PLUG COUNTER AND DOWNHOLE TOOL

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of an earlier filing date from U.S. Non Provisional application Ser. No. 12/564,539 filed Sep. 22, 2009, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

In the Drilling and completion industries it is often desirable to affect tools or formations at a great distance from a surface located facility such as a rig. One example of an operation intended to affect a formation is a fracturing operation. In order to perform such an operation, hydraulic pressure is built within a tubing string until the pressure exceeds formation capability for holding that pressure and fractures form in the formation. This type of operation is most effective if done in small incremental sections of a borehole for reasons related to control and distribution of fractures to serve the ultimate purpose of the borehole. Such purposes include hydrocarbon production, Carbon Dioxide sequestration, etc.

In the art, fracturing discrete locations of the borehole tends to require a number of tools related to the pressuring of discrete locations. Such tools increase expense initially and generally create other issues to be overcome after the fracturing process is complete such as removal of the tools that enabled the pressuring of a discrete location. Where multiple fracturing locations are contemplated, generally a staged system must be built and administered correctly for it to work. One such system uses progressively larger seat diameters from the toe back to surface and then progressively increasing diameter balls. While the system works well, it is limited by the number of different size balls that can be used. Tolerance is also required in any system (due to such things as irregular shape of tubing secondary to borehole irregularity), which therefore further limits the number of diameters usable in a particular system.

Since fracturing and other operations where it is desirable to isolate discrete locations continue to become more prevalent and ubiquitous, alternate systems for accessing and manipulating the downhole environment is always well received.

SUMMARY

A plug counter including a housing sized to receive and pass plugs; a helix sleeve rotatably positioned relative to the housing, the helix sleeve including a helical track having a plurality of consecutive turns; and, a key positionable relative to the helical track and responsive to movement of the helix sleeve in a first rotational direction, wherein the key prevents further movement of the helix sleeve in the first rotational direction after a selected number of plugs pass through the plug counter.

A downhole tool including a housing having a support and one or more plug passage recesses; a movable plug seat positionable to be supported by the support or aligned with the one or more plug passage recesses; a helix sleeve rotatable in response to movement of the movable plug seat, the helix sleeve having a helical track including a plurality of consecutive turns; and, a key responsive to movement of the helix sleeve and configured to prevent further movement of the helix sleeve and movable plug seat after a selected number of movable plug seat movements.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings wherein like elements are numbered alike in the several Figures:

FIGS. 1-4 illustrate a cross sectional view of one embodiment of the tool disclosed herein in four different positions;

FIGS. 5-8 illustrate in partial transparent view a counter portion of the tool disclosed herein in four different positions corresponding to the positions shown in FIGS. 1-4;

FIG. 9 is a perspective view of an alternate moveable seat substitutable in the tool; and

FIG. 10 is a schematic view of a portion of an alternate housing of the tool 10 shown in FIG. 1.

DETAILED DESCRIPTION

Referring to FIGS. 1-4, a plug counter tool 10 is illustrated in longitudinal cross section in four different positions to make apparent not only its structural constituents but its operation as well. It is initially noted that the term “plug” as used herein is intended to encompass tripping balls, darts, and similar structures that can be propagated through a borehole and/or tubing string to reach remote locations therewithin. The plug counter tool embodiments disclosed herein facilitate the use of a single size plug (or fewer sizes, if desired, in a particular application) for multiple actuation sequences. For example, where multiple fracture points are desired in a borehole, traditional fracturing would require a number of different diameter plugs used sequentially from smaller to larger as operations progress up the hole. With the tool embodiments described herein only one size plug is needed.

