Integrated underwater low pressure wellhead

Abstract

The application discloses an integrated underwater low-pressure wellhead, which comprises a low-pressure wellhead connecting part, a low-pressure wellhead functional part and a low-pressure wellhead casing connecting part; a tool guide inclined surface, a limiting structure and a mounting tool connecting structure are formed on the inner wall of the low-pressure wellhead connecting part; the low-pressure wellhead functional part comprises a low-pressure wellhead back-connection section, a mounting limiting section and a connecting transition section; a plurality of guide keys are formed on the outer wall of the low-pressure wellhead back-connection section, and a back-connection joint limiting groove is formed on the inner wall; a plurality of bolt holes and a guide base disc limiting groove are formed on the outer wall of the mounting limiting section; a service tool sealing groove and a high-pressure wellhead bearing ring are formed on the inner wall of the mounting limiting section. The application has the back-connection function, improves the adaptability to the self-elevating platform operation; the back-connection tool is back-connected with the low-pressure wellhead, only needs to be pressed and lifted, and does not need to be rotated, so that the inclination angle of the low-pressure wellhead and the platform positioning precision are required to be lower, and the operation difficulty is reduced; the guide base disc is connected with the low-pressure wellhead quickly and reliably, and the bow direction of the guide base disc is convenient to adjust.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil and gas drilling equipment, and particularly relates to an integrated underwater low-pressure wellhead. BACKGROUND

[0002] The low-pressure wellhead is a part of the underwater wellhead system, which is connected at the top of the surface conduit and is a device for forming the foundation of the underwater wellhead.

[0003] The low-pressure wellhead is equivalent to the wellhead support ring of the onshore wellhead, which is anchored to the seabed to form a firm foundation to support part of the weight of the wellbore, the riser and the blowout preventer stack. The lower part of the low-pressure wellhead can be welded with a 36-inch or 30-inch casing. The upper part of the low-pressure wellhead is provided with a locking ring groove and an anti-rotation groove to facilitate connection with the low-pressure wellhead service tool.

[0004] The friction between the outer wall of the low-pressure wellhead and the casing and the seabed soil forms a firm foundation to support part of the weight of the wellbore, the riser and the blowout preventer stack.

[0005] At present, the conventional low-pressure wellhead is installed using a special installation tool and does not have the function of being connected back to the operation platform. The underwater connection and separation process of the low-pressure wellhead and the service tool need to be implemented by divers or external auxiliary control lines. The time window for underwater operation of the divers is limited by many factors such as sea conditions, and the visibility of the underwater operation tool is also limited. SUMMARY

[0006] The present application is proposed to solve the problems in the prior art, and the purpose is to provide an integrated underwater low-pressure wellhead.

[0007] The present application is implemented by the following technical solutions:

[0008] An integrated underwater low-pressure wellhead comprises a low-pressure wellhead connecting part, a low-pressure wellhead functional part and a low-pressure wellhead casing connecting part which are integrally formed from top to bottom; a tool guide slope, a limiting structure and a running sub connection structure are sequentially formed on the inner wall of the low-pressure wellhead connecting part from top to bottom; the low-pressure wellhead functional part comprises a low-pressure wellhead back connection section, an installation limiting section and a connection transition section which are sequentially connected from top to bottom; a plurality of guide keys are formed on the outer wall of the low-pressure wellhead back connection section, and the interval between adjacent guide keys forms a guide base disc bow direction adjusting groove; a back connection sub limiting groove is formed in the middle of the inner wall of the low-pressure wellhead back connection section; a plurality of bolt holes are formed on the middle outer wall of the installation limiting section; a guide base disc limiting groove is formed on the lower outer wall of the installation limiting section; and a service tool sealing groove and a high-pressure wellhead bearing ring are formed on the inner wall of the installation limiting section.

[0009] In the above technical solution, the tool guide slope is formed on the top surface of the low-pressure wellhead connecting part and is a slope inclined downward from the circumferential wall to the center.

[0010] In the technical scheme, the limiting structure is composed of a plurality of limiting grooves distributed along the circumference, and the limiting groove is a rectangular groove, and a protrusion is formed on one side groove wall.

[0011] In the technical scheme, the mounting tool connecting structure is composed of a plurality of connecting key units distributed along the circumference; each connecting key unit includes a plurality of connecting keys arranged at intervals, and the interval between adjacent connecting keys forms a feeding joint connecting groove; the connecting key is a horizontal rectangular structure, and the top surface of the connecting key is an inclined surface inclined downward to the center of the circle.

