A method for replacing an in-service riser without shutdown

Abstract

The application discloses a method for replacing a riser in service without stopping production, which comprises the following steps: selecting a mechanical clamp, an inner sealing device, a tee joint, a riser short section and a branch pipeline; fixing one end of the mechanical clamp to a riser section below a hanging flange and fixing the other end of the mechanical clamp to a guide pipe rack; lowering the inner sealing device from the top end of the riser to the riser section below the hanging flange and sealing, cutting off the hanging flange and the riser section above the hanging flange; connecting the top end of a tee joint main pipe to the bottom end of the riser short section, connecting the bottom end of the tee joint main pipe to a replacement hanging flange and a lower riser section, and connecting a tee joint branch pipe to one end of the branch pipeline; lifting the inner sealing device to the riser short section and opening the branch pipeline; installing a riser main pipeline at the top end of the riser short section, closing the tee joint branch pipeline, recovering the inner sealing device and removing the branch pipeline, opening the riser main pipeline, and completing the replacement of the riser; the method has a short downtime, and ensures the economy and safety of the replacement of the riser in service.

Description

Technical Field

[0001] This invention relates to the field of marine engineering technology, and more particularly, to a method for replacing in-service risers without shutting down production. Background Technology

[0002] Riser pipes in oil and gas export pipelines are a crucial component of export oil and gas systems. Stationary export risers bear the pressure of internal media, environmental loads, and platform movement. As their service life increases, the number of riser replacements due to corrosion and other reasons also rises. Currently, the conventional approach to retrofitting and replacing in-service risers involves shutting down the pipeline, cleaning it, and then replacing the riser entirely or partially. This approach results in long downtime and significant economic losses, which is generally unacceptable for export pipelines. Therefore, there is a need to develop a method for replacing in-service risers without shutting down the pipeline, ensuring riser safety while minimizing economic losses caused by riser outages. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for replacing the suspended flange and the pipe section above it without interrupting or briefly stopping the production of the riser.

[0004] To solve the above-mentioned technical problems, the present invention provides a method for replacing in-service risers without production interruption, applicable to fixed guide rail risers that require replacement of suspension flanges and upper riser sections, comprising the following steps:

[0005] S1: Select matching mechanical clamps, internal plugs, tees, riser shorts and branch pipelines through analysis and design;

[0006] S2: Fix one end of the mechanical clamp to the riser section below the suspension flange to be replaced, and fix the other end to the guide frame;

[0007] S3: Lower the inner plug from the top of the riser to the riser section below the above-mentioned suspension flange and seal it; cut off the suspension flange and the riser section above it.

[0008] S4: Connect the top of the tee main pipe to the bottom of the riser short section. The bottom of the tee main pipe is connected to the cut lower riser section through a new suspension flange. The tee branch pipe is connected to one end of the branch pipeline.

[0009] S5: Raise the internal plug to the riser section and open the branch line;

[0010] S6: Install the main riser line at the top of the riser short section, close the branch line, retrieve the inner plug and remove the branch line, open the main riser line, and complete the riser replacement.

[0011] According to a preferred embodiment of the present invention, in step S1, the maximum tension that the mechanical clamp needs to bear is determined based on the results of the temporary operation analysis of the riser, and the material grade and main dimensions of the mechanical clamp and its components are determined by finite element strength analysis.

[0012] According to a preferred embodiment of the present invention, in step S1, the model of the internal plug is selected based on the pressure of the medium being transported in the riser and the pipe diameter.

[0013] According to a preferred embodiment of the present invention, in step S1, the interface load of the tee is determined based on the overall dynamic analysis results of the riser, and the tee is subjected to finite element analysis to determine the tee size.

[0014] According to a preferred embodiment of the present invention, in step S2, the outer coating of the riser section below the suspension flange needs to be removed, and one end of the mechanical clamp is fixed to the riser section after the outer coating has been removed.

[0015] According to a preferred embodiment of the present invention, in step S3, nitrogen gas needs to be injected from the opening of the riser section above the inner plug, and the gas is tested until it reaches a safe value before being cut off.

