A method of subsea pipeline base crossing treatment

Abstract

The application discloses a kind of seabed pipeline bottom crossing processing methods, belong to marine engineering technical field, including the following steps: when new pipeline is laid to the crossing point position near the built pipeline, install temporary short section across the built pipeline;Crossing processing work ship is anchored in place in the crossing preset position;Remove temporary short section and recycle to cross processing work;Excavate the soil around the built pipeline;Excavate the soil around the new pipeline;Measure the distance between the flange end faces of the new pipeline;Prefabricate permanent short section;Crossing processing work ship is lowered in the crossing area design position permanent short section;Permanent short section and new pipeline flange are connected;The new pipeline at crossing position is protected by adding concrete block according to design requirements;Sand is thrown backfill to the built pipeline.The application effectively reduces the adverse effects on the built pipeline through the processing scheme of crossing from the bottom of the built pipeline, while improving the safety protection level of the new seabed pipeline.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering technology, and in particular relates to a method for handling the bottom crossing of submarine pipelines. Background Technology

[0002] Currently, with the large-scale development of offshore oil and gas, subsea pipeline networks are becoming increasingly complex, frequently encountering the problem of newly constructed subsea pipelines inevitably crossing existing pipelines. When a new pipeline crosses an existing buried pipeline, two conventional methods are used to handle this situation:

[0003] (1): Without treating the existing pipeline, lay the new pipeline directly on the seabed, or lay concrete blocks on the seabed before laying the new pipeline, and finally lay concrete blocks or sand and gravel on top of the new pipeline for manual backfilling and protection.

[0004] (2): Treat the existing pipeline, that is, spray and sink the existing pipeline in a local area, then lay concrete blocks on top of it for protection, and finally lay the new pipeline and backfill it with sand and gravel for protection.

[0005] The above-mentioned methods for handling submarine pipeline crossings have the following problems:

[0006] (1) After the new pipeline is located above the seabed and protective construction is carried out, a high protrusion will be formed on the seabed, which will have a certain impact on navigation in the waters. At the same time, if the waters are frequently navigable, the new pipeline will be subject to a high risk of accidental damage.

[0007] (2) There is a possibility that the owner of the existing pipeline may not allow construction operations on it. If permitted, spraying and sinking of the existing pipeline within a certain range may be carried out during the operation, which may affect the stress on the existing pipeline due to improper operation, thereby posing a risk of damage to the pipeline.

[0008] Therefore, there is an urgent need to design a method for handling the bottom crossing of submarine pipelines to solve the problems mentioned above. Summary of the Invention

[0009] The purpose of this invention is to provide a method for handling the bottom crossing of submarine pipelines, which has the advantages of effectively reducing the adverse effects on existing pipelines and improving the safety protection level of newly built submarine pipelines, thus solving the problems mentioned in the background art.

[0010] To achieve the above objectives, the specific technical solution of the method for bottom crossing treatment of submarine pipelines according to the present invention is as follows:

[0011] A method for handling the bottom crossing of a subsea pipeline includes the following steps:

[0012] S1. When a new pipeline is laid to a point where it crosses an existing pipeline, a temporary short section is installed to cross the existing pipeline.

[0013] S2. The crossing handling vessel anchors and takes its position after crossing the preset location;

[0014] S3. Remove the temporary short section and retrieve it for the crossing treatment operation;

[0015] S4. Excavate the soil around the existing pipeline and use sandbags to support the bottom of the suspended pipeline;

[0016] S5. Excavate the soil around the new pipeline;

[0017] S6. Measure the distance between the flange ends of the newly built pipeline;

[0018] S7, Precast permanent short section;

[0019] S8. The crossing handling vessel lowers a permanent short section at the designed location in the crossing area;

[0020] S9. Drag the permanent short section below the existing pipeline;

[0021] S10. Connect the permanent short section and the newly built pipe flange;

[0022] S11. Newly constructed pipelines crossing locations shall be protected by covering them with concrete blocks in accordance with design requirements;

[0023] S12. Backfill the existing pipeline with sand.

