Wells – Processes – Operating valve – closure – or changeable restrictor in a well
Reexamination Certificate
1999-11-29
2001-11-27
Suchfield, George (Department: 3672)
Wells
Processes
Operating valve, closure, or changeable restrictor in a well
C166S212000, C166S319000, C166S382000, C166S383000
Reexamination Certificate
active
06321847
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a pressure activated device and a method for use downhole in oil wells and the like. The device and method can be used to set devices such as packers and hangers which must be mechanically engaged with tubing.
Most setting mechanisms previously used have relied on elastomeric seals to prevent leaks between the tubing and the annulus, but the elastomers degrade with time and this arrangement gives poor reliability in completion strings.
Setting devices have previously been used in which sealing between the tubing and the annulus does not rely on elastomeric seals. Such devices use an electronic module and an explosive charge held within an atmospheric chamber. The electronic module monitors pressure pulse signals applied to the drill or completion string and in response to the correct code ignites the explosive charge to generate a high pressure gas. The gas in turn is used to apply hydraulic pressure to the tool to be set.
This type of setting tool is very complicated and has a number of disadvantages. Atmospheric chambers in the tool are inherently unreliable, and typically dependent upon the elastomeric seals, and in the event of leakage into the chamber the tool becomes inoperable. The electronic module is subject to temperature limitations, especially at depth. Since the explosive charge is housed within the atmospheric chamber, no pressure differential will be generated at the setting piston until the hydrostatic pressure outside the setting tool has been overcome by the charge pressure, which limits the setting load available and puts a depth limit on the setting tool.
BRIEF SUMMARY OF THE INVENTION
According to a first aspect of the present invention, a downhole pressure activated device comprises a chamber having a fluid port for communication between the chamber and downhole fluid located outwith the device, the fluid port comprising a fluid flow control mechanism which permits fluid flow into the chamber and substantially prevents reverse flow, and the chamber being provided with a pressure transmission means by which a pressure in the chamber greater than that in the downhole fluid is capable of being applied to a tool to be operated by the device.
According to a second aspect of the present invention, there is provided a method of operating a tool downhole by applying pressure, the method comprising the steps of:
including in a string for insertion into a borehole a pressure activated device comprising a fluid chamber which communicates with downhole fluid located outwith the device in the borehole in a manner that allows substantially uninhibited flow of fluid into the chamber but substantially restricts flow of fluid out of the chamber, a pressure transmission means in fluid communication with the chamber and the pressure transmission means being connected to the tool operated by applying pressure;
inserting the string into the borehole;
increasing the pressure of fluid within the borehole so that a portion of the fluid flows from the borehole into the chamber;
reducing the pressure of the fluid in the borehole to generate a pressure differential between the fluid in the borehole and the fluid in the chamber;
whereby the pressure differential acts upon the pressure transmission means to operate the tool by applying pressure.
Preferably, the fluid flow control mechanism comprises a check valve and a fluid flow restrictor arranged in parallel, the check valve permitting fluid flow into the chamber and substantially preventing reverse flow.
Preferably, the chamber is a second chamber, and the device further comprises a first chamber, the first and second chambers being interconnected by the fluid port, and the first chamber having a fluid inlet which, in use, is open to the downhole fluid located outwith the device.
Typically, the pressure transmission means is a piston located within the second chamber that causes a mechanical force to be applied to the tool.
Preferably, the piston is provided with means permitting motion of the piston in a tool setting direction and preventing reverse motion.
Alternatively, the pressure transmission means may be a fluid outlet that transmits the pressure of the fluid to the tool.
In a preferred form of the invention, the device comprises an inner mandrel for connection in a borehole string, and an outer mandrel, the annular space between the inner and outer mandrels being divided by a seal ring to define said first and second chambers, the piston being a cylindrical member slidable between the inner and outer mandrels at one end of the device, and said inlet being provided at the opposite end of the device and including filter means.
The check valve may be within the seal ring and communicating with the first chamber via an inlet tube.
The means permitting one way motion may suitably be in the form of a C-shaped annular member interposed between the piston and the outer mandrel, the C-shaped member being provided on its opposite faces with circumferential threads or teeth engaging in matching formations in the pistons and the outer mandrel. Typically, the outwardly facing threads or teeth of the C-shaped mandrel will be relatively coarse and the inwardly facing ones relatively fine.
Typically, the piston is initially locked to the outer mandrel by means such as shear pins adapted to yield under a given applied load.
Preferably, the device is included in a completion string.
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Petroleum Engineering Services Limited
Ratner Allan
Suchfield George
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