Abstract:
In one embodiment, a top drive system for drilling with casing is provided with an access tool to retrieve a downhole tool. The top drive system for drilling with casing comprises a top drive; a top drive adapter for gripping the casing, the top drive adapter operatively coupled to the top drive; and an access tool coupled to the top drive and adapted for accessing a fluid passage of the top drive system. In another embodiment, a method for retrieving a downhole tool through a tubular coupled to a top drive adapter of a top drive system is provided. The method comprises coupling an access tool to the top drive system, the access tool adapted to provide access to a fluid path in the top drive system and inserting a conveying member into the fluid path through the access tool.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims benefit of co-pending U.S. Provisional Patent Application Ser. No. 60/592,708, filed on Jul. 30, 2004, which application is herein incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to methods and apparatus for drilling with top drive systems. Particularly, the invention relates to methods and apparatus for retrieving a downhole tool through a top drive system. More particularly still, the invention relates to running a wireline through the top drive system to retrieve the downhole tool and running a wireline access below the top drive system. The invention also relates to performing a cementing operation with the top drive system.  
         [0004]     2. Description of the Related Art  
         [0005]     One conventional method to complete a well includes drilling to a first designated depth with a drill bit on a drill string. Then, the drill string is removed, and a first string of casing is run into the wellbore and set in the drilled out portion of the wellbore. Cement is circulated into the annulus behind the casing string and allowed to cure. Next, the well is drilled to a second designated depth, and a second string of casing, or liner, is run into the drilled out portion of the wellbore. The second string is set at a depth such that the upper portion of the second string of casing overlaps the lower portion of the first string of casing. The second string is then fixed, or “hung” off of the existing casing by the use of slips which utilize slip members and cones to wedgingly fix the second string of casing in the wellbore. The second casing string is then cemented. This process is typically repeated with additional casing strings until the well has been drilled to a desired depth. Therefore, two run-ins into the wellbore are required per casing string to set the casing into the wellbore.  
         [0006]     As more casing strings are set in the wellbore, the casing strings become progressively smaller in diameter in order to fit within the previous casing string. In a drilling operation, the drill bit for drilling to the next predetermined depth must thus become progressively smaller as the diameter of each casing string decreases in order to fit within the previous casing string. Therefore, multiple drill bits of different sizes are ordinarily necessary for drilling in well completion operations.  
         [0007]     Another method of performing well completion operations involves drilling with casing, as opposed to the first method of drilling and then setting the casing. In this method, the casing string is run into the wellbore along with a drill bit for drilling the subsequent, smaller diameter hole located in the interior of the existing casing string. The drill bit is operated by rotation of the drill string from the surface of the wellbore, and/or rotation of a downhole motor. Once the borehole is formed, the attached casing string may be cemented in the borehole. The drill bit is either removed or destroyed by the drilling of a subsequent borehole. The subsequent borehole may be drilled by a second working string comprising a second drill bit disposed at the end of a second casing that is of sufficient size to line the wall of the borehole formed. The second drill bit should be smaller than the first drill bit so that it fits within the existing casing string. In this respect, this method typically requires only one run into the wellbore per casing string that is set into the wellbore.  
         [0008]     In some operations, the drill shoe disposed at the lower end of the casing is designed to be drilled through by the subsequent casing string. However, retrievable drill bits and drilling assemblies have been developed to reduce the cost of the drilling operation. These drilling assemblies are equipped with a latch that is operable to selectively attach the drilling assembly to the casing. In this respect, the drilling assembly may be preserved for subsequent drilling operations.  
         [0009]     It is known in the industry to use top drive systems to rotate the casing string and the drill shoe to form a borehole. Top drive systems are equipped with a motor to provide torque for rotating the drilling string. Most existing top drives use a threaded crossover adapter to connect to the casing. This is because the quill of the top drive is not sized to connect with the threads of the casing.  
         [0010]     More recently, top drive adapters has been developed to facilitate the casing running process. Top drive adapters that grip the external portion of the casing are generally known as torque heads, while adapters that grip the internal portion of the casing are generally known as spears. An exemplary torque head is disclosed in U.S. patent application Ser. No. 10/850,347, entitled Casing Running Head, which application was filed on May 20, 2004 by the same inventor of the present application. An exemplary spear is disclosed in U.S. patent application Publication No. 2005/0051343, by Pietras, et al. These applications are assigned to the assignee of the present application and are herein incorporated by reference in their entirety.  