[0012] In the technical scheme, the return joint limiting groove is an annular groove, and the groove cross section is a right trapezoid.

[0013] In the technical scheme, the outer diameter of the mounting limiting section is greater than the outer diameter of the low-pressure wellhead return section, and the inner diameter of the mounting limiting section is smaller than the inner diameter of the low-pressure wellhead return section.

[0014] In the technical scheme, the bolt hole is a through hole, and the bolt hole is used for connecting hoisting bolts and / or dismounting bolts.

[0015] In the technical scheme, the service tool sealing groove is located above the plane where the bolt hole is located, and the high-pressure wellhead bearing ring is located below the plane where the bolt hole is located.

[0016] In the technical scheme, the service tool sealing groove is an annular groove, the upper part of the service tool sealing groove is in complete communication with the inside of the low-pressure wellhead return section, and the inner wall of the low-pressure wellhead return section and the groove wall of the service tool sealing groove are smoothly transitioned; the high-pressure wellhead bearing ring is formed at the connection between the mounting limiting section and the connecting transition section; the top surface of the high-pressure wellhead bearing ring is an inclined surface inclined downward to the center of the circle from the circumferential wall.

[0017] In the technical scheme, the outer wall of the connecting transition section gradually shrinks in diameter from top to bottom; the bottom of the low-pressure wellhead casing connection part is a tapered surface gradually shrinking in diameter; the outer diameter of the low-pressure wellhead casing connection part matches the connecting casing.

[0018] The beneficial effects of the present application are:

[0019] The present application provides an integrated underwater low-pressure wellhead, which can be installed to the seabed through a mounting tool and connected to a self-elevating platform through a return tool. The connection and separation process only needs to be pressed and lifted, without rotation, which reduces the requirements for the inclination angle of the low-pressure wellhead and the positioning accuracy of the platform, and reduces the operation difficulty. The connection of the guide base and the low-pressure wellhead is quick and reliable, and the bow adjustment of the guide base is convenient. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a structural schematic diagram of the present application;

[0021] Figure 2 This is a cross-sectional view of the present invention;

[0022] Figure 3 This is a perspective view of the main body of the integrated underwater low-pressure wellhead installation and reconnection tool used in this invention;

[0023] Figure 4 This is a front view of the main body of the integrated underwater low-pressure wellhead installation and reconnection tool used in this invention;

[0024] Figure 5 This is a top view of the main body of the integrated underwater low-pressure wellhead installation and reconnection tool used in this invention;

[0025] Figure 6 yes Figure 5 Cross-sectional view along the BB direction;

[0026] Figure 7 This is a perspective view of the reconnection connector of the integrated underwater low-pressure wellhead installation reconnection tool used in this invention.

[0027] Figure 8 This is a front view of the reconnection connector of the integrated underwater low-pressure wellhead installation reconnection tool used in this invention.

[0028] Figure 9 This is a cross-sectional view of the reconnection joint of the integrated underwater low-pressure wellhead installation reconnection tool used in this invention.

[0029] in:

[0030] 1. Low-pressure wellhead connection; 11. Tool guide ramp; 12. Limiting groove; 13. Feeding connector connection structure; 131. Connecting key; 132. Feeding connector connecting groove;

[0031] 2. Low-pressure wellhead functional section; 21. Low-pressure wellhead reconnection section; 211. Guide key; 212. Guide base plate heading adjustment groove; 213. Reconnection joint limiting groove; 22. Installation limiting section; 221. Bolt hole; 222. Guide base plate limiting groove; 223. Service tool sealing groove; 224. High-pressure wellhead bearing ring; 23. Connection transition section;

[0032] 3. Low-pressure wellhead casing connection;

[0033] 4. Lifting bolts;

[0034] 5. Disassemble and assemble bolts;

[0035] A1, main body; A11, casing collar; A12, body; A121, upper limit ring; A122, lower limit ring; A123, upper anti-rotation block mounting groove; A13, running sub; A131, limiting block; A132, upper locking strip; A133, guide double-cone surface; A134, sealing groove; A14, rotating ring; A141, detachable guide arm connecting panel; A15, detachable guide arm; A151, connecting panel; A152, connecting arm; A153, guide horn; A16, anti-rotation block; A2, back sub; A21, large-diameter section; A211, guide inclined surface; A212, tool limiting groove; A213, connecting structure; A22, small-diameter section; A221, shear pin mounting hole; A222, back sub sealing groove; A3, elastic shear pin.

