Abstract: A method of cleaning a casing-lined borehole comprises the steps of: circulating fluid in the borehole to entrain material in the circulating fluid; separating the entrained material from the fluid within the borehole; and then removing the separated material from the borehole.

Abstract: Hydraulic control assemblies for controlling the operation of one or more downhole tools. In one embodiment of the invention, a hydraulic control assembly (10) includes a tubular member in the form of tubing (12), which carries axial chambers (14), each coupled to a downhole tool and carrying a flow controlling shuttle valve (24) and a gear rod (34). Tool control fluids inlets and outlets (18, 16) are provided in communication with each chamber (14), and flow through the chamber (14) to a downhole tool to control the tool. The shuttle valve (24) is movable by the gear rod (34) to selectively allow flow of control fluid to the tool. The gear rod (34) is movable in response to applied fluid pressure.

Abstract: A downhole valve assembly (10) comprises a tubular body (12), and a valve comprising a valve member (18) and a fluid actuated valve control mechanism (14) adapted to be selectively actuated to move the valve member between an open and a closed configuration, for selectively allowing fluid flow through the body (12). A first hydraulic control conduit (41) is in fluid communication with the valve control mechanism (14) for permitting actuation Of the control mechanism to move the valve member (18) to the open configuration, by application of a first control fluid. A second hydraulic control conduit (41) is in fluid communication with the valve control mechanism (14) to move the valve member (18) to the closed configuration, by application of a second control fluid.