Wellhead 11 : The equipment used to maintain surface control of a well. It is formed of the casing head, tubing head, and appropriate valves. The Christmas tree is installed on top of the tubing head. (WLOP)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}