Drilling tool for underwater installation and recovery of top locking assembly and construction method

Abstract

The invention discloses a drilling tool for underwater installation and recovery of a top locking assembly and a construction method.The tool comprises a mandrel, an outer body, a release ring and a recovery ring, the outer body is in threaded connection with the mandrel through one corresponding step face, and the other step face of the mandrel is sleeved with the release ring in a threaded mode; a C-shaped recycling ring is arranged in the first containing groove, the recycling ring is bounced off or compressed through vertical movement of the release ring, and the recycling ring is clamped to the top locking assembly to recycle the top locking assembly when bounced off. The mandrel is provided with a first transmission block and a second transmission block which both protrude out of the mandrel, and the first transmission block and the second transmission block are correspondingly arranged in the grooves of the top locking assembly in a matched mode. The top locking assembly can be lowered, installed, adjusted in clearance and locked through one-time drilling, and at least one-time drilling is saved; and the underwater unlocking and recycling function of the top locking assembly is integrated, additional special tool allocation is reduced, tool allocation is optimized, the deepwater drilling operation cost is saved, and the operation efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of offshore oil drilling and production equipment technology. More specifically, this invention relates to an offshore drilling tool and construction method for underwater installation and retrieval of a top locking assembly. Background Technology

[0002] As countries around the world gradually strengthen their exploration of offshore oil and gas, subsea wellhead systems, as key equipment for offshore oil and gas exploration and development, are being used more and more widely. During the development of deep-water oil and gas in the South China Sea, subsea wellhead uplift caused by casing thermal deformation has occurred repeatedly, seriously affecting production safety. The top locking assembly, installed on the upper part of the casing hanger, provides additional axial locking force to limit the axial uplift of the casing and is a key device to ensure wellhead safety.

[0003] After the top locking assembly is installed underwater, due to factors such as design dimensions and installation errors, the locking unit and the wellhead locking groove are not tightly fitted axially, leaving a gap. In this case, the casing locking limit is still borne by the lower annular seal, and the top locking does not perform its intended function. This will cause the casing to rise due to heat, leading to the destruction of the annular seal first and potentially causing a safety accident. Therefore, under normal circumstances, to eliminate the axial gap after installation and ensure the top locking assembly bears the load, it is usually necessary to trip the drill string twice. The first trip involves lowering specific tools for inspection or photographing to accurately measure the top locking installation gap; after precisely adjusting the locking ring position, the assembly is lowered again to achieve a precise match in the axial locking position. However, each trip-in / trip-out operation in offshore drilling takes several hours or even tens of hours, which is extremely uneconomical for offshore drilling platforms with daily costs often reaching millions of yuan. Furthermore, under normal circumstances, underwater unlocking and recovery of the top locking assembly also requires specialized tools, increasing the variety of tools and maintenance costs.

[0004] Therefore, it is necessary to design a marine drilling tool that can be installed with a top lock in one trip and has a retrieval function to reduce the number of trips, optimize the number of tools, and reduce the cost of marine drilling. Summary of the Invention

[0005] One objective of this invention is to provide a marine drilling tool and construction method for underwater installation and retrieval of a top locking assembly. This method enables the lowering, installation, clearance adjustment, and locking of the top locking assembly to be completed in a single drilling run, reducing the number of trips compared to conventional service tools that require "first drilling down to measure the clearance, then lowering and installing," thus saving at least one drilling run. Furthermore, it integrates an underwater unlocking and retrieval function for the top locking assembly, enabling underwater unlocking and retrieval of the top locking assembly, reducing the need for additional specialized tools, optimizing tooling, saving deepwater drilling operation costs, and improving operational efficiency.

[0006] To address the aforementioned technical problems, this invention provides a drilling tool for underwater installation and retrieval of a top locking assembly, comprising a mandrel and an outer body, a release ring, and a retrieval ring disposed outside the mandrel. The mandrel is a hollow shaft structure, with multiple stepped surfaces and a concave annular first receiving groove on its outer wall. The outer body is a hollow cylindrical structure, and its inner wall also has multiple stepped surfaces that correspond one-to-one with the stepped surfaces of the outer wall of the mandrel. The outer body and the mandrel are threadedly connected via one of the corresponding stepped surfaces, and a release ring is threaded onto the other stepped surface of the mandrel. The first receiving groove is provided with an elastic C-shaped recovery ring. The inner wall of the release ring is a stepped surface, and the recovery ring is opened or compressed by the up and down movement of the release ring. When the recovery ring opens, it is locked to the top locking assembly for recovery. The outer side wall of the bottom of the outer body is provided with a first inclined surface, which abuts against the inclined surface of the top locking assembly to transfer the downward pressure load of the mandrel to the top locking assembly. The mandrel is provided with a first transmission block and a second transmission block, both protruding from the outer side wall of the mandrel, which respectively cooperate with the groove of the top locking assembly. The grooves corresponding to the first transmission block and the second transmission block are annular inverted L-shaped grooves.

