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WELLHEAD AND CASING HANGER

Question2;

WELLHEAD

A wellhead is the component at the surface of an oil or gas well that provides the structural and pressure containing interface for the drilling and production equipment.

The primary purpose of a wellhead is to provide the suspension point and pressure seals for the casing strings that run from the bottom of the hole sections to the surface of the hole sections to the surface pressure control equipment.

While drilling the oil well, surface pressure control is provided by a blowout preventer (BOP). If the pressure is not contained during drilling operations by the column of drilling fluid, casing, wellhead and BOP, a well blowout could occur.

Once the well has been drilled, it is completed to provide an interface with the reservoir rock and a tubular conduit for the well fluids. The surface pressure control is provided by a Christmas tree which is installed on top of the wellhead with isolation valves and choke equipment to control the flow of well fluids during production.

Wellheads are typically welded onto the first string of casing which has been cemented in place during operations, to form an integral structure of the well. In exploration wells that are later abandoned, the wellhead may be recovered for refurbishment and re-use.

In the offshore, where a wellhead is located on the production platform it is called a surface wellhead and if located beneath the water then it is referred to as a subsea wellhead or mud line wellhead.

CASING HANGER

Casing hanger is that portion of a wellhead assembly which provides support for the casing string when it is lowered into the wellbore. It serves to ensure that the casing is properly located. When the casing string has been run into the wellbore, it is hung off or suspended by a casing hanger which rests on a seal between the casing hanger and the spool.

Casing hangers may also be suspended within the wellhead by means of radial distortion of the wellhead bore e.g. the...