What is Wellhead:
Wellhead is a general term used to describe 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 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 casings, wellhead, and BOP, a well blowout could occur. Once the well has been drilled, a completion is placed in the well to provide an interface with the reservoir rock and the tubular conduit for the well fluids. The surface pressure control is provided by a christmas tree which is installed on top of the wellhead, which has isolation valves and choke equipment to control the flow of well fluids during production. Wellheads are typically cemented in place during drilling operations and form an integral structure of the well. In exploration wells which are later abandoned, the wellhead may be recovered for refurbishment and re-use. Where wellheads are located on the production oil platforms/onshore they are called a surface wellhead, and if located beneath the water then are referred to as a subsea wellhead or mudline wellhead.