Patent Publication Number: US-10309179-B2

Title: Downhole casing pulling tool

Description:
BACKGROUND OF THE DISCLOSURE 
     Various types of fishing tools are used in wells to retrieve tools, tubulars, casing, or other components that become stuck in a well. In a typical technique, a drillpipe lowers a fishing tool into the well, and a grapple at the end of the tool engages the stuck component. An upward force on the drillpipe can then dislodge the component. In other techniques, jars that are hydraulically or mechanically powered can generate a jarring force to dislodge the stuck component. 
     For example, casing can become stuck in the well and may need to be retrieved. Traditional removal of the stuck casing is done either with pilot milling, pulling the casing free with jarring action, and then steady pulling applied through the drillpipe and the derrick&#39;s draw work. Milling is very time consuming and labor intensive. Additionally, using jars to deliver a retrieving force does not effectively retrieve mud stuck casing. 
     To deal with stuck casing, pulling tools or casing jacks, such as those available from HOMCO, Wilson Downhole, Houston Engineers, and others, have been used for some time in the past. As one example, a downhole force generating tool disclosed in U.S. Pat. No. 5,070,941 has an anchor and a piston/cylinder arrangement. 
     In another example, U.S. Pat. No. 8,365,826 discloses a hydraulically powered fishing tool that can be used to retrieve another tool or tubular stuck in a well. The fishing tool is supported in a well on a workstring and has a mandrel with a fishing device that engages stuck tool or tubular in the well. An anchor axially fixes the position of the tool in the well, and pistons disposed on the tool above the anchor move the mandrel so the fishing device on the end of the mandrel can be moved axially and can dislodge the stuck tool or tubular. 
     Older systems use anchoring and pulling that is much too weak to handle the pull loads experienced in wells today. Today, Wellbore A/S of Norway has developed a Down Hole Power Tool (DHPT) that uses the hydraulically powered fishing tool disclosed in U.S. Pat. No. 8,365,826 to retrieve casing. However, the fishing tool mentioned above has the anchor section disposed below the pull section. During operation, the pulling load must pass through the anchor section. Additionally, any torque that is needed to be transmitted downhole through the tool is done through the internal dimensions of the tool&#39;s members. 
     Although most stuck components, such as casing, can be dislodged using the above techniques and tools, some stuck components may require other means to be retrieved and may need techniques that avoid damaging the stuck component or other elements in the well. 
     The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above. 
     SUMMARY OF THE DISCLOSURE 
     A downhole pulling tool deploys on a workstring to retrieve a well component using an implement. The tool has a mandrel, an anchor, and a puller. The mandrel couples to the workstring, and the anchor is disposed on the mandrel. The mandrel can be a unitary component. For assembly purposes, however, the mandrel can include an anchor mandrel for the anchor coupled to a puller mandrel for the puller. 
     On the anchor, at least one slip is hydraulically actuated from an unset condition to a set condition. In this way, the at least one slip in the set condition can be wedged against a portion of the mandrel for engaging the anchor downhole in casing or tubing, for example. The puller, however, extends from the anchor and has at least one puller piston disposed on the mandrel. The at least one puller piston supports the implement and is hydraulically movable relative to the mandrel from an extended condition to a pulled condition. 
     The at least one slip in the set condition can extend outward from the mandrel and can retract inward toward the mandrel in the unset condition. For instance, the portion of the mandrel can define at least one ramped surface against which the at least one slip wedges. 
     The anchor has an anchor piston disposed on the mandrel. The anchor piston is hydraulically movable from a first condition to a second condition. According, the anchor piston in the second condition can wedge the at least one slip against the portion of the mandrel. To move the anchor piston, the mandrel defines a fluid passageway communicating with the workstring and conveying fluid to the anchor piston. A valve in the tool can then selectively communicate fluid conveyed through the fluid passageway to the anchor piston. 
     A number of biasing arrangements can be used to bias and control operation of the anchor, such as the operation of the at least one slip and the anchor piston. For example, the anchor piston can have at least one biasing element biasing the anchor piston to the first condition. The at least one biasing element can be a spring or the like having one portion engaged against the anchor mandrel and having an opposing portion engaged against the anchor piston. 
     In another example, the anchor piston can have at least one biasing element disposed between the anchor piston and the at least one slip. This biasing element can be a spring or the like having one portion engaged against the anchor piston and an opposing portion engaged against the at least one slip. 
