Patent Grant
8118101
The field of this invention is devices used in tubular strings to catch and retain objects previously dropped against a seat to operate a downhole tool and later ejected from the seat. More specifically, the present invention captures the ejected objects and preferably retains them outside a main bore regardless of the flow direction in the string.
A tubular string extending downhole can have a plurality of seats that accept objects, usually spheres, which land on discrete seats so that pressure can be built up and a downhole tool in that string operated. The balls can be the same or different sizes as are the corresponding seats. Regardless of the configuration it is desirable after operating the downhole tool to eject the ball from a given seat by a variety of known techniques and then to capture the balls. The reason capturing the balls is a benefit is that if left in the tubular string and there is a reversal in flow direction the balls can flow backwards and get wedged or jammed. Ideally, capturing the blown out balls will leave a main flow bore through a ball catcher to allow other tools to pass such as those that are supported on wireline or coiled tubing, to provide some examples.
In one design offered by Baker Hughes Incorporated in Catcher Sub Product Family 14077, the central tube catches ejected balls or darts and the differential pressure that develops pushes the ball or dart further into the central tube with flow possible around the central tube. The central tube has a hook feature to prevent escape of the dart or ball if there is a flow reversal. This design left the central passage obstructed which hampered or prevented subsequent operations further downhole from the Catcher Sub. U.S. Pat. No. 6,920,930 captures a ball when landed on a seat and then the seat with the ball breaks one connection and pivots on a remaining connection out of a central passage to allow a shifting sleeve to come down to keep the ball and the seat that traps it out of a main central bore. U.S. Pat. No. 6,732,793 shows a ball retaining device against reverse flow in a ball catcher that locates the captured balls centrally. U.S. Pat. No. 7,416,029 illustrates providing a tortuous path for a deformable ball that moves through a deformable ball seat.
U.S. Pat. No. 7,530,400 shows a ball catcher that has a main bore 18 that is split into two parallel bores 26 and 28 with an entry plate sloping at the top that has openings 38 and 40 aligned with bores 26 and 28 respectively. Only small balls will fit through hole 40 and pass through bore 28 unobstructed. Bigger balls 50 that go through hole 38 are captured at the bottom of bore 26 by a restriction 42, 44. If a small ball 52 goes down passage 38 and into bore 26, it has a way to get from bore 26 to bore 28 as those bores overlap to create a pass through channel so that the small ball 52 can get into bore 28 and escape. There are several issues with this design. First, if there is a flow reversal it will force the balls uphole and out of the ball catcher. Second, the way this ball catcher is set up with parallel bores, it has to have the channel between the bores because it has no way to insure the small balls will go in the pass through passage 28. Another disadvantage is that it has a pass through passage for one size of ball as opposed to catching all balls that enter. While it is recognized that the latter may simply be a design objective when a ball catcher is applied to a specific tubular string, it is recognized that in other applications, this feature can be less than ideal.
The present invention is a ball catcher that is designed to collect and store all the balls that reach its entrance in an annular storage location that surrounds a main bore so that the main bore is left open for other tools to later pass. The annular space preferably has a spiral guide slot that is small enough to prevent the balls being used from exiting the annular space but that advances such balls as they arrive to make efficient use of the annular space. Arriving balls get stopped at the inlet where flow around them displaces a seat that originally stopped the ball and allows the ball to advance past the seat and into the annular space where it stays trapped. These and other features of the invention will become more readily apparent to those skilled in the art from a review of the description of the preferred embodiment that appears below with the associated drawings while recognizing that the full scope of the invention is given by the claims that are attached below.
A ball catcher is designed to stop balls that are the same size or different sizes at an inlet on a seat that is connected to a movable biased sleeve. Once the ball or other shaped object lands at the seat the flow around it increases differential pressure on the seat and sleeve and displaces them against the bias. The ball goes into a surrounding annular space and cannot exit. A preferably spiral sleeve guide the movement of the balls in the annular space so that efficient use of the annular space is made to maximize the number of balls that can be captured per unit length of the annular space. As soon as the ball enters the annular space the sleeve shifts back to the original position to stop the next ball at the inlet. Once in the annular space, the balls cannot escape if there is a flow reversal. The central passage remains open to pass other tools and flow.
The ball catcher 10 has an inlet 12 connected to a tubing string that is not shown. When the ball 14 passes through a ball seat (not shown) that is uphole it continues into inlet passage 16. A movable sleeve 18 has a passage 20 that extends from end 22 at the uphole end to end 24 at the downhole end. Toward the uphole end 22 the passage 20 has a reduced diameter section 26. Adjacent the reduced diameter section 26 is a lateral passage or exit 28 that is best seen in
Ball 14 and sleeve 18 move in tandem to the
As soon as ball 14 rolls or is pushed into spiral slot 46, the spring 36 can return the sleeve 18 and the lateral passage 28 that moves with it back to the
It is worth noting that the spiral groove 46 can have other configurations such as axial but it may be more limited in the number of balls 14 that it can hold for a given unit length of the housing 30. Groove 46 also allows fluid to pass as a way of advancing the ball 14 along the groove 46 using flow in a downhole direction from passage 16 to passage 38. The groove 46 serving as a ball guide is optional and that feature can be eliminated. A port from annular space 42 into the path 20 will also allow flow through the annular space 42 to move a ball 14 along in a more random path to the port that replaces the groove 46. In this case the port instead of the groove 46 should be smaller than the balls 14 that get trapped in the ball catcher 10. Such a port should be preferably located near the outlet passage 38 so that more of the annular space 42 can be used for storage of trapped balls 14.
Note that if balls 14 are used, the ball catcher can accommodate different diameters. If the reduced diameter section 26 is smaller than all the ball sizes used then they all will land on lateral passage 28 and all will be captured in annular space 42. Space 42 need not be annular and go around sleeve 18 for 360 degrees. Optionally, if in a given system balls below a given size do not need to be captured, then the reduced diameter section can be configured to exceed such a given size and balls smaller than that given size will just continue through and not land on lateral passage 28 and not go into annular space 42 to be captured. The passage 20 can be centrally disposed in the housing 30 so that other tools (not shown) can be delivered through passage 20 with wireline or coiled tubing or another known conveyance. Alternatively, it can be offset from the axis of housing 30. Although spheres 14 can be caught other shapes are envisioned including darts and wiper plugs or other shapes that can land in lateral passage such as 28 and enter the surrounding annular space 42. Spring 36 can be a coiled spring, a stack of Belleville washers or a variable volume chamber with a compressible fluid among other ways for creating a return bias force. Other ways to create the bias to the
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.
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| Number | Date | Country | |
|---|---|---|---|
| 20110024106 A1 | Feb 2011 | US |