         [0011]     One of the challenges of drilling with casing is the retrieval of the drilling assembly. For example, the drilling operation may be temporarily stopped to repair or replace the drilling assembly. In such instances, a wireline may be used to retrieve the latch and the drilling assembly. However, many existing top drives are not equipped with an access for the insertion or removal of the wireline, thereby making the run-in of the wireline more difficult and time consuming. Additionally, during the temporary stoppage to retrieve the drilling assembly, fluid circulation and casing movement is also typically stopped. As a result, the casing in the wellbore may become stuck, thereby hindering the rotation and advancement of the casing upon restart of the drilling operation.  
         [0012]     There is a need, therefore, for methods and apparatus for retrieving the drilling assembly during and after drilling operations. There is also a need for apparatus and method for fluid circulation during the drilling assembly retrieval process. There is a further need for apparatus and methods for running a wireline while drilling with casing using a top drive. There is yet a further need for methods and apparatus for accessing the interior of a casing string connected to a top drive.  
       SUMMARY OF THE INVENTION  
       [0013]     In one embodiment, a top drive system for forming a wellbore is provided with an access tool to retrieve a downhole tool. The top drive system for drilling with casing comprises a top drive; a top drive adapter for gripping the casing, the top drive adapter operatively connected to the top drive; and an access tool operatively connected to the top drive and adapted for accessing a fluid passage of the top drive system. In one embodiment, the top drive system is used for drilling with casing operations.  
         [0014]     In another embodiment, a method for retrieving a downhole tool through a tubular coupled to a top drive adapter of a top drive system is provided. The method comprises coupling an access tool to the top drive system, the access tool adapted to provide access to a fluid path in the top drive system and inserting a conveying member into the fluid path through the access tool. The method also includes coupling the conveying member to the downhole tool and retrieving the downhole tool. In another embodiment, the method further comprises reciprocating the tubular. In yet another embodiment, the method further comprises circulating fluid to the tubular. Preferably, the tubular comprises a casing.  
         [0015]     In another embodiment still, a method for releasing an actuating device during drilling using a top drive system is provided. The method comprises providing the top drive system with a top drive, a top drive adapter, and a launching tool, the launching tool retaining the actuating device, and operatively coupling the top drive, the top drive adapter, and the launching tool. The method also includes gripping a tubular using the top drive adapter and actuating the launching tool to release the actuating device.  
         [0016]     In another embodiment still, a method for performing a cementing operation using a top drive system is provided. The method comprises providing the top drive system with a top drive, a top drive adapter, and a cementing tool and operatively coupling the top drive, the top drive adapter, and the cementing tool. The method also comprises gripping the casing using the top drive adapter and supplying a cementing fluid through the cementing tool. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     So that the manner in which the above recited features and other features contemplated and claimed herein are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.  
         [0018]      FIG. 1  shows an exemplary embodiment of a top drive system having an access tool.  
         [0019]      FIG. 2  shows an alternative top drive system having another embodiment of an access tool.  
         [0020]      FIG. 3  shows another embodiment of an access tool.  
         [0021]      FIG. 4  shows yet another embodiment of an access tool.  
         [0022]      FIG. 5  shows an alternative top drive system equipped with yet another embodiment of an access tool.  
         [0023]      FIG. 6  shows yet another embodiment of an access tool.  
         [0024]      FIG. 6A  is a partial cross-sectional view of the access tool of  FIG. 6 .  
         [0025]      FIG. 7  is a partial cross-sectional view of another embodiment of an access tool.  
         [0026]      FIG. 8  shows an embodiment of an access tool having a launching tool.  
         [0027]      FIG. 8A  is a cross-sectional view of the access tool of  FIG. 8 .  
         [0028]      FIG. 8B  illustrates an embodiment of retaining a plug in a casing string.  
         [0029]      FIG. 8C  illustrates another embodiment of retaining a plug in a casing string.  
         [0030]      FIG. 9  shows an alternative top drive system having a cementing tool.  
         [0031]      FIG. 10  is a partial cross-sectional view of the cementing tool of  FIG. 9 .  