     To help hold the at least one slip and control its movement relative to the mandrel, a cage can be disposed on the mandrel and can have the at least one slip movable therein. In this case, at least one biasing element can be engaged between the cage and the at least one slip and can bias the at least one slip to the unset condition. For example, the at least one biasing element can include first and second leaf springs affixed to the cage and engaged against ends of the at least one slip. Additionally, a biasing element, such as a spring or the like, can be engaged between the cage and the mandrel and can bias the at least one slip to the unset condition. 
     Similar to the operation of the anchor, the fluid passageway communicating in the mandrel with the workstring and conveying fluid can use the same or even a different valve for selectively communicating fluid conveyed through the mandrel to the at least one puller piston. Either way, the valve can include a seat disposed in the fluid passageway that is engageable by a deployed ball. 
     In one form of operation to retrieve a well component downhole with an implement, the well component is engaged with the implement on the pulling tool manipulated downhole with the workstring. The well component can be a stuck pipe or the like in the casing downhole, and the implement can be a fishing tool or the like. 
     With the implement engaged, the well component is then pulled by hydraulically moving at least one puller piston along a mandrel of the pulling tool in response to fluid pressure communicated down the workstring. The pulling tool is also anchored at a point uphole of the puller piston by hydraulically moving an anchor piston along the mandrel of the pulling tool in response to the communicated fluid pressure and wedging at least one slip outward from the mandrel with the movement of the anchor piston. 
     Before actually engaging the implement, however, some form of initial operations can be performed. In this case, the pulling tool can be initially manipulated downhole while at least temporarily holding the pulling tool in an unextended condition so that initial operations, such as cutting, can be performed. Eventually, the pulling tool can be released to extend to an extended condition so that the pulling operations can then be performed. 
     To at least temporarily holding the pulling tool in the unextended condition, a detachable coupling can be provided for the at least one puller piston to the mandrel. In an attached condition, the detachable coupling holds the at least one puller piston in the unextended condition on the mandrel, while the detachable coupling in a detached condition permits the at least one puller piston to extend on the mandrel. In one arrangement, the detachable coupling includes a collet disposed on the at least one puller piston and detachably engageable with at least one detent on the mandrel. 
     Another form of operation can also be used to retrieve a well component downhole with the implement on the pulling tool. As before, the well component can be engaged with the implement on the pulling tool manipulated downhole. Similarly, the well component can be pulled with the implement by hydraulically moving at least one puller piston along a mandrel of the pulling tool in response to communicated fluid pressure. 
     Anchoring the pulling tool at a point uphole of the puller piston can likewise use at least one slip wedged outward from the mandrel. However, in contrast to using an anchor piston to move the at least one slip, first movement of the at least one puller piston can be translated to second movement of the at least one slip for wedging in the casing. The first movement of the puller tool can permitted up to a first limit in a first direction so that over setting of the at least one slip is avoided. 
     In this way, the at least one slip is hydraulically actuated from the unset condition to the set condition by the at least one puller piston. To do this, the at least one slip can have a slip cage connected to the at least one puller piston. The slip cage can move on the mandrel with the movement of at least one puller piston and can force the at least one slip against a ramp surface on the mandrel. 
     To limit this movement, a detachable coupling can connect the slip cage to the at least one puller piston. The detachable coupling can translate first movement of the at least one puller piston up to the first limit in the first direction to second movement of the slip cage. Up to that limit then, the second movement of the slip cage can thereby wedge the at least one slip against the portion of the mandrel. Yet, the detachable coupling preferably does not translate movement of the puller piston past that limit to movement of the slip cage. 
     The detachable coupling can include a collet disposed on the at least one puller piston and detachably engageable with at least one detent on the slip cage. The at least one detent can use a first detent on the slip cage at least temporarily preventing passage of the collet in the first direction past the first detent. A second detent on the slip cage can prevent passage of the collet in a second opposite direction past the second detent. 
     To provide the desired release after operations, the detachable coupling can also translate third movement of the at least one puller piston in a second direction to fourth movement of the slip cage. This movement of the slip cage can remove the at least one slip from against the portion of the mandrel. 
     The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a wellbore having a workstring deployed from a rig and having a pulling tool according to the present disclosure engaged with a stuck component. 
         FIG. 2A  illustrates a cross-sectional view of a pulling tool according to the present disclosure in an unstroked condition. 
