A method of cleaning a disposal or plugged marine pipeline

Abstract

This invention discloses a cleaning method for abandoned or clogged subsea pipelines, relating to the field of offshore oil engineering technology. The method includes the following steps: pretreatment using a production-reducing medium to push most of the residue inside the pipeline to one end or the clogged location, collecting it and processing it in the platform's buffer system; then, using a cleaning agent to push the cleaning ball back to the bow end, thus completing the cleaning of the abandoned subsea pipeline. For clogged subsea pipelines repaired, an additional drainage operation using a production-restoring medium can be performed, with the discharged cleaning agent also entering the platform's buffer system for processing. This method primarily improves the cleaning efficiency of abandoned subsea pipelines, saves on cleaning agent usage, and solves problems such as the inability to clean or incomplete cleaning of clogged subsea pipelines.

Description

Technical Field

[0001] This invention relates to the field of marine oil engineering technology, and in particular to a method for cleaning abandoned or clogged subsea pipelines. Background Technology

[0002] Offshore oil and gas pipelines are typically designed for a lifespan of 20-30 years, and currently face the prospect of large-scale abandonment, shutdown, relocation, or secondary development. Without proper cleaning and oil removal measures, these pipelines will pollute the marine environment and threaten offshore oil and gas safety. Therefore, choosing low-cost, high-efficiency cleaning methods is essential.

[0003] In the petroleum industry, fluid raw materials include crude oil, natural gas, and water. These media, when traveling through pipelines for extended periods, will form deposits or scale. These deposits or scale, especially grease deposits, adhere to the pipe walls, increasing resistance during fluid transport, causing corrosion and damage to the pipe materials, and potentially leading to pipe rupture and leakage of transported fluids. Leaked fluids are usually quite dangerous and can adversely affect normal production and daily life. Therefore, it is necessary to clean the pipelines regularly.

[0004] In addition, for subsea pipelines (with bypasses) where the ball gets stuck or is accidentally blocked, if the problem cannot be solved by cleaning, it is necessary to cut and replace the faulty section underwater. In this case, the oil content of the medium in the open section must meet the environmental protection emission requirements. Therefore, it is also necessary to clean the oil in pipelines that cannot be cleaned by the ball.

[0005] Common pipeline cleaning technologies include high-pressure water jet technology, mechanical cleaning technology, sandblasting cleaning technology, pipeline cleaning technology, and chemical cleaning technology. However, for oil pipelines that are hundreds or thousands of meters long or even hundreds of kilometers long, the number of cleaning methods available is limited. Large amounts of cleaning agents and water, as well as pipeline cleaning pigs and other equipment, are required for flushing and cleaning, which is costly. Furthermore, it is not possible to perform ball cleaning for blocked pipelines. If ball cleaning is not performed, the effect is poor and it is difficult to achieve the desired results. Summary of the Invention

[0006] The main technical problem to be solved by the present invention is that the existing subsea pipeline cleaning methods are costly, expensive, and have poor cleaning effects. In order to overcome the above-mentioned defects of the existing technology, a cleaning method for discarding or blocking subsea pipelines is provided.

[0007] The technical solution adopted by this invention to solve its technical problem is: A method for cleaning abandoned or clogged subsea pipelines, comprising the following steps: S1. Before production is stopped, place the two-way pig into the launching tube or subsea pipeline; S2 uses the medium from the reduced production of the first oil and gas platform as the ball pushing medium to push the two-way pig from the first oil and gas platform to the last oil and gas platform. Through the interference fit between the two-way pig and the inner diameter of the subsea pipeline, the deposited oil and grease attached to the subsea pipeline wall is pushed to the last oil and gas platform. S3. The oily liquid pushed in step S2 is collected by the terminal platform and enters the platform buffer system, and is discharged separately after treatment; S4. When the two-way pig reaches the end of the subsea pipeline or the pipeline is stuck and cannot continue to advance, a mixture of fresh water and cleaning agent is used as the back-push medium to push the two-way pig back to the head oil and gas platform, so that the subsea pipeline is filled with the mixture of fresh water and cleaning agent. At this time, the subsea pipeline is ready for abandonment or underwater open treatment. S5. Using the production medium restarted by the oil and gas platform at the head end of the subsea pipeline, push the bidirectional pig from the head end oil and gas platform to the tail end oil and gas platform again to remove the residual mixed solution in the pipeline. S6. The oily liquid pushed in step S5 is collected by the terminal oil and gas platform and enters the platform buffer system, and is discharged separately after treatment. Furthermore, the ball-pushing medium in steps S2 and S5 is natural gas. Furthermore, in step S5, if the subsea pipeline is a blocked subsea pipeline that needs repair, after the subsea pipeline repair is completed, the bidirectional pipeline pig will be pushed from the first oil and gas platform to the last oil and gas platform again using the production medium restarted by the oil and gas platform at the first end of the subsea pipeline, so as to discharge the residual mixed solution in the pipeline.

