Patent Publication Number: US-9896914-B2

Title: Downhole tubular expansion tool and method

Description:
BACKGROUND 
     Field of the Invention 
     The present invention relates to an expansion tool and method for expanding the diameter of an expandable tubular liner disposed within a targeted interval of a bore of a casing in an earthen well. More specifically, the present invention relates to an expansion tool and a method to expand an expandable tubular liner along its full length. The expansion tool and method of the present invention provide for an improved installation of an expandable liner to seal with the casing without the necessity and expense of recovering a residual and/or non-expanded portion of the tubular liner from the well to prevent well obstruction. The present invention further relates to an expansion tool and a method for positioning and then restraining the expandable liner within the targeted installation interval of the casing during a stepwise or staged expansion of the liner to engage and seal the targeted interval of the casing. 
     Background of the Related Art 
     Various tools and methods have been devised for expanding a tubular disposed in an earthen well including, but not limited to, those disclosed in U.S. Pat. Nos. 7,225,880, 7,278,492 and 8,132,627. Some tools are intended to provide a tubular patch in a well, as disclosed in U.S. Pat. Nos. 6,622,788, 6,763,893 and 6,814,143. 
     An expandable tubular liner used for lining a targeted interval of a well casing may be installed within a casing to provide added structural and/or sealing integrity to an unstable or leaking interval of a casing. An expandable liner may be installed in a targeted interval of casing to isolate a previously perforated, leaking or otherwise open interval of the casing to prevent fluid exchange between the well and one or more adjacent geologic formations penetrated by the well. 
     Expandable liners may be installed within a targeted interval of a well casing by running an undersized (unexpanded) liner into the targeted interval of the well casing and radially outwardly expanding the liner in-situ. Conventional liner expansion tools include a pulling mandrel that pulls an expander, larger in diameter than the unexpanded liner, from a distal (downhole) end of the liner towards a proximal (uphole) end of the liner. Other liner expansion tools include pushing a mandrel that pushes a connected expander from a proximal end of the liner towards a distal end of the liner. Still other expansion tools rely on hydraulic pressure to generate a force sufficient to displace an expander through the bore of a liner without the use of a mandrel to pull or push the expander. 
     The liner material and the liner dimensions are generally selected to yield radially outwardly as the expander is moved through the bore to radially expand the liner and to engage the expanded liner with the bore of the targeted casing interval without rupture. The elastic limit of the liner material is exceeded to produce plastic deformation of the liner and to cause the liner to retain an expanded diameter engaged with the bore of the casing. It will be understood that the liner may be expanded slightly beyond the intended diameter in order to elastically resist a residual collapsing force applied by the casing after the expander passes. This mode of installation is optimal for improving the sealing integrity between the exterior surface of the expanded liner and the interior bore of the casing. 
     Some conventional expansion tools and method involve pulling or pushing the expander through the bore of the expandable liner by engaging the expander on a distal end of an elongate mandrel that is slidably received through a bore of a housing. The mandrel may be hydraulically displaced within the housing to pull the expander into and then through the bore of a liner disposed axially intermediate an expander, connected at the distal end of the mandrel, and a reaction assembly on the expansion tool to oppose movement of the liner during expansion. The expansion tool may be secured or coupled within the casing using a gripping device. The housing and the mandrel may each include a variety of additional features including, but not limited to, annular pistons, annular chambers, connectors, fittings, ball seats and apertures. 
     A shortcoming of conventional liner expansion tools is that if the slips of the tool are set within the bore of the expandable liner, and if the expandable liner is expanded beginning at an end of the expandable liner that is spaced apart from the portion of the expandable liner in which the slips are set to secure the expandable liner in position, the slips must be eventually displaced from the bore of the liner. This presents a problem because the expandable liner cannot be secured in position for expansion of the full length of the expandable liner, and a portion of the expandable liner will remain in the unexpanded condition. The unexpanded portion may require an additional trip into the well to retrieve the unexpanded portion of the liner. 
     Those skilled in the metallurgical arts will understand that a metal liner that is radially outwardly expanded to a larger diameter exhibits a predictable amount of axial shrinkage. As the diameter of the liner is expanded, the wall thickness of the liner is substantially reduced and the length of the liner shortens to compensate. This shrinkage may complicate the liner expansion process where slips are set in the bore of the casing above the top of the expandable liner and are used to secure the liner in position against the expander. Shrinkage of the liner may cause unwanted movement or shifting of an expanded portion of the liner within the casing if the reaction assembly cannot be favorably repositioned to compensate for axial shrinkage of the liner, thereby compromising the sealing integrity of the expanded liner. Conventional expansion tools that grip the bore of the expandable liner during liner expansion include reaction assemblies that remain in a fixed position within the liner during liner expansion, resulting in a loss of sealing integrity between the expanded liner and the casing due to the axial shrinkage that occurs during expansion of the liner bore. 
