Definition(s)
Wellhead
The point at which fluids exit the wellbore below the annular sealing device via the vent line.
Source: API RP 64, Recommended Practice for Diverter Systems Equipment and Operations, Second Edition, November 2001 (March 1, 2007). Global Standards
Wellhead
All permanent equipment between the uppermost portion of the surface casing and the tubing-head adapter connection.
Source: API SPEC 6A, Specification for Wellhead and Christmas Tree Equipment, Twentieth Edition, October 2010 (Addendum November 2012). Global Standards