An angle-adjustable underwater wellhead and a method of using the same

Abstract

This invention discloses an adjustable-angle subsea wellhead and its usage method, including a high-pressure wellhead, a low-pressure wellhead, and a low-pressure wellhead extension casing. The high-pressure and low-pressure wellheads are positioned and oriented via a first wellhead spherical joint, and are locked together by a locking ring. In the reconnection operation mode, the high-pressure wellhead is connected to a flexible insertion sealing pipe via the high-pressure wellhead thin-walled extension casing. The low-pressure wellhead extension casing contains a reconnectable tailpipe hanger, with a guide cylinder at the upper end and a guide head at the lower end of the flexible insertion sealing pipe. The flexible insertion sealing pipe can enter the reconnectable tailpipe hanger under the guidance of the guide head and guide cylinder. In the non-reconnection operation mode, a regular extension casing is connected below the high-pressure wellhead, and a casing string is connected below the regular extension casing. This application adjusts the inclined high-pressure wellhead to near vertical position as needed, facilitating the installation of service tools, blowout preventers, and Christmas trees, enhancing wellhead stability, and reducing operational risks.

Description

Technical Field

[0001] This invention relates to the field of oil and gas drilling and production equipment technology, and in particular to an adjustable-angle subsea wellhead and its usage method. Background Technology

[0002] Subsea wellheads are crucial equipment for deepwater oil and gas exploration and development, typically consisting of low-pressure and high-pressure wellheads. They are usually lowered from the floating drilling rig and positioned at the mudline, supporting the casing string and sealing the annular space between it and the casing. Subsea wellhead equipment is used in conjunction with subsea blowout preventers (BOPs) to lock and seal the high-pressure wellhead. After drilling is completed, the subsea production tree locks and seals the high-pressure wellhead.

[0003] Subsea wellheads bear complex loads during drilling and completion operations, including the weight of the casing string, blowout preventer, and Christmas tree, equivalent stress generated downhole, and drag force from platform drift. This places high demands on their load-bearing and bending resistance. The subsea wellhead is fixed by the bonding force between the casing and cement or soil, and its stability directly affects the safety and efficiency of drilling and completion operations.

[0004] Tilting of the subsea wellhead during installation can affect the installation of service tools, blowout preventers, and Christmas trees, increasing operational risks and significantly increasing the stress on the wellhead and surface casing, thus affecting wellhead stability. For example, when the well inclination reaches 0.5°, the bending moment on the wellhead and surface casing is 2-3 times that in the vertical state; for every additional 0.5° increase in inclination, the bending moment increases by another 5%-10%. This additional load accelerates wellhead fatigue and can even lead to structural failure.

[0005] On the other hand, wellhead pre-inclination plays a crucial role in directional drilling. By pre-designing and implementing wellhead inclination, wellbore trajectory control can be simplified, adaptability to complex geological conditions can be improved, wellbore structure can be optimized, and operational risks can be reduced. Pre-inclination design not only improves drilling efficiency but also creates more favorable conditions for subsequent well completion and production operations. Summary of the Invention

[0006] The purpose of this application is to provide an adjustable-angle underwater wellhead and its usage method to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, this application provides the following technical solution:

[0008] An adjustable-angle subsea wellhead includes a high-pressure wellhead, a low-pressure wellhead, a low-pressure wellhead extension casing, and a high-pressure wellhead thin-walled extension casing. The high-pressure and low-pressure wellheads are positioned and oriented via a first wellhead spherical joint, and are locked together by a locking ring. A low-pressure wellhead extension casing is located below the low-pressure wellhead, and a high-pressure wellhead thin-walled extension casing is located below the high-pressure wellhead. In a reconnection operation mode, the lower part of the high-pressure wellhead thin-walled extension casing is connected to a flexible insertion sealing pipe. A reconnectable tailpipe hanger is located inside the low-pressure wellhead extension casing. A guide cylinder is located at the upper end of the reconnectable tailpipe hanger, and a guide head is located at the lower end of the flexible insertion sealing pipe. The flexible insertion sealing pipe enters the reconnectable tailpipe hanger under the guidance of the guide head and guide cylinder, forming a circulation channel. In a non-reconnection operation mode, a regular extension casing is connected below the high-pressure wellhead, and a casing string is connected below the regular extension casing.