[0007] Preferably, the top of the mandrel is provided with a recessed indicator groove, and after the top locking assembly is installed in place, the indicator groove is exactly flush with the end face of the high-pressure wellhead.

[0008] Preferably, the mandrel has a concave semi-circular annular groove at the top of the multi-step surface, and a retaining ring is installed inside the groove. The retaining ring is an open circular ring structure used to limit the top surface of the outer body.

[0009] Preferably, both the outer body and the release ring are circumferentially secured to the mandrel by screws.

[0010] Preferably, the mandrel is further provided with an indicator block in the lower middle part, which protrudes from the outer wall of the mandrel. When the mandrel moves down, the protruding indicator block is cut by the top locking assembly. The position of the indicator block is set so that it is completely cut off just after the installation of the top locking assembly is completed.

[0011] Preferably, the outer surface of the mandrel is also provided with a blind hole for accommodating the shear pin of the top locking assembly.

[0012] Preferably, the mandrel has multiple vertically penetrating holes distributed circumferentially for mud return.

[0013] Preferably, the first transmission block and the second transmission block are not installed at the same time.

[0014] The present invention also provides a construction method for drilling tools used for underwater installation and retrieval of the top locking assembly, the installation process including the following steps: Step 1: Install the first transmission block so that it extends into the transverse groove of the inverted L-shaped groove to suspend the top locking assembly onto the sleeve hanger. At this time, the shear pin of the top locking assembly extends into the blind hole on the outer surface of the spindle. Step 2: Rotate the mandrel to cut off the shearing pin; Step 3: Release part of the drill rod suspension weight, lower the mandrel, and transmit the downward load to the top locking assembly through the first inclined surface at the bottom of the outer body. The locking ring on the top locking assembly is opened under the action of the downward load. During this process, the first transmission block moves down along the vertical groove section of the inverted L-shaped groove. At the same time, the indicator block is cut by the inclined step surface set on the inner wall of the top locking assembly under the action of the downward load. Step 4: Continue to rotate the mandrel to drive the top locking assembly to rotate and eliminate the gap between it and the inclined surface on the locking groove. At this time, observe that the indicator groove is flush with the end face of the high-pressure wellhead to verify that the installation is in place.

[0015] The present invention also provides a construction method for underwater installation and recovery of drilling tools with a top locking assembly, the recovery process including the following steps: Step 1: Install the second transmission block, move the release ring upwards, and open the recovery ring; Step 2: Lower the mandrel into the high-pressure wellhead. Under the action of the downward pressure load, the recovery ring hooks onto the stepped face of the top locking assembly to suspend the top locking assembly. Step 3: Rotate the mandrel. At this time, the second transmission block transmits the torque of the mandrel to the top locking assembly. Under the action of torque, the locking ring that engages with the wellhead of the top locking assembly retracts, and the mandrel is lifted to complete the retraction of the top locking assembly.

[0016] The present invention has at least the following beneficial effects: 1. The installation tool of the present invention enables the lowering, installation, clearance adjustment and locking of the top locking assembly to be completed in one drilling trip. Compared with conventional operation methods, it reduces at least one tripping in and out of the drill string, saves drilling costs and improves the efficiency of offshore drilling.

[0017] 2. The installation tool of the present invention enables underwater unlocking and recovery of the top locking assembly, reducing the need for special tools and maintenance, and lowering overall costs.

[0018] 3. This invention realizes the function of top locking recovery. The design of the second transmission block avoids the occurrence of the locking ring of the top locking assembly not retracting due to excessive locking force.

[0019] 4. This invention implements a dual verification design of indicator groove and indicator block to ensure that the top locking assembly can be fully verified when it is installed in place under actual working conditions.

