Apparatus for releasing a ball into a wellbore

A wiper plug for a wellbore cementing operation, the wiper plug comprising:

• a mandrel having a bore therethrough;
• and
• a ball-releasing apparatus for releasing a first ball into a wellbore from below the wiper plug, the first ball having a diameter that is greater than a diameter of the mandrel, wherein the ball-releasing apparatus comprises:
• a tubular body, the tubular body having a bore therethrough in fluid communication with the bore of the wiper plug, and a top end connected to the mandrel of the wiper plug;
• a piston having a top end and a bottom end, the top end being disposed within the tubular body, and the bottom end being disposed below the bore of the wellbore tool;
• and
• a connector for releasably connecting the piston to the first ball.

The apparatus of claim, 26,

• wherein the first ball has a lip above the recess;
• wherein the connector comprises a collet, the collet having a body disposed above the recess of the first ball when the first ball is connected to the apparatus, and a plurality of fingers that extend downward from the collet body and into the recess of the first ball for holding the first ball;
• and
• wherein the fingers are pulled from the recess of the first ball as the bottom end of the piston is inserted into the recess of the first ball.

A ball releasing apparatus for use for with a downhole tool, the ball-releasing apparatus comprising:

• a tubular body having a flow path for communication with a bore of the downhole tool;
• a piston having a top end and a bottom end, wherein the top end being disposable within the tubular body;
• and
• a connector for releasably connecting the piston to a first ball, wherein the first ball has a diameter greater than a diameter of a restriction above the first ball.

A wellbore plug assembly for wellbore cementing operations, the assembly comprising:

• a plug carrying member;
• a first plug operatively connected to the plug carrying member;
• a second plug;
• a ball releasing apparatus for releasing a first ball into a wellbore, the first ball having a diameter that is greater than a restriction above the second plug.

A method for cementing a liner in a wellbore, comprising:

• placing a workstring having a wellbore plug assembly disposed at a lower end thereof in the wellbore, the plug assembly including:
• a mandrel having a bore therethrough;
• and
• a ball releasing apparatus having a tubular body, a release member operatively connected to the tubular body and a releasably connected member for connecting the release member to a first ball, wherein the first ball has a diameter greater than a diameter of a restriction above the first ball;
• activating the ball release apparatus, thereby releasing the first ball into a downhole tool below the plug assembly;
• pumping cement through the workstring;
• releasing the plug assembly from the workstring;
• and
• urging cement into an annulus formed between the liner and the wellbore.