[0009] Optionally, the high-pressure wellhead includes a body, a lower support ring, an upper support ring, an adjusting ring, a locking ring, and a downward locking bushing. The lower end of the body is connected to the lower support ring via a thread. The lower support ring contacts and transmits load to the low-pressure wellhead via a first wellhead spherical pair. The middle part of the body is connected to the upper support ring via a thread. An adjusting ring is fitted above the upper support ring. The upper support ring and the adjusting ring contact and transmit load via a second wellhead spherical pair. A locking ring is fitted outside the adjusting ring. The downward locking bushing is adapted to move downward between the adjusting ring and the locking ring. The downward locking bushing forces the locking ring to open so that the locking ring is locked to the low-pressure wellhead. The first wellhead spherical pair and the second wellhead spherical pair are located on the same spherical surface.

[0010] Optionally, the adjusting ring is provided with a check block corresponding to the downward locking bushing, the check block being used to prevent the downward locking bushing from moving downward and then upward.

[0011] Optionally, a centralizing ring is provided on the inner surface of the low-pressure wellhead extension casing. The centralizing ring is used to guide the reversible tailpipe hanger. A connecting ring is provided below the centralizing ring, and a bearing ring is provided on the inner side of the connecting ring. The bearing ring is used to suspend the reversible tailpipe hanger.

[0012] Optionally, the reversible tailpipe hanger includes a tailpipe hanger body and a guide cylinder. The guide cylinder is located at the upper end of the tailpipe hanger body. The tailpipe hanger body has a bearing step at the upper end corresponding to the bearing ring, and the bearing step is locked above the bearing ring.

[0013] Optionally, the flexible insertion sealing tube is composed of several flexible short sections and guide heads connected in series by threads. A composite module sealing ring is provided between the flexible short sections and the guide head, and the composite module sealing ring seals with the inner sealing surface of the tail tube hanger body.

[0014] Optionally, the high-pressure wellhead can be directly connected to the casing below when no reconnection is required.

[0015] A method for using an adjustable-angle underwater wellhead as described above includes the following steps:

[0016] Reconnection operation mode:

[0017] Low-pressure wellheads and surface casings are installed using either the jet-adsorption method or the drilling-cementing method.

[0018] The drilling-cementing method is used to install the reversible tailpipe hanger and casing.

[0019] Lower the high-pressure wellhead, connect the flexible insertion sealing pipe and the reversible tailpipe hanger, sit the high-pressure wellhead on the low-pressure wellhead, and adjust the angle of the high-pressure wellhead to the predetermined angle by adjusting the boat and moving the derrick.

[0020] The downward locking bushing is pressed down and moves downward to between the adjusting ring and the locking ring. The downward locking bushing forces the locking ring to open so that the locking ring locks with the low-pressure wellhead, thereby locking the high-pressure wellhead and the low-pressure wellhead.

[0021] Carry out subsequent drilling and completion operations;

[0022] Non-return operation mode:

[0023] Low-pressure wellheads and surface casings are installed using either the jet-adsorption method or the drilling-cementing method.

[0024] The high-pressure wellhead and casing string are lowered, the high-pressure wellhead is positioned above the low-pressure wellhead, and the angle of the high-pressure wellhead is adjusted to the predetermined angle by adjusting the boat and moving the derrick.

[0025] The downward locking bushing is pressed down and moves downward to between the adjusting ring and the locking ring. The downward locking bushing forces the locking ring to open so that the locking ring locks with the low-pressure wellhead, thereby locking the high-pressure wellhead and the low-pressure wellhead.

[0026] Carry out subsequent drilling and completion operations.

