Patent ID: 6405803
Filing Date: 2002-06-18
Classification: E21B,Y10T

Abstract:
A valve for use in a wellbore, the valve comprising:a) a body; b) a piston disposed in the body for engaging a valve seat disposed in the body, the piston having: i) a longitudinal piston bore allowing communication of a wellbore fluid through the piston; ii) a sealing end having a first piston surface formed thereon for communication with a wellbore pressure to create a first force thereupon and a second piston surface formed thereon for communication with a tubing pressure to create a second force thereupon; iii) a third piston surface formed on the piston for communication with the wellbore pressure to create a third force thereupon, the third force and the first force forming an effective force; and c) a biasing member producing a biasing force to urge the sealing end of the piston into engagement with the valve seat; whereby the valve opens when the second force exceeds a combination of the biasing force and the effective force.