A drilling riser self-adapting locking and sealing threaded joint

Abstract

The application discloses a kind of drilling riser self-adaptive locking and sealing threaded joint, including outer threaded joint, inner threaded joint, outer threaded section, inner threaded section, second threaded section, inner threaded section stepped locking threaded section and outer threaded section stepped locking threaded section;Outer threaded joint and inner threaded joint are connected, the outer threaded joint is provided with outer threaded section, inner threaded joint is provided with inner threaded section, the outer threaded section of outer threaded joint and the inner threaded section of inner threaded joint are connected, second threaded section is arranged in the axial middle section of inner threaded section, and inner threaded section stepped locking threaded section is arranged on second threaded section, and outer threaded section stepped locking threaded section is correspondingly provided at the junction of outer threaded section and inner threaded section stepped locking threaded section.Processing is simple by the way that multiple stepped locking threaded structures are uniformly distributed along the circumference of pipe body, site assembly is easy to control, anti-reversal effect is immediate, and additional installation of anti-reversal pin block and non-metallic sealing ring and other structures is not needed.

Description

Technical Field

[0001] This invention relates to the field of oil pipe and equipment technology, specifically to an adaptive locking and sealing threaded connection for drilling risers. Background Technology

[0002] Drilling risers are important equipment for offshore oil and gas resource exploration and development. They form a complex system connecting the seabed wellhead and the offshore drilling platform, playing a role in isolating seawater, providing a drilling fluid circulation channel, supporting auxiliary control pipelines, guiding drill pipes and drill tools, and lowering and recovering subsea drilling and completion equipment.

[0003] Threaded joints are a common method for connecting individual riser pipes into a pipe string system. They offer advantages such as simple and efficient assembly procedures, significantly saving valuable offshore drilling rig time compared to flange connections. During service, risers are subjected to complex loads including ocean currents, waves, buoyancy, external seawater pressure, platform movement, their own weight, internal drilling fluid pressure, and tension forces. Threaded joints are required to maintain structural stability and reliable sealing under dynamic combined loads. These stringent structural and sealing integrity requirements make threaded joints both a critical and vulnerable component of the riser system.

[0004] Current riser pipe products mostly use anti-reverse pins to achieve self-locking of the joint. While this provides good anti-reverse performance, it increases installation time and makes uncoupling difficult, affecting the joint's reusability. Most current riser pipe products use rubber rings for sealing. Although this is simple to manufacture and economical, it has poor on-site installation tolerance and increases the risk of seal failure due to improper rubber ring installation. Therefore, how to construct a more reasonable thread structure to achieve anti-reverse joint performance, reliable sealing, convenient manufacturing, and efficient on-site installation is a problem that needs to be solved. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides an adaptive locking and sealing threaded joint for drilling risers. This is achieved by uniformly distributing multiple stepped locking thread structures along the circumference of the pipe body. This method is simple to process, easy to control on-site assembly, provides immediate anti-reverse effect, and eliminates the need for additional anti-reverse pins and non-metallic sealing rings.

[0006] This invention is achieved through the following technical solution: a self-adaptive locking and sealing threaded joint for drilling risers, comprising an external threaded joint, an internal threaded joint, an external threaded segment, an internal threaded segment, a second threaded segment, a stepped locking threaded segment of the internal threaded segment, and a stepped locking threaded segment of the external threaded segment; the external threaded joint and the internal threaded joint are connected, the external threaded joint is provided with an external threaded segment, the internal threaded joint is provided with an internal threaded segment, the external threaded segment of the external threaded joint and the internal threaded segment of the internal threaded joint are connected, the second threaded segment is located in the axial middle section of the internal threaded segment, the second threaded segment is provided with a stepped locking threaded segment of the internal threaded segment, and the stepped locking threaded segment of the external threaded segment is correspondingly provided at the connection between the external threaded segment and the stepped locking threaded segment of the internal threaded segment.

[0007] Furthermore, multiple stepped locking thread segments are arranged in a circumferential array along the external thread joint, and multiple stepped locking thread segments are arranged in an axial array along the external thread joint.

[0008] Furthermore, the internal thread segment includes a first thread segment, a second thread segment, and a third thread segment; the first thread segment is connected to the external thread connector first during the connection process; the first thread segment, the second thread segment, and the third thread segment are connected sequentially, and the pitch of the first thread segment, the second thread segment, and the third thread segment decreases sequentially, while the pitch of the external thread segment is the same as that of the second thread segment.

[0009] Furthermore, the taper of the second threaded segment is smaller than that of the first and third threaded segments, while the taper of the external threaded segment is the same as that of the first threaded segment.