[0027] In summary, the technical effects and advantages of this invention are as follows: This invention provides an adjustable-angle subsea wellhead that can adjust the inclined wellhead to a state within 0.5 degrees of vertical deviation according to operational needs. This means that a high-pressure wellhead can be installed nearly vertically on an inclined low-pressure wellhead, thereby reducing the bending moment borne by the wellhead and surface casing. It also facilitates the installation of service tools, blowout preventers, and Christmas trees, enhances wellhead stability, and reduces operational risks. Furthermore, the adjustable-angle subsea wellhead can also meet wellhead pre-inclination requirements, facilitating subsequent directional well operations, optimizing wellbore trajectory control, adapting to complex geological conditions, and improving overall operational efficiency. Through this design, the wellhead can meet both the stability requirements of vertical wells and the flexible operational needs of directional wells, achieving a multi-functional integrated application. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the adjustable-angle underwater wellhead in one embodiment of the present invention;

[0030] Figure 2 This is a detailed schematic diagram of the high-pressure wellhead and the low-pressure wellhead in one embodiment of the present invention;

[0031] Figure 3 This is a detailed schematic diagram of the flexible insertion sealing tube and the reversible tail tube hanger in one embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram showing the connection between the underwater wellhead angle adjustment tool and the high-pressure wellhead in one embodiment of the present invention.

[0033] The components include: 1. High-pressure wellhead; 2. Low-pressure wellhead; 3. Low-pressure wellhead extension casing; 4. High-pressure wellhead thin-walled extension casing; 5. Flexible insertion sealing pipe; 6. Reconnectable tailpipe hanger; T1. Subsea wellhead angle adjustment tool; E1. High-pressure wellhead insertion tool; Q1. Service tool spherical pair; Q2. First wellhead spherical pair; Q3. Second wellhead spherical pair; 101. Body; 102. Adjusting ring; 103. Check block; 104. Downward locking bushing; 105. Locking ring; 106. Upper support ring; 107. Lower support ring; 301. Centralizing ring; 302. Connecting ring; 303. Bearing ring; 501. Flexible short section; 502. Composite module sealing ring; 503. Guide head; 601. Guide cylinder; 602. Tailpipe hanger body. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] This embodiment proposes an adjustable-angle underwater wellhead, such as... Figures 1-4The system includes a high-pressure wellhead 1, a low-pressure wellhead 2, and a low-pressure wellhead extension casing 3. The high-pressure wellhead 1 and the low-pressure wellhead 2 are positioned and oriented by a first wellhead spherical joint Q2, and are locked together by a locking ring 105. In the reconnection operation mode, a high-pressure wellhead thin-walled extension casing 4 is provided below the high-pressure wellhead 1, and a flexible insertion sealing pipe 5 is connected to the lower part of the high-pressure wellhead thin-walled extension casing 4. A low-pressure wellhead extension casing 3 is provided below the low-pressure wellhead 2, and a reconnectable tailpipe hanger 6 is provided inside the low-pressure wellhead extension casing 3. A guide cylinder 601 is provided at the upper end of the reconnectable tailpipe hanger 6, and a guide head 503 is provided at the lower end of the flexible insertion sealing pipe 5. In the reconnection operation mode, the flexible insertion sealing pipe 5 enters the reconnectable tailpipe hanger 6 under the guidance of the guide head 503 and the guide cylinder 601, forming a circulation channel. In the non-reconnection operation mode, a conventional extension casing is connected below the high-pressure wellhead 1, and a casing string is connected below the conventional extension casing. The casing string enters into the low-pressure wellhead extension casing 3 to form a circulation channel. Specifically, a conventional extension casing is welded below the high-pressure wellhead 1 and connected to the casing string below through the casing thread of the conventional extension casing.

[0037] In this embodiment, a thin-walled extension casing 4 is welded below the high-pressure wellhead 1; a flexible insertion sealing pipe 5 is welded below the thin-walled extension casing 4. The flexible insertion sealing pipe 5 below the high-pressure wellhead 1 is a flexible short section that can undergo slight deformation and can adapt to the tilt of the low-pressure wellhead in the reconnection operation mode. A low-pressure wellhead extension casing 3 is welded below the low-pressure wellhead 2.