[0024] Furthermore, in S1, the new pipeline is laid using a pipelaying vessel, and when installing temporary short sections on the normal pipe section of the new pipeline, the temporary short sections are connected to the normal pipe section through welded neck flanges. The temporary short sections are laid to the seabed together with the new pipeline.

[0025] Furthermore, in S2, the anchor cable maintains a safe distance from both newly constructed and existing pipelines.

[0026] Furthermore, in S3, divers go underwater to loosen the flange bolts, and after the water inside the pipeline has stabilized, the temporary short section is removed and retrieved to the crossing treatment vessel.

[0027] Furthermore, in S4, a non-contact trenching machine is first used to partially blow away the soil above the existing pipeline to expose the pipeline. Then, a non-contact trenching machine is used to excavate and blow away the soil below the existing pipeline. After the soil below both sides of the existing pipeline is excavated, sandbags are used to support the bottom of the suspended pipeline. Then, the unexcavated soil below the existing pipeline is excavated to form the working pit.

[0028] Furthermore, in S5, a non-contact trenching machine is used to excavate the conventional section, transition section, and locally deepened crossing section of the newly built pipeline, and the excavation depth must meet the design requirements.

[0029] Furthermore, in S7, a swivel flange and a ball flange are welded to both ends of the permanent short section, and the weld joints are subjected to non-destructive testing. After passing the inspection, the flanges at both ends are sealed with blind flanges, and flange protectors are installed at the bottom of the flanges at both ends.

[0030] Furthermore, in S8, after the crossing handling vessel is precisely positioned at the designed location in the crossing area, it uses the ship's crane and slings to lower the permanent short section and place it on the muddy surface of the seabed at the designated crossing point. After the lowering is completed, the slings and slings are removed.

[0031] Furthermore, in S9, a winch is deployed on the crossing handling vessel, a guide pulley foundation is installed at a designated location on the seabed, a wire rope is guided through the guide pulley and the existing pipeline, the wire rope is connected to the lifting lug on the end face of the permanent short section blind plate, and the winch is started to drag the permanent short section under the existing pipeline.

[0032] Furthermore, in S10, the blind flanges at both ends of the permanent short section are removed, and the flange faces of the permanent short section and the newly built pipe head are adjusted and aligned. The flange bolts are tightened by hydraulic wrench or hydraulic tensioner to enable the flanges to be assembled, sealed and connected underwater. Then, the back pressure test is carried out on the connecting flanges on both sides. After passing the test, the wire rope and guide pulley foundation are removed and recovered.

[0033] The present invention has the following advantages: By using a treatment method that passes through the bottom of an existing pipeline, the present invention effectively reduces the adverse effects on the existing pipeline and improves the safety protection level of the newly built submarine pipeline. Attached Figure Description

[0034] Figure 1 This is a schematic flowchart of the method for handling the bottom crossing of a submarine pipeline according to the present invention;

[0035] Figure 2 This is a schematic diagram of the structure of the pipelaying vessel laying temporary short sections at the crossing position according to the present invention;

[0036] Figure 3 For the present invention Figure 2 Enlarged structural diagram at point A;

[0037] Figure 4 This is a schematic diagram of the anchoring structure of the vessel used for the crossing treatment operation according to the present invention;

[0038] Figure 5 This is a schematic diagram of the structure for the crossing and placement of the newly constructed pipeline and the existing pipeline in this invention.

