Drilling Casing Head

1. Classification of sealing rings: BT type, FS type, Y type, P type. - Mainly used for secondary sealing of casing head and bottom of tubing head. - Usually the pressure of one BT seal is less than or equal to 5000 PSI, and two BT seals can be used for high pressure. - The pressure through injection molding shall not be higher than 80% of the casing's anti-extrusion strength.

2. The meanings of the letters BT are: B stands for balanced type T stands for pressure-free double seal, also called tandem seal

3.Purpose of casing head The casing head is generally made of 35 or 42 chromium-molybdenum high-quality alloy structural steel. The function of the casing head is to set a casing hanger inside the casing head to hang the casing string of corresponding specifications and seal the annular space. A blowout preventer group should be installed on it. After the oil well is completed, a Christmas tree is installed on the casing head. The casing head is an important equipment for controlling the wellhead pressure during the drilling process, and the side outlet is equipped with a VR plugging thread. (1) Hang the weight of each layer of casing except the surface casing. (2) Connect the blowout preventer group (3) Form a pressure seal between the inner and outer casing strings (4) Release the pressure that may accumulate in the casing annulus (5) Special operations: a. Side hole cement injection B. Side hole injection of pressure balance liquid

4. Classification of casing heads

4.1 Connection methods with surface casing: (1) slip type, (2) threaded type, (3) welded type

4.2 Oil layer and technical casing suspension: slip type and mandrel type. Slip type is further divided into: W (WD) slip hanger, CG-21 slip hanger, CG-22 slip hanger, CG-29 slip hanger

4.3 Slip connection at the bottom WD slip is used to connect the surface casing, and BT secondary seal is used at the same time.

WD casing hanger adopts an integral opening and closing structure. Once the casing head is inserted into the surface casing and in place, tighten the bottom screws. There are two BT sealing rings on the upper part of the slips to seal the surface casing and prevent the casing annulus from being pressurized.

4.4Bottom threaded connection

4.5The bottom welded annulus has a pressure test hole to verify the welding effect.