What is the service life of oil casing pipe?

The service life of oil casing pipe is affected by many factors, but generally speaking, it can range from 15 to 30 years or even longer.

1. Casing Material
From a material perspective, oil casing made of high-quality steel offers excellent corrosion and wear resistance, maintaining stability in harsh downhole environments for extended periods, thereby extending its service life. For example, casing made of special alloy steels significantly enhances corrosion resistance, effectively resisting erosion by acidic substances in the formation, reducing damage caused by corrosion and extending its service life.

The quality of the casing thread machining and the accuracy of the make-up torque determine the tightness and strength of the connection. Many leaks and fractures occur in the threaded area.

2. Operating Environment
The operating environment significantly impacts the service life of oil casing.

If the formation pressure is moderate, the temperature is relatively stable, and the fluid properties are mild, the casing will experience relatively little stress and chemical attack, resulting in a longer service life. Conversely, if the formation conditions are harsh, such as high pressure, high temperature, or fluids rich in corrosive substances, the casing will experience accelerated wear and corrosion, potentially shortening its service life.

3. Construction Quality
Construction quality is also crucial to the service life of oil casing. Strict construction techniques ensure that the casing is securely installed, preventing damage from loosening during use. If the casing is lowered too quickly during drilling, or if the connection between the casing and the wellhead is not secure during completion, it may damage the casing during use, shortening its service life.

4. Post-maintenance
Regular inspection and maintenance can detect and address potential casing problems, such as cracks and corrosion, and effectively extend its service life. By comprehensively considering these factors, selecting and using oil casing appropriately, and maintaining it properly, its service life is expected to be extended.

Casing is generally not replaced individually. When an oil well reaches its economic production life, the casing is scrapped along with the well. In special circumstances, if repairs are necessary, casing repair technology can be used to extend the service life, but the overall service life is still limited by the design life of the well.

How to Extend Casing Service Life?

1. Optimize Design
Accurately select the casing steel grade, wall thickness, and material based on the drilling objectives, predicted formation pressure, and corrosive environment. Use hardbanding or thicker casing for well sections prone to wear.

2. Corrosion Control
Use anti-corrosion materials: Choose chromium-containing corrosion-resistant alloy casing for harsh environments.
Add chemical corrosion inhibitors: Regularly inject corrosion inhibitors into the well to form a protective film on the inner wall of the casing.
Control injection fluid quality: Deoxygenate, sterilize, and descale the injection water.

3. Operational Control
Ensure cementing quality and provide good isolation.
Use non-rotating drill pipe during drilling to reduce wear on the casing.
Strictly follow specifications when making up the casing to ensure threaded connections.

4. Monitoring and Evaluation
Perform regular multi-finger caliper logging to monitor corrosion, wear, and deformation on the inner wall of the casing.
Perform downhole television logging to visually inspect casing damage.
Establish a corrosion monitoring system, regularly collect water samples for analysis, and assess corrosion rates.

Conclusion:
The service life of oil casing depends on multiple factors, including material, operating environment, and operation. It generally ranges from 15 to 30 years, but specific circumstances require evaluation based on actual conditions. To ensure the long-term and safe use of oil casing, strict control is required in material selection, construction, and routine maintenance.

Read more: Carbon steel Casing vs. Alloy steel Casing or Seamless Casing Specifications 

Source of information: https://www.hu-steel.com/news364_2089.html