[0039] Figure 6This is a schematic diagram of the excavation of the soil around the existing pipeline according to the present invention;

[0040] Figure 7 This is a schematic diagram of the multi-segment excavation structure for the newly constructed pipeline according to the present invention;

[0041] Figure 8 This is a schematic diagram of the structure of the permanent short section of the present invention;

[0042] Figure 9 This is a schematic diagram of the permanent short section lowering structure of the present invention;

[0043] Figure 10 This is a schematic diagram of the structure of the permanent short section of the present invention crossing an existing pipeline;

[0044] Figure 11 This is a schematic diagram of the permanent short section connection structure of the present invention;

[0045] Figure 12 This is a schematic diagram of the cross-position protection structure of the present invention;

[0046] The markings in the diagram are as follows: 1. New pipeline; 11. Temporary stub; 12. Weld neck flange; 13. Existing pipeline; 14. Regular section; 15. Transition section; 16. Crossing section with local deepening; 2. Pipeline laying vessel; 21. Sandbag; 3. Crossing handling vessel; 31. Buoy; 32. Anchor cable; 4. Permanent stub; 41. Blind flange; 42. Flange protector; 43. Ball flange; 44. Swivel flange; 45. Lifting lug; 46. Lifting rope; 47. Swing rope; 5. Sea level; 51. Seabed; 52. Sand; 6. Winch; 61. Guide pulley foundation; 62. Wire rope; 7. Concrete block. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0049] The following is a reference to the appendix. Figure 1 To be continued Figure 12This invention describes a method for handling the bottom crossing of a submarine pipeline.

[0050] Current methods for handling submarine pipeline crossings have the following problems:

[0051] (1) After the new pipeline is located above the seabed and protective construction is carried out, a high protrusion will be formed on the seabed, which will have a certain impact on navigation in the waters. At the same time, if the waters are frequently navigable, the new pipeline will be subject to a high risk of accidental damage.

[0052] (2) There is a possibility that the owner of the existing pipeline may not allow construction operations on it. If permitted, spraying and sinking of the existing pipeline within a certain range may be carried out during the operation, which may affect the stress on the existing pipeline due to improper operation, thereby posing a risk of damage to the pipeline.

[0053] Therefore, the present invention includes the following steps:

[0054] S1. When the newly constructed pipeline 1 is laid to the point of intersection with the existing pipeline 13, a temporary short section 11 is installed to cross the existing pipeline 13.

[0055] Specifically, the new pipeline 1 is laid by the pipelaying vessel 2, and when the temporary short section 11 is installed on the normal pipe section of the new pipeline 1, the temporary short section 11 is connected to the normal pipe section through the weld neck flange 12. The temporary short section 11 is laid together with the new pipeline 1 to the seabed 51.

[0056] S2. Crossing handling vessel 3 anchors and takes its position at the preset crossing location;

[0057] Specifically, the crossing handling vessel 3 anchors at the pre-set crossing position and deploys warning buoys 31 of different colors in the sea area above the existing pipeline 13 to achieve a 24-hour warning effect.

[0058] Preferably, the anchor cable 32 maintains a safe distance from the newly built pipeline 1 and the existing pipeline 13.

[0059] S3. Remove temporary section 11 and retrieve it for crossover processing;

[0060] Specifically, divers went underwater to loosen the flange bolts, and after the water inside the pipeline stabilized, they removed the temporary short section 11 and retrieved it to the crossing treatment vessel 3.

[0061] S4. Excavate the soil around the existing pipeline 13 and support the bottom of the suspended pipeline with sandbags 21.

[0062] Specifically, firstly, a non-contact trenching machine is used to partially blow away the soil above the existing pipeline 13 to expose the pipeline. Then, a non-contact trenching machine is used to excavate and blow away the soil below the existing pipeline 13. After the soil below both sides of the existing pipeline 13 is excavated, sandbags 21 are used to support the bottom of the suspended pipeline. Then, the unexcavated soil below the existing pipeline 13 is excavated to form the working pit.

[0063] Preferably, the excavation and purging sequence of the existing pipeline 13 starts from the side away from the crossing point and gradually moves towards the direction of the crossing point. After the soil below the existing pipeline 13 on both sides away from the crossing point has been excavated and supported, the soil directly below the existing pipeline 13 is then excavated.

[0064] S5. Excavate the soil around the newly built pipeline 1;

[0065] Specifically, a non-contact trenching machine is used to excavate the conventional section 14, transition section 15, and locally deepened crossing section 16 of the newly built pipeline. The excavation depth must meet the design requirements. For local trenches where the size and depth do not meet the requirements, divers can carry underwater high-pressure water guns for fine excavation.