[0010] Furthermore, the third thread segment is connected to the internal thread sealing surface, and a first alloy layer is provided on the internal thread sealing surface; the external thread segment is connected to the external thread sealing surface, and a second alloy layer is provided on the external thread sealing surface; the first alloy layer and the second alloy layer are clad titanium-nickel based shape memory alloy layers.

[0011] Furthermore, the internal thread sealing surface is connected to the internal thread shoulder surface, the external thread sealing surface is connected to the external thread shoulder surface, the internal thread shoulder surface is connected to the external thread shoulder surface, and both the internal thread shoulder surface and the external thread shoulder surface are set as negative angle shoulders.

[0012] Furthermore, a first relief groove is provided between the third thread segment and the internal thread sealing surface, and the axial length of the first relief groove is 1.5 to 2 times the average thread pitch.

[0013] Furthermore, the external thread segment is provided with external thread teeth, the external thread teeth including a second guide surface and a second bearing surface; the internal thread segment is provided with internal thread teeth, the internal thread teeth including a first guide surface and a first bearing surface; the first guide surface and the first bearing surface are connected, and the second bearing surface and the second guide surface are connected; the guide surfaces of the first guide surface and the second guide surface are both set to positive angles; the first bearing surface and the second bearing surface are both set to negative angles.

[0014] Furthermore, a second grease reservoir is provided on the external thread, and a first grease reservoir is provided on the internal thread; the second grease reservoir is located at the bottom of the external thread, and the first grease reservoir is located at the bottom of the internal thread; both the second grease reservoir and the first grease reservoir are configured as semi-circular spiral grooves, and the radius of the semi-circular spiral groove is selected to be 0.3 to 0.7 mm.

[0015] Furthermore, a contact width of 3-5 mm and a contact pressure of 500-1500 MPa are provided between the internal thread sealing surface and the external thread sealing surface; the contact width and contact pressure are calculated based on the minimum sealing contact pressure under the combined ultimate load condition.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects:

[0017] This invention provides an adaptive locking and sealing threaded joint for drilling risers. By designing an interference sealing structure for the thread locking mechanism of the external and internal threaded joints, the locking and sealing performance is made adaptive to the marine operating conditions. The adaptive locking mechanism is achieved by a multi-segment stepped locking thread structure evenly distributed along the circumference of the pipe body. This method is simple to manufacture, easy to control on-site assembly, provides immediate anti-reverse effect, and eliminates the need for additional anti-reverse pins and non-metallic sealing rings.

[0018] Furthermore, the stepped locking thread structure of this device improves the uncoupling resistance to prevent reverse rotation; the thread helix angle is periodically changed to 0° along the circumferential direction, making the thread screwing process discontinuous and forming a jam at the stepped thread, thus increasing the thread reverse rotation resistance; on the other hand, it increases the threading resistance, thereby increasing the risk of thread sticking. Once sticking occurs, it will lead to a significant decrease in the load-bearing performance of the joint.

[0019] Furthermore, in existing technologies, after conventional tapered thread locking, the contact stress in the thread engagement area exhibits a saddle-shaped distribution along the axial direction. Under tensile load conditions, the large end of the external thread and the small end of the internal thread are two critical sections. The stepped locking thread design exacerbates the uneven distribution of thread stress.

[0020] Furthermore, the internal threaded connector of this device alters the segmented thread engagement state by varying the thread pitch, thereby homogenizing the thread stress distribution and reducing the stress concentration effect caused by the thread locking structure, thus improving the thread load-bearing capacity and fatigue resistance. Specifically, this is achieved by varying the pitch of the internal thread segment along the pipe body axially. This method is simple to manufacture, requires no special on-site assembly, and exhibits significant stress distribution optimization.

[0021] Furthermore, this device achieves optimization within the double-edged sword effect range of stepped threads by adjusting the taper of the internal thread connector. This is achieved by using a smaller taper in the second thread section and the same taper as the external thread in the sections near the inner and outer edges. This step significantly reduces the locking resistance of the stepped thread locking structure, simplifies the manufacturing process, requires no special on-site assembly, and achieves dual optimization of anti-reverse rotation and anti-sticking.

[0022] Furthermore, this device, through its stepped locking thread structure, variable pitch, and variable taper, achieves comprehensive performance improvements in joint anti-reverse, load-bearing capacity, fatigue resistance, and anti-galling. This is effectively demonstrated in the optimization of design parameters and the verification of physical performance through full-scale transverse vibration simulation tests, rotational bending fatigue tests, and buckling tests.

