Bidirectional sealing mechanically shifted ball valve for downhole use

A downhole ball valve is mounted n a string and features a rotating ball that turns on its axis as it is held against an upstream and a downstream seal by a cage. The cage accepts a slide that engages the ball off-center to rotate it between the open and closed positions. The slide is operated by a sleeve attached to a piston assembly. The sleeve is mechanically operated in opposed directions such as by a wireline shifting tool. Differential pressure on a closed ball does not affect the actuation piston because pressure across the actuating piston is balanced while holding pressure differential across the closed ball. A check valve allows the actuation piston to be in pressure balance as the ball stays closed.

FIELD OF THE INVENTION

The field of the invention relates to downhole shutoff valves, that can be used in a lubricator application, that allow a string to be made up in a live well by isolation of a lower portion of it and more particularly to features regarding such valves relating to mechanically operating them and design features that prevent applied differential pressure from above to inadvertently open them.

BACKGROUND OF THE INVENTION

Lubricator valves are valves used downhole to allow long assemblies to be put together in the well above the closed lubricator valve with well pressure further below the closed lubricator valve. These valves are frequently used in tandem with sub-surface safety valves to have redundancy of closures against well pressures below.

Lubricator assemblies are used at the surface of a well and comprise a compartment above the wellhead through which a bottom hole assembly is put together with the bottom valve closing off well pressure. These surface lubricators have limited lengths determined by the scale of the available rig equipment. Downhole lubricators simply get around length limitations of surface lubricators by using a lubricator valve downhole to allow as much as thousands of feet of length in the wellbore to assemble a bottom hole assembly.

In the past ball valves have been used as lubricator valves. They generally featured a pair of control lines to opposed sides of a piston whose movement back and forth registered with a ball to rotate it 90 between an open and a closed position. Collets could be used to hold the ball in both positions and would release in response to control pressure in one of the control lines. An example of such a design can be seen in U.S. Pat. Nos. 4,368,871; 4,197,879 and 4,130,166. In these patents, the ball turns on its own axis on trunnions. Other designs translate the ball while rotating it 90 degrees between and open and a closed position. One example of this is the 15K Enhanced Landing String Assembly offered by the Expro Group that includes such a lubricator valve. Other designs combine rotation and translation of the ball with a separate locking sleeve that is hydraulically driven to lock the ball turning and shifting sleeve in a ball closed position as shown in U.S. Pat. No. 4,522,370. Some valves are of a tubing retrievable style such as Halliburton's PES® LV4 Lubricator Valve. Lock open sleeves that go through a ball have been proposed in U.S. Pat. No. 4,449,587. Other designs, such as U.S. Pat. No. 6,109,352 used in subsea trees have a rack and pinion drive for a ball and use a remotely operated vehicle (ROV) to power the valve between open and closed positions claiming that either end positioned is a locked position but going on to state that the same ROV simply reverses direction and the valve can reverse direction. Ball valves that are not used downhole are shown in U.S. Pat. Nos. 6,695,286; 4,289165 and 5,417,405.

What is lacking and addressed by the present invention is a more elegant solution to a downhole ball type valve for use in applications such as a barrier or in a sand control application, for a few examples. The present invention is directed to a mechanical actuation of a ball valve through a shifting of a sleeve that can in one instance be actuated with a shifting tool run on wireline. It further provides a pressure equalizing mechanism on the actuation assembly in the event the ball is closed and pressure differential comes from above the ball. The pressure is equalized on the actuation mechanism but not across the closed ball so as to prevent pressure differential from moving a sleeve in the actuation mechanism that would otherwise rotate the ball open. These and other features of the present invention will become more readily apparent to those of ordinary skill in the art from a review of the description of the preferred embodiment that appears below in conjunction with the associated drawings while recognizing that the appended claims are the full measure of the invention.