         [0032]      FIG. 10A  is another cross-sectional view of the cementing tool of  FIG. 9 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0033]     In one embodiment, a top drive system for drilling includes a top drive adapter for gripping and rotating the casing and a top drive access tool. The top drive access tool is adapted to allow access into the various components connected to the top drive. The access tool is equipped with a sealing member to prevent leakage and hold pressure during fluid circulation. In another embodiment, the access tool is adapted to allow the top drive to reciprocate the casing during wireline work.  
         [0034]      FIG. 1  shows an embodiment of a top drive system  100  fitted with a top drive access tool  110 . As shown, the system  100  includes a spear type top drive adapter  20  and a top drive  10  for energizing the spear  20 . The spear  20  includes radially actuatable gripping members  22  for engaging the inner diameter of the casing. Although a mechanically actuated spear is preferred, spears actuated using hydraulics, pneumatics, or electric are equally suitable. The lower portion of the spear  20  includes a valve  24  for supplying fluid and a seal member  26  to prevent leakage. Fluids such as drilling mud may be introduced into the top drive system  100  through a fluid supply line  5  disposed at an upper portion of the top drive  10 . An elevator  30  is suspended below the top drive  10  by a pair of bails  35  coupled to the top drive  10 . It must be noted that in addition to the spear, other types of top drive adapters such as a torque head are also contemplated.  
         [0035]     In one embodiment, the top drive access tool  110  is coupled to the upper portion of the top drive  10 . The access tool  110  is adapted to allow wireline access into the interior of the casing in order to perform wireline operations such as retrieval of the drilling assembly or the latch attached to a drilling assembly. As shown in  FIG. 1 , the access tool  110  includes a connection member  112  for connecting to the top drive  10 . The connection member  112  includes a bore to receive the wireline  15  and a pack-off assembly  114  for preventing leakage. The pack-off assembly  114  may comprise an elastomeric seal element and sized to accommodate different wireline sizes. A sheave assembly  116  is connected to the connection member  112 . The sheave assembly  116  facilitates and supports the wireline  15  for entry into the top drive  10 . Preferably, the sheave assembly  116  is arranged such that it does not obstruct the operation of the traveling block, which is typically used to translate the top drive  10 . In one embodiment, the sheave assembly  116  includes two wheels  117 A,  117 B adapted for operation with the top drive  10 . The wheels  117 A,  117 B may include grooves disposed around the circumference of the wheels  117 A,  117 B for receiving the wireline  15 . The wireline  15  may be routed around the wheels  117 A,  117 B of the sheave assembly  116  to avoid the traveling block and directed into the pack-off assembly  114  and the connection member  112 . In another embodiment, the fluid supply line  5  may be connected to the connection member  112  of the access tool  110 . A suitable access tool is disclosed in U.S. Pat. No. 5,735,351 issued to Helms, which patent is herein incorporated by reference in its entirety. During wireline operations, the top drive system  100  provided in  FIG. 1  may be operated to reciprocate the casing in the wellbore and circulate fluid through the casing. It is believed that these operations will reduce the likelihood of the casing sticking to the wellbore. In addition to a wireline  15 , the embodiments described herein are equally applicable to a cable or other types of conveying members known to a person of ordinary skill in the art.  
         [0036]      FIG. 2  illustrates another embodiment of a top drive system  200  equipped with an access tool  210 . Similar to the embodiment shown in  FIG. 1 , the top drive system  200  includes a spear type top drive adapter  20  coupled to the top drive  10 . However, the elevator and the bails have been removed for clarity. In this embodiment, the access tool  210  is disposed between the top drive  10  and the spear  20 . The access tool  210  defines a tubular having a main portion  212  and one or more side portions  214  attached thereto. The upper end of the main portion  212  is connected to the top drive  10 , and the lower end is connected to the spear  20 . Extension subs or tubulars  220 A,  220 B may be used to couple the access tool  210  to the top drive  10  or the spear  20 . A central passage  213  in the main portion  212  is adapted for fluid communication with the top drive  10  and the spear  20 . The side entry portions  214  have side entry passages  215  in fluid communication with the central passage  213 . In the embodiment shown, the access tool  210  includes two side portions  214 . Each side portion  214  may include a pack-off assembly  230  to prevent leakage and hold pressure. In this respect, the pack-off assembly  230  also functions as a blow out preventer. In operation, the wireline  15  accesses the casing through one of the side portions  214 . Additionally, the access tool  210  allows the top drive system  200  to reciprocate the casing and circulate drilling fluid using the spear  20  during wireline operation. Fluid may be supplied to the top drive  10  through the fluid supply line  5 . In another embodiment, the access tool  210  may optionally include a valve  216  to isolate the fluid in the top drive  10  from fluid supplied through one of the side entry passages  215 . Exemplary valves include a ball valve, one-way valves, or any suitable valve known to a person of ordinary skill in the art.  