[0023] Furthermore, in the structure of the internal and external thread sealing surfaces, the sealing surfaces maintain a contact width of 3-5 mm and a contact pressure of 500-1500 MPa after the upper thread engagement, achieving the anti-leakage capability against internal and external pressure media. This ensures limited deformation resistance and ductility during the material's elastic stage. Once it enters the plastic stage, the sealing surface configuration changes with the deformation history, and the elastic-plastic resistance decreases due to the Bauschinger effect. This results in insufficient adaptability to the conditions of large bending disturbance amplitudes and long cycles during the marine service of the riser.

[0024] Furthermore, the first and second alloy layers of this device employ clad titanium-nickel-based shape memory alloy layers. These layers utilize unique superelasticity and shape memory properties to maintain stable sealing surface contact pressure under complex dynamic composite loads. Based on the design criterion of meeting the minimum sealing contact pressure under composite ultimate load conditions for the riser, reasonable sealing surface contact pressure and width are determined, thereby defining the key process parameters for the clad titanium-nickel-based shape memory alloy layer. This design demonstrates strong manufacturing feasibility, can adaptively and continuously maintain the dimensional accuracy and material strength reliability of the sealing structure under complex marine conditions, requires no additional sealing components, and exhibits strong adaptability and high efficiency in on-site operations.

[0025] Furthermore, both the internal and external thread shoulder surfaces of this device adopt a negative angle shoulder structure, which takes into account the joint's resistance to compression, resistance to torsion, and reverse support for the sealing structure.

[0026] Furthermore, the internal and external threads of this device are provided with semi-circular cross-section spiral grooves at the root, which can be used for the storage and transportation of thread grease. This is especially suitable for solving the problem of significant thread grease blockage caused by factors such as large outer diameter of the water-proof pipe and large thread engagement length.

[0027] Furthermore, the thread profiles of both the external and internal thread sections of this device adopt a positive angle on the guide surface and a negative angle on the bearing surface. This step ensures good thread engagement, smooth threading, and load-bearing performance. 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 A schematic diagram of a stepped locking thread section of an external thread of a water-tight pipe provided in an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of a stepped locking thread section of an internal thread of a water-proof pipe provided in an embodiment of the present invention;

[0031] Figure 3 A cross-sectional view of the internal thread segment of a water-proof pipe provided in an embodiment of the present invention;

[0032] Figure 4 A cross-sectional view of the internal thread segment of a water-proof pipe provided in an embodiment of the present invention;

[0033] Figure 5 A cross-sectional view of the internal thread sealing surface of a water-proof pipe provided in an embodiment of the present invention;

[0034] Figure 6 A cross-sectional view of the external thread sealing surface of a water-proof pipe provided in an embodiment of the present invention;

[0035] Figure 7 A cross-sectional view of the internal thread teeth of a water-proof pipe provided in an embodiment of the present invention;

[0036] Figure 8 A cross-sectional view of the external thread of an internal thread in a water-proof pipe provided in an embodiment of the present invention;

[0037] Figure 9 Test results of a sealing performance design criterion for a water-proof pipe provided in an embodiment of the present invention;

[0038] Figure 10 This is a schematic diagram of the composite load envelope of a water-proof pipe provided in an embodiment of the present invention.

[0039] In the diagram: 1. External thread connector; 2. Internal thread connector; 5. First alloy layer; 6. Second alloy layer; 7. Internal thread tooth; 8. External thread tooth; 11. External thread segment; 12. Stepped locking thread segment of external thread segment; 21. Internal thread segment; 22. Stepped locking thread segment of internal thread segment; 31. First thread segment; 32. Second thread segment; 33. Third thread segment; 34. First relief groove; 35. Internal thread sealing surface; 36. Internal thread shoulder surface; 42. External thread sealing surface; 43. External thread shoulder surface; 71. First grease reservoir; 72. First guide surface; 73. First bearing surface; 81. Second guide surface; 82. Second grease reservoir; 83. Second bearing surface. Detailed Implementation

[0040] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0041] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used 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.

[0042] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0043] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0044] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0045] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0046] Example 1:

[0047] The purpose of this invention is to provide an adaptive locking and sealing threaded joint for drilling risers, which can effectively improve the working condition applicability of the joint's self-locking and sealing structure.

[0048] It includes an external threaded connector 1, an internal threaded connector 2, a first alloy layer 5, a second alloy layer 6, an internal thread 7, an external thread 8, an external thread segment 11, a stepped locking thread segment 12, an internal thread segment 21, a stepped locking thread segment 22, a first thread segment 31, a second thread segment 32, a third thread segment 33, a first relief groove 34, an internal thread sealing surface 35, an internal thread shoulder surface 36, an external thread sealing surface 42, an external thread shoulder surface 43, a first guide surface 72, a first grease reservoir 71, a first guide surface 72, a first bearing surface 73, a second guide surface 81, a second grease reservoir 82, and a second bearing surface 83.