[0016] According to a preferred embodiment of the present invention, in step S4, a new suspension flange needs to be installed at the target position of the jacket support, and the pre-fabricated tee and riser short section are installed in place.

[0017] According to a preferred embodiment of the present invention, in step S4, the bottom end of the tee main pipe, the new suspension flange and the riser pipe section are connected in series and the nodes are protected against corrosion.

[0018] According to a preferred embodiment of the present invention, in step S5, the opening and closing of the branch is controlled by controlling the branch ball valve installed on the branch.

[0019] The technical effects of this invention are as follows:

[0020] 1. This invention provides a method for replacing in-service risers without interrupting production. It achieves pressurized replacement of the target pipe section above the suspension flange through a secondary sealing operation using an internal plug; provides support tension to the riser after the suspension flange is cut using a mechanical clamp; establishes a temporary external transmission branch by installing a tee on the replacement pipe section to connect it to the branch pipeline; connects the main riser pipeline to the riser via the tee; and establishes an external transmission path for the modified riser by shutting down the branch ball valve and retrieving the main pipeline internal plug. This method achieves the beneficial effect of replacing the pipe section above the suspension flange without interrupting production or with only a short-term shutdown.

[0021] 2. The present invention provides a method for replacing in-service risers without interrupting production. It features short downtime, structural reliability, and high construction safety. Compared with traditional methods of replacing risers with interrupted production, it ensures the economy and safety of in-service riser renovation, saves downtime, improves work efficiency, and reduces economic losses. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the mechanical clamp installation in step S2 of the method for replacing an in-service riser without interrupting production according to the present invention;

[0023] Figure 2 This is a schematic diagram of the installation of the internal plug in step S3 of the method for replacing an in-service riser without interrupting production according to the present invention.

[0024] Figure 3 This is a schematic diagram of step S3 of the method for replacing an in-service riser without interrupting production according to the present invention.

[0025] Figure 4 This is a schematic diagram of the T-junction main pipe connection in step S4 of the method for replacing an in-service riser without interrupting production according to the present invention.

[0026] Figure 5 This is a schematic diagram of the connection between the tee branch pipe and the branch pipeline in step S4 of the method for replacing an in-service riser without interrupting production according to the present invention.

[0027] Figure 6 This is a schematic diagram of the secondary sealing position of the internal plug in step S5 of the method for replacing an in-service riser without interrupting production according to the present invention.

[0028] Figure 7 This is a schematic diagram of the main pipeline installation of the riser in step S6 of the method for replacing an in-service riser without interrupting production according to the present invention.

[0029] Figure 8 This is a schematic diagram of the completion of riser replacement in step S6 of the method for replacing in-service risers without production interruption according to the present invention.

[0030] Figure 9 This is a schematic diagram of the mechanical clamp structure of a method for replacing in-service risers without interrupting production, according to the present invention.

[0031] Figure 10 This is a schematic diagram of the structure of the suspended flange in the method for replacing in-service risers without interrupting production according to the present invention;

[0032] Figure 11 This is a schematic diagram of the internal plug of the present invention, which is a method for replacing in-service risers without interrupting production.

[0033] Figure 12 This is a schematic diagram of the tee structure of a method for replacing in-service risers without interrupting production, according to the present invention.

[0034] Attached reference numerals: 1-Riser; 2-Pole receiving / launching bucket; 3-SDV valve; 4-Suspension flange; 5-Mechanical clamp; 6-Internal plug; 7-Tee; 8-Riser short section; 9-New suspension flange; 10-Branch pipeline; 11-Branch ball valve; 12-Riser main pipeline; 13-Weld diameter flange. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments are not intended to limit the invention.

