fall relative to the protective cap 1.

[0047] Preferred, such as Figure 2 and Figure 5 As shown, the top of the liquid storage section 22 is provided with a filling hole 223 communicating with the liquid storage chamber 221 and a plug 224 for sealing the filling hole 223. Specifically, the number of plugs 224 corresponds one-to-one with the number of filling holes 223. The filling hole 223 is opened at the top of the liquid storage section 22, and the axial direction of the filling hole 223 is vertical. The filling hole 223 is a threaded hole. In this embodiment, there are two filling holes 223, and the two filling holes 223 are symmetrically arranged with the mounting part 21 as the center. In other embodiments, the number of filling holes 223 may be one, three or more.

[0048] Preferred, such as Figure 2 and Figure 6 As shown, the inner circumferential surface of the cap 1 is provided with locking claws 4. Each locking claw 4 includes a bent portion 41, a connecting portion 42, and a locking portion 43 connected sequentially from top to bottom. The connecting portion 42 is rotatably connected to the cap 1. The bent portion 41 bends inward and extends to abut against the underwater wellhead to drive the locking portion 43 to rotate inward. Specifically, the cross-section of the locking claw 4 is inverted L-shaped. The inner side of the locking portion 43 is provided with a locking boss that mates with the locking groove of the wellhead. The locking boss is arc-shaped, and its inner surface is a circular arc surface. The number of locking bosses corresponds one-to-one with the number of locking grooves on the wellhead. In this embodiment, there are four locking claws 4, evenly arranged around the circumference of the cap 1. In other embodiments, the number of locking claws 4 can be two, three, or more.

[0049] Preferred, such as Figure 2 and Figure 4 The storage cylinder 2 is adjustable relative to the cap 1. A protruding flange 23 is provided on the outer circumferential surface of the storage cylinder 2. A bent portion 41 abuts against the bottom of the flange 23, and the bent portion 41 is rotatable relative to the cap 1 to separate the bent portion 41 from the flange 23. Specifically, the flange 23 is annular, and the inner side of the bent portion 41 matches the outer circumferential surface of the flange 23. The upper edge of the end of the bent portion 41 is rounded to facilitate rotation of the bent portion 41 relative to the flange 23. During the insertion of the underwater wellhead anti-corrosion cap, the flange 23 of the storage cylinder 2 is placed on the bent portion 41. When the cap 1 is fitted onto the wellhead, the peripheral wall of the wellhead abuts against the bent portion 41, thereby driving the bent portion 41 to rotate upwards until it separates from the flange 23. Subsequently, the storage cylinder 2 moves downwards relative to the cap 1 until the flange 23 abuts against the peripheral wall of the wellhead.

[0050] Preferred, such as Figure 2 and Figure 4 As shown, the underwater wellhead anti-corrosion cap also includes an elastic element 5. The two ends of the elastic element 5 abut against the liquid storage cylinder 2 and the protective cap 1, respectively, so that the liquid storage cylinder 2 moves downward relative to the protective cap 1. In this embodiment, the elastic element 5 is preferably a spring. The elastic element 5 is sleeved on the outside of the mounting part 21, located between the assembly part 11 and the mounting part 21. The top of the assembly part 11 protrudes inward to form a limiting shoulder. The top end of the elastic element 5 abuts against the bottom surface of the limiting shoulder, and the bottom end of the elastic element 5 abuts against the top surface of the liquid storage part 22. In other embodiments, the elastic element 5 can be a spring pad or a spring sheet.

