Multiple Spring Subsurface Safety Valve

Abstract

A subsurface safety valve features vertically stacked springs that are each independently supported in the valve housing and each having an opposite end that bears on a shoulder connected to the flow tube. When mounted this way their applied force is additive as they are in effect mounted in parallel between the housing and the flow tube for overcoming hydrostatic pressure in deep set applications that can exceed 20,000 feet. The stacking also allows the cross-sectional area of the flow tube to be maximized for a given housing outside diameter dictated by well conditions.

Description

FIELD OF THE INVENTION

[0001] The field of this invention is subsurface safety valves and more particularly those intended for use in deep applications where closure depends on overcoming hydrostatic pressure in a well.BACKGROUND OF THE INVENTION

[0002] Subsurface safety valves are commonly used to prevent unwanted flow from reaching the surface and causing a dangerous condition. A common design involves a flapper that is held open by a flow tube. A control line from the surface extends to a piston in the housing of the safety valve which is coupled to the flow tube. Applied pressure on the piston shifts the flow tube down against a flapper that rotates about a pivot that is generally spring loaded. The advancing flow tube comes down in front of the rotated flapper and the safety valve remains in the open position as long as pressure is maintained in the control line from the surface. The act of opening the safety valve by moving the flow tube also compresses a closure spring. The closu...

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