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The Collaborative International Dictionary

Wellhead \Well"head`\, n. A source, spring, or fountain.

At the wellhead the purest streams arise.

Our public-school and university life is a great wellhead of new and irresponsible words.


n. 1 The place where a spring breaks out of the ground; the source of water for a stream or well. 2 (context figuratively English) The source of something; a fountainhead. 3 The surface structure of an oil well etc.

  1. n. the source of water for a well [syn: wellspring]

  2. a structure built over a well


A wellhead is the component at the surface of an oil or gas well that provides the structural and pressure-containing interface for the drilling and production equipment.

The primary purpose of a wellhead is to provide the suspension point and pressure seals for the casing strings that run from the bottom of the hole sections to the surface pressure control equipment.

While drilling the oil well, surface pressure control is provided by a blowout preventer (BOP). If the pressure is not contained during drilling operations by the column of drilling fluid, casings, wellhead, and BOP, a well blowout could occur.

When the well has been drilled, it is completed to provide an interface with the reservoir rock and a tubular conduit for the well fluids. The surface pressure control is provided by a Christmas tree, which is installed on top of the wellhead, with isolation valves and choke equipment to control the flow of well fluids during production.

Wellheads are typically welded onto the first string of casing, which has been cemented in place during drilling operations, to form an integral structure of the well. In exploration wells that are later abandoned, the wellhead may be recovered for refurbishment and re-use.

Offshore, where a wellhead is located on the production platform it is called a surface wellhead, and if located beneath the water then it is referred to as a subsea wellhead or mudline wellhead.

Usage examples of "wellhead".

Revealing formal gardens with stone hermae, geysering fountains, lamps, a marble wellhead, terra-cotta jars tall as a man, and statues of sylphs and mythical animals so lifelike that they almost seemed to move through the boughs and terraced pathways.

Jess looked down at the wellheads and pumping stations surrounded by igloo-style hangars, large water-tanker ships for delivering supplies to settlements, and elevator passages that descended to the subcrustal settlement.

So many people were moving about in the great stone courtyard, in and out of the arcades from brilliant sun to brittle shadow, rubber-necking up at the long Renaissance facade of the eastward side, or the Baroque clock-tower under which she had entered, or climbing about the two enormous wellheads to find good places for taking photographs.

Not far away were other geothermal wellheads, their natural pressurized steam deflected into huge insulated pipes.

On the credit side, he had an experienced, smoothly functioning crew, nine rigs with four more on order, and nearly four billion tons of sweet crude ready to gush up from the wellheads.

Somewhere far down below among the twisted spars and drill pipe and cables and the flooded wreckage of the quarter boat were the bodies of my father and nineteen other men who went down with the rig when the drill bit punched into a pay sand and the wellhead blew.

If the reservoir lacks sufficient driving force (gas or water) to push the oil up to the surface, the wellhead will be connected to a pump, which then provides the lifting force.

Curtis climbs onto the foot-high wooden platform surrounding the wellhead, grips the pump handle with both hands, and works it as if it were a jack.