         FIG. 2B  illustrates a cross-sectional view of the pulling tool according to the present disclosure in a stroked condition. 
         FIGS. 3A-3B  illustrates cross-sectional and end-sectional views of the anchor section of the disclosed pulling tool in an unset condition. 
         FIG. 3C  illustrates a detailed cross-section of a slip and an anchor piston of the tool&#39;s anchor in the unset condition. 
         FIGS. 4A-4B  illustrates cross-sectional and end-sectional views of the anchor section of the disclosed pulling tool in a set condition. 
         FIG. 4C  illustrates a detailed cross-section of the slip and the anchor piston of the tool&#39;s anchor in the set condition. 
         FIG. 5A  illustrates an isolated cross-sectional view the power section of the disclosed pulling tool in the unstroked condition. 
         FIGS. 5B-5D  show details of the unstroked power section in  FIG. 5A . 
         FIG. 6A  illustrates an isolated cross-sectional view the power section of the disclosed pulling tool in the stroked condition. 
         FIGS. 6B-6E  show details of the stroked power section in  FIG. 6A . 
         FIGS. 7A-7E  illustrate cross-sectional views of portion of the disclosed pulling tool having a detachable coupling between the anchor and the puller during stages of operation. 
         FIG. 7F  shows a detail of one type of detachable coupling for the disclosed pulling tool. 
         FIG. 8  shows the disclosed pulling tool with the detachable coupling in use with other downhole tools. 
         FIGS. 9A-9D  illustrate cross-sectional views of portion of the disclosed pulling tool having an alternative slip setting arrangement between the anchor and the puller during stages of operation. 
         FIG. 9E  shows a detail of the alternative slip setting arrangement. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     When a well component  15  becomes stuck downhole, operators use a retrieval assembly  20  as shown in  FIG. 1  to retrieve the well component  15 . In general, the well component  15  can be casing, liner, pipe, tool, or the like that has become stuck downhole. Reference is made herein for convenience to stuck casing  15 . Sections of stuck casing  15  to be pulled can be anywhere from 10 to 100-ft or more in length and may be stuck due to any number of reasons. 
     The retrieval assembly  20  has a pulling tool  100  according to the present disclosure. The pulling tool  100  may be used as a replacement for surface casing jack systems to retrieve stuck casing  15  or the like. In fact, the pulling tool  100  can be used to retrieve stuck casing  15  in applications where the drilling rig  30 , platform, drillship, etc. or where the workstring  35  does not have sufficient capacity to pull the casing  15 . Indeed, being able to remove casing  15  with the pulling tool  100  and without the need to perform milling operations can save rig time, reduce wear on rig equipment, and can eliminate swarf handling. 
     Operators deploy the pulling tool  100  on the workstring  35  into the wellbore from the rig  30 , which has a pump system  32 . Various types of implements  50  and fishing tools can be used depending on the implementation and the operation to be performed. Accordingly, the pulling tool  100  can be used with various types of implements  50 , such as standard casing cutting and fishing tools. When the implement  50  is engaged with the casing  15 , the pulling tool  100  is used to exert the pulling force required to retrieve the casing  15 . 
     The pulling tool  100  has an anchor  160  and a puller  110 . The anchor  160  couples to the workstring  35 , and the puller  110  extends further downhole from the anchor  160 . At its distal end, the pulling tool  100  has the implement  50  supported on the puller  110  for engaging the well component  15 . Further details of the tool  100  with its anchor  160  and puller  110  are shown in  FIGS. 2A-2B . 
     In a pulling operation, for example, the pulling tool  100  is run on the workstring  35  downhole to a section of stuck casing  15  to be pulled uphole. The fishing tool  50  on the end of the pulling tool  100  is then located and tagged in the end of the stuck casing  15 . For example, the fishing tool  50  may be a spear, although any suitable type of tool, such as a basket grapple, spiral grapple, die collar, tapered taps, etc., can be used depending on the implementation. 
     The fishing tool  50  is then set to engage the stuck casing  15 . With the fishing tool  50  set, the pulling tool  100  is in an unstroked condition, such as shown in cross-section in  FIG. 2A . In the unstroked condition, the puller  110  is stroked open with its piston(s)  130  extended on the puller&#39;s mandrel  120 . The anchor&#39;s slips  180  are also retracted on the anchor&#39;s mandrel  162  so the pulling tool  100  can be manipulated downhole by the workstring  35 . Fluid flow down the workstring  35  can pass through the pulling tool  100 . 