[0049] Specifically, this is achieved by using a tapered external thread connector 1 and an internal thread connector 2 for connection; the internal thread connector 2 is provided with an internal thread section 21, the internal thread section 21 is provided with an internal thread tooth 7, and at the axial middle position of the internal thread tooth 7, a stepped locking thread section 22 is evenly distributed along the circumference of the pipe body, which is achieved by periodically changing the thread helix angle;

[0050] The external thread section 11 has a fixed pitch, the internal thread section 21 has a variable pitch along the pipe body axis, the second thread section 32 in the middle axial section of the internal thread section 21 has the same pitch as the external thread section 11, the third thread section 33 near the inner shoulder section has a smaller pitch, and the first thread section 31 near the outer end face section has a larger pitch; the external thread tooth 8 has a fixed taper.

[0051] The internal thread tooth 7 has a tapered change along the axial direction of the pipe body. The second thread section 32 in the middle axial section of the internal thread section 21 has a smaller tapered change. The third thread section 33 near the inner side and the first thread section 31 near the outer side have the same tapered change as the external thread section 11.

[0052] In this device, the number and circumferential dimensions of the stepped self-locking threaded sections are verified and determined through full-size transverse vibration simulation test, rotational bending fatigue test, and upper and lower buckle test, and the pitch and taper changes are reasonably matched.

[0053] The nose of the external threaded connector 1 includes an external thread shoulder surface 43, an external thread sealing surface 42, and an external thread cylindrical transition section connected in sequence. The external thread cylindrical transition section is located between the external thread section 11 and the external thread sealing surface 42. The external thread sealing surface 42 ensures the stability of the machining dimensions of the external thread sealing surface 42 and the external thread shoulder surface 43. It also avoids interference between the nose of the inner and outer connectors during the threading process, avoids the first relief groove 34, and effectively reduces the impact of thread interference on the sealing contact pressure.

[0054] The nose end of the external threaded connector 1 corresponds to the internal threaded connector 2. The internal threaded connector 2 includes an internal threaded shoulder surface 36, an internal threaded sealing surface 35, and a first relief groove 34 connected in sequence. The first relief groove 34, the internal threaded sealing surface 35, and the internal threaded shoulder surface 36 are connected in sequence.

[0055] When the external threaded connector 1 and the internal threaded connector 2 are engaged, the external thread sealing surface 42 is in close contact with the internal thread sealing surface 35, and the external thread shoulder surface 43 is in close contact with the internal thread shoulder surface 36.

[0056] A second alloy layer 6 and a first alloy layer 5 are provided on the external thread sealing surface 42 and the internal thread sealing surface 35, respectively. The second alloy layer 6 and the first alloy layer 5 are clad with a titanium-nickel-based shape memory alloy layer using an additive manufacturing method. This allows them to maintain uniform and sufficient sealing surface contact pressure under complex dynamic composite loads due to their unique superelasticity and shape memory properties. The radial sealing surface contact pressure of the clad titanium-nickel-based shape memory alloy layer is compared with the sealing capacity S of the thread structure. C and sealing requirements under service conditions S D The size is used to evaluate the design.

[0057] Threaded structure sealing capacity SC The resistance to leakage is represented by the contact pressure and contact length of the sealing surface.

[0058] S C =∫ L σ n (l)dl

[0059] σ represents the sealing contact pressure, in MPa; L represents the sealing contact width, in mm.

[0060] Service condition sealing requirements S D This represents the potential for leakage to occur, and it is determined by an equation consisting of the pressure difference, the pipe outer diameter, and the leakage threshold:

[0061] S D =AD k Q m P

[0062] D represents the outer diameter of the pipe, in mm; P represents the pressure difference between the inside and outside of the pipe, in MPa; A, k, Q, and m are design parameters, determined based on interference fit sealing physical tests.

[0063] In this embodiment, the leakage threshold Q is the minimum leakage threshold specified in ISO 12835, ISO 13679, and API RP 5C5. Recommended values ​​for A, m, and k are shown in the table below.

