Downhole valve

Details Downhole valve Downhole valve

1999-10-14

2001-09-11

Neuder, William (Department: 3672)

Wells

Packers or plugs

With controllable passage between central chamber and space...

C166S334400

Reexamination Certificate

active

06286594

ABSTRACT:

This invention relates to a downhole valve for mounting on a string, and in particular to a downhole valve for location below a packer.
In oil and gas exploration and production operations bores are drilled to gain access to subsurface hydrocarbon-bearing formations or reservoirs. The bores are lined with steel tubing, known as casing or liner, set in concrete, which liner is perforated at selected locations where the bore intersects the hydrocarbon-bearing formation. Testing and analysis of the formation, and also production of fluid from the formation, is normally achieved by utilising a tubular string which extends from the surface, through the lined bore, to the perforated section of bore which intersects the formation. The string is formed from a large number of tubing lengths which are threaded together and a packer is mounted on the lower end of the string to provide a seal between the exterior of the string and the bore wall and thus isolate the formation from the annulus above the packer. By providing a valve at the lower end of the string it is then possible to control access to the formation through the string. However, particularly during initial production operations, fluid flowing through the valve may be carrying sand, gravel, drill cuttings and other debris, and on closing such a valve there may be difficulties in obtaining an effective seal due to the accumulation of debris on the valve seals, or from erosion of the seals. Further, actuation of such valves will often require manual intervention, which is time consuming and expensive. It would be possible to utilise tubing pressure to open such valves, however this requires provision of controls or mechanisms to ensure that the valve will not open inadvertently when the tubing experiences elevated pressures, for example during completion testing. Further, it is not possible to close such a valve utilising tubing pressure without exposing the formation to elevated pressures, which is considered undesirable in most circumstances.
It is among the objectives of embodiments of the present invention to obviate or mitigate these disadvantages.
According to the present invention there is provided downhole apparatus for mounting on a string for location in a drilled bore, the apparatus comprising a tubular body defining a bore, a packer mounted on the body for sealing the annulus between the body and the wall of the bore, means for closing the body bore below the packer, a fluid actuated valve in the body between the closing means and the packer for permitting selective fluid communication between the body bore and the exterior of the body, and means for transferring fluid pressure from above the packer to the valve, whereby fluid pressure applied to the annulus above the packer may be utilised to operate the valve.
According to another aspect of the present invention there is provided a valve for mounting on a downhole string below a packer and for providing selective fluid communication between the tubing and an annulus, the valve being fluid actuated and adapted for communication with a fluid line extending from above a packer to the valve, whereby fluid pressure applied to the annulus above the packer may be utilised to operate the valve.
As the valve is located below the packer, the presence of the valve does not affect the completion or pressure integrity of the string in the event of valve leakage or failure.
The valve may be used as a downhole shut-in-tool for conducting build-up and reservoir analysis, or as a deep-set safety valve. Further, the valve may be used for flowing a well after a completion has been run and then isolating the reservoir until the well is ready to produce; for production, the closing means may be removed or opened to provide full-bore access to the reservoir.
Preferably, the valve is normally closed, such that, for example, in the event of a system failure the valve will close or remain closed.
Preferably also, the valve is full bore, that is, at least in the open position, it does not create a significant restriction in the body bore; the valve does not therefore restrict the flow of fluid from the reservoir to the surface and does not impede access to the reservoir through the string.
Preferably also, the valve comprises a sleeve. Most preferably, the sleeve is axially moveable relative to the body. In a preferred embodiment the sleeve defines one or more ports which may be selectively aligned with corresponding ports in the body. The sleeve is preferably mounted on the exterior of the body.
The use of a sleeve avoids many of the difficulties experienced by existing arrangements where it is desired to open and close a valve providing fluid communication between tubing and the bore below a packer; such existing arrangements utilise ball or flapper valves, and while the valves remain open there is a likelihood that debris will collect on the valve seat, or erode the valve seat, such that it may be difficult to achieve a seal when the valve is closed.
Preferably also, the means transferring fluid pressure from above the packer to the valve includes a piston having one face for communication with fluid above the packer and the other face in communication with a volume of fluid in a fluid line. Most preferably, said volume of fluid communicates with a piston face defined by the valve, via the fluid line.
Preferably also, the valve is biassed to a closed position, preferably by one or both of fluid pressure and spring force. Where a fluid pressure biassing force is utilised, a chamber may be defined between the valve and the body for containing the fluid. The chamber may accommodate a spring. The chamber may be filled with pressurised fluid on surface to provide a desired spring force. However, it is preferred that the fluid is pressurised at the operating depth of the apparatus. This may be achieved by providing the chamber with a moveable wall in fluid communication with the body bore or body exterior such that the wall experiences at least hydrostatic pressure and will thus move into the chamber to pressurise the fluid in the chamber to at least hydrostatic pressure. Most preferably, the wall is adapted to be selectively exposed to the body bore or exterior; this permits the fluid spring to be pressurised to a predetermined level by exposing the wall to pressure at a selected interval, and then isolated once more to avoid the wall being exposed to elevated pressures, for example during completion testing. Conveniently, the apparatus may be provided in conjunction with apparatus for providing selective fluid communication between the body bore and a valve as described in W097/05759 or W097/06344, the disclosures of which are incorporated herein by reference. The wall preferably includes means for conserving movement, such as a ratchet.
Where a spring biassing force is utilised to close the valve, the rate or precompression of the spring may be selected for compatibility with the fluid pressure experienced at the depth where the apparatus is expected to operate; at greater depths the actuating pressure will be higher than at lesser depths. Alternatively, or in addition, the valve may include means which may be configured to vary the valve opening force provided by a given pressure. In the preferred embodiment this is achieved by providing a plurality of valve actuating pistons which may be configured for communication with the fluid line. A face of each piston is preferably in communication with a low pressure volume, for example an atmospheric chamber. The number of pistons in communication with the fluid line may be selected such that the force necessary to overcome the spring and open the valve is produced by a predetermined overpressure in the annulus. The fluid line may define a plurality of branches, one leading to each piston. A connector may be provided in each branch, one form of connector providing fluid communication therethrough and another forming a plug or barrier. The pistons may be defined by shuttles, one end of each shuttle bearing on or otherwise coupled to a valve memb

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