[0020] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of the mandrel of the marine drilling tool used for underwater installation and retrieval of the top locking assembly, as described in this application. Figure 2 This is a front view of the mandrel of the marine drilling tool used for underwater installation and retrieval of the top locking assembly, as described in this application. Figure 3 This is a cross-sectional view of the marine drilling tool used for underwater installation and recovery of the top locking assembly according to this application; Figure 4 This is a front view of the marine drilling tool used for underwater installation and retrieval of the top locking assembly according to this application; Figure 5 This is a partial enlarged view of the marine drilling tool used for underwater installation and recovery of the top locking assembly, as described in this application; Figure 6 This is a structural schematic diagram of the top locking assembly corresponding to the marine drilling tool used for underwater installation and recovery of the top locking assembly in this application; Figure 7 This is a schematic diagram of the structure of the tool and the top locking assembly in this application. Figure 8 This is a schematic diagram showing the structure of the top locking assembly in conjunction with the external casing hanger and wellhead during the application of this application.

[0022] Explanation of reference numerals in the attached figures: 1. Mandrel; 11. Indicator groove; 12. Semi-circular annular groove; 13. First thread; 14. Second thread; 15. Through hole; 16. First receiving keyway; 17. Second receiving keyway; 18. Third receiving keyway; 19. Blind hole; 110. First receiving groove; 2. Retaining ring; 3. Outer body; 31. Anti-loosening screw; 32. First inclined surface; 4. Release ring; 5. Retrieval ring; 6. First transmission block; 7. Second transmission block; 8. Indicator block; 91. Drive ring; 92. Locking ring; 93. Inverted L-shaped groove; 94. Shear pin; 95. Upper body; 96. Lower body; 97. Wellhead; 98. Casing hanger; 99. Stepped clamping surface. Detailed Implementation

[0023] To better understand the purpose, structure, and function of this invention, the invention will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0024] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0026] like Figures 1 to 5 As shown, this invention provides a marine drilling tool for underwater installation and retrieval of a top locking assembly, including a mandrel and an outer body, a release ring, and a retrieval ring disposed outside the mandrel. The mandrel is a hollow shaft structure, and its outer wall is provided with a multi-stage stepped surface and a concave annular first receiving groove. The outer body is a hollow cylindrical structure, and its inner wall is also provided with a multi-stage stepped surface that corresponds one-to-one with the multi-stage stepped surface of the outer wall of the mandrel. The outer body and the mandrel are threadedly connected through one of the corresponding stepped surfaces, and a release ring is threaded onto the other stepped surface of the mandrel. The first receiving groove is provided with an elastic C-shaped recovery ring. The inner wall of the release ring is a stepped surface, and the recovery ring is opened or compressed by the up and down movement of the release ring. When the recovery ring opens, it is locked to the top locking assembly for recovery. The outer side wall of the bottom of the outer body is provided with a first inclined surface, which abuts against the inclined surface of the top locking assembly to transfer the downward pressure load of the mandrel to the top locking assembly. The mandrel is provided with a first transmission block and a second transmission block, both protruding from the outer side wall of the mandrel, which respectively correspond to the groove of the top locking assembly. The groove corresponding to the first transmission block is an inverted L-shaped annular groove.

[0027] This application provides a marine drilling tool for one-pass lowering and installation of a top locking assembly, comprising: a spindle 1, a retaining ring 2, an outer body 3, a release ring 4, a recovery ring 5, a first transmission block 6, a second transmission block 7, and an indicator block 8.

[0028] The mandrel 1 is a hollow shaft structure. A recessed indicator groove 11 is provided on the top of the outer surface of the mandrel 1. Under actual working conditions, after the top locking assembly is installed in place, the indicator groove is exactly flush with the end face of the high-pressure wellhead, which is used to indicate and verify that the top locking assembly is installed in place.

[0029] The top of the mandrel (on the top of the multi-step surface) has a concave semi-circular groove 12 on its outer surface for installing an open retaining ring 2. The retaining ring 2 is an open circular ring structure that is installed in the semi-circular groove of the mandrel and protrudes to limit the top surface of the outer body and prevent the outer body 3 from accidentally coming out of the mandrel 1.

[0030] The outer surface of the mandrel is provided with a first thread 13. The outer body is a hollow cylindrical structure. The inner surface thread engages with the first thread 13 on the outer surface of the mandrel 1 to transmit the downward load of the mandrel 1. The outer body is provided with multiple countersunk threaded holes around its circumference for installing anti-loosening screws 31 to hold the mandrel. The bottom of the outer body is provided with a first inclined surface 32, which is used to transfer the downward load of the mandrel to the top locking assembly when the top locking assembly is installed, that is, to transfer the pressure to the inclined surface of the drive ring 91 of the top locking assembly.

