Underwater continuous laying method of pipeline with or without counterweight

Abstract

The present application relates to a kind of, with or without counterweight pipeline underwater continuous laying method, comprising the following steps: the underwater laying of non-counterweight pipeline is carried out, and the laying length is according to route wave flow condition, water depth variation tendency and simulation software simulation, analysis, so that pipeline laying stress, strain and local buckling in the process of launching pipeline are within the allowable range;Wherein, first water-blocking structure is pre-installed in non-counterweight pipeline, and one-way air release valve is installed on first water-blocking structure;The laying of counterweight pipeline is carried out, wherein second water-blocking structure is pre-installed in counterweight pipeline, water is injected into the laid non-counterweight pipeline, so that air in non-counterweight pipeline is discharged to the direction of counterweight pipeline through one-way air release valve, in the process of air release, air pressure will push first water-blocking structure to move to the direction of counterweight pipeline, until air in non-counterweight pipeline is discharged between first water-blocking structure and second water-blocking structure through one-way air release valve;The present application can meet engineering quality, reduce cost.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering technology, and in particular relates to a method for continuous underwater laying of pipelines with and without counterweight. Background Technology

[0002] Submarine pipelines are typically either entirely unweighted or entirely weighted. Unweighted pipelines are generally suitable for projects with favorable wave and current conditions and water depths of 0-25 meters, while weighted pipelines have their weight thickness designed according to specific project conditions. If a project uses both unweighted and weighted pipelines, the usual practice is to lay one pipeline at a time, followed by the next, and finally connect them. However, this method undoubtedly increases the difficulty and risk of underwater connections, whether it's lifting the pipeline out of the water for welding or using subsea expansion bends.

[0003] Considering the high cost of concrete counterweights, and taking into account the wave flow conditions and water depth of the project route, as well as current domestic cases of uncounterweighted subsea pipeline construction, this invention innovatively proposes an installation scheme that combines uncounterweighted and counterweighted methods, reducing pipeline procurement costs while lowering the difficulty and engineering risks of pipeline laying. Summary of the Invention

[0004] The technical problem solved by this invention is achieved through the following technical solution:

[0005] A method for continuous underwater pipeline laying with and without counterweight includes the following steps:

[0006] The unbalanced pipelines are laid underwater sequentially. The laying length is determined based on the route wave flow conditions, water depth variation trend, and simulation software analysis to ensure that the pipeline laying stress, strain, and local buckling are within the allowable range during the laying process. The unbalanced pipelines are pre-installed with a first water-blocking structure, and a one-way venting valve is installed on the first water-blocking structure.

[0007] The counterweight pipe is laid, and a second water-blocking structure is pre-installed inside the counterweight pipe. Water is injected into the laid non-counterweight pipe, so that the air in the non-counterweight pipe is discharged towards the counterweight pipe through a one-way vent valve. During the venting process, the air pressure will push the first water-blocking structure towards the counterweight pipe until the air in the non-counterweight pipe is discharged into the space between the first and second water-blocking structures through the one-way vent valve.

[0008] Furthermore, the non-counterweight pipes and counterweight pipes are welded one by one on the assembly line of the pipelaying vessel. After welding, the pipes are laid flat on the seabed by moving the pipelaying vessel.

[0009] Further, the transition protector is installed on the non-counterweight pipeline to realize the transition of different pipe diameters of the non-counterweight pipeline and the counterweight pipeline, so that the non-counterweight pipeline can pass through the tensioner.

[0010] Further, the first water blocking structure is freely movable in the non-counterweight pipeline and can prevent water from passing through.

[0011] Further, the second water blocking structure is installed in the counterweight pipeline and can prevent water from passing through.

[0012] Further, the simulation software adopts OFFPIPE software.

