A dual bore completion sub-sea test tree (10) is described which has main bore (18)and an auxiliary or annulus bore (20). Two identical ball valves (22, 24) are located in serieswithin the main bore (18) and two smaller identical ball valves (26, 28) are located in series inthe annulus bore (20). The ball valves (22, 24, 26, 28) are operated by respective independentcontrol lines acting on the operating mechanisms of the respective valves within the test tree(10)to move the valves between open and closed positions to allow or deny communication throughthe respective bores (18, 20). The completion sub-sea test tree (10) provides isolation of themain bore (18) and/or the annulus bore (20) when required by application of hydraulic pressureto assist closure to spring forces sufficient to cut coil tubing in the event of an emergencysituation requiring rapid disconnect. Hydraulic across the tree disconnect isachieved using independent hydraulic stabs which can selectively isolate or allow the hydraulicsystems to vent when disconnected. A helical guide (82) and axial slot (81) are provided onthe surface (16, 83) of the housing to engage with a pin (84) on a BOP stack to orientate thetree (10) correctly to a tubing hanger (86).
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