Ann V Fitzgerald

US Patent:

20150204162, Jul 23, 2015

Filed:

Jan 22, 2015

Appl. No.:

14/602886

Inventors:

- Irving TX, US
Ann Kamel Fitzgerald - Dallas TX, US
Theodore Lee Cottrell - Keller TX, US
Phillip Graham Knight - Allen TX, US

International Classification:

E21B 34/06
E21B 21/10

Abstract:

A valve for limiting differential pressure applied to a downhole tool includes a housing and a movable piston/mandrel assembly therein. In a closed position, drilling mud or other fluid may be communicated through a central bore of the valve to the tool. When the differential pressure between the central bore and the wellbore exceeds a first predetermined value, the piston/mandrel assembly moves from a first position obstructing one or more relief ports to a second position not obstructing them, thereby providing a fluid path from the central bore of the valve to the wellbore bypassing the tool and relieving the differential pressure thereacross. When the differential pressure decreases to less than another preselected value, the piston/mandrel assembly returns to its original position again obstructing the relief ports. A trigger mechanism is provided to allow more precise control and separation of the preselected differential pressure values.