Types of oil tube casing
Oil tube casing is a steel pipe used to support the wall of oil and gas Wells to ensure the normal operation of the drilling process and the entire well after completion. There are many types of oil tube casing, which can be classified mainly according to the use and function.
Catheter:
Function: Seal the surface, prevent wellhead collapse, and form a drilling fluid circulation channel, which is convenient for long-term drilling.
Bottom depth: generally 20-30 meters, the cement outside the pipe returns to the ground.
Pipe: Generally use spiral pipe or straight seam pipe.
Surface casing:
Function: To seal the unstable soft, collapsible and leaky strata and water layer in the upper part; Support the partial weight of the technical casing and the reservoir casing.
Depth: generally tens of meters to hundreds of meters or deeper (30 ~ 1500m), depending on the situation.
High cement return: Usually back to the surface, and may need to be deeper when drilling high-pressure gas Wells.
Technical casing:
Function: To block complex formations that drilling fluid is difficult to control, serious leakage layers, and oil, gas, and water layers with wide pressure differences, etc., to prevent well diameter expansion; In directional well with large inclination, it is beneficial to the safe drilling of directional well. It provides conditions for the installation of well control equipment, blowout prevention, leakage prevention and liner hanging, and also protects the oil formation casing.
Depth: Depending on the complex formation to be sealed, the cement return height should reach 100 meters above the formation to be sealed, and the cement is often returned to the ground for high-pressure gas Wells.
Reservoir casing:
What it does: pull oil and gas out of subsurface reservoirs; Protect the well and layer the drilling mud.
Depth: Depends on the depth of the target zone and the completion method.
Slurry return height: generally return to the top of the oil and gas layer more than 100 meters, for high pressure Wells, should return to the surface.