[0031] The outer surface of the mandrel is provided with a second thread 14. The release ring 4 is a hollow cylindrical structure, which engages with the second thread 14 on the outer surface of the mandrel 1 through an inner surface thread. The outer surface of the release ring is limited by the inner surface of the outer body. The inner surface of the release ring 4 is provided with a stepped surface. When the top locking assembly is lowered, the limiting keeps the recovery ring in a compressed state. The release ring 4 is provided with multiple threaded holes around its circumference for installing stop screws on the mandrel. When the recovery ring is in a compressed state, the threaded holes or open holes of the release ring are aligned with the threaded holes of the mandrel, and the screws are installed to prevent the recovery ring from moving up and down due to external force, which would cause the release ring to open. The outer surface of the mandrel corresponding to the semi-circular annular groove 12, the first thread 13, and the second thread 14 is sequentially formed into a stepped shape. The inner surface of the outer body is also sequentially set into a stepped shape, and corresponds one-to-one with the outer surface of the mandrel corresponding to the semi-circular annular groove 12, the first thread 13, and the second thread 14.

[0032] The recovery ring 5 has a C-shaped ring structure. The spindle has a recessed annular first receiving groove 110 below the second thread 14, and the recovery ring 5 is installed within the first receiving groove 110. When the top locking assembly is in operation, if the release ring 4 moves upward on the spindle 1, the recovery ring 5 is released, disengaging from the inner stepped surface of the release ring. The recovery ring expands under its own elasticity, reaching the recovery state. Conversely, if the release ring 4 moves downward, the recovery ring 5 is compressed, reaching the tightened state. The recovery ring can engage with the inner stepped face of the top locking assembly (i.e., the inner stepped face 99 corresponding to the drive ring 91) to lock the top locking assembly. The deformation rate of the recovery ring can be designed to ensure that it does not detach from the spindle in the released recovery state.

[0033] The outer surface of the spindle 1 is provided with a first receiving keyway 16, a second receiving keyway 17 and a third receiving keyway 18 to accommodate the first transmission block 6, the second transmission block 7 and the indicator block 8.

[0034] The first transmission block 6 is installed in the first receiving keyway 16 of the spindle 1 to transmit torque. The first transmission block 6 has a cuboid structure with a rounded top surface and a countersunk threaded hole on the rounded top surface for mounting screws to engage with the spindle 1.

[0035] The second transmission block 7 is installed within the second receiving keyway 17 of the mandrel 1 to transmit torque. The second transmission block 7 has a cuboid structure with a countersunk hole for mounting an inter-shaft screw and mandrel engagement, and a blind hole on its bottom surface for mounting a spring. The spring causes the second transmission block to spring out above the outer diameter of the mandrel. Rotating the drilling tool causes the second transmission block to slide into the vertical groove of the inverted L-shaped groove to transmit torque. The second transmission block is installed when retrieving the top locking assembly, and it transmits torque within the vertical groove of the inverted L-shaped groove in the top locking assembly. In practical engineering applications, the first transmission block 6 and the second transmission block 7 are installed under different drilling conditions and cannot be installed simultaneously.

[0036] The indicator block 8 is made of a relatively soft metal, such as lead; it is elongated and installed within the third receiving keyway 18 of the mandrel 1, protruding from the outer wall of the mandrel. The axial position of the third receiving keyway on the mandrel is determined by the position of the top locking assembly within the high-pressure wellhead. As the mandrel moves downward, the top locking assembly cuts the protruding indicator block, typically cutting the elongated section of the indicator block completely after installation. The indicator block is completely cut after the top locking assembly is installed, thus serving to indicate and verify proper installation.

[0037] The top and bottom of the mandrel 1 are threaded, and in engineering applications, it is connected to the drill rod at the top and bottom to apply downward pressure load.

[0038] The outer surface of the mandrel is provided with a blind hole 19 to accommodate the shear pin 94 of the top locking assembly.

[0039] The mandrel has multiple through holes 15 distributed circumferentially for mud backflow, ensuring that the mandrel can be smoothly lowered into the high-pressure wellhead.

[0040] This application also provides a construction method for installing and recovering the top locking assembly using the marine drilling tool described above for underwater installation and recovery of the top locking assembly.