[0066] S6. Measure the distance between the flange ends of the newly built pipeline 1;

[0067] Specifically, a flange measuring instrument is used to measure the distance between the flange ends connected to the normal pipe sections on both sides of the crossing point of the newly built pipeline 1, and the data is recorded.

[0068] S7, Precast permanent short section 4;

[0069] Specifically, a permanent short section 4 is prefabricated on land or on a ship, and a swivel flange 44 and a ball flange 43 are welded to both ends of the permanent short section 4, respectively. The weld joints are subjected to non-destructive testing. After the inspection is qualified, the flanges at both ends are sealed with blind flanges 41, and flange protectors 42 are installed at the bottom of the flanges at both ends.

[0070] Preferably, the permanent short section 4 is connected to a swivel flange 44 on one side and a ball flange 43 on the other side. This method can reduce the difficulty of underwater connection between the permanent short section 4 and the end flange of the newly built pipeline 1. The ball flange 43 can provide a connection deviation of ±10°, and the swivel flange 44 has a ring body that can rotate 360°, which facilitates the assembly of bolts.

[0071] S8, the crossing handling vessel 3 lowers the permanent short section 4 at the designed position in the crossing area;

[0072] Specifically, after the crossing operation vessel 3 accurately locates the designed position in the crossing area, it uses the ship's crane and lifting rope 46 to lower the permanent short section 4 to below the sea level 5 and place it on the muddy surface at the bottom of the seabed 51 designated at the crossing point. After the lowering is completed, the lifting rope 46 and the sway rope 47 are removed.

[0073] Preferably, to prevent the permanent submersible 4 from sinking into the muddy surface of the seabed 51, an airbag can be attached to the permanent submersible 4 and inflated to make the negative buoyancy of the permanent submersible 4 close to zero.

[0074] S9. Drag the permanent short section 4 below the existing pipe 13;

[0075] Specifically, a winch 6 is installed on the crossover handling vessel 3, a guide pulley foundation 61 is installed at a designated position at the bottom of the seabed 51, a guide wire rope 62 is passed through the guide pulley and the existing pipeline 13, the wire rope 62 is connected to the lifting lug 45 on the end face of the blind flange 41 of the permanent short section 4, and the winch 6 is started to drag the permanent short section 4 below the existing pipeline 13.

[0076] Preferably, the dimensions of the guide pulley foundation 61, the anti-sinking measures, and the wire rope 62 are determined based on the bearing capacity of the seabed 51 and the towing force of the permanent short section 4.

[0077] S10. Connect the permanent short section 4 and the flange of the newly built pipe 1;

[0078] Specifically, with the cooperation of ship cranes and divers, the blind flanges 41 at both ends of the permanent short section 4 are removed, and the flange faces of the permanent short section 4 and the newly built pipeline 1 are adjusted and aligned. The flange bolts are tightened with hydraulic wrenches or hydraulic tensioners to enable the flanges to be assembled, sealed and connected underwater. Then, the back pressure test is carried out on the connecting flanges on both sides. After passing the test, the wire rope 62 and the guide pulley foundation 61 are removed and retrieved.

[0079] Subsequently, divers conducted underwater exploration and inspection. If any gaps were found in the permanent short section 4, sandbags 21 could be used to fill the gaps to ensure that the soil beneath the permanent short section 4 could provide support after the connection was completed.

[0080] S11. For newly constructed pipelines 1 crossing locations, concrete blocks 7 shall be added to protect them in accordance with design requirements;

[0081] S12. Backfill 13 sections of the existing pipeline with 52 tons of sand.

[0082] Specifically, the working pit below the existing pipeline 13 and the trench above it will be backfilled with sand 52 to restore the existing pipeline 13 to its buried state according to the design requirements.

[0083] The present invention effectively reduces the adverse effects on the existing pipeline 13 by using a method of passing through the bottom of the existing pipeline 13, while improving the safety protection level of the newly built submarine pipeline.