[0036] like Figures 1 to 12 As shown, the present invention provides a method for replacing an in-service riser without interrupting production. This method requires replacing the suspended flange 4 and the fixed guide pipe support riser of the upper riser section 1, and includes the following steps:

[0037] S1: Select and confirm the mechanical clamp 5, internal plug 6, tee 7, riser short section 8, and branch pipeline 10;

[0038] S2: Fix one end of the mechanical clamp 5 to the riser pipe section below the suspension flange 4, and fix the other end to the guide frame;

[0039] S3: Lower the inner plug 6 from the inside of the top of the riser 1 to the riser section below the above-mentioned suspension flange 4 and seal it, then cut off the suspension flange 4 and the riser section above it.

[0040] S4: Connect the top of the main T-junction 7 to the bottom of the riser section 8. Connect the bottom of the main T-junction 7 to the replaced suspension flange 9 and the lower riser in series. Connect the branch T-junction 7 to one end of the branch pipeline 10.

[0041] S5: Raise the internal plug 6 to the riser short section 8 and open the branch pipeline 10;

[0042] S6: Install the main riser line 12 at the top of the riser section 8, close the branch ball valve 11, retrieve the inner plug 6 and remove the branch line 10, open the main riser line 12, and complete the replacement of riser 1.

[0043] A method for replacing in-service risers without interrupting production is mainly applied to the replacement and modification of in-service risers 1. The riser 1 includes a ball receiving / launching tank 2, an SDV valve 3, a suspension flange 4, a mechanical clamp 5, an internal plug 6, a tee 7, a riser short section 8, a new suspension flange 9, a branch pipeline 10, a branch ball valve 11, a main riser pipeline 12, and a welded diameter flange 13. This replacement method mainly achieves the replacement of damaged risers 1 through the combined application of the internal plug 6, the mechanical clamp 5, the forged tee 7, and the matching ball valve. The pressurized replacement of the target pipe section, including the riser suspension flange 4 and above, is achieved through the sealing operation using the internal plug 6. The mechanical clamp 5 provides approximately 15 tons of support tension to the riser after the flange 4 is cut. A forged tee 7, a welded diameter flange 13, and a branch ball valve 11 are installed on the replacement pipe section to connect it to the branch pipeline 10, establishing a temporary external transmission branch. The main riser pipeline 12 is connected via the welded diameter flange 13. By shutting down the branch ball valve 11 and retrieving the main pipeline internal plug 6, the external transmission path of the modified riser 1 is restored, enabling normal production of riser 1. The specific implementation steps are as follows:

[0044] Step 1: Select the model of internal plug 6 based on the pressure and diameter of the medium being transported by the target riser 1, and determine the plugging scheme.

[0045] Step 2: Based on the temporary and operational analysis results of the target modified riser 1, determine the maximum tension that the mechanical clamp 5 needs to bear, and determine the material grade and main dimensions of the mechanical clamp 5 and key components through finite element strength analysis.

[0046] Step 3: Based on the overall dynamic analysis results of the target riser 1, determine the interface load of the forged tee 7, perform finite element analysis on the mechanical tee 7, and check the strength of the main pipeline 12 and branch pipeline 10 of the riser.

[0047] Step 4: Based on the form and materials of the mechanical clamp 5 and tee 7 proposed in this patent, the manufacturer shall design and manufacture them in the factory.

[0048] Step 5: As Figure 1 As shown, the mechanical clamp 5 is transported to the target platform, a temporary construction platform is set up, the outer coating of the lower section of the target riser suspension flange 4 is removed, one end of the mechanical clamp 5 is connected to the section of the riser 1 where the coating has been removed, and the other end is welded to the guide frame.

[0049] Step Six: As Figure 2 and Figure 3 As shown, the inner sealing device 6 is lowered from the ball receiving and launching bucket 2 at the upper end of the riser 1 to the target pipe section area below the suspension flange 4 and sealed. Nitrogen gas is injected into the opening at the upper part of the sealed section. After the explosion is measured to a safe value, the suspension flange 4 and the upper riser are cut off.

[0050] Step Seven: As Figure 4As shown, the prefabricated weld diameter flange 13, tee 7, riser short section 8, bend and new suspension flange 9 are installed in place and welded to the original riser pipe section below, joint anti-corrosion is performed, and mechanical clamp 5 is removed.