[0008] Furthermore, the material of the bidirectional pipeline pig is selected based on the pollutant situation inside the pipeline and the length of the pipeline; for longer pipelines, a bidirectional pipeline pig is replaced for each single trip of forward and reverse pushing.

[0009] Furthermore, bidirectional pigs that require single forward and reverse propulsion have bidirectional sealing capabilities. Furthermore, the cleaning agent is a reagent that has both emulsifying and cleaning functions, or is mixed with fresh water in the order of front-end emulsifier and back-end cleaning agent. Furthermore, in step S4, when the bidirectional pig is pushed back, a pre-mixed cleaning agent aqueous solution is first injected into the subsea pipeline. When the injected volume reaches 2 / 3 of the subsea pipeline capacity, fresh water is used to continue the injection until the bidirectional pig returns to the head oil and gas platform. Furthermore, in step S4, after the bidirectional pipeline pig is pushed back to the upstream oil and gas platform, samples of the pipeline are collected from the upstream and downstream oil and gas platforms respectively, and the oil content of the samples is tested. If both meet the standards, the pipeline can be cut and replaced underwater. Furthermore, in step S4, the method for determining that the bidirectional pig has reached the jamming position is as follows: monitor the pressure at the head of the subsea pipeline, and when the pressure at the head continues to rise, determine that the bidirectional pig has reached the jamming position. Furthermore, the bidirectional pig is a high-density foam pig; in step S4, when injecting the reverse thrust medium, the reverse thrust medium is injected through an injection pump connected to the oil and gas platform at the end of the subsea pipeline.

[0010] The beneficial effects of this invention are: The method of cleaning abandoned or blocked subsea pipelines using a bidirectional ball-push approach can efficiently remove residual oil from the pipeline while minimizing the cost of construction equipment and materials. Firstly, multiple ball-push processes (either forward or reverse) remove deposited grease from the inner wall of the pipeline, with only one of the two or more processes requiring external injection pumps. Secondly, the cleaning agent solution used in the reverse push process emulsifies solidified or residual grease, achieving a secondary flushing effect, and only requires a single-pipe volume of cleaning agent solution, saving both material and processing costs. Finally, the production medium is used for forward push to send all the mixed solution back to the platform buffer system for final cleaning and drainage. This method provides a new approach for cleaning abandoned oil and gas pipelines and pre-treating blocked subsea pipelines, significantly improving construction convenience and effectively ensuring the efficiency and safety of deepwater oil and gas field development. Attached Figure Description

[0011] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0012] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a schematic diagram of the structure of the present invention.

[0013] Explanation of the labels in the diagram: 1-First-end oil and gas platform; 2-Second-end oil and gas platform; 3-Pipeline blockage point; 4-Pipeline. Detailed Implementation

[0014] The present invention will be further described below with reference to specific embodiments. The illustrative embodiments and descriptions herein are used to explain the present invention, but are not intended to limit the present invention.