[0064] Recommended values ​​for sealing criterion parameters

[0065] parameter Recommended value unit A 35 <![CDATA[MPa n-1 mm 1-k (mL / min) -m ]]> k 0.8 / m -0.08 / n 1.95 /

[0066] The radial metal-metal interference sealing structure used in the water-tight pipe joint maintains a contact width of 3-5 mm and a contact pressure of 500-1500 MPa after engagement, achieving leakage resistance to internal and external pressure media with the minimum sealing contact pressure design criterion S that prevents leakage. C ≥S D Based on the design principle of meeting the minimum sealing contact pressure under the combined ultimate load of the full envelope of the equivalent yield stress of the riser under internal pressure, external pressure, tension, compression and bending, the reasonable sealing surface contact pressure and width are optimized and determined. Then, the key process parameters of the cladding titanium-nickel-based shape memory alloy layer are determined, including but not limited to the particle size of titanium-nickel-based spherical powder, oxygen content of the coating environment, laser power, scanning speed, laser spot diameter, synchronous powder feeding speed, coating pass overlap rate, and single pass material thickness. This ensures the dimensional accuracy of the thread and the equal or high strength matching between the sealing surface material and the pipe body substrate.

[0067] Both the external thread section 11 and the internal thread section 21 adopt a trapezoidal thread profile with a positive guide surface angle, a negative bearing surface angle, and the tooth tip surface parallel to the generatrix of the tapered thread.

[0068] The root of the external thread section 11 and the internal thread section 21 are respectively provided with a second grease storage and transportation groove 82 and a first grease storage and transportation groove 71. Both the second grease storage and transportation groove 82 and the first grease storage and transportation groove 71 are set as semi-circular spiral grooves for storing and transporting thread grease.

[0069] In this embodiment, the stepped locking thread section 22 of the internal thread segment is selectively provided with 4, 6, or 8 sets of evenly distributed thread segments with a helix angle of 0° along the circumference of the pipe body. The length of the thread segment can be selectively set to 1 / 8, 1 / 12, or 1 / 16 of the circumference of its position on the pipe body. The internal thread teeth 7 and external thread teeth 8 can be selectively set to 3 to 5 teeth per inch. The normal pitch of the second thread segment 32 is selected to be 8.47 mm, 6.35 mm, or 5.08 mm. The corresponding smaller pitch of the third thread segment 33 of the internal thread is selected to be 8.39 mm, 6.28 mm, or 5.02 mm. The larger pitch of the first thread segment 31 of the internal thread is selected to be 8.54 mm, 6.41 mm, or 5.14 mm. One to two linear pitch transition sections within the pitch range are set before and after the second thread segment 32 in the middle section of the internal thread, gradually approaching the smaller and larger pitch thread segments. The normal taper of the external thread segment 11 and the internal thread segment 21 is 25.4 mm per increment; the diameter increments along the axial length are selected as 1.59 mm, 3.175 mm, and 4.23 mm. Correspondingly, the smaller taper of the second internal thread segment 32 is set at 25.4 mm per increment; the diameter increments along the axial length are 1.53 mm, 3.105 mm, and 3.43 mm. One to two axial arc transition sections within the pitch range are provided before and after the second thread segment 32 in the middle section of the internal thread, approximating the smaller and normal taper thread segments with different taper tolerance zones. The guide surface of the thread tooth is selected as 25°, 30°, and 40°; the bearing surface of the thread tooth is selected as -3° and -5°; the side fit clearance of the thread tooth is 0.02–0.1 mm; and the crest fit clearance of the thread tooth is 0.01–0.08 mm.

[0070] The root of the internal thread 7 and the external thread 8 is provided with a semi-circular cross-section spiral groove with a radius of 0.3 to 0.7 mm; the shoulder surfaces of the internal thread shoulder surface 36 and the external thread shoulder surface 43 are both negative angles, selected from -5 to -15°; the radial sealing structure of the thread adopts the inner conical surface-outer conical surface or the inner conical surface-outer arc surface sealing surface fit, and the taper angle of the conical sealing surface is 10 to 25°; the axial length of the internal thread sealing surface 35 is greater than or equal to 3.35 mm, the radius of the arc sealing surface is 50 to 120 mm, and the roughness is controlled to be 0.5 to 0.8 μm.

[0071] The titanium-nickel-based shape memory alloy spherical powder has a particle size of 75–120 μm; the cladding environment is controlled to have an oxygen content of less than 50 ppm; the input laser power is 1.0 kW–1.5 kW, the scanning speed is 5 mm / s–10 mm / s, the laser spot diameter is 1–2 mm, and the synchronous powder feeding speed is 0.4 g / min–0.7 g / min; the shape memory alloy layers are stacked layer by layer in multiple passes, with a multi-pass overlap rate of 40%, and the thickness of the material stacked in a single pass is less than 0.2 mm. The first unloading groove 34 is used for unloading the tool and storing thread grease, and the axial length of the unloading groove is 1.5–2 times the average pitch.

