Patent ID: 6772842
Filing Date: 2004-08-10
Classification: E21B,F16K

Abstract:
A flapper valve for deployment in a wellbore, comprising:a housing; a bore through the housing having a longitudinal axis; a curved flapper hingedly connected to the housing and rotatable between an open state to allow flow through the bore and a closed state to prevent flow through the bore, the flapper having a first sealing surface; a seat within the housing, the seat having a second sealing surface substantially conforming to the first sealing surface and on which the first sealing surface bears when the flapper is in the closed state; and in which the first and second surfaces are variably tapered such that a bearing force from the first surface onto the second surface has, along a first portion of the sealing surfaces, a first component directed radially inward relative to the longitudinal axis and, along a second portion of the sealing surfaces, a second component directed radially outward relative to the longitudinal axis.