     With the fishing tool  50  set as in  FIG. 1 , the anchor  160  on the pulling tool  100  is then set in the casing  10 , and the puller  110  on the pulling tool  100  is stroked as the anchor  160  holds the tool  100  in place in the outer casing  10 . In particular, hydraulic pressure is applied down the workstring  35  via the pump system  32  to the puller  110 , which is already stroked to the open position. Applying the hydraulic pressure may involve closing a valve by deploying a ball, plug, dart, or the like down the workstring  35  to close off fluid flow through a ball seat and apply the pressure to the tool&#39;s internal components. 
     The applied pressure sets the anchor  160  in the outer casing  10  and strokes the piston(s)  130  of the puller  110  to a closed position. In the stroked condition as shown in  FIG. 2B , the puller  110  is stroked closed so that the end  104  where the implement or fishing tool ( 50 ) couples can be pulled uphole toward the anchor  160 , which has its slips  180  extended outward from the mandrel  162  to set the tool  100  in place downhole. 
     This stoked action of the tool  100  jacks (pulls) the stuck casing  15  of  FIG. 1  uphole, as the pulling tool&#39;s stroke pulls the stuck casing  15  inside the outer casing  10 . With the stroke complete, hydraulic pressure to the tool  100  from the workstring  35  is ceased, and the anchor  160  on the pulling tool  100  is unset by a straight pull up on the tool  100  by the workstring  35 . Continued pulling then releases the stroke of the pulling tool  100 , resetting the puller  110  to the extending condition for additional strokes. At this point, the pulling tool  100  can be reset to pull the stuck casing  15  again. If the stuck casing  15  has been sufficiently dislodged, then the assembly  20  can be retrieved along with the stuck casing  15  by tripping out the workstring  35 . 
     On the disclosed pulling tool  100 , the anchor  160  is disposed uphole from the puller  110 , which means the major pull loads are taken by the heavy body of the puller  110  and not by the smaller inner dimensions of the anchor&#39;s components. The gives operators the ability to exert larger pulling forces due to the larger cross-section of the pulling mandrel  162  resulting from this arrangement. Additionally, when manipulating the tool  100  and the workstring  35 , all downhole torque is done through the larger OD members of the puller  110 . 
     For some example details on one implementation, the implement  50  can be a spear. The workstring  35  is rotated to set the spear  50  in the stuck casing  15 , which can be a section of 9⅝-in. casing stuck in 13⅜-in. casing  10 . When operated, the pulling tool  100  may be capable of generating a minimum 2,000,000-lbs downhole pulling force, can be about 50-ft long, can operate with maximum pressure of about 6,700-psi, and may have a 36-in. stroke length to pull the stuck casing  15 . Other implementations and variables are possible as will be appreciated by one skilled in the art. 
     With an understanding of the operation of the pulling tool  100 , discussion now turns to particular details related to the anchor  160  and the puller  110  of the disclosed tool  100 . 
     Looking first at the anchor  160 ,  FIGS. 3A-3B  illustrate cross-sectional and end-sectional views of the anchor  160  of the disclosed pulling tool  100  in an unset condition, whereas  FIGS. 4A-4B  illustrate cross-sectional and end-sectional views of the anchor  160  of the disclosed pulling tool  100  in a set condition. 
     The anchor  160  has an anchor mandrel  162  that can couple to the workstring ( 35 ) at an uphole end in a conventional manner and can form a part of the overall mandrel of the pulling tool ( 100 ). The anchor mandrel  162  defines a fluid passageway or bore  164  communicating with the workstring ( 35 ) and conveying fluid to various components of the tool ( 100 ) as discussed below. 
     The anchor  160  has an anchor piston  170  and at least one slip  180  disposed on the anchor mandrel  162 . Preferably, multiple slips  180  are disposed around the circumference of the anchor mandrel  162  (See  FIG. 3B ). The slips  180  are hydraulically actuated from an unset condition ( FIGS. 3A-3B ) to a set condition ( FIGS. 4A-4B ) during operations discussed below. In the set condition, the anchor slips  180  wedge against portion of the anchor mandrel  162  and specifically wedge against ramps  168  on the surface of the mandrel  162 . 
