Casing spool is a very important equipment for drilling. The casing cross can control the wellhead pressure. The flange end of the casing spool is usually located at the top of the casing head and connected with the bottom of the tubing head. It is a part of the wellhead system of the oil well.

The casing spool in a conventional wellhead system is the component that allows for an additional string of casing to be set in the well. Depending on the casing program for the well, there can be one or more casing spools and they perform the following functions:

Allows for suspending the next casing string in the well

Supports the blowout preventers (BOP’s) while drilling

Provides outlets for fluid returns

Provides a means to test the blowout preventers while drilling

Has flanges on both the top and bottom of the assembly

Has a seal area in the bottom flange for a secondary seal between the casing annulus and the flanged connection

Utilize a test port in the bottom flange that allows for the secondary seal and the flanged connection to be pressure tested