A wellhead is that part of an oil well which terminates at the surface, whether on land or offshore, where petroleum or gas hydrocarbons can be withdrawn.

The primary role of the wellhead is pressure containment & to hold the casings and the production tubing. Within the wellhead lies the tubing hanger, from which the production tubing hangs. The Christmas tree sits on top of the wellhead housing. Casing hangers serve to hold the different casings. Valves between these hangers then allow access to the different annuli for pressure control and particularly gas lift.