[0036] For those skilled in the art, other related drawings can be obtained from the above drawings without creative labor. DETAILED DESCRIPTION

[0037] In order for those skilled in the art to better understand the technical solutions of the present application, the technical solutions of the present application will be further described below in combination with the drawings of the specification and through specific embodiments.

[0038] As shown in Figure 1 , Figure 2 , an integrated underwater low-pressure wellhead comprises a low-pressure wellhead connecting part 1, a low-pressure wellhead functional part 2 and a low-pressure wellhead casing connecting part 3 which are integrally formed from top to bottom;

[0039] The low-pressure wellhead connecting part 1 is a sleeve structure which is connected with the running sub A13 or back sub A2 of the installation back tool of the integrated underwater low-pressure wellhead through various structures of the inner wall;

[0040] The inner wall of the low-pressure wellhead connecting part 1 sequentially forms a tool guide inclined surface 11, a limiting structure and a running sub connecting structure 13 from top to bottom;

[0041] The tool guide inclined surface 11 is formed on the top surface of the low-pressure wellhead connecting part 1 and is an inclined surface tool guide inclined surface 11 which is inclined downward from the circumferential wall to the center, which is used to butt joint the running sub A13 or back sub A2 of the installation back tool of the integrated underwater low-pressure wellhead, and provides guide and centralizing functions for the tool;

[0042] The limiting structure is composed of a plurality of limiting grooves 12 which are uniformly distributed along the circumference, and the limiting groove 12 is a rectangular groove with a protrusion formed on one side of the groove wall; the protrusion of the limiting groove 12 cooperates with the groove wall of the limiting groove 12 to limit the limiting block A131 of the installation back tool of the integrated underwater low-pressure wellhead, and at the same time, the limiting groove 12 provides a mounting position for the setting of the anti-rotation block A16 when the integrated underwater low-pressure wellhead is connected with the tool;

[0043] The feed-through joint connecting structure 13 is composed of multiple groups of connecting key units distributed evenly along the circumference; each connecting key unit includes multiple connecting keys 131 arranged at intervals, and the intervals between adjacent connecting keys 131 form feed-through joint connecting grooves 132; the connecting keys 131 are horizontally placed rectangular strip structures, and the top surface of the connecting key 131 is an inclined surface that tilts downward toward the center of the circle; the feed-through joint connecting structure 13 cooperates with the locking structure of the feed-through joint A13, and is used to connect the feed-through joint A13 of the integrated underwater low-pressure wellhead installation back-connection tool with the integrated underwater low-pressure wellhead;

[0044] The low-pressure wellhead functional part 2 includes, from top to bottom, a low-pressure wellhead back-connection section 21, an installation limiting section 22, and a connection transition section 23;

[0045] The outer wall of the low-pressure wellhead back-connection section 21 is evenly distributed with multiple guide keys 211 along the circumference, and the intervals between adjacent guide keys 211 form guide base disc bow direction adjustment grooves 212; the guide base disc bow direction adjustment grooves 212 cooperate with the anti-rotation blocks installed on the guide base disc to provide vertical shaft direction anti-rotation for the guide base disc, and by installing the anti-rotation blocks in different guide base disc bow direction adjustment grooves 212 during installation, the bow direction adjustment function is achieved; the guide keys 211 are long strip structures with a trapezoidal cross-section, and both the top surface and the bottom surface are inclined surfaces;

[0046] The inner wall of the low-pressure wellhead back-connection section 21 has a back-connection joint limiting groove 213 formed in the middle; the back-connection joint limiting groove 213 is an annular groove with a straight-angle trapezoidal cross-section, i.e., the upper section of the back-connection joint limiting groove 213 has a consistent diameter, and the lower section gradually tapers; the back-connection joint limiting groove 213 cooperates with the upper elastic shear pin A3 of the back-connection joint A2, and when the elastic shear pin A3 is embedded in the back-connection joint limiting groove 213, it cannot be withdrawn, establishing the connection between the back-connection joint A2 and the low-pressure wellhead; by forcibly lifting to a certain tension, the elastic shear pin A3 is sheared, and the back-connection joint A2 is separated from the low-pressure wellhead;

[0047] The outer diameter of the installation limiting section 22 is greater than that of the low-pressure wellhead back-connection section 21, and the inner diameter of the installation limiting section 22 is smaller than that of the low-pressure wellhead back-connection section 21;

