The function of the casing head

The function of the casing head
1. Suspend the tubing string in the well.
2. Seal the annular space between the oil pipe and the casing.
3. Provide transitional connections between the casing head and the Christmas tree.
4. The two side ports on the tubing head cross can be used for water injection and well flushing operations.
The tubing head consists of a tubing head spool, tubing hanger, sealing device, top screw, gate valve, pressure gauge, and flange. The top of the oil pipe head is connected to the Christmas tree through a special flange, which can be in the form of a flange or a clamp.
1) . Tubing hanger
The tubing hanger is a device that sits in the conical seat of the tubing head, used to suspend the tubing string and provide a seal between the suspended tubing and the tubing head conical seat. Offshore oil and gas completion generally has underground safety valves, so the tubing hanger must have a channel to connect to the hydraulic control pipeline, and the electric submersible pump well must also have an underground vent valve channel and cable crossing and sealing. After connecting the oil pipes, they form a circular whole and sit in the double oil pipe hanger seat. When sitting, they must be aligned with the guide block on the oil pipe seat
2) Oil pipe head cross
The tubing head cross is the main structure of the tubing head. The bottom of the tubing head cross is connected to the casing head, the top is connected to the Christmas tree, and both the top and bottom are sealed with steel rings. The tubing head cross provides a carrier and container for the tubing hanger.
The tubing head cross is used to perform forward and reverse circulation well flushing, observe casing pressure, and perform various operations through the annular space of the oil sleeve.
3) Hanging thread of casing hanger
After the oil pipe hanger is installed in place, the top screw of the oil pipe hanger must be installed. The function of the tubing hanger top screw is to lock the tubing hanger and prevent it from moving up and down and rotating.
4) Top screw flange plate
The top thread flange plate is installed on the casing spool, and the oil pipe is hung on the seat of the top thread flange, playing a role in squeezing the packing and sealing the annular space of the oil sleeve. At the same time, the oil pipe is clamped to prevent the oil pipe column from being pushed out when the pressure in the well is too high.