[0038] Specifically, the high-pressure wellhead 1 includes a body 101, a lower support ring 107, an upper support ring 106, an adjusting ring 102, a locking ring 105, and a downward locking bushing 104. The lower end of the body 101 is connected to the lower support ring 107 by a thread. The lower support ring 107 contacts and transmits load to the low-pressure wellhead 2 through a first wellhead spherical joint Q2. The middle part of the body 101 is connected to the upper support ring 106 by a thread, and a sleeve is fitted on the upper support ring 106. An adjusting ring 102 is provided, and the upper support ring 106 contacts the adjusting ring 102 through the second wellhead spherical joint Q3 to transmit the load. A locking ring 105 is fitted on the outside of the adjusting ring 102. A downward locking bushing 104 is adapted to move downward between the adjusting ring 102 and the locking ring 105. The downward locking bushing 104 forces the locking ring 105 to open so that the locking ring 105 is locked to the low-pressure wellhead 2. The first wellhead spherical joint Q2 and the second wellhead spherical joint Q3 are located on the same spherical surface. In this embodiment, the spherical diameters corresponding to the first wellhead spherical joint Q2 and the second wellhead spherical joint Q3 are 775mm. There are no special requirements for the fit tolerance, and the fit tolerance is H13 / h13 or H14 / h14. In this embodiment, the first wellhead spherical joint Q2 and the second wellhead spherical joint Q3 must be on the same spherical surface so that the high-pressure wellhead 1 can rotate around the center of the first wellhead spherical joint Q2 and the second wellhead spherical joint Q3, thereby adjusting the tilt of the high-pressure wellhead 1.

[0039] In this embodiment, the downward locking bushing 104 and the locking ring 105 can be made of 5160 steel. The rigid downward locking bushing 104 and the locking ring 105 can increase the connection strength between the high-pressure wellhead 1 and the low-pressure wellhead 2 and improve the fatigue life of the wellhead.

[0040] Optionally, the adjusting ring 102 is provided with a check block 103 corresponding to the downward locking bushing 104. The check block 103 is used to prevent the downward locking bushing 104 from moving downward and then moving upward.

[0041] In this embodiment, the check block is a C-shaped thin sheet with teeth on its outer surface. The upper surface of the teeth is, for example, 15 degrees, and the lower surface is, for example, 75 degrees. The inner surface of the downward locking bushing 104 has corresponding teeth. After installation, the check block 103 is in a retracted state, and the teeth automatically engage with the teeth of the downward locking bushing 104. The downward locking bushing 104 experiences less resistance when sliding down the check block, but cannot slide up from the bottom due to the small tooth angle.

[0042] Specifically, a centralizing ring 301 is provided on the inner surface of the low-pressure wellhead extension casing 3. The centralizing ring 301 is used to guide the reversible tailpipe hanger 6, and the upper end of the guide cylinder 601 is located inside the centralizing ring 301. A connecting ring 302 is provided below the centralizing ring 301, and a bearing ring 303 is provided on the inner side of the connecting ring 302. The bearing ring 303 is used to suspend the reversible tailpipe hanger 6. In this embodiment, the bearing ring 303 and the connecting ring 302 are welded together.

[0043] Optionally, the reversible tailpipe hanger 6 includes a tailpipe hanger body 602 and a guide cylinder 601. The guide cylinder 601 is located at the upper end of the tailpipe hanger body 602. The tailpipe hanger body 602 is provided with a bearing step at the upper end of the bearing ring 303. The bearing step is locked above the bearing ring 303.

[0044] Specifically, the flexible insertion sealing tube 5 is composed of several flexible short sections 501 and guide heads 503 connected in series by threads. A composite module sealing ring 502 is provided between the flexible short sections 501 and the guide heads 503, and the composite module sealing ring 502 seals with the inner sealing surface of the tail tube hanger body 602.

[0045] Specifically, the high-pressure wellhead 1 can be directly connected to the casing below when no reconnection is required.

[0046] A method for using an adjustable-angle underwater wellhead as described above, which allows for both reconnection and non-reconnection operation modes during installation, includes the following steps:

[0047] Reconnection mode:

[0048] The low-pressure wellhead 2 and surface casing are installed using either the jet-adsorption method or the drilling-cementing method; the jet-adsorption method or the drilling-cementing method is existing technology;

[0049] The drilling-cementing method was used to install the reconnectable tailpipe hanger and casing.

