Wells – Processes – Placing or shifting well part
Reexamination Certificate
1999-12-09
2001-10-02
Will, Thomas B. (Department: 3672)
Wells
Processes
Placing or shifting well part
C166S375000, C166S324000, C166S332700, C166S332800
Reexamination Certificate
active
06296061
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a subsurface safety valve used for controlling fluid flow in a well conduit and, more particularly, to an equalizing subsurface safety valve.
2. Description of the Related Art
Subsurface safety valves are commonly used in wells to prevent uncontrolled fluid flow through the well in the event of an emergency, such as to prevent a well blowout. Conventional safety valves use a flapper which is biased by a spring to a normally closed position, but is retained in an open position by the application of hydraulic fluid from the earth's surface. A typical subsurface safety valve is shown and described in U.S. Pat. No. 4,161,219, which is commonly assigned hereto.
When the flapper is in the closed position, well fluid pressure below the flapper acting upon a relatively large surface area of the flapper makes opening of the flapper difficult. This difficulty in opening cannot be easily overcome simply by increasing the force exerted against the flapper by an opening piston and cylinder assembly because the relatively small cross-sectional area of the opening piston and cylinder assembly would require a fluid pressure that may burst the control line carrying hydraulic fluid from the earth's surface to the piston and cylinder assembly, or destroy critical seals therein. Additionally, when the flapper is opened the initial flow of well fluid is relatively rapid which tends to etch, or erode, the primary sealing surface of the flapper. Any damage to this primary sealing surface is extremely critical because it is this sealing surface which must be intact to prevent uncontrolled flow of well fluids and to prevent a possible well blow out. The present invention solves these difficulties by providing a subsurface safety valve with an equalizing mechanism to allow the pressure above and below the flapper to equalize prior to the complete opening of the flapper.
SUMMARY OF THE INVENTION
The present invention is directed generally to a subsurface safety valve with a pressure equalizing mechanism. In one aspect, the invention may be an equalizing subsurface valve for controlling fluid flow in a well conduit, comprising: a body member having a longitudinal bore extending therethrough; a valve closure member mounted within the body member to control fluid flow through the longitudinal bore, and having a first surface and a second surface; a valve actuator disposed within the body member and remotely shiftable to move the valve closure member between open and closed positions; a pilot activator movably disposed within a pilot bore in the valve in response to movement of the valve actuator; a pilot piston movably disposed within a cylinder in the valve, a first surface of the pilot piston being in fluid communication with the pilot bore through a pilot passageway in the valve, the pilot activator alternately permitting and preventing fluid communication between the longitudinal bore adjacent the second surface of the valve closure member and the first surface of the pilot piston through the pilot passageway; and an equalizing plug movably disposed within a plug bore in the valve in response to movement of the pilot piston, the equalizing plug alternately permitting and preventing fluid communication between the longitudinal bore adjacent the second surface of the valve closure member and the longitudinal bore adjacent the first surface of the valve closure member through at least one equalizing passageway in the valve. Another feature of this aspect of the present invention is that the first surface of the pilot piston includes a first active surface area intermittently in fluid communication with fluid pressure in the longitudinal bore adjacent the second surface of the valve closure member through the pilot passageway, and the equalizing plug includes a head portion having a second active surface area in fluid communication with fluid pressure in the longitudinal bore adjacent the second surface of the valve closure member, the first active surface area being greater than the second active surface area. Another feature of this aspect of the present invention is that the valve actuator includes a sleeve member disposed for movement within the longitudinal bore and an operating piston disposed within the body member and remotely shiftable to move the sleeve member within the longitudinal bore. Another feature of this aspect of the present invention is that the operating piston is a rod piston movably disposed within a cylinder in the body member with one side of the operating piston adapted to be in communication with a source of hydraulic fluid for moving the sleeve member within the longitudinal bore. Another feature of this aspect of the present invention is that the operating piston is a hydraulic operating piston that is moveable in response to application of hydraulic fluid and includes an operating piston surface area in communication with the hydraulic fluid; the pilot activator includes a pilot valve seat defined by a first annular sealing surface on the pilot activator and a second annular sealing surface about the pilot bore, the pilot valve seat defining a pilot surface area, the equalizing plug includes a plug valve seat defined by a third annular sealing surface on the equalizing plug and a fourth annular sealing surface within the valve, the plug valve seat defining a plug surface area; the pilot surface area is smaller than the operating piston surface area; and the plug surface area is greater than the operating piston surface area. Another feature of this aspect of the present invention is that the pilot activator includes a distal end extending from the pilot bore into the longitudinal bore above the first surface of the valve closure member when the pilot activator is in a closed position. Another feature of this aspect of the present invention is that the pilot bore, the pilot passageway, the cylinder, and the plug bore are disposed within the valve closure member. Another feature of this aspect of the present invention is that the pilot bore, the pilot passageway, the cylinder, and the plug bore are disposed within an annular housing connected to the valve body. Another feature of this aspect of the present invention is that the valve actuator includes a sleeve member having a first recessed profile and a second recessed profile, a distal end of the pilot activator being disposed within the first recessed profile when the valve closure member is in a fully-open position, against an intermediate portion of the an outer surface of the sleeve member when the pilot activator and equalizing plug are in equalizing positions, and within the second recessed profile when the valve closure member is in a fully-closed position the at least one equalizing passageway is disposed within the annular housing. Another feature of this aspect of the present invention is that the at least one equalizing passageway is disposed within the valve closure member. Another feature of this aspect of the present invention is that the valve closure member further includes an annular tapered surface joining the second surface of the valve closure member and the plug bore, and the at least one equalizing passageway establishes fluid communication between the first surface of the valve closure member and the tapered surface. Another feature of this aspect of the present invention is that the at least one equalizing passageway is an internal fluid passageway through the equalizing plug. Another feature of this aspect of the present invention is that the internal fluid flow passageway includes a generally longitudinal passageway extending from a second end of the equalizing plug and is in fluid communication with at least one generally radially-disposed opening exiting the plug at a location between the second end of the plug and the annular sealing surface of the plug. Another feature of this aspect of the present invention is that the pilot activator includes a first annular sealing surface for cooperable sealing e
Camco International Inc.
Goldstein & Healey LLP
Walker Zakiya
Will Thomas B.
LandOfFree
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