[0048] The middle outer wall of the installation limiting section 22 forms multiple bolt holes 221 evenly distributed along the circumference; the bolt holes 221 are through holes, and are used to connect hoisting bolts 4 and / or disassembly bolts 5; the hoisting bolts 4 are used to hoist the low-pressure wellhead during land testing, and the disassembly bolts 5 are used to compress the high-pressure wellhead outer locking ring embedded in the low-pressure wellhead, so as to separate the high-pressure wellhead from the low-pressure wellhead;

[0049] The lower outer wall of the installation limiting section 22 forms a guide base limiting groove 222, which is an annular groove and cooperates with an elastic limiting latch installed on the guide base to provide vertical limiting effect for the guide base, to hang the guide base and prevent the guide base from separating from the low-pressure wellhead;

[0050] The inner wall of the installation limiting section 22 forms a service tool sealing groove 223 and a high-pressure wellhead bearing ring 224; the service tool sealing groove 223 is located above the plane where the bolt hole 221 is located, and the high-pressure wellhead bearing ring 224 is located below the plane where the bolt hole 221 is located;

[0051] The service tool sealing groove 223 is an annular groove, the upper part of the service tool sealing groove 223 is in complete communication with the inside of the low-pressure wellhead return section 21, and the inner wall of the low-pressure wellhead return section 21 and the groove wall of the service tool sealing groove 223 are smoothly transitioned; the service tool sealing groove 223 cooperates with the sealing structure on the running sub and the return sub to realize the sealing of the low-pressure wellhead and the running sub and the return sub, and to build a closed circulation channel required for drilling;

[0052] The high-pressure wellhead bearing ring 224 is formed at the connection between the installation limiting section 22 and the connection transition section 23; the top surface of the high-pressure wellhead bearing ring 224 is a downwardly inclined surface from the circumferential wall to the center of the circle; the high-pressure wellhead bearing ring 224 cooperates with the high-pressure wellhead to hang the high-pressure wellhead;

[0053] The outer wall of the connection transition section 23 gradually reduces in diameter from top to bottom; the inner diameter of the connection transition section 23 is the same as the inner diameter of the high-pressure wellhead bearing ring 224;

[0054] The bottom of the low-pressure wellhead casing connection part 3 is a gradually tapered inclined surface; the outer diameter of the low-pressure wellhead casing connection part 3 cooperates with the connection casing.

[0055] When the integrated underwater low-pressure wellhead is running, the running sub A13 of the integrated underwater low-pressure wellhead installation return tool is connected with the integrated underwater low-pressure wellhead;

[0056] When connected, first, the locking structure of the running sub A13 is aligned with the limiting structure and the running sub connection structure 13 on the inner wall of the low-pressure wellhead connection part 1 of the integrated underwater low-pressure wellhead, that is, the corresponding grooves and protrusions are aligned, and then the running sub is pressed into place and reversed, at which time the limiting block A131 is limited between the protrusion of the limiting groove 12 and the groove wall of the limiting groove 12, and then the anti-rotation block A16 is installed into the limiting groove 12; when separated, the anti-rotation block A16 is removed first, and then the integrated underwater low-pressure wellhead is separated;

[0057] When the integrated underwater low-pressure wellhead is returned, the running sub A13 of the integrated underwater low-pressure wellhead installation return tool is first connected to the return sub A2, and then connected to the integrated underwater low-pressure wellhead;

[0058] During connection, the elastic shear pin A3 of the tie-back sub A2 cooperates with the tie-back sub limiting groove 213 of the integrated underwater low-pressure wellhead, and the installation process is direct pressing, the inside of the shear pin is retractable spring, and the shear pin is installed to the position of the tie-back sub limiting groove 213 and is clamped out. During separation, the elastic shear pin A3 is cut off by lifting, and the separation is achieved, so that the installation and recovery do not need to rotate.

