Tell you the structural characteristics and sealing principle of casing head!

Tell you the structural characteristics and sealing principle of casing head!

Casing head is a wellhead component installed at the upper end of surface casing string, which is used to hang all casing layers except surface casing and seal the annular space of casing.

The role of casing head

1. Hang part or all weight of each layer of casing except surface casing with hanger;

2. A pressure seal is formed between the inner and outer casing strings;

3. Connect wellhead devices such as BOP;

4. Provide an outlet to relieve the pressure that may accumulate between 20% casing strings;

5. In case of emergency, killing fluid or fire extinguishing agent can be pumped into the well through the side hole of casing head;

Structural characteristics and sealing principle of casing head

Casing head is mainly composed of bottom casing head, casing hanger, casing head spool and valve.

The casing head seal consists of casing head body, BT rubber seal ring, casing hanger, dovetail rubber seal ring, ejector V-ring and sealing washer.

The casing hanger is hung on the step of casing head body. Due to the hanging weight of casing, the contact between metal and metal produces rigid passive seal, and the seal between casing hanger and casing is spiral seal.

The casing head short pipe has BT seal matched with casing hanger outer diameter (or casing outer diameter), and corresponding grease injection and pressure test hole. When using, high pressure sealing grease should be injected from the grease injection valve to make BT sealing work.

If the seal leaks, the grease should be injected from the grease injection valve and pressure test valve respectively to make the seal continue to work.

The grease injection pressure shall not exceed the rated working pressure of the flange; if the casing is sealed, it shall not exceed the rated allowable collapse pressure of the casing.

The pressure test hole is used for the outer sealing test of casing hanger.

There is a top thread on the flange for locking the wear sleeve (protecting the sealing surface) and locking the casing hanger behind the casing hanger.