         [0037]     In another embodiment, the top drive system  240  may include a sheave assembly  250  attached to the pack-off assembly  245 , as illustrated in  FIG. 3 . The sheave assembly  250  may include a sheave wheel  255  to reduce the friction experienced by the wireline  15 . In yet another embodiment, the top drive system  240  may include two spears  261 ,  262 , two torque heads, or combinations thereof to increase the speed of modifying the top drive  10  for wireline operation. As shown, a first spear  261  is connected to the top drive  10  and initially retains a casing string for drilling operations. When wireline operation is desired, the first spear  261  may release the casing and retain an access assembly  270  having an access tool  275 , an extension tubular  277 , and a spear  262 . The spear  262  of the access assembly  270  can now be used to retain the casing string and reciprocate the casing string and/or circulate fluid during the wireline operation. After completion of the wireline operation, the access assembly  270  may be quickly removed by disengagement of the spears  261 ,  262 . It should be appreciated the spears may be torque heads or a combination of spears and torque heads.  
         [0038]      FIG. 4  is a partial cross-sectional view of another embodiment of the access system  230 . The access system  230  is attached to a spear  20  having gripping members  22  adapted to retain a casing. The access system  230  includes a main portion  231  and a side portion  233 . It can be seen that the side entry passage  234  is in fluid communication with the main passage  232 . The side portion  233  is equipped with a pack-off assembly  235  and a sheave assembly  236 . The sheave assembly  236  includes a sheave wheel  237  supported on a support arm  238  that is attached to the main portion  231 . As shown, a cable  15  has been inserted through the pack-off assembly  235 , the side entry passage  234 , the main passage  232 , and the spear  20 .  
         [0039]     In yet another embodiment, a top drive system  280  may include an external gripping top drive adapter  285  for use with the top drive  10  and the access tool  290 , as illustrated in  FIG. 5 . An exemplary top drive adapter is disclosed in U.S. patent application Ser. No. 10/850,347, entitled Casing Running Head, filed on May 20, 2004 by Bernd-Georg Pietras. The application is assigned to the same assignee as the present application and is herein incorporated by reference in its entirety. In this embodiment, the top drive adapter  285 , also known as a torque head, may release the casing and retain the access tool  290 . The access tool  290 , as shown, is adapted with one side entry portion  292  having a pack-off assembly  293  and a sheave assembly  294 . A casing collar clamp  295  attached to the access tool  290  is used to retain the casing string  3 . It must be noted that other types of casing retaining devices such as an elevator or a cross-over adapter may be used instead of the casing collar clamp, as is known to a person of ordinary skill in the art.  
         [0040]      FIG. 6  illustrates another embodiment of the access system  300 . The access system  300  includes an upper manifold  311  and a lower manifold  312  connected by one or more flow subs  315 . Each manifold  311 ,  312  includes a connection sub  313 ,  314  for coupling to the top drive  10  or the spear  20 .  FIG. 6A  is a cross-section view of the access system  300 . Fluid flowing through the upper connection sub  313  is directed toward a manifold chamber  317  in the upper manifold  311 , where it is then separated into the four flow subs  315 . Fluid in the flow subs  315  aggregates in a chamber  318  of the lower manifold  312  and exits through the lower connection sub  314 , which channels the fluid to the spear  20 . Although the embodiment is described with four flow subs, it is contemplated any number of flow subs may be used.  
         [0041]     The lower manifold  312  includes an access opening  320  for insertion of the wireline  15 . As shown, the opening  320  is fitted with a pack-off assembly  325  to prevent leakage and hold pressure. Preferably, the opening  320  is in axial alignment with the spear  20  and the casing  3 . In this respect, the wireline  15  is centered over the hoisting load, thereby minimizing wireline wear, as shown in  FIG. 6 . The access system  300  may also include a sheave assembly  330  to facilitate the axial alignment of the wireline  15  with the opening  320 . The sheave wheel  331  is positioned with respect to the upper manifold  311  such that the wireline  15  routed therethrough is substantially centered with the opening  320 .  