[0059] The installation tie-back tool structure of the integrated underwater low-pressure wellhead used in the application is shown in Figures 3-9 The installation tie-back tool structure of the integrated underwater low-pressure wellhead used in the application is shown in

[0060] The main body A1 comprises a casing collar A11, a body A12 and a running sub A13 which are sequentially welded from top to bottom, the body A12 is externally sleeved with a rotary ring A14, and a plurality of detachable guide arms A15 are uniformly distributed on the outer part of the rotary ring A14 in a circumferential direction;

[0061] The casing collar A11 is a sleeve structure, and a casing box thread is formed on the inner wall of the casing collar A11; the casing collar A11 is connected and sealed with the male thread of a large-size casing through the casing box thread on the inner wall of the casing collar A11, a circulation channel required in drilling operation is constructed, and tensile and bending loads during drilling are borne;

[0062] The body A12 is a sleeve structure, and an upper limiting ring A121 and a lower limiting ring A122 are welded on the outer wall of the body A12, and the rotary ring A14 is arranged between the upper limiting ring A121 and the lower limiting ring A122; the upper limiting ring A121 and the lower limiting ring A122 provide vertical direction limiting for the rotary ring A14;

[0063] An upper anti-rotation block mounting groove is formed at the lower end of the body A12;

[0064] The inner diameter of the rotary ring A14 is greater than the outer diameter of the body A12; a plurality of detachable guide arm connecting panels A141 are uniformly distributed on the outer wall of the rotary ring A14 in a circumferential direction, the number of the detachable guide arm connecting panels A141 is consistent with the number of the detachable guide arms A15, and in the embodiment, both are provided as two; the detachable guide arms A15 are connected with the detachable guide arm connecting panels A141 through bolts;

[0065] The detachable guide arm A15 comprises a connecting plate A151, a connecting arm A152 and a guide horn A153 which are sequentially connected; the connecting plate A151 is connected with the detachable guide arm connecting panel A141 through a bolt; the detachable guide arm A15 cooperates with a guide pile and a guide rope to provide guiding and centralizing functions for the tool;

[0066] The running sub A13 is connected with the low-pressure wellhead or the tie-back sub A2 to construct a circulation channel required in drilling operation;

[0067] The feeding joint A13 is a sleeve structure, and an outer wall thereof sequentially forms a locking structure, a guide double-cone surface A133 and a sealing structure from top to bottom;

[0068] The locking structure comprises a plurality of locking units distributed along a circumference, and each locking unit is composed of a plurality of upper locking strips A132 arranged at intervals. The gap between adjacent upper locking strips A132 forms an upper locking groove. The upper locking strip A132 is a horizontally placed rectangular strip structure, and a top surface of the upper locking strip A132 is a downwardly inclined surface inclined towards the center of the circle. The locking structure cooperates with the connecting structure of the low-pressure well head or the tie-in joint to realize connection and bear tensile and bending loads during drilling;

[0069] A limiting block A131 is arranged above the locking unit;

[0070] The guide double-cone surface A133 is a V-shaped groove structure composed of an upper cone surface gradually reducing in diameter and a lower cone surface gradually expanding in diameter. The guide double-cone surface A133 cooperates with the guide inclined surface of the low-pressure well head or the tie-in joint to provide a guide and centralizing effect during the connection of the tie-in tool and the low-pressure well head or the tie-in joint.

[0071] The sealing structure comprises at least one sealing groove A134, and a sealing ring is arranged in the sealing groove A134. In this embodiment, two sealing grooves are arranged. The sealing structure realizes sealing between the low-pressure well head or the tie-in joint and constructs a circulation channel required during drilling operations.

[0072] An outer wall of the feeding joint A13 forms a lower anti-rotation block mounting groove, which is in communication with an upper anti-rotation block mounting groove at a lower end of the body A12. The anti-rotation block A16 is arranged in the upper and lower anti-rotation block mounting grooves to limit the vertical axis rotation of the feeding joint A13 and the low-pressure well head or the tie-in joint.

[0073] The outer diameter of the casing collar A11 is greater than that of the body A12. The outer diameter of the feeding joint A13 is greater than that of the body A12. The inner diameters of the casing collar A11, the body A12 and the feeding joint A13 are the same.

[0074] The tie-in joint A2 comprises an integrally formed large-diameter section A21 and a small-diameter section A22, and the large-diameter section A21 and the small-diameter section A22 are smoothly connected.

[0075] An inner wall of the large-diameter section A21 sequentially forms a guide inclined surface A211, a tool limiting structure and a connecting structure A213 from top to bottom.

[0076] The guide inclined surface A211 is formed on a top surface of the large-diameter section A21. The guide inclined surface A211 is a downwardly inclined surface inclined from the circumference to the center. The guide inclined surface A211 provides a guide and centralizing effect during the connection of the main body A1 and the tie-in joint A2.

