Corrosion and protection of oil and gas pipelines

In the case of oil and gas pipelines, because the medium they transport is often quite corrosive, which can cause corrosion of the pipeline, resulting in perforation and leakage accidents, which in turn cause losses to oil and gas production.

This paper carries out relevant analysis, discusses the causes of corrosion of oil and gas pipelines, and formulates corresponding protective measures, hoping that this research can help the development of oil and gas industry.

1. Analysis of the causes of oil pipeline corrosion

Generally speaking, oil and gas pipelines are often laid underground, with the help of long-distance pipelines to transport operations, thereby promoting the economic performance of oil and gas transportation can be improved. After analyzing the specific situation of the production site, it can be seen that pipeline transportation is the best solution, so it is well promoted and used.

Since pipelines are usually laid underground, there is a large degree of soil corrosion and electrochemical corrosion, resulting in a decrease in pressure-bearing capacity and mechanical strength of the pipeline, which can cause oil and gas leakage, and may lead to fires and other accidents, bringing economic losses to the enterprise. Because of the presence of corrosive media in the soil, which makes the formation of primary cells in the pipeline conditions, resulting in corrosion perforation, causing harm to the safety of the pipeline. The quality of the pipeline can also have a large negative impact on the entire transport work.

Usually for metal pipelines, often with cathodic protection technology to carry out the corresponding protection, and in the pipeline construction process, if there is a lack of cathodic protection quality problems, not to achieve a better cathodic protection effect, is the main cause of serious corrosion of the pipeline, and make the service life is greatly reduced.

In the petroleum medium, there is a certain content of sulfur, which is a core factor causing corrosion of the pipeline, because crude oil often contains sulfur, which will cause a certain degree of sulfur precipitation compounds in the pipeline. In the case of these compounds, they will generally react with iron in the pipeline to produce ferrous sulfate compounds, but in the case of ferrous sulfate, they contain free acid, which in turn will cause hydrolysis reactions, which will aggravate corrosion based on the above.

In the process of natural gas transmission, there are often transport stress, once this aspect shows a certain degree of fluctuation, it will cause the appearance of corrosion, and thus produce some minor rupture, when the resulting small cracks after a period of time, is to show the expansion of the expansion of the situation, resulting in the final large breach.

2. Oil and gas pipeline corrosion protection technology

Overall, in the form of pipeline corrosion is divided, mainly for two forms, that is, internal corrosion and external corrosion. As the situation of pipeline corrosion there are differences, so should be carried out with the help of targeted anti-corrosion measures to carry out operations.

Nowadays, the internal coating technology has been very well promoted and applied. Generally speaking, internal corrosion prevention technology can be divided into several types, mainly corrosion inhibitor technology, internal coating technology and composite pipe technology. Specifically in terms of corrosion inhibitor technology, the application of this technology is specifically, the proportion of corrosion inhibitor, and will be injected into the pipe, so as to achieve the purpose of corrosion mitigation.

As for the internal coating, the technology originated in other countries and is now being promoted extremely well. However, due to the late entry into China, the technology has been in a stagnant state in the country, and advanced technology has a gap. Nowadays, China's oil and gas pipeline radiation-proof inner coating mainly contains epoxy type, improved epoxy type, epoxy phenolic type, polyurethane type, which are several types. And in the third technology composite pipe, it is mainly made of ceramic and other materials.

Through the comparison with other technologies can be seen, glass-lined composite pipe can play a great role, first of all, to ensure the strength of the steel pipe, followed by the ability to promote the effective strengthening of anti-corrosion performance.

3. Analysis of oil and gas pipeline corrosion protection measures

(1) Cathodic protection technology measures

In order to promote pipeline corrosion rate can be weakened, must be carried out cathodic protection to be protected pipeline as a cathode, to be protected, so as to avoid corrosion of metal pipelines. Detailed operational countermeasures are cathodic protection measures of sacrificial anode and cathodic protection measures of applied current. Depending on the differences in the pipeline system, targeted cathodic protection operations can be carried out.

From the field analysis, it is clear that regular maintenance and servicing are the most effective countermeasures in terms of implementation effect and are well used in oil and gas transmission projects. In terms of anode material selection, some of the best materials should be used, such as graphite, etc., so as to achieve efficient protection of the pipeline and avoid corrosion of the metal pipeline and the resulting safety hazards and eventual losses.

(2) Monitoring technical measures for the corrosion of oil and gas transmission pipelines

In the process of laying oil and gas pipelines, often laid in different nature of the soil, so its corrosion situation there is a great difference. In general, even a gas pipeline may be in contact with many different soils.