[0013] The advantages and positive effects of the present application are as follows:

[0014] The method of the present application can realize the laying of a sea pipeline with no counterweight and with counterweight by deeply researching the wave flow condition and the water depth variation trend, and by analyzing the pipeline laying stress, strain and local buckling in detail, and the laying method is feasible and can meet the engineering quality, reduce the cost and minimize the engineering risk. BRIEF DESCRIPTION OF DRAWINGS

[0015] The technical solutions of the present application will be further described in detail below in combination with the drawings and examples, but it should be understood that these drawings are designed only for the purpose of explanation, and therefore, they do not limit the scope of the present application. In addition, unless specifically indicated, these drawings are only intended to conceptually illustrate the structural configuration described herein, and are not necessarily drawn to scale.

[0016] Figure 1 The step-by-step schematic diagram of the connection between the counterweight pipeline and the non-counterweight pipeline provided by the embodiment of the present application;

[0017] Figure 2 The step-by-step schematic diagram of the connection between the counterweight pipeline and the non-counterweight pipeline provided by the embodiment of the present application;

[0018] Figure 3 The step-by-step schematic diagram of the connection between the counterweight pipeline and the non-counterweight pipeline provided by the embodiment of the present application;

[0019] Figure 4 The structural schematic diagram of the connection between the counterweight pipeline and the non-counterweight pipeline after installation provided by the embodiment of the present application. DETAILED DESCRIPTION

[0020] First, it needs to be noted that the following will be described in an exemplary manner, the specific structure, features and advantages of the present application, however, all the description is only used to illustrate, and should not be understood as forming any limitation on the present application. In addition, any single technical features described or implied in the embodiments described herein can still continue to be combined or deleted between these technical features (or their equivalents), so as to obtain more other embodiments of the present application that can not be directly mentioned herein.

[0021] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0022] Embodiment 1

[0023] The present application provides a kind of, with or without counterweight pipeline underwater continuous laying method, comprising the following steps:

[0024] Carrying out underwater sequentially laying of non-counterweight pipeline, and the laying length is according to route wave flow condition, water depth variation trend and simulation software simulation, analysis, so that pipeline laying stress, strain and local buckling in the process of launching pipeline are within the allowable range;Wherein, non-counterweight pipeline is pre-installed with first water-blocking structure, and one-way air release valve is installed on the first water-blocking structure;

[0025] Carrying out the laying of counterweight pipeline, wherein the counterweight pipeline is pre-installed with second water-blocking structure inside, water is injected into the laid non-counterweight pipeline, so that the air in the non-counterweight pipeline is discharged to the direction of counterweight pipeline through one-way air release valve, and in the process of air release, air pressure will push the first water-blocking structure to move to the direction of counterweight pipeline, until the air in the non-counterweight pipeline is discharged to the space between the first water-blocking structure and the second water-blocking structure through the one-way air release valve.

[0026] Specifically, the non-counterweight pipeline and the counterweight pipeline are welded one by one through the flow line on the pipe-laying ship, and after welding, the pipeline is laid flat on the seabed by moving the pipe-laying ship;Transition protector is installed on the non-counterweight pipeline to realize the transition of different pipe diameters of the non-counterweight pipeline and the counterweight pipeline, so that it can pass through the tensioner;The first water-blocking structure can move freely in the non-counterweight pipeline and can prevent water from passing through;The second water-blocking structure is installed in the counterweight pipeline and can prevent water from passing through;The simulation software uses OFFPIPE software.

[0027] Embodiment 2

[0028] This embodiment is described by taking the tail water sea discharge project of Lianjiang County Kemeng Economic and Technological Development Zone Sewage Treatment Plant as an example:

[0029] The first 6 km of the project is cancelled, and in the range of the first 3 km, according to the route water depth, the pipeline can be normally laid in the full water state, and through OFFPIPE software simulation and analysis, the pipeline stress is within the allowable range; however, the full water between KP3-KP6 cannot be achieved, and the full water will cause excessive pipeline stress and bending damage, so the water injection amount needs to be controlled and accurately injected to ensure the stability of the pipeline;

[0030] It should be noted that during construction, the pipe-laying ship injects water when each pipe is welded, and the total length of the pipeline is 5885m. Through OFFPIPE calculation, the water level in the riser is within the range of 0m-6m, which meets the stress requirements of normal pipeline laying.