[0051] Step 8: As Figure 5 As shown, the tee 7 connects to the branch ball valve 11 and the branch pipeline 10;

[0052] Step Nine: As Figure 6 As shown, lift the inner plug 6 to the upper short section of the tee 7 and seal it, open the branch ball valve 11, and start the branch medium transportation;

[0053] Step 10: As Figure 7 and Figure 8 As shown, install the main riser pipeline 12 on the riser short section 8, close the branch ball valve 11, retrieve the inner plug 6, remove the branch pipeline 10, realize the main pipeline medium transportation, and complete the riser replacement.

[0054] like Figure 9 and Figure 10 As shown, the working tension of the mechanical clamp 5 is determined by the overall dynamic analysis of the riser 1. The mechanical clamp 5 is wrapped around the lower riser section of the suspension flange 4 after the coating has been removed. The working tension is provided by the mechanical meshing force of the mechanical clamp 5. The mechanical clamp 5 is connected to the guide frame through the cross brace to realize the final transmission of tension.

[0055] like Figure 11 As shown, the internal plug 6 is suitable for pipelines with an internal pressure of 10 MPa and an inline diameter of 28 inches or less. It can achieve wireless positioning, sealing, and autonomous lifting inside the pipeline.

[0056] like Figure 12 As shown, tee 7 is made of ASTM A694 F65 material and coated with FBE anti-corrosion material. The interface load of mechanical tee 7 is determined by the overall dynamic analysis of riser 1. The dimensions and stress of tee 7 are determined by finite element analysis to meet the requirements of ASME VIII and DNV-OS-F101.

[0057] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method of replacing an in-service riser without production downtime, suitable for fixed platform risers requiring replacement of a suspended flange and an upper riser section, characterised in that, The method comprises the following steps: S1: selecting matched mechanical clamp, inner sealing device, tee, riser short section and branch pipeline through analysis design; S2: fixing one end of the mechanical clamp to the riser section below the suspension flange to be replaced and the other end to the guide tube frame; S3: lowering the inner sealing device from the top of the riser to the riser section below the suspension flange and sealing, cutting the suspension flange and the riser section above the suspension flange; S4: connecting the top of the tee main pipe to the bottom of the riser short section, connecting the bottom of the tee main pipe to the riser section below the suspension flange through the new suspension flange, and connecting the tee branch pipe to one end of the branch pipeline; S5: lifting the inner sealing device to the riser short section and opening the branch pipeline; S6: installing the riser main pipeline at the top of the riser short section, closing the branch pipeline, recovering the inner sealing device and removing the branch pipeline, opening the riser main pipeline, and completing the riser replacement.

2. A method of replacing an in-service riser without production shutdown according to claim 1, characterized in that, In the step S1, the maximum tension borne by the mechanical clamp is determined according to the temporary operation analysis result of the riser, and the material grade and main size of the mechanical clamp and the assembly are determined through finite element strength analysis.

3. The method of claim 1, wherein, In the step S1, the type of the inner sealing device is selected according to the medium pressure and the pipe diameter of the riser.

4. The method of claim 1, wherein, In the step S1, the tee size is determined through finite element analysis of the tee according to the interface load of the tee determined by the overall dynamic analysis result of the riser.

5. The method of claim 1, wherein, In the step S2, the outer coating of the riser section below the suspension flange is removed, and one end of the mechanical clamp is fixed to the riser section with the outer coating removed.

6. The method of claim 1, wherein, In the step S3, nitrogen is injected from the opening of the riser section above the inner sealing device, and the cutting is performed after the explosion is measured to a safe value.

7. The method of claim 1, wherein, In the step S4, the new suspension flange is arranged at the target position of the guide tube frame, and the tee and the riser short section connected in advance are installed in place.

8. The method of claim 1, wherein, In the step S4, the tee main pipe bottom, the new suspension flange and the riser section are connected in sequence and the nodes are anticorrosion.

9. The method of claim 1, wherein, In the step S5, the opening and closing of the branch pipeline are controlled by controlling the branch ball valve arranged on the branch pipeline.

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