     As can be surmised, the slips  180  in the set condition can engage downhole by setting in the outer casing  10 , for example. Preferably, the each slip  180  distributes the load of the pulling tool ( 100 ) along a length of the outer casing  10 . In one implementation, for example, the slips  180  can be long rectangular bodies with a length of about 30-in. 
     As best shown in the end-sections of  FIGS. 3B and 4B , the anchor slips  180  also preferably form an almost full circumference around the anchor  160 . This allows for high anchoring loads and less hoop stress loading on the casing  10 . For example, there may be preferably about six slips  180  around the diameter of the anchor mandrel  162  to form an almost full circle contact with the surrounding casing  10 . This accommodates the high anchoring loads needed to pull stuck casing or the like. 
     The anchor piston  170  is hydraulically movable from a first condition ( FIG. 3A ) to a second condition ( FIG. 4A ) on the mandrel  162  relative to the slips  180  and slip cage  182 . As shown, the cage  182  is disposed on the anchor mandrel  162  and supports the slips  180  movable on the anchor mandrel  162 . In the first condition ( FIG. 3A ), the anchor piston  170  is moved away from the slips  180 . In fact, a detachable coupling having a collet  173  on the piston&#39;s body  172  can engage a shoulder, rim, or detent  163  on the mandrel  162  to hold the anchor piston  170  in place. 
     In the second condition ( FIG. 4A ), fluid pressure communicated through the anchor bore  164  and cross-ports  167  enters a chamber  176  of the anchor piston  170 . Pressure trapped in the chamber  176  by a seal block  174  pushes the anchor piston&#39;s body  172  toward the slips  180 , unlatching the collet  173  from the detent  163 . Pushing against the slips  180  via the cage  182 , the anchor piston  170  extends the slips  180  outward from the anchor mandrel  162  to engage in the surrounding casing  10 . 
     The slips  180  in the unset condition ( FIGS. 3A-3C ) are retracted inward toward the anchor mandrel  162 , whereas the slips  180  in the set condition ( FIGS. 4A-4C ) are extended outward from the anchor mandrel  162 . The anchor mandrel  162  defines at least one (and preferably multiple) ramped surfaces  168  against which complementary ramped surfaces  188  on the slips  180  extend and retract when pushed thereagainst by the anchor piston  170 . 
     As best shown in the detailed views of  FIGS. 3C and 4C , the anchor piston  170  has at least one first biasing element  178   a  biasing the anchor piston  170  to the first condition ( FIG. 3C ). This first biasing element  178   a  can be a retract spring having one portion engaged against a shoulder of the anchor mandrel  162  and having an opposing portion engaged against the anchor piston  170 . 
     The anchor piston  170  also has at least one second biasing element  178   b  disposed between the anchor piston  170  and the slips  180 . This second biasing element  178   b  can be a push spring having one portion engaged against the anchor piston  170  and having an opposing portion engaged against the slips  180  via the slip cage  182 . 
     As also best shown in the detailed views of  FIGS. 3C and 4C , the anchor slips  180  each have at least one third biasing element  184   a - b  biasing the slip  180  to its unset condition ( FIG. 3C ). These third biasing elements  184   a - b  can be leaf springs affixed to the cage  182  and engaged against ends of the slip  180 . Finally, a return spring  186  may also be used at the uphole ends of the slips  180  to urge them to return to the unset condition ( FIG. 3C ). 
     The spring retainers  184   a - b  on each end of the slips  180  are multi-functional. The spring retainers  184   a - b  during operations not only hold each slip  180  in place, but they also assist in the return of the slips  180  to the reset positions. Additionally, the screws holding the spring retainers  184   a - b  on the split cage  180  are removable, which allows operators to easily replace slips  180  if worn or if new slips  180  are needed to accommodate a change in casing weights. This can be done on the rig floor if needed. 
     When internal pressure is applied, the anchor piston  170  moves up toward the slip cage  182  with the piston&#39;s force transferred to the cage  182  by the push spring  178   b . Movement of the slip cage  182  forces the slips  180  out against the casing  10  by riding the slips&#39; ramps  188  against the mandrel&#39;s ramps  168  and wedging the slips  180  against the mandrel  162 . The movement of the anchor piston  170  is limited by a shoulder  165  on the mandrel  162 . As can be seen, the push spring  178   b  allows for some play and adjustment between the components, which may be desirable during operations. 