[0041] like Figure 6The diagram shows the structure of the top locking assembly to be installed and recycled. The upper body 95 of the top locking assembly has an inverted L-shaped groove 93 on its inner wall to accommodate the first transmission block 6 for movement. The lower body 96 of the top locking assembly has a shear pin 94, part of which protrudes from the interior of the lower body 96. A drive ring 91 is located at the top of the top locking assembly, and a locking ring 92 is located on its outer stepped surface. When the drive ring is pressed down, it can push the locking ring outwards. The drive ring 91 at the top of the top locking assembly can move up and down relative to the upper body 95. The top of the drive ring 91 has a slope, and its inner wall also has a stepped locking surface 99. The lower body 96 is connected to the casing hanger 98. The casing hanger 98, the tool of this application, and the outer side of the top locking assembly form a wellhead 97. Figure 7 The diagram shown is a structural schematic of the top locking assembly in conjunction with the tool of this application. Figure 8 The diagram shows the structure of the top locking assembly in conjunction with the external casing hanger and wellhead.

[0042] The installation process includes the following steps: Step 1: Install the first transmission block so that it extends into the transverse groove of the inverted L-shaped groove to suspend the top locking assembly onto the sleeve hanger. At this time, the shear pin of the top locking assembly extends into the blind hole on the outer surface of the spindle. In the application of lowering and installing the top locking assembly, only the first transmission block 6 is installed. The first transmission block 6 mates with the annular groove of the top locking assembly. The annular groove is a pair of inverted L-shaped grooves 93 that are symmetrically distributed at 180 degrees, so as to suspend the top locking assembly on the "9-5 / 8" sleeve hanger 98. The first transmission block extends into the transverse groove of the inverted L-shaped groove. At this time, the shear pin of the top locking assembly extends into the blind hole 19 on the outer surface of the mandrel to prevent accidental rotation during the lowering process.

[0043] Step 2: Rotate the mandrel to cut off the shearing pin; When the spindle 1 is rotated clockwise, the shear pin 94 is cut off, at which point the locking ring 92 of the top locking assembly is in the locking groove at the high-pressure wellhead.

[0044] Step 3: Release part of the drill pipe suspension weight, lower the mandrel, and transmit the downward load to the drive ring 91 on the top locking assembly through the first inclined surface 32 at the bottom of the outer body 3. The locking ring 92 on the top locking assembly opens under the action of the downward load. During this process, the first transmission block 6 moves down along the vertical groove section of the inverted L-shaped groove. The top of the drive ring is provided with an inclined surface to cooperate with the first inclined surface at the bottom of the outer body to realize the force transmission. At the same time, the indicator block 8 is exactly cut by the inclined step surface provided on the inner wall of the top locking assembly under the action of the downward load.

[0045] Step 4: The mandrel 1 continues to rotate clockwise, driving the upper body 95 of the top locking assembly to rotate, eliminating the gap between it and the inclined surface of the locking groove, so as to withstand the upward extrusion stress caused by casing deformation. At this time, observe that the indicator groove 11 should be flush with the end face of the high-pressure wellhead 97 to verify whether the installation is in place.

[0046] The recycling process includes the following steps: Step 1: In the engineering application of the top locking assembly for recycling, only the second transmission block 7 is installed. At this time, the right-hand thread moves the release ring 3 upward, and the recycling ring 4 is opened.

[0047] Step 2: Insert the mandrel 1 into the high-pressure wellhead. Under the action of the downward pressure load, the recovery ring 4 hooks onto the stepped surface of the top locking assembly, that is, the stepped locking surface 99 protruding from the inner wall of the drive ring 91, so as to suspend the top locking assembly.

[0048] Step 3: Rotate the mandrel 1 clockwise. At this time, the second transmission block 7 slides into the vertical groove of the inverted L-shaped groove, transmitting the torque of the mandrel 1 to the upper body 95 of the top locking assembly. Under the action of torque, the locking ring 92, which engages with the wellhead of the top locking assembly, retracts. When the locking ring opens during the installation of the top locking assembly, the recovery ring hooks and drives the mandrel to pull upward. It is possible that the friction generated by the circumferential locking force is too large and it cannot be pulled out. At this time, first rotate the upper body to retract the locking ring to avoid this situation. Then, lift the mandrel 1 to complete the recovery of the top locking assembly.

