Abstract: A multi-cycle circulating sub apparatus having a control member for controlling the movement of a sleeve between a first or closed position and a second or open position. The control member is slidably mounted in a body and is moveable by fluid pressure in the body in a first axial direction relative to the body. The control member also has a spring biasing the control member in an opposite axial direction of the body. A pin is secured to either the body or the control member. A central groove, in which a portion of the pin is received, is formed in the other of the body or control member. The central groove is shaped to limit axial displacement of the control member in response to pressure variations in the body such that only after a predetermined number of movements of the control member to a first limit position is the control member able to move to a second limit position to displace the sleeve into the second position. The apparatus may also be reset many times while remaining in a downhole position.

Abstract: The invention relates to bypass valves for use in wellbores, particularly but not exclusively to bypass valves used during the setting of hydraulic anchor packers. The invention provides a bypass valve for selectively isolating the interior of a down-hole assembly from the exterior thereof, the bypass valve comprising guide pin in received slot being adapted to permit movement of a piston (30) from a first position to a second position in response to a predetermined pressure differential between a bore (58) of the piston (30) and the exterior of a body (4) but normally preventing movement of the piston (30) to a third position in which the bore (58) of the piston (30) is substantially isolated from the exterior of the body (4), and an extension of the guide slot for overriding the guide pins in the slot, so as to permit movement of the piston (30) to the third position.