[0072] Example 2:

[0073] like Figure 1 , Figure 2 As shown, the present invention provides an adaptive locking and sealing threaded joint for drilling risers, including an external threaded joint 1 and an internal threaded joint 2 with tapered thread connection;

[0074] The external threaded connector 1 includes an external threaded section 11, an external threaded sealing surface 42, and an external threaded shoulder surface 43 connected in sequence; the external threaded section 11 includes a stepped locking threaded section 12; the internal threaded connector 2 includes an internal threaded section 21, a first relief groove 34, an internal threaded sealing surface 35, and an internal threaded shoulder surface 36 connected in sequence; the internal threaded section 21 includes a stepped locking threaded section 22;

[0075] The internal thread segment 21 includes a first thread segment 31, a second thread segment 32, and a third thread segment 33; the first thread segment 31, the second thread segment 32, and the third thread segment 33 are connected in sequence; the first thread segment 31 adopts a larger pitch and a normal taper, the second thread segment 32 adopts a normal pitch and a smaller taper, and the third thread segment 33 adopts a smaller pitch and a normal taper.

[0076] The sealing surfaces of the external thread sealing surface 42 and the internal thread sealing surface 35 are respectively clad with a titanium-nickel-based shape memory alloy layer, a first alloy layer 5 and a second alloy layer 6; the internal thread tooth 7 adopts a positive angle first guide surface 72, a negative angle first bearing surface 73 and a first grease storage groove 71 located at the bottom of the tooth; the external thread tooth 8 adopts a positive angle second guide surface 81, a negative angle second bearing surface 83 and a second grease storage groove 82 located at the bottom of the tooth.

[0077] Both the external threaded connector 1 and the internal threaded connector 2 are steel pipe connectors. The outer diameter of the external threaded connector 1 is set to 508 mm, and the outer diameter of the internal threaded connector 1 is set to 550 mm.

[0078] At the position of the second thread segment 32 in the axial middle section of the internal thread segment 21 of the internal thread connector 2, multiple stepped locking thread segments 22 are evenly distributed along the circumference of the pipe body. This is achieved by periodically changing the thread helix angle. Specifically, 4 groups (90°), 6 groups (60°), and 8 groups (45°) of thread segments with a helix angle of 0° are selectively arranged along the circumference of the pipe body. The length of the thread segment can be selectively set to 1 / 12 of the circumference of the pipe body. The external thread tooth 41 adopts a fixed pitch, that is, 3 to 5 teeth per inch are selectively set, and the fixed pitch is selected to be 6.35 mm.

[0079] The pitch of the internal thread 21 varies along the axial direction of the pipe body. The second thread segment 32 in the middle section of the internal thread adopts the same pitch as the external thread, that is, 6.35mm. The third thread segment 33 near the inner shoulder adopts a smaller pitch, that is, 6.28mm. The first thread segment 31 near the outer end face adopts a larger pitch, that is, 6.41mm. Two linear pitch transition segments are set before and after the middle section 32 of the internal thread, gradually approaching the smaller and larger pitch thread segments.

[0080] The external thread 41 adopts a fixed taper, that is, the diameter increment is selected as 3.175mm for every 25.4mm axial length; the internal thread 21 has a varying taper along the pipe body axial direction, and the second thread section 32 in the middle of the internal thread axial direction adopts a smaller taper, that is, the diameter increment is selected as 3.105mm for every 25.4mm axial length; the third thread section 33 near the inner side and the first thread section 31 on the outer side adopt the same taper as the external thread section 11; an axial arc transition section within the pitch range is set before and after the second thread section 32, with different taper tolerance zones to approximate the smaller and normal taper thread sections.

[0081] The nose end of the external threaded connector 1 includes an external threaded shoulder surface 43 and an external threaded sealing surface 42 connected in sequence; corresponding to the nose end of the external threaded connector 1, the inner side of the internal threaded connector 2 includes an internal threaded shoulder surface 36, an internal threaded sealing surface 35, and a first relief groove 34 connected in sequence.

