A tapered stress joint for butt-welded connection of risers

Abstract

This utility model discloses a tapered stress joint for butt-welded risers, belonging to the field of marine oil and gas resource extraction equipment. It includes a suspension body with a constant inner diameter. The outer wall of the pipe is thicker in the middle and thinner at both ends, with a concave arc transition from the thickest part of the outer wall to the top and a concave arc transition from the thickest part to the bottom. An upper connecting flange for connection to a marine oil and gas resource extraction platform is fixed to the top of the suspension body. A deformable cone with the same inner diameter as the suspension body is sleeved on the lower part of the suspension body. A lower adapter for connection to a marine oil and gas riser is fixed to the lower end of the deformable cone. This utility model solves the problems of easy cracking at the weld seam and high maintenance costs in existing tapered stress joints for butt-welded risers. During maintenance, only the threaded connection part needs to be disassembled, eliminating the need to cut the weld seam, greatly simplifying the maintenance process and reducing maintenance costs.

Description

Technical Field

[0001] This utility model belongs to the field of marine oil and gas resource extraction equipment, specifically relating to a tapered stress joint for butt-welded connection of risers. Background Technology

[0002] In offshore subsea oil and gas exploration and development systems, riser systems, serving as the connection channel between surface platforms and subsea equipment, are the "throat" for media transmission between the platform and the seabed, and a crucial component of the subsea production system. Steel catenary risers (SCRs) are an important riser type for deepwater oil and gas development. Stress joints, as key devices in the SCR system, connect the riser to the platform, bearing the constant tension of hundreds of tons while also enduring the long-term swaying of the riser under environmental loads. Due to the complex loads borne by stress joints and the special properties of their materials, stress joints are a weak point in the SCR system, posing a risk of structural failure and leakage.

[0003] Patent application number 202421811861.3 discloses a butt-welded connection method for risers. The tapered stress joint with composite material structure includes a main tube. One end of the main tube is fixed with a connecting flange for connection to an offshore oil and gas resource extraction platform, and the other end is connected to an offshore oil and gas riser via butt welding. The inner diameter of the main tube is constant, and an outer reinforcing layer is attached to its outer surface. The thickness of the outer reinforcing layer decreases sequentially, making the main tube tapered after attachment. However, the outer reinforcing layer is only attached through metallurgical adhesion on the outer surface, resulting in limited adhesion. It is only suitable for working conditions with low bending moment and low bending stress. Furthermore, the stress joint is connected to the riser by welding, which brings the risk of weld fatigue. If replacement is required later, the weld must be cut first, which is complicated and has high maintenance costs. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the purpose of this utility model is to provide a tapered stress joint for butt-welded connection of risers, which solves the problems of insufficient anti-peeling ability of existing stress joints leading to limited application scenarios and easy cracking at the joint weld causing high maintenance costs in the later stage.

[0005] This utility model is achieved through the following technical solution: A tapered stress joint for butt-welded risers includes a suspension body with a constant inner diameter. The outer wall of the pipe body is thicker in the middle and thinner at both ends. The thickest part of the outer wall transitions to the top with a concave arc surface, and the thickest part of the outer wall transitions to the bottom with an arc surface. An upper connecting flange for connecting to an offshore oil and gas resource extraction platform is fixed at the top of the suspension body. A deformable cone is sleeved on the lower part of the suspension body. The deformable cone has the same inner diameter as the suspension body. A lower adapter for connecting to an offshore oil and gas riser is fixed at the lower end of the deformable cone.

[0006] Furthermore, the inner diameter of the deformed vertebra remains unchanged, while the thickness of the outer wall gradually decreases from top to bottom.

[0007] Furthermore, the lower inner wall of the suspension body is provided with an internal thread, the upper part of the deformable cone is provided with an upper external thread adapted to the internal thread, and a first rubber sealing ring is provided between the suspension body and the deformable cone and fixedly connected by a first connecting thread.

[0008] Furthermore, the lower part of the deformable vertebra is provided with a lower external thread, and the lower adapter is provided with an internal thread adapted to the lower external thread. A second rubber sealing ring is provided between the deformable vertebra and the lower adapter and they are fixedly connected by a second connecting thread.

[0009] Furthermore, the first connecting thread and the second connecting thread are API standard round threads or trapezoidal threads.

[0010] Furthermore, the suspension body is fixed to the upper connecting flange by welding.

[0011] Furthermore, the suspension body and the upper connecting flange are integrally formed.

[0012] Furthermore, the upper connecting flange, suspension body, and lower adapter are made of ASTM A694 F56 or F70 forgings, and the deformable cone is made of ASTM B 265 Gr-23 or Gr-29 titanium.