[0084] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for handling the bottom crossing of a subsea pipeline, characterized in that, Includes the following steps: S1. When a new pipeline is laid to a point where it crosses an existing pipeline, a temporary short section is installed to cross the existing pipeline. S2. The crossing handling vessel anchors and takes its position after crossing the preset location; S3. Remove the temporary short section and retrieve it for the crossing treatment operation; S4. Excavate the soil around the existing pipeline and support the bottom of the suspended pipeline with sandbags. First, use a non-contact trenching machine to locally blow away the soil above the existing pipeline to expose the pipeline. Then, use a non-contact trenching machine to excavate and blow away the soil below the existing pipeline. After the soil below both sides of the existing pipeline is excavated, use sandbags to support the bottom of the suspended pipeline. Then, excavate the unexcavated soil below the existing pipeline to form a working pit. S5. Excavate the soil around the new pipeline; S6. Measure the distance between the flange ends of the newly built pipeline; S7, Precast permanent short section; S8. The crossing handling vessel lowers a permanent short section at the designed location in the crossing area; S9. Drag the permanent short section below the existing pipeline; S10. Connect the permanent short section and the newly built pipe flange; S11. Newly constructed pipelines crossing locations shall be protected by covering them with concrete blocks in accordance with design requirements; S12. Backfill the existing pipeline with sand.

2. The method for handling the bottom crossing of a subsea pipeline according to claim 1, characterized in that, In S1, the new pipeline is laid using a pipelaying vessel. When installing temporary short sections on the normal pipe section of the new pipeline, the temporary short sections are connected to the normal pipe section through weld neck flanges. The temporary short sections are laid to the seabed together with the new pipeline.

3. The method for handling the bottom crossing of a subsea pipeline according to claim 1, characterized in that, In S2, the anchor cable maintains a safe distance from both newly constructed and existing pipelines.

4. The method for handling the bottom crossing of a subsea pipeline according to claim 1, characterized in that, In S3, divers go underwater to loosen the flange bolts. After the water inside the pipeline has stabilized, the temporary short section is removed and retrieved to the crossover treatment vessel.

5. The method for handling the bottom crossing of a subsea pipeline according to claim 1, characterized in that, In S5, a non-contact trenching machine is used to excavate the conventional section, transition section and the section crossing the locally deepened section of the new pipeline, and the excavation depth must meet the design requirements.

6. The method for handling the bottom crossing of a subsea pipeline according to claim 1, characterized in that, In S7, a swivel flange and a ball flange are welded to both ends of the permanent short section, and the weld joints are subjected to non-destructive testing. After the inspection is passed, the flanges at both ends are sealed with blind flanges, and flange protectors are installed at the bottom of the flanges at both ends.

7. The method for handling the bottom crossing of a subsea pipeline according to claim 1, characterized in that, In S8, after the crossing handling vessel is precisely positioned at the designed location in the crossing area, it uses the ship's crane and slings to lower the permanent short section and place it on the muddy surface of the seabed at the designated crossing point. After the lowering is completed, the slings and slings are removed.

8. The method for handling the bottom crossing of a subsea pipeline according to claim 6, characterized in that, In S9, a winch is set up on the crossing handling vessel, a guide pulley foundation is installed at a designated location on the seabed, a wire rope is guided through the guide pulley and the existing pipeline, the wire rope is connected to the lifting lug on the end face of the permanent short section blind plate, and the winch is started to drag the permanent short section under the existing pipeline.

9. The method for handling the bottom crossing of a subsea pipeline according to claim 8, characterized in that, In S10, the blind flanges at both ends of the permanent short section are removed, and the flange faces of the permanent short section and the newly built pipe head are adjusted and aligned. The flange bolts are tightened by hydraulic wrench or hydraulic tensioner to enable the flange to be assembled, sealed and connected underwater. Then, the back pressure test is carried out on the connecting flanges on both sides. After passing the test, the wire rope and guide pulley foundation are removed and retrieved.

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