1. Wellhead Casing Structure

Wellhead casing usually consists of four-way, casing hanger, top wire assembly, flange parallel gate valve, connector, pressure display mechanism, etc;

2. Working principle of Rubber Seal

The wellhead casing consists of the wellhead casing body, BT seal, casing hanger, dovetail seal , lockdown screw seal and sealing gasket. The casing hanger seat is hung on the steps of the casing body. Due to the suspension weight of the casing, metal to metal contact produces a rigid passive seal, and the seal between the casing hanger and the casing is thread seal.

The four-way of casing head is equipped with BT seal and corresponding grease injection and pressure test holes that match the outer diameter of casing hanger (or casing outer diameter). During use, high-pressure sealing grease must be injected from the grease injection valve to make BT seal work. If the seal leaks, the sealing grease shall be injected into the grease injection valve and the pressure test valve respectively to make the seal continue to take effect. The grease injection pressure shall not exceed the rated working pressure of the flange; If the casing is sealed, the rated allowable collapse pressure of the casing shall not be exceeded. The pressure test hole is used for the external sealing test of casing hanger.

There are lockdown screw seals on the flange, which are used to lock the wear sleeve (protect the sealing surface). After the casing hanger is seated, the casing hanger can be locked. If there is leakage at the lockdown screw, tighten the pressure cap to make the seal effective. One end is connected with flat valve (or blind flange) and the other end is connected with flat valve, screw flange, joint, stop valve and pressure gauge. The annulus pressure between the two casing layers can be observed through the pressure gauge.