         [0042]     In another embodiment, a swivel may be disposed between the access system  300  and the spear  20 . An exemplary swivel may comprise a bearing system. The addition of the swivel allows the casing string  3  to be rotated while the sheave assembly  330  remains stationary. The casing string  3  may be rotated using a kelly, a rotary table, or any suitable manner known to a person of ordinary skill in the art.  
         [0043]      FIG. 7  illustrates another embodiment of an access tool  335 . The access tool  335  includes a housing  337  having an upper connection sub  338  and a lower connection sub  339 . The connection subs  338 ,  339  are adapted for fluid communication with a chamber  336  in the housing  337 . The housing  337  includes an access port  340  for receiving the wireline  15 . The access port  340  is equipped with a pack-off assembly  341  to prevent fluid leakage and hold pressure. In one embodiment, a sheave assembly  345  is installed in the chamber  336  to facilitate movement of the wireline  15 . Preferably, the sheave assembly  345  is positioned such that the wireline  15  is aligned with the lower connection sub  339 . In another embodiment, a fluid diverter  342  may be installed at the upper portion of the chamber  336  to divert the fluid entering the chamber  336  from the upper connection sub  338 . The fluid diverter  342  may be adapted to diffuse the fluid flow, redirect the fluid flow, or combinations thereof.  
         [0044]     In another embodiment, the top drive system  350  may be equipped with a tool  360  for releasing downhole actuating devices such as a ball or dart. In one embodiment, the launching or releasing tool  360  may be used to selectively actuate or release a plug  371 ,  372  during a cementing operation, as shown in  FIGS. 8-8A .  FIG. 8A  is a cross-sectional view of the access tool  350  with the launching tool  360 . The access tool  350  is similar to the access tool  300  of  FIG. 6 . As shown, the access tool  350  includes an upper manifold  377  and a lower manifold  376  connected by one or more flow subs  375 . Each manifold  377 ,  376  includes a connection sub  373 ,  374  for coupling to the top drive  10  or the spear  20 . In  FIG. 8A , the launching tool  360  has replaced the packing-off assembly  325  shown in  FIG. 6 . The launching tool  360  is adapted to selectively drop the two balls  361 ,  362  downhole, thereby causing the release of the two plugs  371 ,  372  attached to a lower portion of the spear  20 . The launching tool  360  includes a bore  363  in substantial alignment with the bore of the connection sub  374 . The balls  361 ,  362  are separately retained in the bore by a respective releasing pin  367 ,  368 . Fluids, such as cement, may be pumped through upper portion  364  of the launching tool  360  and selectively around the balls  361 ,  362 . Actuation of the releasing pin  367 ,  368  will cause these balls  361 ,  362 , aided by the fluid pumped behind, to be launched into the flow stream to release the plugs  371 ,  372 . It must be noted that any suitable launching tool known to a person of ordinary skill in the art may also be adapted for use with the access tool. In addition, the components may be arranged in any suitable manner. For example, the launching tool  360  may be disposed between the access tool  350  and the spear  20 . In this respect, fluid exiting the access tool  350  will flow through the launching tool  360  before entering the spear  20 .  
         [0045]     In operation, the first release pin  367  is deactivated to allow the first ball  361  to drop into the lower manifold  376  and travel downward to the spear  20 . The first ball  361  is preferably positioned between the drilling fluid and the cement. The first ball  361  will land and seat in the first, or lower, plug  371  and block off fluid flow downhole. Fluid pressure build up will cause the first plug  371  to release downhole. As it travels downward, the first plug  371  functions as a buffer between the drilling fluid, which is ahead of the first plug  371 , and the cement, which is behind the first plug  371 . When sufficient cement has been introduced, the second release pin  368  is deactivated to drop the second ball  362  from the launching tool  360 . The second ball  362  will travel through the bore and land in the second, or upper, plug  372 . Seating of the ball  362  will block off fluid flow and cause an increase in fluid pressure. When a predetermined fluid pressure is reached, the second plug  372  will be released downhole. The second plug  372  will separate the cement, which is in front of the second plug  372 , from the drilling fluid or spacer fluid, which is behind the second plug  372 .  