[0051] Preferred, such as Figure 2 and Figure 6As shown, the underwater wellhead corrosion-resistant cap also includes a cover 6 and a rotating shaft 44. A window 121 is provided on the peripheral wall of the cap 1. The two sides of the opening of the window 121 on the outer peripheral surface of the cap 1 are recessed inward to form mounting grooves 122. The rotating shaft 44 passes through the connecting part 42, and both ends of the rotating shaft 44 are respectively located in the two mounting grooves 122. The cover 6 is fixedly connected to the cap 1 to close the opening of the window 121 on the outer peripheral surface of the cap 1. Specifically, the number of the cover 6, rotating shaft 44, window 121, and locking claw 4 are arranged in a one-to-one correspondence, with four lock claws corresponding to the number of the cover 6, rotating shaft 44, and window 121. The rotating shaft 44 is cylindrical and its axial direction is horizontal. The connecting part 42 of the locking claw 4 has a through hole for the rotating shaft 44 to pass through. The window 121 is rectangular. The cover 6 is a rectangular plate, and both sides of the cover 6 are fixedly installed on the outer peripheral surface of the cap 1 by multiple screws. The outer edge of the bottom of the cap 6 is beveled to prevent foreign objects such as fishing nets from accidentally getting caught on the bottom of the cap, which could generate excessive drag and cause the wellhead cap to detach from the underwater wellhead. The inner side of the cap 6 is also provided with a recessed groove to accommodate part of the locking claw 4, which helps to provide sufficient support for the rotating shaft 44, so as to ensure that the locking claw 4 generates sufficient locking force on the wellhead.

[0052] Preferred, such as Figure 1 and Figure 3 As shown, a shearing ring 31 is fitted onto the mandrel 3, and a protruding shearing pin 24 is provided on the inner wall of the liquid storage cylinder 2, with the shearing pin 24 abutting against the bottom of the shearing ring 31. Specifically, annular third grooves are provided on the outer circumferential surface of the mandrel 3, and annular third limiting bosses that mate with the third grooves are provided on the inner circumferential surface of the shearing ring 31. The shearing pin 24 is preferably a screw, and a threaded through hole for the shearing pin 24 to pass through is provided on the peripheral wall of the mounting part 21. There are two shearing pins 24, which are evenly distributed around the circumference of the mounting part 21. The shearing ring 31 is fitted onto the top end of the mandrel 3, and a receiving groove for accommodating the shearing ring 31 is provided on the inner side of the top end of the mounting part 21. The top surfaces of the shearing ring 31, the mandrel 3, and the mounting part 21 are flush. In other embodiments, it is also feasible to provide the third groove on the inner circumferential surface of the shearing ring 31 and the third limiting boss on the outer circumferential surface of the mandrel 3.

[0053] The working principle of Embodiment 1 of the present invention is briefly described as follows: Before use, the mandrel 3 is inserted through the liquid storage cylinder 2 and the sealing boss 32 is used to seal the liquid outlet 222. Anticorrosive liquid is then filled into the liquid storage chamber 221 through the filling hole 223. After filling, the filling hole 223 is sealed with a plug 224. Subsequently, the mandrel 3 and the liquid storage cylinder 2 are installed inside the protective cap 1, and the bent portion 41 of the locking claw 4 is rotated inward to its limit position, so that the flange 23 of the liquid storage cylinder 2 is positioned above the end of the bent portion 41 (e.g., ...). Figure 2As shown), at this time, the elastic element 5 is compressed. In use, the J-groove 211 is connected to the feeding tool on the drill string, and the subsea wellhead anti-corrosion cap is sent to the top of the subsea wellhead through the feeding tool; the cap 1 is fitted onto the wellhead, so that the peripheral wall of the wellhead extends between the cap 1 and the reservoir 2; the subsea wellhead anti-corrosion cap continues to descend, so that the peripheral wall of the wellhead abuts against the bending part 41; the bending part 41 is forced to rotate upward, and the locking part 43 rotates inward until it is engaged in the locking groove on the outer peripheral surface of the wellhead to fix the subsea wellhead anti-corrosion cap on the wellhead. The bending part 41 no longer supports the flange 23, and the reservoir 2 and the mandrel 3 move downward under the elastic force of the elastic element 5 until the flange 23 abuts against the peripheral wall of the wellhead (as shown). Figure 4 As shown), at this time, the end of the bent part 41 abuts against the outer peripheral surface of the flange 23, which can effectively prevent the locking part 43 from rotating outward and exiting the locking groove of the wellhead, resulting in the wellhead being accidentally unlocked; by applying a downward axial thrust to the mandrel 3 through the drill string, the mandrel 3 overcomes the friction from the shear ring 31 and the liquid storage cylinder 2 and moves downward relative to the liquid storage cylinder 2 to open the liquid outlet 222, and then the anti-corrosion liquid in the liquid storage cavity 221 can be injected into the wellhead through the liquid outlet 222.