     When pressure is released, the slips  180  may remain in their extended (catch) position due to the downward weight and the pull of the puller ( 110 ) and other components. The upward pull of the mandrel  162 , however, relieves the wedging between the ramped surfaces  168 / 188  so the slips  180  can dislodge from inside of the casing  10  and release the anchor  160  to the reset position. The return spring  178   a  on the mandrel  162  also presses back against the anchor piston  170  (in the absence or release of pressure) to help move the piston  170  back in the reset position, which also helps place the slips  180  in their retracted (released) position as well. Finally, the other springs  184   a - b  and  186  can further assist with unsetting the slips  180 . 
     Looking now at the puller  110 ,  FIGS. 5A-5D  show the puller  110  and sections thereof in the unstroked condition, while  FIGS. 6A-6D  show the puller  110  and sections thereof in the stroked condition. 
     The puller  110  has a puller mandrel  120  that couples at its uphole end to the anchor ( 160 ) and extends from the anchor mandrel ( 162 ). The puller mandrel  120  therefore forms part of the overall mandrel of the tool ( 100 ). At least one puller piston  130  is disposed on the puller mandrel  120  at at least one piston head  140  on the mandrel  120 . 
     Although one puller piston  130  is shown in  FIGS. 5A-6D , multiple pistons  130  can be stacked along the length of the puller  110  with an extended puller mandrel  120 . In fact, the puller  110  may have a number of puller pistons  130  to increase the stroke power of the tool  100 . In this way, the puller  110  can be configured for a particular pull load by adding or removing the pistons  130 . For example, up to five pistons  130  can be used with the pulling tool  100 , but if the pull loads are lower for whatever reasons, the pulling tool  100  can be modified at the rig or at the shop to have the desired number of pistons  130 . 
     The puller piston  130  is hydraulically movable relative to the puller mandrel  120  from an extended condition ( FIG. 5A ) to a pulled condition ( FIG. 6A ) during operations as discussed herein. The puller piston  130  includes a body  131  defining an upper chamber  132  and a lower chamber  134  with an intermediate chamber  136  disposed between them. To form these chambers  132 ,  134 , and  136 , the body  131  of the piston  130  is disposed on the mandrel  120  and includes external members or cylinders  135  that transmit all the pull loads and torque downhole. To transmit torque from the mandrel  120  to the piston, the puller&#39;s mandrel  120  can have a torque transmission, splines, or hex drive  125  that engages the piston  130 . An end body  138  is disposed at the distal end of the tool (i.e., past the last piston  130  if multiple pistons are used) for coupling to other components of the pulling tool ( 100 ), such as the implement or fishing tool ( 50 ). 
     The puller mandrel  120  defines a fluid passageway or bore  122  communicating with the workstring ( 35 ) via the anchor ( 160 ). A valve  126  in the puller bore  122  can selectively communicate fluid conveyed through the puller mandrel  120  to the puller piston(s)  130  and the anchor ( 160 ). For example, the valve  126  can be a ball seat to engage a dropped ball  128  deployed to the puller  110  during operations. Other types of valves, seats, or the like could be used. 
     In one example, a sleeve and port arrangement can be used for the valve  126  that is activated by a Radio Frequency Identification (RFID) tag or the like, using techniques known in the art. When an appropriate RFID tag is deployed to the tool  100 , for example, the valve  126  can close to selectively communicate fluid through the puller mandrel  120  to the puller piston  130 . In other examples, a mechanical sleeve using j-slots and the like can be used to mechanically open and close circulation to the puller piston  130 . 
     During operations when fluid pressure is pumped behind the closed valve  126 , the hydraulic pressure actuates the puller piston(s)  130 . In particular, the hydraulic pressure exits from the mandrel&#39;s bore  122  to the intermediate chamber  136  via cross-ports  142  at the piston head  140  (see  FIG. 5C ). Trapped pressure builds in the intermediate chamber  136  being sealed therein by seals against the exterior of the mandrel  120  and seals on the piston head  140 . As shown in  FIGS. 6C-6D , the intermediate chamber  136  expands as the upper and lower chambers  132  and  134  decrease in volume and vent through ports  133 . As a result, the entire body  131  of the piston  130  as well as the end body  138  stroke up a length along the mandrel  120 . This stroke length can be 36-in. for example. 