         [0046]     In another embodiment, the plugs may be coupled to the casing string instead of the top drive adapter. As shown in  FIG. 8C , a plug  400  is provided with a retaining member  410  for selective attachment to a casing string  3 . Preferably, the retaining member  410  attaches to the casing string  3  at a location where two casing sections  403 ,  404  are threadedly connected to a coupling  405 . Particularly, the retaining member  410  includes a key  412  that is disposable between the ends of the two casing sections  403 ,  404 . The plug  400 , in turn, is attached to the retaining member  410  using a shearable member  420 . The plug  400  and the retaining member  410  include a bore  422  for fluid flow therethrough. The plug  400  also includes a seat  425  for receiving an actuatable device such as a ball or dart. Preferably, the retaining member  410  and the plug  400  are made of a drillable material, as is known to a person of ordinary skill in the art. It must be noted that although only one plug is shown, more than one plug may be attached to the retaining member for multiple plug releases.  
         [0047]     In operation, a ball dropped from the launching tool  360  will travel in the wellbore until it lands in the seat  425  of the plug  400 , thereby closing off fluid flow downhole. Thereafter, increase in pressure behind the ball will cause the shearable member  420  to fail, thereby releasing the plug  400  from the retaining member  410 . In this manner, a plug  400  may be released from various locations in the wellbore.  
         [0048]      FIG. 8B  shows another embodiment of coupling the plug to the casing string. In this embodiment, the retaining member comprises a packer  440 . The packer  440  may comprise a drillable packer, a retrievable packer, or combinations thereof. The packer  440  includes one or more engagement members  445  for gripping the wall of the casing  3 . An exemplary packer is disclosed in U.S. Pat. No. 5,787,979, which patent is herein incorporated by reference in its entirety. As shown, two plugs  451 ,  452  are selectively attached to the packer  440  and are adapted for release by an actuatable device such as a ball. Preferably, the first, or lower, plug  451  has a ball seat  453  that is smaller than the ball seat  454  of the second, or upper, plug  452 . In this respect, a smaller ball launched from the launching tool may bypass the second plug  452  and land in the seat  453  of the first plug  451 , thereby releasing the first plug  451 . Thereafter, the second plug  452  may be released by a larger second ball. In this manner, the plugs  451 ,  452  may be selectively released from the packer  440 . After the plugs  451 ,  452  have been released, the packer  440  may be retrieved or drilled through.  
         [0049]     In another embodiment, the launching tool may be installed on an access tool similar to the one shown in  FIG. 3 . For example, the sheave assembly  236  and pack-off  235  may be removed and a launching tool such as a ball launcher with a top entry may be installed on a side portion  233 . In this respect, one or more balls may be launched to release one or more cementing plugs located below the spear or torque head.  
         [0050]     In another aspect, the top drive system  500  may include a top drive  510 , a cementing tool  515 , and a top drive adapter, as illustrated in  FIG. 9 . As shown, the top drive adapter comprises a spear  520 . The cementing tool  515  is adapted to selectively block off fluid flow from the top drive  510  during cementing operations.  
         [0051]      FIG. 10  is a partial cross-sectional view of an embodiment of the cementing tool  515 . The cementing tool  515  includes a central bore  522  for fluid communication with the top drive  510  and the spear  520 . A valve  525  is disposed in an upper portion of the bore  522  to selectively block off fluid communication with the top drive  510 . The valve  525  is actuated between an open position and a close position by operation of a piston  530 . As shown, the piston  530  is biased by a biasing member  532  to maintain the valve  525  in the open position. To close the valve  525 , an actuating fluid is introduced through a fluid port  541  to move the piston  530  toward the valve  525 . In this respect, movement of the piston  530  compresses the biasing member  532  and closes the valve  525 , thereby blocking off fluid communication of the cementing tool  515  and the top drive  510 . Thereafter, cement may be introduced into the bore  522  through the cementing port  545 .  