Referring directly to FIG. 1, an outer housing 12 includes a support 14 to support a moveable plug seat 16, which in the case of FIG. 1 is presented by a set of collet fingers 18. The support 14 and movable seat 16 operate together to catch a plug 20 after which the plug is passed or denied passage as discussed hereunder. The fingers 18 are supported by support 14 while the collet fingers are in the position shown in FIG. 1. Support for the fingers 18 is dependent upon the position of collet 22, which is dependent upon the ability of a spring 24 to hold the collet 22 in the position shown in FIG. 1. More specifically, when a plug is seated in the seat 16 pressure can and will in operation be built uphole of the plug. The spring rate of the spring 24 selected dictates the amount of fluid pressure that can be resisted before the collet 22 moves in a downhole direction and the fingers 18 become unsupported. The spring 24 is a compression spring and as illustrated is a coil spring. It will hold the collet 22 in the illustrated position until a plug 20 engages the seat 16 and sufficient fluid pressure uphole of the plug overcomes the spring force of spring 24 and compresses the same. As the spring 24 is overcome by fluid pressure, the collet 22 moves in a downhole direction (to the right in the Figure) and moves the fingers 18 off of the support 14. Just downhole of the support 14 is a plug passage recess 28 that will allow radial expansion of the fingers 18 (see FIG. 2) by an amount sufficient to allow passage of the plug 20 through the seat 16. After passage of the plug, fluid pressure equalizes across the seat 16 and the collet 22 returns to the position of FIG. 1 under the bias of the spring 24.

Connected to the collet 22 is j-slot sleeve 30. Sleeve 30 moves axially of the tool 10 along with the collet 22. At a downhole end of the housing 12, an anti-rotation sleeve 32 is attached to the housing. Sleeve 32 does not move relative to housing 12 in any way once the tool is assembled. Anti-rotation sleeve 32 includes one or more pin openings 34 into which one or more pins 36 will be individually inserted. Each pin 36 will thus be fixed to the anti-rotation sleeve 32 and extend into an alignment groove 38 of which there will be one or more in the j-slot sleeve 30. The one or more pins 36 and respective alignment grooves 38 ensure that the j-slot sleeve 30 is not rotatable but is permitted to move only axially during operation of the tool 10. Upon movement of the collet 22 induced by fluid pressure uphole of plug 20 as described above, the j-slot sleeve 30 will cycle back and forth axially of the tool 10.

Radially inwardly of the anti-rotation sleeve 32 and rotatable relative thereto is a helix sleeve 40 exhibiting a helical track 42 at an outside surface thereof. The helix sleeve 40 includes one or more j-slot followers 44 (one shown), which may be a part of the helix sleeve 40 or may be a separate component that is engaged with the helix sleeve 40. In either event, the j-slot follower(s) 44 are configured to contact angled surfaces 46 and 48 of a j-slot 50 (see FIG. 5) disposed at the j-slot sleeve 30 upon axial movement of the j-slot sleeve 30. Because followers 44 are fixed to the helix sleeve 40, the helix sleeve 40 will move rotationally about the j-slot sleeve 30 as the followers 44 move along each angled surface 46 or 48. The impetus for this movement is the axial cycling of the j-slot sleeve 30 as described above. Each time a plug 20 lands at the seat 16, thereby allowing pressure to build from uphole against the plug 20, and hence urging the collet 22 to a position aligning the fingers 18 with recess 28, the followers 44 will contact and slide along one of the angled surfaces 46. This will cause a measured rotation of the helix sleeve 40. Because the spring 24 is compressed during this pressure induced axial movement, energy is stored that will be used to urge the followers 44 along the next adjacent angled surface 48 pursuant to the j-slot sleeve 30 moving uphole under spring bias, causing another measured rotation of the helix sleeve 40. The spring 24 induces such movement only after the plug 20, against which fluid pressure had been applied, is released.

As the helix sleeve 40 rotates, a key 52 that is engaged with the helical track 42 moves leftwardly in the drawing closer to an end 54 of a keyway 56. It is to be appreciated that although the illustrated embodiment moves in an uphole direction, the tool 10 can easily be configured to allow movement of the key 52 in a downhole direction by reversing the helix angle of the helical track 42 and reversing the surface angles of surfaces 46 and 48. As illustrated in FIGS. 1 and 5, the key 52 is in a position that will allow the greatest number of plugs to pass before preventing passage of the next plug to be seated. FIGS. 4 and 8 show the key in the position where the next plug to seat will not pass.