[0077] The tool limiting structure is composed of a plurality of circumferentially distributed tool limiting grooves A212, the tool limiting grooves A212 are long direction grooves, a protrusion is formed on one side groove wall; the protrusion of the tool limiting groove A212 cooperates with the groove wall of the tool limiting groove A212 to limit the limiting block A131, and when the tool limiting groove A212 is integrated with the underwater low-pressure wellhead, the setting of the anti-rotation block A16 leaves an assembly position;

[0078] The connecting structure A213 is the same as the locking structure of the running joint A13, and the two cooperate to realize the connection of the running joint A13 and the tieback joint A2;

[0079] A plurality of elastic shear pin mounting holes A221 are circumferentially distributed on the outer wall of the lower end of the small diameter section A22, and an elastic shear pin A3 is arranged in the elastic shear pin mounting hole A221, which cannot be withdrawn when embedded in the tieback joint limiting groove of the low-pressure wellhead, thereby establishing the connection between the tieback joint and the low-pressure wellhead, forcibly lifting to a certain tension, shearing the elastic shear pin, and separating the tieback joint from the low-pressure wellhead.

[0080] The bottom end outer wall of the small diameter section A22 is provided with a sealing structure, which includes at least one circle of tieback joint sealing grooves A222, the tieback joint sealing grooves A222 realize sealing with the low-pressure wellhead, and construct the circulation channel required in the drilling operation;

[0081] In this embodiment, two circles of tieback joint sealing grooves A222 are provided, eight elastic shear pin mounting holes A221 and eight elastic shear pins A3 are provided.

[0082] The use method of the present application:

[0083] The installation working condition is:

[0084] Firstly, during the land preparation or deck preparation, the low-pressure wellhead installation tool is connected with the low-pressure wellhead, and the wire rope and the lifting rigging are connected on the low-pressure wellhead installation tool and the low-pressure wellhead extension casing.

[0085] Then, the guide base is hoisted to the small platform, and the guide pile and accessories are installed.

[0086] Then, the running casing string is connected, and the casing is passed through the center hole of the guide base, and the casing string is hung on the rotary table by using the casing slips.

[0087] Then, the low-pressure wellhead and the extension casing are horizontally hoisted to the catwalk by using the lifting rigging. The service tool mandrel is connected with the platform top drive hook, the low-pressure wellhead extension casing is bundled with the wire rope to keep connected with the crane hook, the top drive and the crane are cooperated to lift the low-pressure wellhead and the extension casing, the conversion of the low-pressure wellhead and the extension casing from the horizontal state to the vertical state is completed, and the low-pressure wellhead and the extension casing are connected with the casing hung on the rotary table.

[0088] Then, the low-pressure wellhead is lowered to connect the low-pressure wellhead with the guide base.

[0089] Finally, after lowering to the designated depth, the low-pressure wellhead is rotated to adjust the heading of the guide base, cementing is performed for subsequent operation, and the running-in tool is rotated and recovered according to the operation requirement.

[0090] Subsea tieback operation

[0091] First, the platform prepares the low-pressure wellhead tieback tool, and the guide rope is moved to the range of the guide base.

[0092] Then, the low-pressure wellhead tieback tool is lowered to the vicinity of the guide pile, and the low-pressure wellhead tieback tool is slowly lowered so that the horn of the tieback tool passes through the guide pile.

[0093] The low-pressure wellhead tieback tool is continuously lowered until the low-pressure wellhead tieback tool enters the low-pressure wellhead, the elastic shear pin installed on the low-pressure wellhead tieback tool is embedded into the tieback joint limiting groove 213, the low-pressure wellhead tieback tool is pulled up to a certain tension, and it is confirmed that the low-pressure wellhead tieback tool is normally connected with the low-pressure wellhead.

[0094] Finally, according to the operation requirement, the low-pressure wellhead tieback tool is pulled up to shear the elastic shear pin, and the low-pressure wellhead tieback tool is recovered.

[0095] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0096] In the description of the application, it should be noted that unless otherwise expressly specified and limited, the terms "mounting", "connection", "connecting" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; can be mechanical connection, or electrical connection; can be directly connected, or indirectly connected through intermediate medium, or the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0097] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by any person skilled in the art, and all of them fall within the protection scope and disclosure scope of the present application.