[0082] When the external threaded connector 1 and the internal threaded connector 2 are engaged, the external threaded sealing section 42 and the internal threaded sealing section 35, and the external threaded shoulder section 43 and the internal threaded shoulder section 36 are in close contact; the radial sealing structure of the thread adopts the inner conical surface-outer conical surface or the inner conical surface-outer arc surface sealing surface fit, the taper angle of the conical sealing surface is 15°, the axial length of the sealing surface of the internal threaded sealing section is greater than or equal to 3.35mm, the radius of the arc sealing surface is 70mm, and the roughness is controlled to be 0.6um;

[0083] The external thread sealing surface 42 and the internal thread sealing surface 35 are clad with a first alloy layer 5 and a second alloy layer 6 of titanium-nickel based shape memory alloy using an additive manufacturing method. With its special superelasticity and shape memory properties, it maintains uniform and sufficient contact pressure on the sealing surface under complex dynamic composite loads. The titanium-nickel based shape memory alloy spherical powder has a particle size of 75-120μm. The oxygen content in the cladding environment is controlled to be less than 50ppm. The input laser power is 1.0kW-1.5kW, the scanning speed is 5mm / s-10mm / s, the laser spot diameter is 1-2mm, and the synchronous powder feeding speed is 0.4g / min-0.7g / min. The shape memory alloy layers are stacked layer by layer in multiple passes, with a multi-pass overlap rate of 40% and a single-pass stacking material thickness of less than 0.2mm.

[0084] The radial metal-metal interference sealing structure used in the water-tight pipe joint maintains a contact width of 3-5 mm and a contact pressure of 500-1500 MPa after engagement, achieving leakage resistance to internal and external pressure media with the minimum sealing contact pressure design criterion S that prevents leakage. C ≥S D Based on the goal of meeting the minimum sealing contact pressure design criterion under the combined ultimate load conditions of the water-proof pipe bearing internal pressure, external pressure, tension, compression and bending 95% equivalent yield stress full envelope, the reasonable sealing surface contact pressure and width are optimized and determined. Then, the key process parameters of the cladding titanium-nickel-based shape memory alloy layer are determined, including but not limited to the particle size of titanium-nickel-based spherical powder, oxygen content of the coating environment, laser power, scanning speed, laser spot diameter, synchronous powder feeding speed, coating pass overlap rate, and single pass material thickness. This ensures the dimensional accuracy of the thread and the equal or high strength matching between the sealing surface material and the pipe body substrate.

[0085] Both the external thread section 41 and the internal thread section 21 adopt a thread profile with positive angles of 25°, 30° and 40° for the first guide surface 72 and the second guide surface 81, and negative angles of -3° and -5° for the bearing surfaces of the first bearing surface 73 and the second bearing surface 83. The thread profile is a trapezoidal shape with the tooth tip surface parallel to the generatrix of the tapered thread. The thread flank clearance is 0.02 to 0.1 mm, and the thread tip clearance is 0.01 to 0.08 mm.

[0086] The bottom of the internal thread 7 and the external thread 8 is provided with a semi-circular cross-section spiral groove, a first grease storage and transportation groove 71 and a second grease storage and transportation groove 82, for storing and transporting thread grease. The bottom of the internal and external threads is provided with a semi-circular cross-section spiral groove with a radius of 0.3 to 0.7 mm.

[0087] The shoulder surfaces of the internal thread shoulder 36 and the external thread sealing surface 42 of the internal and external thread shoulder sections both adopt negative angles, ranging from -5° to -15°; the first unloading groove 34 is used for unloading the tool and storing thread grease.

[0088] This invention achieves adaptive locking and sealing performance to marine operating conditions by designing a threaded locking mechanism and a metal-metal interference sealing structure for the joint, eliminating the need for additional anti-reverse pins and non-metallic sealing rings.

[0089] The adaptive locking mechanism achieves this by uniformly distributing multiple stepped locking thread structures along the circumference of the pipe body. This results in a discontinuous thread engagement process, creating a jam at the stepped thread and increasing the resistance to thread reversal. By varying the thread pitch, the engagement state of the thread segments is altered, making the thread stress distribution more uniform and reducing the stress concentration effect caused by the thread locking structure, thereby improving the thread load-bearing capacity and fatigue resistance. The thread tapering scheme reduces the thread engagement resistance of the stepped thread segments, and the manufacturing process is simple with no special requirements for on-site assembly, achieving the dual objectives of preventing reversal and preventing sticking. By combining the stepped locking thread, variable pitch, and variable taper schemes, the joint achieves comprehensive performance improvements in preventing reversal, increasing load-bearing capacity, fatigue resistance, and preventing sticking. The design process involved full-scale transverse vibration simulation tests, rotational bending fatigue tests, and threading / unthreading tests to optimize design parameters and verify physical performance.

[0090] The riser joint adopts a radial metal-metal interference sealing structure. After the upper thread engages, the sealing strength achieves anti-leakage capability against internal and external pressure media. The internal and external thread sealing surfaces are clad with a titanium-nickel-based shape memory alloy layer using additive manufacturing. Its unique superelasticity and shape memory properties maintain stable sealing surface contact pressure under complex dynamic composite loads, improving its adaptability to the large bending disturbance amplitude and long cycle of the riser during marine service. The design principle is based on the minimum sealing contact pressure S that prevents leakage. C ≥S D Based on the goal of meeting the minimum sealing contact pressure design criterion under the combined ultimate load of the full envelope of the equivalent yield stress of the riser under internal pressure, external pressure, tension, compression and bending, the reasonable sealing surface contact pressure and width are determined, and then the key process parameters of the cladding titanium-nickel based shape memory alloy layer are determined.