[0054] In summary, the underwater wellhead anti-corrosion cap provided by this invention is lowered to the top of the wellhead on the seabed using a delivery tool connected to the drill string, until the cap is fitted onto the top of the wellhead. A portion of the liquid storage cylinder located inside the cap enters the underwater wellhead. At this point, only internal pressurization of the drill string is needed to drive the mandrel downward relative to the liquid storage cylinder, thereby opening the liquid outlet. This allows the anti-corrosion liquid in the liquid storage chamber to be injected into the wellhead through the liquid outlet, completing the operation of adding anti-corrosion liquid into the wellhead. This eliminates the need for an underwater robot, is time-efficient, and has high timeliness and economy.

[0055] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A corrosion-resistant cap for an underwater wellhead, characterized in that: The device includes a protective cap for being fitted onto a subsea wellhead, a liquid storage cylinder installed inside the protective cap, and a mandrel penetrating through the liquid storage cylinder. The liquid storage cylinder has a liquid storage cavity, and the bottom of the liquid storage cylinder has a liquid outlet hole communicating with the liquid storage cavity. The top end of the mandrel is exposed outside the protective cap, and the bottom end of the mandrel is located in the liquid outlet hole. The mandrel is slidable relative to the liquid storage cylinder to open and close the liquid outlet hole. The inner circumferential surface of the protective cap is provided with a locking claw. The locking claw includes a bent part, a connecting part, and a locking part connected sequentially from top to bottom. The connecting part is rotatably connected to the protective cap. The bent part bends and extends inward, and the bent part is used to abut against the subsea wellhead to drive the locking part to rotate inward. The liquid storage cylinder is adjustable relative to the protective cap. The outer circumferential surface of the liquid storage cylinder is provided with a protruding flange. The bent portion abuts against the bottom of the flange, and the bent portion is rotatable relative to the protective cap to separate the bent portion from the flange. It also includes an elastic element, the two ends of which abut against the liquid storage cylinder and the protective cap respectively, so that the liquid storage cylinder moves downward relative to the protective cap.

2. The underwater wellhead anti-corrosion cap according to claim 1, characterized in that: The liquid storage cylinder includes an installation part and a liquid storage part connected below the installation part. The liquid storage part has a liquid storage cavity and a liquid outlet. The end of the installation part away from the liquid storage part is exposed outside the protective cap. J-shaped grooves are respectively formed on the outer peripheral surfaces of the installation part and the protective cap.

3. The underwater wellhead anti-corrosion cap according to claim 2, characterized in that: A limiting ring is fitted onto one end of the mounting part that is exposed on the protective cap.

4. The anti-corrosion cap for underwater wellheads according to claim 2, characterized in that: The mounting part and the protective cap are respectively provided with anti-rotation pins and anti-rotation slots that cooperate with the anti-rotation pins.

5. The anti-corrosion cap for underwater wellheads according to claim 2, characterized in that: The top of the liquid storage section is provided with a filling hole that communicates with the liquid storage chamber and a plug for sealing the filling hole.

6. The underwater wellhead anti-corrosion cap according to claim 1, characterized in that: It also includes a cap and a pivot. A window is provided on the peripheral wall of the cap. The two sides of the opening on the outer peripheral surface of the window are recessed inward to form mounting grooves. The pivot passes through the connecting part, and the two ends of the pivot are respectively located in the two mounting grooves. The cap is fixedly connected to the cap to close the opening of the window on the outer peripheral surface of the cap.

7. The anti-corrosion cap for underwater wellheads according to claim 1, characterized in that: A shearing ring is fitted onto the mandrel, and a protruding shearing pin is provided on the inner wall of the liquid storage cylinder, with the shearing pin abutting against the bottom of the shearing ring.

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