Claims

1. An integrated subsea low pressure wellhead, characterized by: The low-pressure wellhead connection part (1), the low-pressure wellhead function part (2) and the low-pressure wellhead casing connection part (3) are integrally formed from top to bottom. The inner wall of the low-pressure wellhead connection part (1) is sequentially formed from top to bottom with a tool guide slope (11), a limiting structure and a running sub connection structure (13); the limiting structure is composed of a plurality of limiting grooves (12) uniformly distributed along the circumference, and the limiting grooves (12) are rectangular grooves, one side of which is formed with a protrusion. The running sub connection structure (13) is composed of a plurality of connection key units uniformly distributed along the circumference; each connection key unit includes a plurality of spaced connection keys (131), and the space between adjacent connection keys (131) forms a running sub connection groove (132); the connection key (131) is a long rectangular structure horizontally placed, and the top surface of the connection key (131) is a slope inclined downward to the center of the circle; the running sub connection structure (13) cooperates with the locking structure of the running sub (A13). The low-pressure wellhead function part (2) includes a low-pressure wellhead back connection section (21), a mounting limiting section (22) and a connection transition section (23) connected in sequence from top to bottom. The outer wall of the low-pressure wellhead back connection section (21) forms a plurality of guide keys (211), and the space between adjacent guide keys (211) forms a guide base disc bow adjustment groove (212); the inner wall of the low-pressure wellhead back connection section (21) forms a back connection sub limiting groove (213) in the middle; the back connection sub limiting groove (213) cooperates with the elastic shear pin (A3) of the back connection sub (A2) to establish the connection between the back connection sub (A2) and the low-pressure wellhead. The outer wall of the middle part of the mounting limiting section (22) forms a plurality of bolt holes (221); the outer wall of the lower part of the mounting limiting section (22) forms a guide base disc limiting groove (222); The inner wall of the mounting limiting section (22) forms a service tool sealing groove (223) and a high-pressure wellhead bearing ring (224); The low-pressure wellhead connection part (1) is connected with the running sub (A13) or the back connection sub (A2) of the integrated underwater low-pressure wellhead installation back connection tool through the various structures of the inner wall; When the integrated underwater low-pressure wellhead is running, the running sub (A13) of the integrated underwater low-pressure wellhead installation back connection tool is connected with the integrated underwater low-pressure wellhead; when the integrated underwater low-pressure wellhead is back connected, the running sub (A13) of the integrated underwater low-pressure wellhead installation back connection tool is first connected with the back connection sub (A2), and then connected with the integrated underwater low-pressure wellhead.

2. The integrated subsea low pressure wellhead of claim 1, wherein: The tool guide slope (11) is formed on the top surface of the low-pressure wellhead connection part (1) and is a slope inclined downward to the center of the circle from the circumferential wall.

3. The integrated subsea low pressure wellhead of claim 1, wherein: The back connection sub limiting groove (213) is an annular groove, and the groove cross section is a right trapezoid.

4. The integrated subsea low pressure wellhead of claim 1, wherein: The outer diameter of the mounting limiting section (22) is greater than that of the low-pressure wellhead back connection section (21), and the inner diameter of the mounting limiting section (22) is smaller than that of the low-pressure wellhead back connection section (21).

5. The integrated subsea low pressure wellhead of claim 1, wherein: The bolt hole (221) is a through hole, and the bolt hole (221) is used for connecting the lifting bolt (4) and / or the dismounting bolt (5).

6. The integrated subsea low pressure wellhead of claim 1, wherein: The service tool sealing groove (223) is located above the plane where the bolt hole (221) is located, and the high-pressure wellhead bearing ring (224) is located below the plane where the bolt hole (221) is located.

7. The integrated subsea low pressure wellhead of claim 1, wherein: The service tool sealing groove (223) is an annular groove, the upper part of the service tool sealing groove (223) is in complete communication with the inside of the low-pressure wellhead return section (21), and the inner wall of the low-pressure wellhead return section (21) and the groove wall of the service tool sealing groove (223) are smoothly connected; the high-pressure wellhead bearing ring (224) is formed at the joint of the installation limiting section (22) and the connecting transition section (23); the top surface of the high-pressure wellhead bearing ring (224) is a downwardly inclined surface from the circumferential wall to the center of the circle.

8. The integrated subsea low pressure wellhead of claim 1, wherein: The outer wall of the connecting transition section (23) gradually reduces in diameter from top to bottom; the bottom of the low-pressure wellhead casing connection part (3) is a gradually reduced inclined surface; the outer diameter of the low-pressure wellhead casing connection part (3) is matched with the connecting casing.

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