wellheads

A wellhead is the surface or subsea equipment that forms the structural and pressure-containing interface for a petroleum well. It provides the foundation for the subsurface casing and tubing strings, supports the well along its life, and connects to production equipment and safety systems. In conventional wells, the wellhead sits atop the conductor and casing strings and includes components that establish the pressure boundary and allow access to the wellbore for intervention and production.

A typical wellhead assembly comprises a casing head, tubing head or tubing head adapter, hangers, and a pressure-containing housing. It is designed to withstand reservoir pressures and mechanical loads from the well and surface equipment. Valves such as the master valve and wing/gate valves, along with choke and kill lines, facilitate control of wellbore fluids and emergency shutoff. Spools, adaptors, and connectors enable attachment to the blowout preventer stack, production tubing, and surface piping. Atop the wellhead, a Christmas tree is installed to regulate production, isolate the well, and route fluids through produced lines and control lines.

Subsea wells employ a subsea wellhead on the seabed, connected to a subsea tree and surface infrastructure by flowlines and control umbilicals. The subsea wellhead provides a barrier and attachment point for the tree and BOP stacks and is engineered to resist marine conditions and corrosion while enabling remote operation.

Standards and testing: Wellhead equipment is governed by industry specifications, notably API standards for wellhead and tree equipment. Hydrostatic testing, leak testing, and regular integrity inspections are used to verify performance and safety. Materials commonly include carbon steel and corrosion-resistant alloys.