Surface Controlled Downhole Valve with Supplemental Spring Closing Force for Ultra Deep Wells

Abstract

Apparatus for the activation of a deep set surface controlled subsurface valve such as a SCSSV or a gas vent valve by means of hydraulic pressure applied to an externally mounted control line includes the use of supplemental forces to assist the normal closing force to close the valve. The valve comprises a valve body with a longitudinal bore for fluid flow through, a bore closure member such as a flapper or sleeve, a hydraulic piston to provide for valve opening when pressure is applied to the control line and a plurality of spring assemblies to provide for valve closure when applied hydraulic pressure is removed. This spring closure mechanism can be configured in order to enable the valve to be set and safely operate at very deep setting depths. Another approach is the use of magnets of opposite polarity positioned in the valve, one of which is attached to an axially movable flow tube located within the valve. As the flow tube moves upwardly, the magnetic attraction force increases thereby increasing the total force available to overcome the hydraulic pressure on the piston, with a minimum magnitude of control line pressure.

What is claimed is: 
     
         1 . A surface controlled, subsurface safety valve comprising:
 a housing having an inlet and an outlet,   a flapper valve positioned within the housing and having a flapper and a valve seat,   an axially movable flow tube positioned within the housing, said flow tube adapted to open the flapper valve,   a spring surrounding the flow tube and adapted to be compressed by axial movement of the flow tube,   a piston adapted to move the flow tube in a downhole direction in response to fluid pressure applied from the surface to a portion of the piston, and means for supplementing the force available to move the flow tube uphole in addition to the force applied by the compressed spring to overcome the hydrostatic force acting on the piston.   
     
     
         2 . A surface controlled, subsurface safety valve as claimed in  claim 1  wherein the means for supplementing the force includes a first magnet embedded in the flow tube and a second magnet of opposite polarity embedded in the housing. 
     
     
         3 . A surface controlled subsurface safety valve as claimed in  claim 2  wherein the magnets are rare earth magnets. 
     
     
         4 . A surface controlled subsurface safety valve as claimed in  claim 2  wherein the flow tube includes a shoulder and the first magnet is embedded in the shoulder. 
     
     
         5 . A surface controlled subsurface safety valve as claimed in  claim 1  further including a hydraulic chamber having an inlet connectable to a control line extending from the surface, said piston positioned within the hydraulic chamber for axial movement. 
     
     
         6 . A surface controlled subsurface safety valve as claimed in  claim 1  wherein the means for supplementing the force includes one or more additional springs adapted to be compressed by axial movement of the flow tube. 
     
     
         7 . The surface controlled subsurface safety valve of  claim 6  further including one or more spring stops secured to the housing, said one or more additional springs being compressed between the one or more spring stops and one or more shoulders located on the flow tube. 
     
     
         8 . The surface controlled subsurface safety valve of  claim 6  wherein the flow tube includes a plurality of tube portions interconnected to each other. 
     
     
         9 . A surface controlled, downhole valve comprising:
 a housing having an inlet and an outlet,   a valve member positioned within the housing,   an axially movable flow tube positioned within the housing, said flow tube adapted to open the valve member,   a spring acting on the flow tube to close the valve member, the spring adapted to be compressed by axial movement of the flow tube,   a piston adapted to move the flow tube in a downhole direction in response to fluid pressure applied from the surface to a portion of the piston, and means for supplementing the force available to move the flow tube uphole in addition to the force applied by the compressed spring to overcome the hydrostatic force acting on the piston.   
     
     
         10 . A surface controlled, subsurface valve as claimed in  claim 9  wherein the means for supplementing the force includes a first magnet embedded in the flow tube and a second magnet of opposite polarity embedded in the housing. 
     
     
         11 . A surface controlled subsurface valve as claimed in  claim 10  wherein the magnets are rare earth magnets. 
     
     
         12 . A surface controlled subsurface valve as claimed in  claim 10  wherein the flow tube includes a shoulder and the first magnet is embedded in the shoulder. 
     
     
         13 . A surface controlled subsurface valve as claimed in  claim 9  further including a hydraulic chamber having an inlet connectable to a control line extending from the surface, said piston positioned within the hydraulic chamber for axial movement. 
     
     
         14 . The valve according to  claim 9  wherein the housing includes one or more outlets and the flow tube includes one or more ports that register with the one or more outlets when the valve is an open position.