As configured the tool 10 will pass a number of plugs and then prevent further passage of plugs because the helix sleeve 40 is prevented from rotating by the contact between key 52 and an end 54 of keyway 56. The prevention of rotation of the helix sleeve 40 correspondingly prevents the j-slot sleeve 30 from cycling downhole sufficiently to allow the fingers 18 to reach the recess 28. Consequently the plug 20 cannot pass. This position is illustrated best in FIG. 8 where key 52 is at end 54 and follower 44 is at surface 46 but it cannot slide on surface 46 because the key will no longer allow rotation of the helix sleeve 40 due to having run out of helical track 42. It is to be understood, then, that the maximum number of plugs that are passable through tool 10 are fixed by design during manufacture by the length of the helical track 42 and the keyway 56. This is not to say however that this maximum number of plugs is the only number of plugs that will be passable before a plug is denied passage. Rather, because the key is placable in the keyway 56 as the tool is being run into the hole, at any point on the helical track 42 that is exposed to the keyway 56, any number from the maximum number down to a single plug may be selected.

More specifically, the key 52 is a component of the tool 10 that is removable and replaceable at any point along the keyway 56 where the helical track 42 crosses the keyway 56. The helix sleeve 40 itself may be marked to show how many plugs will pass before denying passage to make it a simple operation in the field for a rig worker to place the key in the keyway 56 to select a number of plug passages to facilitate a particular operation. It should be noted that because of the high pressures generally encountered in the wellbore for operations related to seating plugs and the potential operations that might be effected by pressuring up on such a plug, for example fracturing at about 10,000 psi, the key 52 should be robust in size and construction as it is, in the end, the key that stops movement of the balance of the components.

Another feature of the tool 10 is that if for any reason, after plug passage has been denied, it is necessary to pass the denied plug, the follower(s) 44 may be released by, for example, shearing and the collet will be able to move to the recess 28 allowing the plug to pass. This is accomplished by pressuring up higher on the tubing to greater than a threshold pressure that is set prior to running the tool 10 in the hole by the number and strength of the followers 44 employed in the tool 10. Thereafter all plugs will pass and no further counting will be possible with the tool 10 without removal thereof from the hole and replacement of one or more followers 44.

Referring to FIGS. 9 and 10, an alternate embodiment of the tool disclosed above is illustrated. The embodiment operates similarly to the tool 10 and identically operating components are not discussed again. The tool is distinct in that a dog-based seat structure 122, having a plug seat 116, is substituted for the collet 22 in the FIG. 1 embodiment. For clarity, numerals are mimicked in the 100 series. In normal operation the dogs function, as do the fingers 18 from the previous embodiment. The housing 112 is also distinct in that an additional plug passage recess 150 is provided uphole of the support 114 so that in reverse flow, the one or more dogs 118 can be moved into alignment with the recess 150 to allow passage of one or more plugs in the uphole direction as part of a reverse circulation operation to remove the plugs from the borehole. In order for the structure 122 to move uphole, a plug that had been passed in normal operation of the tool 110 is moved in reverse circulation into a seat 117 on the backside of seat 116. The pressure of reverse circulation acts on the plug in the same manner as in the original operation but in the opposite direction. A spring 152 is disposed uphole of the structure 122 and will be compressed against a top sub 154 at a selected force from fluid pressure on the plug. Movement of the structure 122 in the uphole direction mirrors that of movement in the downhole direction and aligns the dogs 118 with the recess 128, which allows the plug to pass. While an embodiment could eliminate spring 152 and simply allow the structure 122 to stay in the uphole position, including the spring 152 provides the added benefit that the device will automatically revert to a functional state after passage of the plug in the uphole direction so that normal operation of the tool 110 could be resumed if desired.

While one or more embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.