     The above pulling tool  100  may be deployed and manipulated downhole while the puller  110  is in an extended condition. Closing of fluid communication through the tool  100  and the build-up of hydraulic pressure would then activate the puller  110  to its pulled condition. It may be desirable, however, to deploy and manipulate the disclosed pulling tool  100  downhole while it is in its unextended condition. Accordingly, another pulling tool  100  according to the present disclosure shown in  FIGS. 7A-7E  has a detachable coupling  150  for this purpose. 
     This pulling tool  100  is similar to that disclosed above and has the anchor  160 , the puller  110 , and other similar components so that the same reference numerals are used for similar components. The pulling tool  110  includes the detachable coupling  150  between the anchor  160  and the puller  110 . Using the detachable coupling  150 , the pulling tool  110  can be held in an unextended condition when deployed downhole so various operations can be performed with other tools on the end of the pulling tool  100 . 
     The detachable coupling  150  is disposed at the end of the pistons  130 , such as the end that rides on a torque transmission, splines, or hex drive  125  of the puller&#39;s mandrel  120 . The detachable coupling  150  as shown here includes a collet  137  that engages a detent  127 , ridge, circumferential shoulder, etc. on the puller&#39;s mandrel  120 .  FIG. 7F  shows a detail of the detachable coupling&#39;s collet  137  with the detent  127  for the disclosed pulling tool  100 . As opposed to the collet and detent arrangement, other forms of detachable coupling  150  can be used, such as shear screws, shear pins, shear rings, snap rings, and the like. 
     Assembled as shown in  FIG. 7A , the detachable coupling  150  can be engaged so that the collet  137  fits over the mandrel&#39;s detent  127 . During run in as shown in  FIG. 7B , the weight of the tool  100  from the pistons  130  and other downhole components can engage the collet  137  on the detent  127 . In this way, the pulling tool  100  can be held in an unextended condition when deployed (i.e., the pistons  130  do not extend along the puller mandrel  120  toward the end of the tool  110 ). After certain operations, such as engaging a spear, fishing tool, or other implement (not shown), operators can pull up on the pulling tool  110 , causing the collet  137  to snap past the detent  127  as shown in FIG.  7 C. With the detachable coupling  150  disengaged, the tool  110  can be extended (i.e., the pistons  130  can be stretched), as shown in  FIG. 7D . 
     Finally, subsequent operations of the pulling tool  100  can commence. For example,  FIG. 7E  shows setting of the anchor slips  180  by the anchor piston  170  once fluid flow has been diverted to actuate the tool  100 . This operation can follow the procedures outlined previously in other embodiments so that they are not repeated here. 
     As noted above, the disclosed pulling tool  100  with the detachable coupling  150  to hold the tool  100  unextended can be used in other operations, which may use other downhole tools. As shown in  FIG. 8 , for example, the pulling tool  100  having the detachable coupling  150  can be configured with a cutter  200  extending from a coupling  210  to the spear  50  at the end of the puller  110 . When deployed, the detachable coupling  150  maintains the puller  110  in the unextended condition. The detachable coupling  150  can hold the puller  110  in place until operations are done with spearing and cutting. 
     For instance, the cutter  200  can be operated using communicated fluid and a mud motor, although other types of cutters could be used. Operators can cut casing with the cutter  200 . Then, by pulling up, operators can detach the coupling  150  so that the piston  130  and mandrel  120  can be stroked to prepare for activation and pulling of the newly cut casing section. 
     As will be appreciated, in addition to a cutter and cutting operation, any number of other tools and operates can benefit from the detachable coupling  150  that maintains the pulling tool  100  unextended during use. 
     Yet another pulling tool  100  according to the present disclosure shown in  FIGS. 9A-9D  has an alternative slip setting arrangement. This pulling tool  100  has similarities to the tools  100  disclosed above and has the anchor  160 , the puller  110 , and other similar components. Therefore, the same reference numerals are used for similar components. Instead of including an anchor piston  170  and associated components to actuate the slips  180 , the anchor  160  for this tool  100  has the slip cage  182  engaged with the piston  130  of the puller  110 , and the tool  100  uses the puller piston  130  to set the slips  180 . 
     As only schematically shown here, the anchor&#39;s mandrel  162  couples to the puller&#39;s mandrel  120  to form the overall mandrel of the tool  100 . An extension or sleeve  183  of the cage  182  extends from the anchor&#39;s slips  180  to the uppermost piston  130 . A detachable coupling  139  connects the piston&#39;s end to the cage&#39;s sleeve  183 , which has detents  187 . As shown, the detachable coupling  139  includes a collet that can telescopically fit over the cage&#39;s sleeve  183  to engage and disengage relative to the sleeve&#39;s detents  187 . A reverse arrangement could also be used. 