[0091] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0092] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A self-adaptive locking and sealing threaded joint for drilling risers, characterized in that, It includes an external threaded connector (1), an internal threaded connector (2), an external threaded section (11), and an internal threaded section (21); the external threaded connector (1) and the internal threaded connector (2) are connected, the external threaded connector (1) is provided with an external threaded section (11), the internal threaded connector (2) is provided with an internal threaded section (21), the external threaded section (11) of the external threaded connector (1) and the internal threaded section (21) of the internal threaded connector (2) are connected, a second threaded section (32) is provided in the axial middle section of the internal threaded section (21), and an internal threaded section stepped locking threaded section (22) is provided on the second threaded section (32), and an external threaded section stepped locking threaded section (12) is provided at the connection between the external threaded section (11) and the internal threaded section stepped locking threaded section (22); The internal thread segment (21) includes a first thread segment (31), a second thread segment (32), and a third thread segment (33); the first thread segment (31) is connected to the external thread connector (1) first during the connection process; the first thread segment (31), the second thread segment (32), and the third thread segment (33) are connected in sequence, and the pitch of the first thread segment (31), the second thread segment (32), and the third thread segment (33) decreases in sequence, and the pitch of the external thread segment (11) is the same as that of the second thread segment (32); The taper of the second thread segment (32) is smaller than that of the first thread segment (31) and the third thread segment (33), and the taper of the external thread segment (11) is the same as that of the first thread segment (31); The third thread segment (33) is connected to the internal thread sealing surface (35), and a first alloy layer (5) is provided on the internal thread sealing surface (35). The external thread segment (11) is connected to the external thread sealing surface (42), and a second alloy layer (6) is provided on the external thread sealing surface (42). The first alloy layer (5) and the second alloy layer (6) are clad titanium-nickel based shape memory alloy layers. A contact width of 3-5 mm and a contact pressure of 500-1500 MPa are provided between the internal thread sealing surface (35) and the external thread sealing surface (42); the contact width and contact pressure are calculated based on the minimum sealing contact pressure under the combined ultimate load condition.

2. The self-adaptive locking and sealing threaded joint for drilling risers according to claim 1, characterized in that, The stepped locking thread segment (22) of the internal thread segment is arranged in an axial array along the external thread joint (1) with multiple stepped locking thread segments (22).

3. The self-adaptive locking and sealing threaded joint for drilling risers according to claim 1, characterized in that, The internal thread sealing surface (35) is connected to the internal thread shoulder surface (36), the external thread sealing surface (42) is connected to the external thread shoulder surface (43), the internal thread shoulder surface (36) is connected to the external thread shoulder surface (43), and both the internal thread shoulder surface (36) and the external thread shoulder surface (43) are set as negative angle shoulders.

4. The self-adaptive locking and sealing threaded joint for drilling risers according to claim 1, characterized in that, A first relief groove (34) is provided between the third thread segment (33) and the internal thread sealing surface (35), and the axial length of the first relief groove (34) is 1.5 to 2 times the average thread pitch.

5. The self-adaptive locking and sealing threaded joint for drilling risers according to claim 1, characterized in that, The external thread segment (11) is provided with an external thread tooth (8), the external thread tooth (8) includes a second guide surface (81) and a second bearing surface (83); the internal thread segment (21) is provided with an internal thread tooth (7), the internal thread tooth (7) includes a first guide surface (72) and a first bearing surface (73); the first guide surface (72) and the first bearing surface (73) are connected, and the second bearing surface (83) and the second guide surface (81) are connected; the guide surfaces of the first guide surface (72) and the second guide surface (81) are both set to positive angles; the first bearing surface (73) and the second bearing surface (83) are both set to negative angles.

6. A self-adaptive locking and sealing threaded joint for drilling risers according to claim 5, characterized in that, A second grease reservoir (82) is provided on the external thread (8), and a first grease reservoir (71) is provided on the internal thread (7). The second grease reservoir (82) is located at the bottom of the external thread (8), and the first grease reservoir (71) is located at the bottom of the internal thread (7). Both the second grease reservoir (82) and the first grease reservoir (71) are set as semi-circular spiral grooves, and the radius of the semi-circular spiral grooves is selected to be 0.3~0.7mm.

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