Oil casing is a kind of large-caliber pipe, which plays the role of fixing oil and natural gas well wall or well hole. The casing is inserted into the borehole and cemented in place to help keep the borehole apart from rock layers and prevent it from collapsing, while allowing drilling mud to circulate and flow to facilitate drilling.

Steel class of OIL casing: H40, J55, K55, N80, L80, C90, T95, P110, Q125, V150, etc. Casing end processing form: short round thread, long round thread, trapezoidal thread, special buckle, etc. It is mainly used to support the well wall during the drilling process and after the completion of the well, so as to ensure the normal operation of the whole oil well after the drilling process.

Different types of steel casing used in oil production:

Surface oil casing: Protects the well from shallow-water and shallow-gas contamination, supports wellhead equipment and maintains the weight of the rest of the casing.

Technical oil casing: Separate the pressure at different levels to allow proper flow of drilling fluid and protect production casing. Install anti-blowout devices, leak preventers and liner in the well.

Reservoir casing: The removal of oil and gas from a reservoir beneath the surface. It is used to protect drilling and stratify drilling mud. Oil casing is typically produced with an outside diameter of 114.3 mm to 508 mm.

According to SY/T6194-96 "PETROLEUM CASING", the types and packaging of petroleum casing are divided into two types: short threaded casing and its collar and long threaded casing and its collar.

Anti-corrosion measures for oil casing

1, first of all, do a good job of water quality standards, strict water quality testing and management. Carry out cleaning and separate injection, strengthen the cleaning work of the main water pipeline, make sure that the water quality in the station and at the bottom of the well reaches the standard, reduce the corrosion source into the annular space;

2. For the newly put into production water injection Wells, the annulus protection fluid mainly containing sterilization shall be added, and a system shall be formed to add it regularly;

3. In view of the accelerated effect of mechanical abrasion on the corrosion of oil casing, it is suggested to add a rubber ring on the tubing collar or a centralizer at the severely deviated part of the well to avoid scraping casing and contacting casing on one side of the tubing in the process of operation and water injection.

4. In view of the serious corrosion of bacteria under scale and the slow growth and killing of SRB at high temperature, high temperature water or steam of 100 degrees Celsius can be regularly injected into the annulus to kill SRB under scale.

5. It is not recommended to popularize the use of cathodic protection and coated casing before the corrosion in the casing of injection Wells is effectively controlled.