SUMMARY OF THE INVENTION

A downhole ball valve is mounted n a string and features a rotating ball that turns on its axis as it is held against an upstream and a downstream seal by a cage. The cage accepts a slide that engages the ball off-center to rotate it between the open and closed positions. A sleeve is attached to a piston assembly which in turn is attached to the slide for tandem movement to rotate a ball. The sleeve is mechanically operated in opposed directions such as by a wireline shifting tool. Differential pressure on a closed ball does not affect the actuation piston because pressure across the actuating piston is balanced while holding pressure differential across the closed ball. A check valve allows the actuation piston to be in pressure balance as the ball stays closed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIGS. 1 and 5, the valve V is part of a string (not shown) that goes downhole and is connected to the top end10and the bottom end12of the housing14. An inner sleeve16has an internal groove18to be engaged and moved in opposed directions preferably by a wireline tool represented schematically by double headed arrow20. Movement of sleeve16shifts the piston assembly22and with it slide24relative to stationary cage26. Ball28is pinned with opposed pins30so that it can rotate about them on its central axis. Pins32extend from arms34and engage ball28off-center so as to be able to rotate ball28in opposed directions when the slide24moves with respect to the stationary cage26. Upper seat36and lower seat34are retained to the ball28with the cage26.

With the major components now described, a detailed description of the remaining components will be more readily understood using the enlarged views ofFIGS. 2-4. Sleeve16has a retaining nut40held to it externally at thread42. Nut40bears down on piston connector44for downward tandem movement. During upward movement of sleeve16a shoulder46engages the piston connector44for tandem movement. Connector44is attached to upper piston48, which is in turn attached to a lower piston50at thread52. Lower piston50moves in a bore54in housing10and is sealed in bore54with seals56. As seen inFIG. 5, the lower end of lower piston50is attached to slide24so that pins32can be shifted relative to pins30that fix the ball28to the cage26to allow ball28to be rotated about pins30between an open and a closed position that represent preferably 90 degree rotation of ball28. One way to limit the downward movement of sleeve16is when shoulder58hits shoulder60of body10. While a single piston assembly22has been described in detail, those skilled in the art that additional assemblies can be used and are preferably disposed on equal spacing circumferentially in housing10so as to minimize any moment that is applied to the slide24from motion imparted from a tool moving sleeve16.

Body10has at least one bore62with a check valve64which allows pressure from above represented by arrow66to enter bore62with the ball28in the closed position. When the ball28is in the closed position, passage68is obstructed as is bore54due to the seals56on lower piston50. Normally, without bore62and check valve64pressure could build on connector44and urge the piston assembly22down. This could have an undesirable effect of shifting the piston assembly22and ultimately the ball28from the closed to the open position. The presence of bore62and check valve64allows a differential from uphole of a closed ball28to avoid putting a net force on the piston assembly22by equalizing pressure to it but without equalizing pressure across the closed ball28. Reference toFIG. 3further clears up this concept.

FIG. 3shows a redundant check valve70at the lower end of bore62and oriented in the same direction as check valve64to serve as a backup to it. Preferably they are the same and feature a poppet74biased against a seat76by a spring78. Other one way flow device can be used instead. Bore62opens into annular space72which is also in communication with lower piston50. In that way, when the flow is past the check valves in bore62to the annular space72the piston assembly22is in pressure balance from pressure in passage68above the closed ball28.

Upper seat36has a seal stack80against the housing10and a ball seal82to contact ball28that together effectively hold pressure above the closed ball28and out of space84where the slide24and the cage26are disposed. In fact spaces72and84are contiguous.FIG. 3also shows lower seat assembly38with a resilient seal86in contact with ball28. Seat assembly38continues intoFIG. 4further showing seal stack88, which is similar in size and function to seal stack80. A shoulder90on housing10supports a ring92and a wave spring or Belleville washer stack94that push on nut96secured at thread98to the lower seat assembly38. Set screw100holds the position of nut96. Stack94puts a preload on seals82and86that are in contact with the ball28. Seal88as with seal80help to retain the pressure in passage68and isolate spaces84and72from the pressure in passage68.

Those skilled in the art will appreciate that the ball valve of the present invention can be used downhole and operated mechanically within the string preferably by a wireline shifting tool to move from the open to the closed position and back. Other shifting tools that are run on coiled or rigid tubing can be used instead. It has an equalization provision to prevent unintended opening of the ball28when it is in the closed position by pressure buildup from above the closed ball28. The equalization occurs on the piston assembly22that is above the ball without equalizing pressure across the closed ball. In the closed position, the ball28seals against differential pressures in opposed directions using ball seals82and86that remain in contact with ball28regardless of the direction of differential pressure on the closed ball28. The pressure equalization on the piston assembly22is not dependent on any initial ball rotation of ball28. Wave spring94provides a preload to enhance contact between ball28and seals82and86when there is differential from downhole and it resists separation of ball28from seal82in situations of net differential pressure in a downhole direction.

It is to be understood that this disclosure is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended other than as described in the appended claims.