[0031] The installation of the water-blocking ball realizes water isolation between different pipe sections: the weight of the unweighted pipeline is light, and if there is a certain amount of air in the pipeline, it may cause the pipeline to float and not sink. The last 7 km is a weighted pipeline, and if water is injected into the weighted pipeline, the weight of the pipeline will increase, the stress of the pipe-laying ship will increase when the pipe-laying ship is lowered into the seabed, and the pipeline will bend, causing damage to the pipe-laying ship. Therefore, water needs to be prevented from entering the weighted pipeline through a water-blocking structure, and the specific method is as follows:

[0032] The method of controlling the position of air in the unweighted pipeline and the weighted pipeline connection is used for continuous laying: a double water-blocking ball and a one-way valve are used to control the position of the air column, replacing the original expansion bend and the method of slowly exhausting air to the nearshore section. This method is more time-saving and cost-effective than installing an expansion bend. Specifically, a check valve (DN150 opening pressure 2KPa) is installed in the middle of the first water-blocking structure to exhaust air and prevent air leakage, and a second water-blocking ball is installed in the weighted pipeline to prevent water from entering the weighted pipeline.

[0033] The unweighted pipeline and the weighted pipeline of different diameters are smoothly transitioned on the tensioner: due to the different diameters of the unweighted pipeline and the weighted pipeline, the diameter of the unweighted pipeline is 1219mm, and the diameter of the weighted pipeline is 1379mm. The transition of the tensioner needs to be considered, and a transition protector is tied on the unweighted pipeline to achieve smooth transition of the unweighted pipeline and the weighted pipeline of different diameters, so that they can smoothly pass through the tensioner.

[0034] In summary, the construction process of the pipeline near KP6 in the embodiment is as follows:

[0035] ①, Install 3 3t floating buoys at KP5.841, 5.878, and 5.915 (counting the 7th / 10th / 13th unweighted pipeline, pipe number 466 / 469 / 472);

[0036] ②, Weld the first water-blocking ball 1 with a one-way air exhaust valve to the unweighted pipeline at KP5.951 (counting the 4th unweighted pipeline, pipe number 475);

[0037] ③, continue to weld 3 non-weighted pipes; (pipe number 476-478);

[0038] ④, continue to weld 7 weighted pipes (pipe number 479-485);

[0039] ⑤, after the third buoy enters the water, the middle oil pipeline 681 is disassembled near the shore section to control the water injection equipment (the blind plate can be installed in advance, but the water flow must be maintained);

[0040] ⑥, weld the weighted pipe with the second built-in water-blocking ball 2 (the 8th weighted pipe, pipe number 486), at the same time, close the underwater valve of the middle oil pipeline 681, and blind the blind plate to ensure no water leakage;

[0041] ⑦, continue the normal laying procedure, and arrange divers to observe the contact of the tail end of the pipe support frame after laying 18 weighted pipes.

[0042] It should be noted that the gradual schematic diagram of the connection between the weighted pipe and the non-weighted pipe is shown in Figures 1-3 When the weighted pipe is installed and launched, the air in the non-weighted pipe A is discharged to the weighted pipe direction through the one-way air valve. During the air discharge process, the air pressure will push the first water-blocking structure to move towards the weighted pipe B direction until the air pressure on both sides of the first and second water-blocking structures reaches balance. For details, see Figure 4 .