[0015] This invention discloses a cleaning method for abandoned or clogged subsea pipelines. It utilizes a combination of a forward and reverse bidirectional pipeline cleaning device and a cleaning agent to clean abandoned subsea pipelines. This method aims to solve the problems of existing subsea pipeline cleaning methods, such as high cost, high price, unsatisfactory cleaning effect on clogged pipelines, and inability to meet the limits for pollutant discharge concentrations in marine pipelines (oil content less than 30 ppm in marine oily wastewater discharge). The method includes the following steps: Before production is stopped, place the two-way pigging device into the launching tube or subsea pipeline; The pig is dispatched using a medium that reduces production; this medium is typically natural gas. Because the diameter of the pig has a certain interference fit with the inner diameter of the pipeline, it can push the deposited grease adhering to the pipeline wall towards the end. Oily waste liquid is collected by the terminal oil and gas platform and enters the platform buffer system, where it is treated and then discharged separately. When the pig reaches the end or gets stuck and can no longer advance, a mixture of fresh water and cleaning agent is used as the pushing medium to push the cleaning ball back to the beginning. At this time, the pipe is filled with a fresh water solution with added cleaning agent, and it is ready for disposal or underwater open treatment. Finally, using the restarted production medium, push the pig back to the end. If the pipeline is blocked, perform this step after the repair is completed. Similarly, the oily liquid is collected by the terminal oil and gas platform and enters the platform buffer system, where it is treated and then discharged separately.

[0016] Preferably, the selection of the pipeline pig should be based on the pipeline conditions and the pipeline distance, and the specific material should be selected accordingly. For relatively long pipelines, a new pipeline pig should be replaced after each forward and reverse push. Otherwise, the poor sealing performance after wear will affect the cleaning effect. At the same time, the pipeline pig that requires a single forward and reverse push should have bidirectional sealing performance.

[0017] Preferably, the cleaning agent is selected to have both emulsifying and cleaning functions, or is mixed with fresh water in the order of front-end emulsifier and back-end cleaning agent.

[0018] By using the cleaning method for abandoned or blocked subsea pipelines provided by this invention, a low-cost and high-efficiency cleaning process is achieved for long pipelines or pipelines that cannot be circulated by a ball, with good cleaning effect and overcoming the problem of blocked subsea pipelines that cannot be circulated by a ball.

[0019] The technical solutions of the embodiments of the present invention will be clearly and thoroughly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] by Figure 1 Taking the situation shown as an example, refer to Figure 1 and Figure 2As shown, the conventional transport medium of this subsea pipeline is natural gas. A blockage occurred near the terminal oil and gas platform, resulting in a bypass. However, it could not be pushed out using a pigging tool, necessitating underwater cutting and replacement. Pre-treatment with internal cleaning is a necessary step to prevent exposure of the subsea pipeline 4, resulting in media leakage and environmental pollution. Using the method of this invention, a high-density foam pig is first deployed using the reduced production from the upstream oil and gas platform 1 to remove residual oil from the pipe wall. The pipeline is then pushed into the buffer treatment device of the downstream oil and gas platform 2 in the production process of the terminal platform, where it undergoes separate treatment before being discharged. However, due to the blockage in subsea pipeline 4, i.e. Figure 2 At point 3 of the subsea pipeline blockage, the pig cannot directly reach the end of the pipeline until a continuous increase in pressure is observed at the head end, indicating that the pig has reached the blockage location. At this point, the end end connects to the subsea pipeline via an injection pump and enters the injection pump process, injecting a pre-mixed cleaning agent solution into the pipeline. Generally, a cleaning agent with emulsifying and cleaning functions is selected, and one pipe volume of cleaning agent is injected. This process pushes the pig back to the head end. When two-thirds of the pipe volume has been injected, fresh water can be used instead of cleaning agent to continue injection. After the head end oil and gas platform receives the pig, both the head and tail end oil and gas platforms take a sample of the liquid from the pipeline to test the oil content. If both meet the standards, underwater cutting and replacement can be performed. After the underwater subsea pipeline replacement is completed, the head end platform's natural gas production system will resume production. Using the initial stage of the resumed production natural gas, another high-density foam pig will be sent for drainage, pushing the mixed solution in the pipeline to the buffer treatment device of the tail end oil and gas platform for separate treatment before discharge. Following the above method, only one external device is used to inject the ball, reducing costs associated with mobilization, cleaning agents, and personnel, thus efficiently completing the cleaning process for blocked subsea pipelines. The cleaning methods for abandoned, shut-down, relocated, or redeveloped subsea pipelines are similar.

