Single-trip deployment and isolation using ball valve

A downhole deployment and isolation system for a wellbore comprising a work string releasably connected to a completion string using a valve remote reopening mechanism with an axially shiftable sleeve and catch. An upper work string 114 is connected to a lower completion string or assembly 119 wherein the connector includes a mandrel (142, Fig 3) that operates to allow disconnection of the tubing strings. A ball valve (184, Fig 2) that is coupled to the lower completion tubing, is initially open whilst the work and completion strings are connected and closes when they are disconnected. The system also comprises a remote reopening mechanism that urges the ball valve to re-open. This is achieved by applying fluid pressure to an axially shiftable sleeve (170, Fig 2) that is held in place with a catch (242, Fig 10) when the valve is closed, and releases the sleeve in response to application of fluid pressure.