[0043] After the above pipeline installation is completed, the installation effect is verified regularly:

[0044] (1) 2021-1-23-16:30, KP6.248 first verification, water depth 31m

[0045] The 498th intersection of the operation line is being matched. According to the contact condition of the underwater probe, the pipeline is about 1m away from the S12 roller and about 0.7m away from the S11 roller. The calculation result is consistent with the water inlet of 8m. At present, the first water-blocking ball is located underwater 26m away from the mud, and there are 4 pipes to the mud. The second water-blocking ball is located underwater 7m away from the mud, and there are 12 pipes to the mud;

[0046] (2) 2021-1-24-8:00, KP6.506 second verification

[0047] The 519th intersection of the operation line is being matched. The pipeline is about 0.6m away from the S12 roller, about 0.4m away from the S11 roller, and about 0.25m away from the S10 roller;

[0048] (3) 2021-1-25-10:00, KP6.966 third verification, water depth 31m

[0049] The job line No. 556 crossing is being matched, the pipeline is about 0.6 m away from the S12 roller, about 0.4 m away from the S11 roller, about 0.25 m away from the S10 roller, and the total length of the bending section is 278 m, which is basically consistent with the theoretical calculation of 0.8 m, 0.5 m, 0.3 m and 278.2 m;

[0050] After the diving exploration, the sinking amount of the water injection non-weighted pipeline on the seabed is 1 m, and the sinking amount of the weighted pipeline is 200 mm, which verifies from another aspect that the water stop ball has already cut off the water: if the weighted pipeline is filled with water, it is much heavier than the water injection non-weighted pipeline, and the two kinds of pipelines now have a height difference, so it is difficult for the water stop ball to move backward; the data of the pipeline mud point, the data of the pipe support frame and the calculation are consistent, after three days of diving exploration, it is verified that compared with other methods, the method of the present application improves the efficiency and reduces the cost while reducing the installation risk to the minimum, provides a new construction method for similar projects in the future, the inventive technology creatively adopts the double water stop ball plus one-way valve mode to block the water flow and control the air column position, ensures continuous laying instead of the original gas pipeline expansion bend, is more time-saving than the expansion bend and the short section, has lower cost, and has achieved success in actual construction, and saves a large amount of cost and time.

[0051] The above embodiments have been described in detail, but the content described is only the preferred embodiments of the present application and cannot be considered as limiting the scope of the present application. Any equivalent changes and improvements made according to the scope of the present application should still belong to the scope of the present application.

Claims

1. A method for underwater continuous laying of a pipeline with or without counterweight, characterized in that, Comprise the following steps: Carrying out the underwater laying of the non-weighted pipeline in sequence, the laying length is according to the wave flow condition of the route, the change trend of the water depth and the simulation software simulation and analysis, so that the pipeline laying stress, strain and local buckling of the pipeline during the launching process are within the allowable range; wherein, the first water blocking structure is pre-installed in the non-weighted pipeline, and the one-way air release valve is installed on the first water blocking structure; Carrying out the laying of the weighted pipeline, wherein, the second water blocking structure is pre-installed in the weighted pipeline, water is injected into the laid non-weighted pipeline, so that the air in the non-weighted pipeline is discharged to the direction of the weighted pipeline through the one-way air release valve, in the process of air discharge, the air pressure will push the first water blocking structure to move to the direction of the weighted pipeline, until the air in the non-weighted pipeline is discharged to the space between the first water blocking structure and the second water blocking structure through the one-way air release valve; The non-weighted pipeline and the weighted pipeline are welded one by one through the flow line on the pipelaying ship, and after welding, the pipeline is laid flat on the seabed by moving the pipelaying ship; The first water blocking structure can move freely in the non-weighted pipeline and can prevent water from passing through; The second water blocking structure is installed in the weighted pipeline and can prevent water from passing through.

2. A method of underwater continuous pipelaying with or without a counterweight according to claim 1, characterized in that: Transition protectors are installed on the non-weighted pipeline to realize the transition of different pipe diameters of the non-weighted pipeline and the weighted pipeline, so that they can pass through the tensioner.

3. A method of underwater continuous pipelaying with or without a counterweight according to claim 1, characterized in that: The simulation software adopts OFFPIPE software.

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