[0050] Using the underwater wellhead angle adjustment tool T1, the high-pressure wellhead 1 is lowered, and a flexible insertion sealing pipe 5 and a retractable tailpipe hanger 6 are connected. The high-pressure wellhead 1 is then positioned above the low-pressure wellhead 2. The angle of the high-pressure wellhead 1 is adjusted to a predetermined angle by adjusting the boat and moving the derrick. A level can be used to guide the operation, making it easy to adjust the high-pressure wellhead 1 to a near-vertical state. Adjusting the angle of the high-pressure wellhead 1 by adjusting the boat and moving the derrick is existing technology.

[0051] The hydraulic cylinder of the underwater wellhead angle adjustment tool T1 is driven by a hydraulic pipeline to press down and lock the bushing 104 downward. The downward locking bushing 104 moves downward between the adjusting ring 102 and the locking ring 105, forcing the locking ring 105 to open so that the locking ring 105 locks with the low-pressure wellhead 2, thereby locking the high-pressure wellhead 1 and the low-pressure wellhead 2. The downward locking bushing 104 can be hydraulically driven to move downward. The specific process of adjusting and locking the high-pressure wellhead is as follows: the bottom of the hydraulic cylinder piston of the underwater wellhead angle adjustment tool T1 contacts the downward locking bushing 104 of the high-pressure wellhead 1 through the service tool spherical pair Q1 and transmits the load. The service tool spherical pair Q1 contacts the first wellhead spherical pair Q2 and the second wellhead spherical pair. The spheres of Q3 are concentric; in order to better position and support the subsea wellhead angle adjustment tool T1, the upper end face of the adjusting ring 102 and the lower end face of the subsea wellhead angle adjustment tool T1 also contact each other through the spherical pair. In the initial state when the downward locking bushing 104 has not moved downward, the spherical pair is coplanar with the spherical pair of the service tool Q1. At this time, the spherical diameter of the spherical pair of the service tool Q1 is 1000mm. There are no special requirements for the fit tolerance. The fit tolerance is H13 / h13 or H14 / h14. During the installation of the high-pressure wellhead 1, the drill pipe connects the high-pressure wellhead feeding tool E1, the subsea wellhead angle adjustment tool T1 and the high-pressure wellhead 1. The flexible short section 501 of the high-pressure wellhead 1 is passed through the low-pressure wellhead 2 and inserted into the reversible tailpipe hanger 6. The subsea wellhead angle adjustment tool T1 is first pressurized to 200 psi. The hydraulic cylinder of the subsea wellhead angle adjustment tool T1 is pressed down to lock the bushing 104 downwards a certain distance. At this time, the locking ring 105 is only partially opened. The outer wall of the locking ring 105 has a toothed locking part. The inner wall of the low-pressure wellhead 2 has a corresponding locking ring groove. A small part of the locking ring 105 is embedded in the locking ring groove of the inner wall of the low-pressure wellhead 2. Since the high-pressure wellhead 1 can contact the low-pressure wellhead 2 through the first wellhead spherical joint Q2 and the second wellhead spherical joint Q3, the angle of the high-pressure wellhead 1 can be adjusted by adjusting the boat and moving the derrick. The vertical adjustment distance can be adjusted by 1-3 mm. However, the high-pressure wellhead 1 cannot be pulled out of the low-pressure wellhead 2 by raising the drill pipe. During the adjustment process, due to the configuration of the spherical joint Q1 of the service tool, the subsea wellhead angle adjustment tool will not interfere with the downward locking bushing 104. Next, the drill pipe is pulled up by approximately 20 klbs to straighten the drill pipe and high-pressure wellhead. The reading on the level gauge on the subsea wellhead angle adjustment tool T1 is observed to drop to within 0.5 degrees. The subsea wellhead angle adjustment tool T1 is then pressurized to 500-1000 psi. The hydraulic cylinder of the subsea wellhead angle adjustment tool T1 presses down the downward locking bushing 104, fully opening the locking ring 105. The locking force generated by the locking ring 105 is approximately several hundred klbs, generating friction on the second wellhead spherical joint Q3 to inhibit the high-pressure wellhead 1 from rotating along the second wellhead spherical joint Q3, preventing the high-pressure wellhead from moving relative to the low-pressure wellhead. At this point, the reading on the level gauge on the subsea wellhead angle adjustment tool T1 is the final tilt angle of the high-pressure wellhead 1.

