Patent ID: 6293342
Filing Date: 2001-09-25
Classification: E21B

Abstract:
A bypass valve for selectively isolating the interior of a downhole assembly from the exterior thereof, the bypass valve comprising: a body having a bore for allowing the passage of wellbore fluid therethrough; a chamber defined in the body; at least one aperture provided in the body for allowing fluid communication between the bore and the chamber; at least one aperture provided in the body for allowing fluid communication between the chamber and the exterior of the bypass valve; a piston slidably mounted in the chamber and movable between a first position in which fluid communication between the bore and the exterior of the bypass valve by means of the apertures is permitted and a second position in which fluid communication between the bore and the exterior of the bypass valve by means of the apertures is prevented, the piston being movable from the first position to the second position in response to a first predetermined fluid pressure differential; means for selectively exposing the piston to the first predetermined fluid pressure differential; and a cavity defined between the piston and the body such that the cavity changes volume when the piston moves from the first to the second position, wherein the cavity is sealed by sealing means comprising a one-way seal for allowing the passage therepast of fluid either from or to the cavity in a first direction as a consequence of said volume change but for preventing the passage therepast of fluid in a direction opposite to the first direction.