[0021] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for cleaning abandoned or clogged subsea pipelines, characterized in that, Includes the following steps: S1. Before production is stopped, place the two-way pig into the launching tube or subsea pipeline; S2 uses the medium from the reduced production of the first oil and gas platform as the ball pushing medium to push the two-way pig from the first oil and gas platform to the last oil and gas platform. Through the interference fit between the two-way pig and the inner diameter of the subsea pipeline, the deposited oil and grease attached to the subsea pipeline wall is pushed to the last oil and gas platform. S3. The oily liquid pushed in step S2 is collected by the terminal platform and enters the platform buffer system, and is discharged separately after treatment; S4. When the two-way pig reaches the end of the subsea pipeline or the pipeline is stuck and cannot continue to advance, a mixture of fresh water and cleaning agent is used as the back-push medium to push the two-way pig back to the head oil and gas platform, so that the subsea pipeline is filled with the mixture of fresh water and cleaning agent. At this time, the subsea pipeline is ready for abandonment or underwater open treatment. S5. Using the production medium restarted by the oil and gas platform at the head end of the subsea pipeline, push the bidirectional pig from the head end oil and gas platform to the tail end oil and gas platform again to remove the residual mixed solution in the pipeline. S6. The oily liquid pushed in step S5 is collected by the terminal oil and gas platform and enters the platform buffer system, and is discharged separately after treatment.

2. The cleaning method for abandoned or blocked subsea pipelines according to claim 1, characterized in that, The ball-pushing medium in both steps S2 and S5 is natural gas.

3. The cleaning method for abandoned or blocked subsea pipelines according to claim 1, characterized in that, In step S5, if the subsea pipeline is a blocked subsea pipeline that needs repair, after the pipeline repair is completed, the bidirectional pipeline pig will be pushed from the first oil and gas platform to the last oil and gas platform again using the production medium restarted by the oil and gas platform at the first end of the pipeline, so as to remove the residual mixed solution in the pipeline.

4. The cleaning method for abandoned or blocked subsea pipelines according to claim 1, characterized in that, The material of the bidirectional pipeline pig is selected according to the pollutant situation in the pipeline and the length of the pipeline; for longer pipelines, a bidirectional pipeline pig is replaced for each single trip of forward and reverse pushing.

5. A cleaning method for abandoned or blocked subsea pipelines according to claim 4, characterized in that, For bidirectional pigging systems that require single forward and reverse propulsion, bidirectional sealing is provided.

6. The cleaning method for abandoned or blocked subsea pipelines according to claim 1, characterized in that, The cleaning agent is a reagent that has both emulsifying and cleaning functions, or it is mixed with fresh water in the order of front-end emulsifier and back-end cleaning agent.

7. The cleaning method for abandoned or blocked subsea pipelines according to claim 1, characterized in that, In step S4, when the bidirectional pig is pushed back, a pre-mixed cleaning agent solution is first injected into the subsea pipeline. When the injected volume reaches 2 / 3 of the subsea pipeline capacity, fresh water is used to continue the injection until the bidirectional pig returns to the head oil and gas platform.

8. The cleaning method for abandoned or blocked subsea pipelines according to claim 1, characterized in that, In step S4, after the bidirectional pipeline pig is pushed back to the first oil and gas platform, samples are collected from the pipeline at both the first and last oil and gas platforms. The oil content of the samples is then tested. If both samples meet the standards, the pipeline can be cut and replaced underwater.

9. The cleaning method for abandoned or blocked subsea pipelines according to claim 1, characterized in that, The method for determining whether the bidirectional pig has reached the jamming position in step S4 is as follows: monitor the pressure at the head of the subsea pipeline, and when the pressure at the head of the pipeline continues to rise, determine that the bidirectional pig has reached the jamming position.

10. The cleaning method for abandoned or blocked subsea pipelines according to claim 1, characterized in that, The bidirectional pig is a high-density foam pig; in step S4, when injecting the reverse thrust medium, the reverse thrust medium is injected through an injection pump connected to the oil and gas platform at the end of the subsea pipeline.

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