       FIG. 9E  shows a detail of the collet  139  and detents  187 . The collet  139  has a hard shoulder that can engage a fixed shoulder detent  189   a , preventing telescopic extension between the piston  130  and the cage sleeve  183  and tending to hold the collet  139  and sleeve  183  together axially. The distal end of the collet  139 , however, can engage against an intermediate detent  189   b  on the cage&#39;s sleeve  183 . When the collet  139  is moved telescopically toward the intermediate detent  189   b  from the position shown in  FIG. 9E , the piston  130  can tend to push the cage&#39;s sleeve  183  along with it, at least until the collet  139  can snap past and over the intermediate detent  189   b . The reverse is also true when the collet  139  is moved back over the intermediate detent  189   b  in the opposite direction. 
     During run in as shown in  FIG. 9A , the piston&#39;s collet  139  is fixed at the detents  187 , and more particularly, the collet  139  can engage the hard shoulder detent  189   a  preventing telescopic extension between the sleeve  183  and piston  130 . When pulling operations are to commence (e.g., an implement has been affixed to stuck casing), operators can initiate the piston  130  of the pulling tool  100  by diverting communicated fluid to the piston  130 . The collet  139  at the end of the piston  130  can then move upward a slight movement before engaging against the intermediate detent  189   b.    
     Should operation of the tool  100  fail at this point for whatever reason, the small amount of play will enable operators to stop activation of the tool  100  and release the tool  100  using the slack provided by the offset in the detents  189   a - b . For example, if the fishing implement ( 50 ) does not move the stuck casing as the piston  130  is first activated, the offset in the movement can allow operators to pull up on the tool  100  even after starting the stroke of the piston  130 . 
     Nevertheless, activation of the piston  130  pushes the collet  139  against the intermediate detent  189   b  as shown in  FIG. 9B . In this way, the piston&#39;s movement translates to movement of the cage&#39;s sleeve  183 . As a result, the cage  182  moves and pushes the anchors  180  against the ramps  168  on the anchor&#39;s mandrel  162 , tending to wedge and set the slips  180 . 
     Eventually, as shown in  FIG. 9C , enough setting of the anchor&#39;s slips  180  is reached, and the collet  139  snaps past the intermediate detent  189   b . At this point, continued movement of the piston  130  does not translate to the anchor&#39;s slips  180  so that they are not overset. Further activating of the piston  130 , however, tends to mechanically pull the mandrel  160  toward the pistons  130 , wedging the anchor slips  180 , while the pistons  130  pull against the implement and the stuck casing disposed at the end of the tool  100 . Further retraction of the piston  130  along the cage&#39;s sleeve  183  can continue as shown in  FIG. 9D  during this pulling activity without the piston&#39;s telescopic movement translating to the cage  182 . 
     Unsetting the pulling tool  100  involves a reverse operation. While fluid flow is ceased, operators pull up on the pulling tool  100 . The anchor mandrel  162  can move relative to the slips  180  biting into the casing  10  so that the ramped surfaces  168  and  188  can unwedge. The springs  184   a - b  and  186  (if present) can tend to retract the unwedged slips  180 . The piston&#39;s collet  139  can slide freely along the cage&#39;s sleeve  183  as the piston  130  tends to extend along the puller mandrel  120 . Eventually, the collet  139  can reach the intermediate detent  189   b  and tend to further pull the cage  182  to unset the slips  180 . Finally, the collet  139  can reach the hard detent  189   a  that pulls the cage  182  to its initial, unset condition. Repeat pulling operations can then be performed if necessary. 
     The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. As disclosed above, certain components have been disclosed as being modular in nature, which can facilitate assembly and use. This is not strictly necessary as certain components can be combined and integrated with one another to construct the disclosed tool. In this regard, the anchor mandrel and the puller mandrel need not be separately coupleable elements but may in fact be constructed as an integral mandrel component. This and other modifications will be appreciated by one skilled in the art having the benefit of the present disclosure. 
     It will be appreciated with the benefit of the present disclosure that features described above in accordance with any embodiment or aspect of the disclosed subject matter can be utilized, either alone or in combination, with any other described feature, in any other embodiment or aspect of the disclosed subject matter. 
     In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.