Patent ID: 6123152
Filing Date: 2000-09-26
Classification: E21B

Abstract:
A shut-off valve for use in a downhole string of tools adapted to be retrieved from a well under pressure, the valve comprisinga housing having upper and lower ends configured for attachment to upper and lower portions, respectively, of the tool string, the valve defining an internal passage for hydraulic communication between the upper and lower tool string portions; anda piston slidably disposed within an axial bore of the housing and arranged to, in first and second positions, permit and block, respectively, hydraulic communication along the internal passage;the housing having an outer surface defining upper and lower outer surface regions for engagement by two spaced apart seals of a retrieval head, the housing also defining an outer port disposed between the upper and lower outer surface regions and arranged for hydraulic communication between the piston and the outer housing surface;the piston adapted to be moved to its second position by an elevated pressure applied to the outer port, thereby blocking the internal passage and enabling the upper end of the housing to be disconnected from the upper tool string portion while the lower tool string portion is exposed to elevated well pressure.