A method for controlling seawater corrosion during the laying process of subsea pipelines

Abstract

The present invention discloses a method for controlling seawater corrosion during the laying process of subsea pipelines. The method of the present invention comprises the following steps: during the laying process of subsea pipelines, at regular intervals, a certain mass of solid anti-seawater corrosion agents is bonded to the inner wall of the pipeline using an adhesive. The present invention provides a safe, reliable and simple method for adding anti-corrosion agents during the laying and installation process of subsea pipelines, which can effectively control the corrosion risk caused by seawater entering the subsea pipeline during the laying and installation process of subsea pipelines, and provides a simple and effective prevention and control measure to ensure the corrosion safety integrity during the laying and installation process of subsea pipelines.

Description

Technical Field

[0001] The invention relates to a method for controlling seawater corrosion during the laying of a submarine pipeline, and belongs to the technical field of marine submarine pipelines. Background Art

[0002] At present, the main measures for corrosion prevention in submarine pipelines include the use of anti-corrosion agents and the improvement of pipe materials. Among them, the anti-corrosion agent is added at the entrance of the submarine pipeline. For example, corrosion inhibitors and / or fungicides can be injected intermittently or continuously for corrosion prevention.

[0003] During the laying and installation of submarine pipelines, seawater may enter the submarine pipelines due to typhoon avoidance or expansion bend installation. Since the seawater has a high salt content and will introduce dissolved oxygen and microorganisms, there is a risk of corrosion in the submarine pipelines. In particular, the microorganisms introduced by seawater may be one of the bases for microbial corrosion of submarine pipelines, leading to rapid corrosion and even local corrosion perforation of submarine pipelines, causing great economic losses and environmental damage. Therefore, strictly controlling the entry of seawater or controlling the corrosiveness of entering seawater during the laying and installation of submarine pipelines is an important prevention and control measure to ensure the integrity of submarine pipelines. At present, there is no disclosure of any technology for controlling seawater corrosion by adding anticorrosive agents during the laying and installation of submarine pipelines. Summary of the invention

[0004] The purpose of the present invention is to provide a method for controlling seawater corrosion by injecting an anticorrosive agent during the laying of a submarine pipeline. The method is safe, reliable and easy to operate.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] The present invention provides a method for controlling seawater corrosion by injecting anticorrosive agents during the laying of submarine pipelines, comprising the following steps: during the laying of submarine pipelines, a certain mass of anti-seawater corrosion solid agents are bonded to the inner wall of the pipeline at intervals using an adhesive.

[0007] In the above method, the solid anti-seawater corrosion agent has multiple functions of sterilization, deoxidation and corrosion inhibition and has the performance of rapid dissolution in seawater. The solid anti-seawater corrosion agent can be a mixed agent of bactericide, corrosion inhibitor and deoxidizer, or it can be an antiseptic agent with multiple functions of sterilization, corrosion inhibition and deoxidation.

[0008] In the above method, the anti-seawater corrosion solid agent is in block form. The anti-seawater corrosion solid agent can be a whole block or several blocks. The number and size of the block-shaped anti-seawater corrosion solid agent can be appropriately adjusted within a reasonable range according to the quality of the required anti-seawater corrosion solid agent and the specifications of the pipeline.

[0009] In the above method, the adhesive is a water-based adhesive, which can achieve rapid bonding between the metal pipeline and the solid anti-corrosion agent, has the characteristics of being easily degradable and dispersible in seawater, and does not affect the effectiveness of the anti-corrosion agent after dissolution. The water-based adhesive is preferably a homopolymer water-based adhesive.

[0010] In the above method, after the adhesive is evenly applied on the surface of the solid agent resistant to seawater corrosion, the bonding is carried out. The application amount of the adhesive ensures that the agent can be fixed on the inner wall of the pipeline, or can still be ensured within the agent injection area of this section even if it falls off.

[0011] In the above method, the "every certain distance" can be every 244 - 610 meters.

[0012] In the above method, the "certain mass", that is, the mass of the single-point injection agent, is calculated according to the following formula (1):

[0013]

[0014] In formula (1), M is the mass of the single-point injection agent, with the unit of kg; ID is the inner diameter of the submarine pipeline, with the unit of mm; n is the number of submarine pipelines at the agent injection interval; L is the length of a single submarine pipeline, with the unit of m; C is the agent injection concentration, with the unit of mg / L; C e is the effective concentration of the agent, in terms of mass concentration, with the unit of %; f is the margin coefficient, taking any value from 1.05 to 1.2. In the actual design and implementation process, a certain margin can be considered according to the actual situation.

[0015] In the above method, the material of the submarine pipeline is carbon steel.

[0016] The present invention has the following beneficial effects:

[0017] The present invention provides a method for injecting anti-corrosion agent during the laying and installation of submarine pipelines, which is safe, reliable and easy to operate. It can effectively control the corrosion risk caused by seawater entering the submarine pipeline during the laying and installation of the submarine pipeline, and provides a simple and effective prevention and control measure to ensure the corrosion safety integrity during the laying and installation of the submarine pipeline. Specific Embodiments

[0018] The following further describes the present invention in detail in combination with specific embodiments. The provided embodiments are only for clarifying the present invention, rather than limiting the scope of the present invention. The following provided embodiments can be used as a guide for those of ordinary skill in the art to make further improvements, and do not limit the present invention in any way.