[0013] Compared with the prior art, the beneficial effects of this utility model are as follows: This invention employs a method of connecting the suspended body and the deformable cone, which ensures both the sealing and stability of the connection while also taking into account structural strength and corrosion resistance in marine environments. This solves the problems of insufficient anti-peeling ability and limited application scenarios of stress joints in existing technologies. A lower adapter is fixed at the lower end of the deformable cone and connected to the marine oil and gas riser through the lower adapter, avoiding direct exposure to thermal stress at the weld, thereby reducing the risk of cracking. Furthermore, the deformable cone and the lower adapter are connected by threads, so that only the threaded connection needs to be disassembled during later maintenance, without cutting the weld, which greatly simplifies the maintenance process and reduces maintenance costs. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the tapered stress joint provided in Embodiment 1 of this utility model.

[0015] In the figure, 1-upper connecting flange, 2-suspension body, 3-rubber sealing ring, 4-first connecting thread, 5-deformed cone, 6-second connecting thread, 7-rubber sealing ring, 8-lower adapter, 9-butt weld. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0017] Example 1 refer to Figure 1 As shown, this utility model provides a tapered stress joint for butt-welded connection of risers, including a suspension body 2. The inner diameter of the suspension body 2 remains unchanged. The outer wall of the pipe is thicker in the middle and thinner at both ends. The thickest part of the outer wall of the pipe transitions to the top with a concave arc surface, and the thickest part of the outer wall of the pipe transitions to the bottom with an arc surface. The top of the suspension body 2 is fixed with an upper connecting flange 1 for connection with an offshore oil and gas resource exploitation platform. The suspension body 2 and the upper connecting flange 1 are fixed by welding, and the connection is a butt weld 9. A deformable cone 5 is sleeved on the lower part of the suspension body 2. The deformable cone 5 has the same inner diameter as the suspension body 2, and the inner diameter of the deformable cone 5 remains unchanged, while the outer wall thickness gradually decreases from top to bottom. The lower end of the deformable cone 5 is fixed with a lower adapter 8 for connection with an offshore oil and gas riser.

[0018] The lower inner wall of the suspension body 2 is provided with an internal thread, and the upper part of the deformable cone 5 is provided with an upper external thread adapted to the internal thread. A first rubber sealing ring 3 is provided between the suspension body 2 and the deformable cone 5 and they are fixedly connected by a first connecting thread 4. The first connecting thread 4 is an API standard round thread.

[0019] The lower part of the deformable cone 5 is provided with a lower external thread, and the lower adapter 8 is provided with an internal thread adapted to the lower external thread. A second rubber sealing ring 7 is provided between the deformable cone 5 and the lower adapter 8 and is fixedly connected by a second connecting thread 6. The second connecting thread 6 is an API standard round thread.

[0020] The upper connecting flange 1, the suspension body 2 and the lower adapter 8 are made of ASTM A694 F56 forging material, and the deformable cone 5 is made of ASTM B 265 Gr-23 material.

[0021] The upper end of the tapered stress joint of this utility model is connected to the offshore oil and gas resource development platform through the upper connecting flange 1, and the lower end is connected to the offshore oil and gas riser through the lower adapter 8 by butt welding.

[0022] A tapered stress joint for butt-welded connection of risers, the manufacturing method of which includes the following steps: Step 1: The upper connecting flange 1 and the suspension body 2 are manufactured by forging. The two parts are formed by separate forging. Before forging and finishing, they can be welded into one piece by argon arc welding. The connection is a butt weld 9. After welding heat treatment, the suspension body 2 is then finished. API standard round threads are machined inside the lower part of the suspension body 2. Step 2: Manufacture the deformed cone 5 using a forging process, and machine API standard round threads at both ends of the deformed cone 5; Step 3: Manufacture the lower adapter 8 using forging technology. Machining API standard round threads in the inner hole of one end of the lower adapter 8, and machining a butt weld bevel at the other end to match the riser. Step 4: Connect the suspension body 2 and the deformed cone 5 together using a torque wrench, and connect the deformed cone 5 and the lower adapter 8 together.

[0023] Example 2 This utility model provides a tapered stress joint for butt-welded connection of risers, including a suspension body 2. The inner diameter of the suspension body 2 is constant, the outer wall of the pipe is thicker in the middle and thinner at both ends, the thickest part of the outer wall of the pipe transitions to the top with a concave arc surface, and the thickest part of the outer wall of the pipe transitions to the bottom with an arc surface. The top of the suspension body 2 is fixed with an upper connecting flange 1 for connection with an offshore oil and gas resource exploitation platform. The suspension body 2 and the upper connecting flange 1 are integrally formed. A deformable cone 5 is sleeved on the lower part of the suspension body 2. The deformable cone 5 has the same inner diameter as the suspension body 2, and the inner diameter of the deformable cone 5 is constant, while the outer wall thickness gradually decreases from top to bottom. The lower end of the deformable cone 5 is fixed with a lower adapter 8 for connection with an offshore oil and gas riser.

