The lubricator valve for the subsea test tree is a surface-operated hydraulic valve that is run from one or two joints below the flow­head. It enables the top of the string to be used as a lubricator during wireline, slick­-line, or coiled tubing intervention operations, thereby reducing the amount of lubricator sections needed above the flowhead.

The lubricator valve is connected by a two- or three-line hose bundle to a surface-operating console. The third line may be used for injection of a hydrate inhibitor, such as glycol or metha­nol, just below the valve. In event of control line pressure failure, the valve will remain in the last position, open or closed, that it was placed in before the pressure loss occurred.

The lubricator valve is a pump-through valve and can be pressure tested from above (with hydraulic pressure maintained in the close line). When it is closed, the lubricator valve seals from either above or below to

• withstand the well pressure when tools are introduced or removed from the upper section of the test string being used as a lubricator
• test the flowhead and surface wireline or coiled tubing equipment.