[0052] Retrieve the subsea wellhead angle adjustment tool and carry out subsequent drilling and completion operations;

[0053] No callback mode:

[0054] The low-pressure wellhead 2 and surface casing are installed using either the jet-adsorption method or the drilling-cementing method; the jet-adsorption method or the drilling-cementing method is existing technology;

[0055] Using the underwater wellhead angle adjustment tool T1, the high-pressure wellhead 1 and casing string are lowered, and the high-pressure wellhead 1 is positioned on the low-pressure wellhead 2. The angle of the high-pressure wellhead 1 is adjusted to the predetermined angle by adjusting the boat and moving the derrick. A level instrument can be used to guide the operation, making it easy to adjust the high-pressure wellhead 1 to a vertical position. Adjusting the angle of the high-pressure wellhead 1 by adjusting the boat and moving the derrick is existing technology.

[0056] The hydraulic cylinder of the underwater wellhead angle adjustment tool T1 is driven by the hydraulic pipeline to press down and lock the bushing 104 downward. The downward locking bushing 104 moves downward to between the adjusting ring 102 and the locking ring 105. The downward locking bushing 104 forces the locking ring 105 to open so that the locking ring 105 locks with the low-pressure wellhead 2, thereby locking the high-pressure wellhead 1 and the low-pressure wellhead 2. The downward locking bushing 104 can be driven by hydraulic pressure to move downward. The specific process of adjusting and locking the high-pressure wellhead is the same as the specific process of adjusting and locking the high-pressure wellhead in the reconnection mode, and will not be described again here.

[0057] Retrieve the underwater wellhead angle adjustment tool and carry out subsequent drilling and completion operations.

[0058] Inclination of the high-pressure wellhead is permissible, as long as the inclination angle does not exceed 0.5 degrees. For low-pressure wellheads that have inclination exceeding 1 degree, the high-pressure wellhead can be adjusted to within 0.5 degrees using the first wellhead spherical joint Q2 and the second wellhead spherical joint Q3. However, it may not be possible to completely guarantee that the adjustment will reach 0 degrees.

[0059] In summary, the adjustable-angle subsea wellhead of this embodiment can adjust the inclined wellhead to a near-vertical state according to operational requirements, thereby reducing the bending moment borne by the wellhead and surface casing and improving wellhead stability. Reducing well inclination facilitates the installation of service tools, blowout preventers, and Christmas trees, further enhancing wellhead stability and reducing operational risks. Furthermore, the adjustable-angle subsea wellhead can also meet wellhead pre-inclination requirements, facilitating subsequent directional well operations, optimizing wellbore trajectory control, adapting to complex geological conditions, and improving overall operational efficiency. Through this design, the wellhead can meet both the stability requirements of vertical wells and the flexible operational needs of directional wells, achieving a multi-functional integrated application.

[0060] For ease of explanation, spatial relative terms such as "upper," "lower," "outer," and "inner" are used in the embodiments to describe the relationship of one element or feature relative to another element or feature shown in the figures. It should be understood that, in addition to the orientations shown in the figures, spatial terms are intended to include different orientations of the device during use or operation. Therefore, the exemplary term "lower" can encompass both upper and lower orientations.

[0061] Moreover, relational terms such as “3” and “4” are merely used to distinguish one component from another that has the same name, without necessarily requiring or implying any such actual relationship or order between the components.

[0062] Although preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not limiting. Those skilled in the art can make many specific modifications under the guidance of the present invention without departing from the spirit of the invention and the scope of protection of the claims, and these modifications all fall within the scope of protection of the present invention.