In the pipeline, because of its surface layer there are a lot of physical and chemical properties, so it will cause the deepening of the corrosion of the pipeline. To face this situation, it is necessary to complete the corresponding anti-corrosion work. In this process, the chemical reaction should be given sufficient attention, and in this, electrochemical reaction is one of the key components. Specifically to electrochemical reaction to analyze, there should exist as electrodes of metal at the same time, there should also be able to reflect the environment of the electrolyte, the third must have a conductive circuit.

In general, when the pipeline laying operation, must pay attention to the necessary testing operations, especially to pay attention to the environmental corrosion work, if you want to achieve the effective completion of this work, to be able to carry out positive measurements of soil corrosion, through the work carried out, and ultimately can have a more comprehensive and in-depth study of the actual corrosion of the pipeline. In our country's reality, has established a series of evaluation parameters and evaluation criteria based on soil corrosion to judge the internal corrosion degree of optical fiber.

For example, the specific pipeline corrosion detection process, the technical staff should first complete the work for, scientific and effective grasp of the region's soil corrosion, including corrosion patterns, corrosion patterns and other related content. Next, focus on the soil in the region, the current to carry out effective measurement, to achieve effective analysis and assessment of the entire corrosion situation, in addition, but also on the current use of the pipeline period to carry out research and judgment. As for the external corrosion layer without excavation detection, its monitoring operations are often carried out with the help of the destruction of the external corrosion layer of the pipeline, and now this technology has been better developed and relatively mature.

It should be noted that, in the process of detection, if this technology is adopted, then the staff should carry out the effective evaluation of the current attenuation value, and also carry out the closely spaced potential test associated with it. In the cathodic protection monitoring, the specific application process, the relevant staff must measure the potential of the oil pipeline and the potential along the pipeline, and after obtaining the corresponding values, should use the power-off measurement method and the near reference method to achieve effective analysis of the internal corrosion protection layer peeling condition of the pipeline.

(3) Enhance the corrosion resistance of LPG pipelines with the help of different types of coating technologies

In order to strengthen the corresponding anti-corrosion measures, the technician should also carry out coating operations, thus contributing to the effective strengthening of corrosion resistance. Coating technology is widely used throughout the oil pipeline corrosion prevention work, and with the help of these special anti-corrosion materials, it is good to promote the effective extension of the pipeline life cycle, and will make the appearance and corresponding performance of the pipeline better.

For example, technicians use coal tar enamel coating technology to carry out the corresponding anti-corrosion operations. The application of this material, especially on the surface of the pipe, provides a good barrier to external moisture and prevents erosion of the pipe, and the use of this material also enhances the antibacterial properties of the pipe to a significant extent. However, it is important to note that the use of this type of coating material must be careful with regard to contamination.

Nowadays, this technology is no longer used in large quantities and is slowly being withdrawn from the market. In addition, technicians are able to use epoxy powder for coating protection. After it is applied to the surface of the pipe, it can well promote the internal stress, and at the same time, it can make the anti-wear ability of the inside of the pipe to be very good reinforcement, as far as the epoxy resin material is concerned, it has a considerable degree of rigidity, and can also play a good role in isolating water.

(4) Improve the corrosion resistance of the pipeline by means of the patching technology

If there are corrosion gaps in the pipeline, we should pay attention to this technology, so as to achieve effective repair of the corrosion gaps, which will strengthen the anti-corrosion performance and extend the life of the pipeline. In today's specific case, the following two technologies are often used for pipeline patching operations: hot asphalt pouring patching technology and polyethylene material patching technology.

For example, if the operation is carried out with the hot asphalt pouring patching technology, the division of labor should be carried out, first of all, to melt the asphalt material, and then pour it into the corrosion gap parts, after the end of the pouring, the technician must also start covering operations, that is, the corresponding protection of the outside of the pipe winding, so as to prevent the entry of impurities, and avoid causing harm to the patching effect. However, this technique is often applied to relatively old pipes.

In addition to the above mentioned technology, the patching can also be carried out with the help of polyethylene material. In this technique, the patching is done by applying a primer to the anticorrosive gap, followed by an external wrap, which must be polyethylene tape, for effective protection. With the aid of polyethylene material, the external performance of the pipe can be significantly improved.

4. Analysis

In general, in order to deeply strengthen the overall corrosion resistance of oil and gas pipelines and pipeline stress, so the technical staff must pay sufficient attention to some points. A solid study of the causes of pipeline corrosion, and then take it as a starting point to build the corresponding protective measures. From the above, it can be seen that the effective protection of the pipeline can be achieved with the help of technologies such as in-line coating. The application of scientific and feasible anti-corrosion measures can largely contribute to the extension of the service life of the pipeline, and can also make the effective reduction of transportation costs.

Author: Yang Yongliang

Source: China Piping Solutions Provider - Yaang Pipe Industry Co., Limited (www.yaang.com)

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