Apparatus for releasing a ball into a wellbore
View Patent ↗The present invention relates to an apparatus for dropping a ball into a wellbore. The apparatus is particularly useful for dropping a ball that has a diameter that is larger than the diameter of a bore within a wellbore tool above the apparatus. The ball-releasing apparatus first comprises a tubular body. The tubular body has a bore therethrough that is in fluid communication with the bore of the wellbore tool. A piston is placed within the tubular body. The piston has a top end disposed within the tubular body, and a bottom end disposed below the bore of the wellbore tool. The ball-releasing apparatus further comprises a connector for releasably connecting the piston to the ball. In one arrangement, the ball-releasing apparatus is connected to the bottom of a wiper plug for dropping a ball during a wellbore cementing operation. In one aspect, the ball is dropped by dropping a second ball having a diameter that will pass through the wellbore restriction, and then injecting fluid under pressure against the second smaller ball in order to actuate the releasable connection.
1. A method for cementing a liner in a wellbore,
comprising:
placing a workstring having a plug assembly in the wellbore, the plug assembly including:
a wiper plug having an equalizing mandrel, the equalizing mandrel having a fluid pathway through a wall thereof; and
a valve member for selectively controlling the fluid pathway;
equalizing a pressure between an annulus formed between the workstring and the wellbore and a bore of the plug assembly by moving the valve member to allow fluid through the fluid pathway;
pumping cement through the workstring;
releasing the equalizing mandrel from the valve member thereby releasing the wiper plug from the workstring; and
urging cement into an annulus formed between the liner and the wellbore.
2. The method of claim 1 , further including dropping a hydraulic obstruction from the surface of the wellbore into a seat of the plug assembly.
3. The method of claim 1 , wherein the plug assembly further includes a second wiper plug.
4. The method of claim 3 , further including releasing the second plug from the workstring.
5. A wiper plug assembly having an equalizing mandrel, the assembly comprising:
a plug having the equalizing mandrel, wherein the mandrel includes a plurality of radial ports formed therein;
a sleeve slideably disposed concentrically around the mandrel, the sleeve configured to selectively obstruct and open the radial ports;
an outer housing disposed around the sleeve and the mandrel, the mandrel being selectively disconnectable from the housing; and
a tubular member concentrically disposed adjacent the sleeve, wherein the tubular member includes a seat for receiving a hydraulic obstruction member.
6. The wiper plug of 5 , wherein the sleeve is slidable between a first position and a second position.
7. The wiper plug of claim 6 , wherein the sleeve is biased in the first position by a biasing member, thereby obstructing the radial ports.
8. The wiper plug of claim 5 , wherein the sleeve includes a plurality of radial ports formed in a wall thereof.
9. The wiper plug of claim 5 , wherein the tubular member includes a plurality of radial ports formed in a wall thereof.
10. A wiper plug assembly, comprising:
an outer housing;
a plug having an equalizing mandrel, the mandrel having a fluid pathway through a wall thereof and the mandrel releaseably disposed within the outer housing;
a movable valve member disposed concentrically around the equalizing mandrel, the valve member configured to selectively control the fluid pathway; and
an inner housing concentrically disposed adjacent the valve member, wherein the inner housing includes a seat configured to receive a hydraulic obstruction member.
11. The wiper plug of claim 10 , wherein the inner housing includes a plurality of radial ports formed in a wall thereof.
12. The wiper plug of 10 , wherein the valve member is movable between an open position and a closed position.
13. The wiper plug of 12 , further including a biasing member to bias the valve member in the closed position.
14. A wiper plug assembly, comprising:
an outer housing;
a plug having an equalizing mandrel, the mandrel having a fluid pathway through a wall thereof and the mandrel releaseably disposed within the outer housing; and
a movable valve member disposed concentrically around the equalizing mandrel, the valve member configured to selectively control the fluid pathway, wherein the valve member includes a plurality of radial ports formed in a wall thereof.