Claims

1. An adjustable-angle underwater wellhead, characterized in that, The system includes a high-pressure wellhead, a low-pressure wellhead, a low-pressure wellhead extension casing, and a high-pressure wellhead thin-walled extension casing. The high-pressure and low-pressure wellheads are positioned and oriented via a first wellhead spherical joint, and are locked together by a locking ring. A low-pressure wellhead extension casing is located below the low-pressure wellhead, and a high-pressure wellhead thin-walled extension casing is located below the high-pressure wellhead. In the reconnection operation mode, the high-pressure wellhead thin-walled extension casing is connected to a flexible insertion sealing pipe at its lower end. A reconnectable tailpipe hanger is located inside the low-pressure wellhead extension casing, with a guide cylinder at the upper end of the reconnectable tailpipe hanger and a guide head at the lower end of the flexible insertion sealing pipe. The flexible insertion sealing pipe enters the reconnectable tailpipe hanger under the guidance of the guide head and guide cylinder, forming a circulation channel. In the non-reconnection operation mode, a regular extension casing is connected below the high-pressure wellhead, and a casing string is connected below the regular extension casing. The high-pressure wellhead includes a body, a lower support ring, an upper support ring, an adjusting ring, a locking ring, and a downward locking bushing. The lower end of the body is connected to the lower support ring via a thread. The lower support ring contacts and transmits load to the low-pressure wellhead through a first wellhead spherical joint. The middle part of the body is connected to the upper support ring via a thread. An adjusting ring is fitted above the upper support ring. The upper support ring and the adjusting ring contact and transmit load through a second wellhead spherical joint. A locking ring is fitted outside the adjusting ring. The downward locking bushing is adapted to move downward between the adjusting ring and the locking ring. The downward locking bushing forces the locking ring to open so that the locking ring is locked to the low-pressure wellhead. The first wellhead spherical joint and the second wellhead spherical joint are located on the same spherical surface. The upper surface of the downward locking bushing is an arc surface.

2. The adjustable-angle underwater wellhead according to claim 1, characterized in that, The adjusting ring is provided with a check block corresponding to the downward locking bushing. The check block is used to prevent the downward locking bushing from moving downward and then moving upward.

3. The adjustable-angle underwater wellhead according to claim 1, characterized in that, The inner surface of the low-pressure wellhead extension casing is provided with a centralizing ring, which is used to guide the reversible tailpipe hanger. A connecting ring is provided below the centralizing ring, and a bearing ring is provided inside the connecting ring. The bearing ring is used to suspend the reversible tailpipe hanger.

4. The adjustable-angle underwater wellhead according to claim 3, characterized in that, The reversible tailpipe hanger includes a tailpipe hanger body and a guide cylinder. The guide cylinder is located at the upper end of the tailpipe hanger body. The tailpipe hanger body has a bearing step at the upper end corresponding to the bearing ring, and the bearing step is locked above the bearing ring.

5. The adjustable-angle underwater wellhead according to claim 4, characterized in that, The flexible insertion sealing tube is composed of several flexible short sections and guide heads connected in series by threads. A composite module sealing ring is provided between the flexible short sections and the guide head, and the composite module sealing ring seals with the inner sealing surface of the tail tube hanger body.

6. A method of using an adjustable-angle underwater wellhead as described in any one of claims 1-5, characterized in that, Includes the following steps: Reconnection operation mode: Low-pressure wellheads and surface casings are installed using either the jet-adsorption method or the drilling-cementing method. The drilling-cementing method is used to install the reversible tailpipe hanger and casing. Lower the high-pressure wellhead, connect the flexible insertion sealing pipe and the reversible tailpipe hanger, sit the high-pressure wellhead on the low-pressure wellhead, and adjust the angle of the high-pressure wellhead to the predetermined angle by adjusting the boat and moving the derrick. The downward locking bushing is pressed down and moves downward to between the adjusting ring and the locking ring. The downward locking bushing forces the locking ring to open so that the locking ring locks with the low-pressure wellhead, thereby locking the high-pressure wellhead and the low-pressure wellhead. Carry out subsequent drilling and completion operations; Non-return operation mode: Low-pressure wellheads and surface casings are installed using either the jet-adsorption method or the drilling-cementing method. The high-pressure wellhead and casing string are lowered, the high-pressure wellhead is positioned above the low-pressure wellhead, and the angle of the high-pressure wellhead is adjusted to the predetermined angle by adjusting the boat and moving the derrick. The downward locking bushing is pressed down and moves downward to between the adjusting ring and the locking ring. The downward locking bushing forces the locking ring to open so that the locking ring locks with the low-pressure wellhead, thereby locking the high-pressure wellhead and the low-pressure wellhead. Carry out subsequent drilling and completion operations.

Images