[0024] The lower inner wall of the suspension body 2 is provided with an internal thread, and the upper part of the deformable cone 5 is provided with an upper external thread adapted to the internal thread. A first rubber sealing ring 3 is provided between the suspension body 2 and the deformable cone 5 and they are fixedly connected by a first connecting thread 4. The first connecting thread 4 is an API standard trapezoidal thread.

[0025] The lower part of the deformable cone 5 is provided with a lower external thread, and the lower adapter 8 is provided with an internal thread adapted to the lower external thread. A second rubber sealing ring 7 is provided between the deformable cone 5 and the lower adapter 8 and they are fixedly connected by a second connecting thread 6. The second connecting thread 6 is an API standard trapezoidal thread.

[0026] The upper connecting flange 1, the suspension body 2 and the lower adapter 8 are made of ASTM A694 F70 forging material, and the deformable cone 5 is made of ASTM B 265 Gr-29 material.

[0027] The upper end of the tapered stress joint of this utility model is connected to the offshore oil and gas resource development platform through the upper connecting flange 1, and the lower end is connected to the offshore oil and gas riser through the lower adapter 8 by butt welding.

[0028] A tapered stress joint for butt-welded connection of risers, the manufacturing method of which includes the following steps: Step 1: The upper connecting flange 1 and the suspension body 2 are manufactured by forging process. The connecting flange 1 and the suspension body 2 are forged as a whole. API standard trapezoidal threads are machined on the inner wall of the lower end of the suspension body 2. Step 2: The deformed cone 5 is manufactured using a forging process, and API standard trapezoidal threads are machined at both ends of the deformed cone 5. Step 3: Manufacture the lower adapter 8 using forging technology. Machining an API standard trapezoidal thread in the inner hole of one end of the lower adapter 8, and machining a butt weld bevel at the other end to match the riser. Step 4: Connect the suspension body 2 and the deformed cone 5 together using a torque wrench, and connect the deformed cone 5 and the lower adapter 8 together.

Claims

1. A tapered stress joint for butt-welded connection of risers, characterized in that, The system includes a suspension body (2), the inner diameter of which remains unchanged, the outer wall of which is thicker in the middle and thinner at both ends, the thickest part of the outer wall of which transitions to the top with a concave arc surface, and the thickest part of the outer wall of which transitions to the bottom with an arc surface. The top of the suspension body (2) is fixed with an upper connecting flange (1) for connecting to an offshore oil and gas resource exploitation platform. The lower part of the suspension body (2) is fitted with a deformable cone (5), the deformable cone (5) having the same inner diameter as the suspension body (2). The lower end of the deformable cone (5) is fixed with a lower adapter (8) for connecting to an offshore oil and gas riser.

2. The tapered stress joint for butt-welded connection of a riser pipe according to claim 1, characterized in that, The inner diameter of the deformed vertebra (5) remains unchanged, while the thickness of the outer wall gradually decreases from top to bottom.

3. The tapered stress joint for butt-welded connection of risers according to claim 1, characterized in that, The lower inner wall of the suspension body (2) is provided with an internal thread, and the upper part of the deformable cone (5) is provided with an upper external thread that is adapted to the internal thread. A first rubber sealing ring (3) is provided between the suspension body (2) and the deformable cone (5) and is fixedly connected by a first connecting thread (4).

4. The tapered stress joint for butt-welded connection of a riser pipe according to claim 1, characterized in that, The The lower part of the deformable vertebra (5) is provided with a lower external thread, and the lower adapter (8) is provided with an internal thread that is compatible with the lower external thread. A second rubber sealing ring (7) is provided between the deformable vertebra (5) and the lower adapter (8) and is fixedly connected by a second connecting thread (6).

5. A tapered stress joint for butt-welded connection of a riser pipe according to claim 1, characterized in that, The suspension body (2) is fixed to the upper connecting flange (1) by welding.

6. A tapered stress joint for butt-welded connection of a riser pipe according to claim 1, characterized in that, The suspension body (2) and the upper connecting flange (1) are integrally formed.

7. A tapered stress joint for butt-welded connection of a riser pipe according to claim 1, characterized in that, The upper connecting flange (1), the suspension body (2) and the lower adapter (8) are made of ASTM A694 F56 or F70 forgings, and the deformable cone (5) is made of ASTM B 265 Gr-23 or Gr-29 titanium.

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