Downhole ball dropping apparatus

[0001] The field of the invention is a ball release device and more particularly a device that is mounted near the hole bottom with the stored ball or balls protected until release after circulation.

[0002] Most prior ball release devices store the ball in the fluid stream and use circulation to transport it to the seat. Several problems can occur with this design. The ball may not release because the carrier gets clogged with debris from the mud. The carrier can become worn resulting in premature release of the ball. The ball is released during high circulation. It can slam against a seat and create high pressure spikes that can damage other equipment. The high circulation rates around the ball can erode parts of it causing it to not hold pressure even if it lands on the ball seat. Some examples of prior designs that have the ball in the circulating path are U.S. Pat. Nos. 6,390,200; 6,220,360; and 5,960,881. U.S. Pat. No. 4,171,019 shows a cement float shoe with a ball in a side pocket such that it can be displaced against a ball seat if the flow direction reverses. Balls have been used to fix a range of motion of a sleeve valve member, as shown in U.S. Pat. No. 4,406,335.

[0003] What the prior devices lacked is addressed by the present invention. The ball is retained near its intended seat near the bottom of the hole. It is retained out of the flowing stream. The ball discharge procedure is such that ball release occurs after circulation is stopped and not during circulation. Once the ball is released it is prevented from reentering its original storage location. These and other benefits of the present invention will be more apparent to those skilled in the art from a review of the description of the preferred embodiment and the claims, which appear below.

[0004] A ball release mechanism is mounted near the intended seat. The ball or balls are kept out of the circulating stream. High circulation rates followed by curtailment of circulation places an outlet port in position to allow the ball or balls to be pushed out by a spring. The spring or one of the balls prevents the return of an ejected ball back into the protected pocket. The ball is delivered to the seat without circulation.

[0008] Referring to FIG. 1, a housing 10 is connected at thread 12 to a string and downhole equipment (not shown). Housing 10 comprises a primary ball seat 14 preferably mounted on ball carrier 16 or in another housing in fluid communication with housing 10. As illustrated, ball seat 14 provides resistance to circulation to move the ball carrier 16. However, that resistance can be from another constriction on ball carrier 16 with the ball seat in another housing in fluid communication with housing 10. In the preferred embodiment, the balls 22 and 24 drop less than a meter to get to ball seat 14. A shear pin 18 initially holds the ball carrier 16 to the housing 10. In the run in position, an outlet port 20 is so positioned that balls 22 and 24 cannot escape. Balls 22 and 24 are biased toward tapered surface 26 on ball carrier 16 by spring 28. Housing 10 further comprises a sleeve 30 biased by spring 32 toward ball carrier 16. A seal 34 seals between ball carrier 16 and housing 10. For run in, sleeve 30 holds in detent pin 36 against the bias of spring 38.

[0009] The operation of the tool will now be reviewed. Circulation is started through housing 10. As a result a net force is applied to ball carrier 16 shifting it down against sleeve 30 and compressing spring 32. While the restriction from ball seat 14 that causes ball carrier 16 to be displaced by circulation is shown at the lower end of the ball carrier 16, the actual restriction that causes the ball carrier 16 to shift can be located elsewhere on ball carrier 16, while the ball seat 14 can be in any other location below balls 22 and 24. The shear pin 18 is broken by movement of ball carrier 16. Balls 22 and 24 are held retained by tapered surface 26. Circulation is then stopped. Spring 32 displaces sleeve 30 to position outlet port 20 in alignment to let balls 22 and 24 escape with a push from spring 28. Ball 22 lands on primary ball seat 14, which is less than a meter away, while ball 24 is optional. Ball 24 keeps ball 22 near seat 14 because the upper end 40 of ball carrier 16 as well as spring 28 in its extended position help to maintain ball 24 in the position shown in FIG. 3. Spring 38 has pushed out detent pin 36 to prevent needless cycling of ball carrier 16 at a later time when circulation is resumed for other purposes.

[0010] A secondary ball seat 42 is provided to accept a ball dropped from the surface in a known manner, in the event ball 22 fails to seal or hold enough pressure against primary ball seat 14.

[0011] Those skilled in the art will appreciate that the present invention has many unique features. The ball or balls are stored out of the flowing path of mud and are less likely to be eroded or deformed by circulation. The balls are not released during circulation. Pressure spikes are eliminated as the balls are released from a location very close to the seat after circulation has stopped. There is no need to wait a long time for the ball to seat from the time of release, because the release point is so close to the ultimate seat location. This tool can be run below tools that would not be able to pass a ball. The tool is of particular advantage on a horizontal run. In the past, a ball dropped from the surface could land in many places short of the desired seat. This is particularly the case when running long lengths of screen to be expanded in a horizontal run. In the present invention, seating occurs almost immediately after release due to the close proximity between the release point and the seat. In the unlikely event of a failure of the tool, a secondary seat is provided to allow a backup ball to be dropped in the known manner. Alternatively, a plurality of balls of different sizes can be stored in the tool. Bigger balls can reuse Ball seat 14 after an initial ball expands the seat a given amount in a known manner. Alternatively, smaller balls can be subsequently released that will pass through seat 14 after the first ball is blown through it and land on another seat further down. While the preferred embodiment has been shown with two balls, one ball or more balls can be used. They can be released all at once or one at a time such as by using a ratchet device actuated by cycling the circulation on and off. To do this the detent pin 36 could be eliminated. No rotation is required to operate the tool making it useful in deviated wells.

[0012] The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.