[0019] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified; the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0020] Example 1

[0021] The subsea pipeline has a diameter of 12 inches, an outer diameter of 323.8 mm, a wall thickness of 12.7 mm, an inner diameter of 298.4 mm, and a single pipe length of 12.2 m. The subsea pipeline is made of carbon steel.

[0022] During the laying process of the subsea pipeline, a solid anti-seawater corrosion agent is injected to control seawater corrosion. The specific steps are as follows: During the laying process, for every 20 subsea pipelines, a certain mass of solid anti-seawater corrosion agent is bonded to the inner wall of the pipeline using an adhesive.

[0023] Among them, the injected solid anti-seawater corrosion agent is a mixed agent of bactericide, corrosion inhibitor, and deoxidizer, which is pressed into a block-shaped solid agent using a briquetting machine. The agent injection concentration is 500 mg / L (the concentration corresponding to the seawater volume of the pipeline volume at the interval distance). The effective concentration of the solid agent is 50%, and the surplus coefficient is 1.2. According to formula (1), the weight of the solid anti-corrosion agent required at each agent injection point is 20.5 kg.

[0024]

[0025] In formula (1), M is the mass of the agent injected at a single point, in kg; ID is the inner diameter of the subsea pipeline, in mm; n is the number of subsea pipelines at the agent injection interval; L is the length of a single subsea pipeline, in m; C is the agent injection concentration, in mg / L; C e is the effective concentration of the agent, in mass concentration, in %; f is the surplus coefficient;

[0026] Among them, the adhesive used is a homopolymer water-based adhesive, which is evenly applied to one side of the above-mentioned block-shaped solid agent and then bonded to the inner surface of the pipeline.

[0027] Anti-corrosion performance test:

[0028] Take seawater samples from the area near a certain platform in the South China Sea, conduct corrosion evaluation experiments and microbial culture test experiments respectively, and then add them to the seawater samples at a drug concentration of 500 mg / L, and conduct corrosion inhibition and sterilization effect evaluation experiments respectively to evaluate the application effect of the drug.

[0029] The corrosion evaluation experiment refers to GB / T 19291-2003, the experimental period is 5 days, and after the experiment, the corrosion products are removed according to the recommended method of GB / T16545-2015, and the average corrosion rate of the experimental materials is calculated by the weight loss method.

[0030] The microbial culture test refers to SY / T 0532-2012, and the extinction dilution method is used to test the content of sulfate-reducing bacteria, saprophytic bacteria, and iron bacteria in seawater.

[0031] Before adding the agent to the seawater sample, the corrosion rate of carbon steel in seawater was 0.61 mm / a. After adding the agent, the corrosion rate of carbon steel was 0.042 mm / a, and the corrosion inhibition efficiency was 93.1%.

[0032] Before adding the agent to the seawater sample, the microbial detection showed that the seawater contained 7.5 mg / L sulfate-reducing bacteria, 9.5 mg / L saprophytic bacteria, and 1.1 mg / L iron bacteria. After adding the agent, no sulfate-reducing bacteria, saprophytic bacteria, or iron bacteria were detected in the water sample.

[0033] The above has described the present invention in detail. For those skilled in the art, without departing from the gist and scope of the present invention and without unnecessary experiments, the present invention can be implemented within a relatively wide range under equivalent parameters, concentrations, and conditions. Although specific embodiments of the present invention are given, it should be understood that the present invention can be further improved. In short, according to the principle of the present invention, this application intends to cover any changes, uses, or improvements to the present invention, including those that depart from the scope disclosed in this application but are made by using conventional techniques known in the art. Some basic features can be applied according to the scope of the following appended claims.

Claims

1. A method for controlling seawater corrosion during the laying of a submarine pipeline, comprising the following steps: during the laying of the submarine pipeline, a certain mass of a solid agent for resisting seawater corrosion is bonded to the inner wall of the pipeline by using an adhesive at intervals; The anti-seawater corrosion solid agent is a mixed agent of a bactericide, a corrosion inhibitor and a deoxidizer, or an antiseptic agent with multiple functions of bactericide, corrosion inhibitor and deoxidizer; The interval is 244 to 610 meters. The certain mass, i.e., the mass of the single-point injection agent, is calculated according to the following formula (1): In formula (1), M is the mass of the single-point dosing agent, with the unit of kg; ID is the inner diameter of the submarine pipeline, with the unit of mm; n is the number of submarine pipelines at the dosing interval; L is the length of a single submarine pipeline, with the unit of m; C is the dosing concentration of the agent, with the unit of mg / L; C e is the effective concentration of the agent, measured by mass concentration, with the unit of %; f is the allowance coefficient, taking any value from 1.05 to 1.2; The submarine pipeline is made of carbon steel.

2. The method according to claim 1, characterized in that: The anti-seawater corrosion solid agent is in block shape.

3. The method according to any one of claims 1-2, characterized in that: The adhesive is a water-based adhesive.

4. The method according to any one of claims 1-2, characterized in that: The bonding is performed after the adhesive is evenly applied on the surface of the anti-seawater corrosion solid agent.

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