How To Perform Anti-corrosion Testing on Casing Pipe?

As an OCTG pipe, casing pipe plays an important role in the oil industry. It is usually used with drill pipes and pup joints during drilling. However, it is easily corroded and affects normal operation if it is exposed to harsh environments for a long time. Therefore, effective anti-corrosion measures must be taken, and casing pipe that has been subjected to anti-corrosion measures must be inspected regularly.

Reasons why casing pipe needs corrosion protection

During use, casing pipe will be subject to various corrosions, including chemical corrosion, electrochemical corrosion, microbial corrosion, etc. If the casing pipe is not anti-corrosion, it will cause the pipeline to be corroded, thus affecting the service life and safety of the pipeline.

Methods and measures for casing pipe corrosion protection

1. Internal corrosion protection

Internal corrosion protection refers to applying a layer of anti-corrosion paint or lining inside the casing pipe to prevent corrosion inside the pipeline. The methods of internal corrosion protection include coating method and lining method. The coating method is to spray a layer of special anti-corrosion paint inside the pipeline, and the lining method is to line the casing pipe with a layer of anti-corrosion material, such as fiberglass, polymer and ceramic.

2. External corrosion protection

External corrosion protection refers to applying a layer of anti-corrosion paint or outsourcing on the outside of the casing pipe to prevent the outside of the pipeline from being corroded. External corrosion protection is generally carried out by coating method, or outsourcing method, that is, a layer of ceramic or fiberglass and other materials are put on the outside of the casing pipe for protection.

3. Use of anti-corrosion materials

In the manufacturing process of the casing pipe, anti-corrosion materials can also be used for corrosion protection, such as PTFE, FEP and other anti-corrosion materials. These materials have good anti-corrosion properties and can effectively protect the casing pipe.

Common anti-corrosion detection methods

1. Visual inspection

Visual inspection is one of the most commonly used anti-corrosion detection methods at present. By inspecting the outer surface of the casing pipe, it is determined whether there are defects such as rust, peeling, and cracks on the surface of the casing pipe. However, this method requires manual participation, requires a lot of time and manpower costs, and is easily affected by the subjective consciousness of personnel, and cannot accurately evaluate the degree of corrosion of the casing pipe.

2. Coating thickness measurement

Coating thickness measurement is another commonly used anti-corrosion detection method that can be used to measure the thickness of the coating. This method can determine whether the coating has reached the designed thickness and can detect whether the thickness of the coating is uniform. However, this method cannot measure the degree of corrosion under the coating.

3. Dielectric constant test

The dielectric constant test uses the characteristics of electromagnetic waves passing through the casing pipe to detect the degree of corrosion of the inner and outer walls of the casing pipe. This method has the advantages of being fast, accurate, and non-contact, and is suitable for detecting longer casing pipe sections. However, this method is not suitable for detecting corrosion under the coating.

Detection methods suitable for downhole casing pipe

In view of the special environment and use requirements of downhole casing pipe, the following methods can be considered for anti-corrosion detection.

1. Ultrasonic detection

Ultrasonic detection uses ultrasonic probes to detect the inner and outer walls of the casing pipe, which can detect the degree of corrosion and thickness of the inner and outer walls of the casing pipe.

This method has the advantages of high precision and high efficiency, and is suitable for detecting long-distance casing pipe. In addition, this technology can be detected using automated instruments to reduce manual intervention.

2. Electrochemical corrosion monitoring

Electrochemical corrosion monitoring is a method of monitoring corrosion using electrochemical principles. The advantage of this method is that it can monitor corrosion in real time and can quantitatively analyze corrosion behavior, which is conducive to formulating corresponding preventive measures.

3. Infrared temperature measurement

Infrared temperature measurement uses an infrared camera to measure the temperature of the casing pipe surface, which can determine whether the casing pipe surface is corroded. This method has the advantages of being fast, accurate, and non-contact, and is suitable for detecting shorter casing pipe sections.

Summary

The casing pipe needs to be anti-corrosion, otherwise it will cause the pipeline to be corroded or even damaged. The methods of casing pipe anti-corrosion include internal anti-corrosion, external anti-corrosion, and the use of anti-corrosion materials. The detection effect can be detected by non-destructive testing, adhesion testing, chemical resistance testing, and other methods. In view of the special needs of downhole casing pipe, it is very important to choose an anti-corrosion detection method suitable for casing pipe. This article introduces three methods: ultrasonic testing, electrochemical corrosion monitoring, and infrared temperature measurement. You can choose an appropriate method to perform casing pipe anti-corrosion detection as needed. It should be noted that safety should be the primary consideration when implementing the test, and appropriate safety measures should be taken to ensure the safety and smooth progress of the detection process.