Wellhead
The surface equipment — including the "christmas tree" of valves — that seals and controls a well; also the basis for the "wellhead price" of production.
The wellhead is the assembly of surface equipment that sits at the top of a well, sealing off the wellbore and controlling the flow coming out of it. On a producing well, the stack of valves and fittings at the top is nicknamed the "christmas tree." It lets the operator open, close, throttle, and monitor the well safely and connect it to the gathering lines that carry production away.
The wellhead is also the reference point for the "wellhead price" — the value of oil or gas right where it leaves the ground, before the cost of transporting, processing, and marketing it. That distinction matters to royalty owners because post-production costs incurred downstream of the wellhead can be deducted from a check depending on the lease, and some states base severance tax on wellhead value.
So the wellhead is both a physical piece of steel and a place on the value chain — knowing which one is meant is half the battle in reading a royalty statement.