         [0052]     In another aspect, the cementing tool  515  may be adapted to release one or more actuating devices into the wellbore. In the embodiment shown in  FIG. 10 , the cementing tool  515  is adapted to selectively launch three balls  561 . It must be noted that the cementing tool  515  may be adapted to launch any suitable number or type of actuating devices. Each ball  561  is retained by a release piston  550 A before being dropped into the wellbore. The piston  550 A is disposed in an axial channel  555  formed adjacent to the bore  522 . In one embodiment, the piston  550 A has a base  551  attached to the body of the cementing tool  515  and a piston head  552  that is extendable or retractable relative to the base  551 . The outer diameter of a portion of the piston head  552  is sized such that an annulus  553  is formed between the piston head  552  and the wall of the axial channel  555 . Seal members or  0 -rings may be suitably disposed in the base  551  and the piston head  552  to enclose the annulus  553 . The annulus  553  formed is in selective fluid communication with an actuating fluid port  542 A. In this respect, the actuating fluid may be supplied into the annulus  553  to extend the piston head  552  relative to the base  551 , or relieved to retract the piston head  552 . Preferably, the piston head  552  is maintained in the retracted position by a biasing member  557 , as shown  FIG. 10 .  
         [0053]     The release piston  550 A is provided with an opening  563  to house the ball  561  and a cement bypass  565 . In the retracted position shown, the cement bypass  565  is in fluid communication with a radial fluid channel  570 A connecting the cement port  545  to the bore  522 . In this respect, cementing fluid may be supplied into the bore  522  without causing the ball  561  to release. When the piston head  552  is extended, the opening  563  is, in turn, placed in fluid communication with the radial fluid channel  570 A.  
         [0054]     As discussed, the cementing tool  515  may be adapted to release one or more actuating devices. In the cross-sectional view of  FIG. 10A , it can be seen that three release pistons  550 A,  550 B,  550 C are circumferentially disposed around the bore  522 . Cementing fluid coming in from either of the cementing ports  545 ,  545 A is initially circulated in an annular channel  575 . Three radial fluid channels  570 A,  570 B,  570 C connect the annular channel  575  to the bore  522  of the cementing tool  515 . Each radial fluid channel  570 A,  570 B,  570 C also intersect the cement bypass  565  of a respective release piston  550 A,  550 B,  550 C.  
         [0055]     To release the first ball  561 , actuating fluid is introduced through the fluid port  542 A and into the annulus  553  of the first release piston  550 A. In turn, the piston head  552  is extended to place the opening  563  in fluid communication with the radial fluid channel  570 A. Thereafter, cement flowing through the cementing port  545 , the annular channel  575 , and the radial channel  570 A urges to the ball  561  toward the bore  522 , thereby dropping the ball  561  downhole. Because either position of the piston head  552  provides for fluid communication with the cementing port  545 , the piston head  552  may remain in the extended position after the first ball  561  is released.  
         [0056]     To release the second ball, actuating fluid is introduced through the second fluid port  542 B and into the annulus  553  of the second release piston  550 B. In turn, the piston head  552  is extended to place the opening  563  in fluid communication with the radial fluid channel  570 B. Thereafter, cement flowing through the radial channel  570 B urges to the ball  561  toward the bore  522 , thereby dropping the ball  561  downhole. The third ball may be released in a similar manner by supplying actuating fluid through the third fluid port  542 C.  
         [0057]     In another aspect, the cementing tool  515  may optionally include a swivel mechanism to facilitate the cementing operation. In one embodiment, the fluid ports  541 ,  542 A,  542 B,  542 C and the cementing port  545  may be disposed on a sleeve  559 . The sleeve  559  may be coupled to the body of the cementing tool using one or more bearings  558 A,  558 B. As shown in  FIG. 10 , two sets of bearings  558 A,  558 B are disposed between the sleeve  559  and the body of the cementing tool  515 . In this respect, the body of the cementing tool  515  may be rotated by the top drive  10  without rotating the ports  541 ,  542 A,  542 B,  542 C,  545  and the fluid lines connected thereto. During the cementing operation, the swivel mechanism of the cementing tool  515  allows the top drive  10  to rotate the drill string  3 , thereby providing a more efficient distribution of cementing in the wellbore.  
         [0058]     In another embodiment, the cementing tool  515  may include additional fluid ports to introduce fluid into the top drive system. For example, hydraulic fluids may be supplied through the additional fluid ports to operate the spear, torque head, weight/thread compensation sub, or other devices connected to the top drive. Additionally, operating fluids may also be supplied through one of the existing ports  541 ,  542 A,  542 B,  542 C,  545  of the cementing tool  515 .  
         [0059]     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.