[0049] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention, and other modifications can be easily implemented by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A drilling tool for underwater installation and retrieval of a top locking assembly, characterized in that, The device includes a mandrel, an outer body, a release ring, and a retrieval ring disposed outside the mandrel. The mandrel is a hollow shaft structure, with multiple stepped surfaces and a concave annular first receiving groove on its outer wall. The outer body is a hollow cylindrical structure, and its inner wall also has multiple stepped surfaces that correspond one-to-one with the stepped surfaces of the outer wall of the mandrel. The outer body and the mandrel are threadedly connected via one of the corresponding stepped surfaces. A release ring is threaded onto the other stepped surface of the mandrel. An elastic C-shaped retrieval ring is disposed within the first receiving groove. The inner wall of the release ring is stepped, and the up-and-down movement of the release ring causes the recovery ring to spring open or compress. When the recovery ring springs open, it engages with the top locking assembly to recover it. The outer side wall of the bottom of the outer body is provided with a first inclined surface, which abuts against the inclined surface of the top locking assembly to transfer the downward pressure load of the mandrel to the top locking assembly. The mandrel is provided with a first transmission block and a second transmission block, both protruding from the outer side wall of the mandrel, which respectively cooperate with the groove of the top locking assembly. The grooves corresponding to the first transmission block and the second transmission block are annular inverted L-shaped grooves.

2. The drilling tool for underwater installation and retrieval of the top locking assembly as described in claim 1, characterized in that, The top of the mandrel is provided with a recessed indicator groove. After the top locking assembly is installed in place, the indicator groove is exactly flush with the end face of the high-pressure wellhead.

3. The drilling tool for underwater installation and retrieval of the top locking assembly as described in claim 1, characterized in that, The mandrel has a concave semi-circular groove at the top of the multi-step surface, and a retaining ring is installed inside it. The retaining ring is an open circular ring structure used to limit the top surface of the outer body.

4. The drilling tool for underwater installation and retrieval of the top locking assembly as described in claim 1, characterized in that, Both the outer body and the release ring are circumferentially secured to the mandrel by screws.

5. The drilling tool for underwater installation and retrieval of the top locking assembly as described in claim 1, characterized in that, The mandrel is also provided with an indicator block in the lower middle part, which protrudes from the outer wall of the mandrel. When the mandrel moves down, the protruding indicator block is cut by the top locking assembly. The position of the indicator block is set so that it is completely cut off just after the installation of the top locking assembly is completed.

6. The drilling tool for underwater installation and retrieval of the top locking assembly as described in claim 1, characterized in that, The outer surface of the mandrel is also provided with blind holes for accommodating the shear pin of the top locking assembly.

7. The drilling tool for underwater installation and retrieval of the top locking assembly as described in claim 1, characterized in that, The mandrel has multiple vertically penetrating holes distributed circumferentially for mud return.

8. The drilling tool for underwater installation and retrieval of the top locking assembly as described in claim 1, characterized in that, The first transmission block and the second transmission block are not installed at the same time.

9. A construction method for drilling tools used for underwater installation and retrieval of top locking assemblies, characterized in that, The installation process includes the following steps: Step 1: Install the first transmission block so that it extends into the transverse groove of the inverted L-shaped groove to suspend the top locking assembly onto the sleeve hanger. At this time, the shear pin of the top locking assembly extends into the blind hole on the outer surface of the spindle. Step 2: Rotate the mandrel to cut off the shearing pin; Step 3: Release part of the drill rod suspension weight, lower the mandrel, and transmit the downward load to the top locking assembly through the first inclined surface at the bottom of the outer body. The locking ring on the top locking assembly is opened under the action of the downward load. During this process, the first transmission block moves down along the vertical groove section of the inverted L-shaped groove. At the same time, the indicator block is cut by the inclined step surface set on the inner wall of the top locking assembly under the action of the downward load. Step 4: Continue to rotate the mandrel to drive the top locking assembly to rotate and eliminate the gap between it and the inclined surface on the locking groove. At this time, observe that the indicator groove is flush with the end face of the high-pressure wellhead to verify whether the installation is in place.

10. A construction method for drilling tools used for underwater installation and retrieval of top locking assemblies, characterized in that, The recycling process includes the following steps: Step 1: Install the second transmission block, move the release ring upwards, and open the recovery ring; Step 2: Lower the mandrel into the high-pressure wellhead. Under the action of the downward pressure load, the recovery ring hooks onto the stepped face of the top locking assembly to suspend the top locking assembly. Step 3: Rotate the mandrel. At this time, the second transmission block transmits the torque of the mandrel to the top locking assembly. Under the action of torque, the locking ring that engages with the wellhead of the top locking assembly retracts, and the mandrel is lifted to complete the retraction of the top locking assembly.

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