     The disadvantages of the prior art are overcome by the present invention, an improved downhole tubular expander and method are herein disclosed. 
     BRIEF SUMMARY OF THE INVENTION 
     An expandable liner provides optimal structural and sealing integrity if it is radially expanded along its full length to radially engage the bore of a targeted interval of casing, and if expanded portions of the liner remain engaged with the wall of the casing as the remaining length of the liner is thereafter expanded. An expandable liner provides improved structural and sealing integrity if the expansion tool is adapted to self-adjust to prevent shifting or movement of a partially-expanded portion of the liner within the targeted interval of the casing. This occurs when slips are set in the casing in which the expandable liner is being expanded as the expansion tool is repeatedly stroked to expand an interval of the expandable liner, and then re-cocked prior to each subsequent stroke that is needed until the entire expandable liner is expanded in the casing. It will be understood that, at some point during the expansion process, enough of the expandable liner will be expanded so that sufficient frictional engagement between the expanded portion of the expandable liner and the casing prevents movement of the expandable liner during expansion of the remaining, unexpanded portion. When this threshold is achieved, the remaining, unexpanded portion of the expandable liner may be expanded by using the draw works on the rig to pull the expansion tool in the uphole direction, thereby causing the expander to move through the bore of the expandable liner until the entire expandable liner is expanded. However, in the event that a tight spot requires an excessive amount of force to applied to the tubular string by the draw works, the draw works can be stopped and the tubular string can be again pressurized to stroke the hydraulic section of the expansion tool to hydraulically move the expander within the bore of the expandable liner without placing too much stress on the draw works. After the tight spot is expanded, the draw works may then be re-engaged to resume expansion. 
     Embodiments of the expansion tool and method of the present invention employ slips that are sized and adapted to be set within the casing in which the expandable liner is to be expanded and installed. This enables the expansion tool to retain radially expanded portions of a partially-expanded liner in position within the casing and to prevent unwanted shifting or sliding of a partially expanded portion of the expandable liner within the casing during the expansion process. Embodiments of the expansion tool of the present invention engage an unexpanded proximal end of the liner with a self-adjusting reaction assembly that is coupled to a slip cage that is, in turn, coupled to a housing of the expansion tool. The self-adjusting reaction assembly engages the proximal end of the expandable liner to oppose an axial displacing force applied by movement of the expander into and through the distal end of the bore of the expandable liner that is the first portion of the expandable liner to be expanded. The reaction assembly self-adjusts to enable re-cocking of the expansion tool for stepwise or staged expansion of the liner starting from the distal end and progressing stepwise to the proximal end. A portion of the self-adjusting ratcheting reaction assembly called a ratcheting component is eventually detached from the proximal end of the bore of the expandable liner before the expander exits the bore of the fully expanded liner. 
     One embodiment of the expansion tool and method of the present invention provides an expansion tool that uses a self-adjusting ratcheting reaction assembly to secure an unexpanded liner in a run-in configuration on the expansion tool. The expansion tool receives and secures the expandable liner to the expansion tool in a run-in configuration at the surface. The expandable liner is received onto the expansion tool to engage the ratcheting component of the self-adjusting ratcheting reaction assembly with a proximal end of the expandable liner and to surround a substantial portion of the elongate ratchet rack extending distally to the original starting position of a ratcheting component movably received on the exterior of the ratchet rack through which the pulling mandrel passes. The expander is then connected to a distal end of the pulling mandrel to axially capture the unexpanded liner on the expansion tool between the expander, engaging the distal end of the expandable liner, and the ratcheting component of the self-adjusting reaction assembly at the proximal end of the expandable liner. The pulling mandrel is slidably received through a bore of the tubular ratchet rack which terminates short of the distal end of the pulling mandrel to allow for stroking of the pulling mandrel towards the ratchet rack during each expansion stroke. This configuration is referred to herein as the run-in configuration of the expansion tool. 
     The expansion tool and the unexpanded liner are run into a well casing on the end of a tubular work string stepwise extended into the well from a rig at the earth&#39;s surface. The expansion tool and liner are positioned within a casing section to be reinforced, stabilized, patched or sealed with an expanded liner. 
     Embodiments of the expansion tool of the present invention include a tubular housing having a proximal end connected to a distal end of a tubular work string and a distal end coupled to a slip cage and a rack retainer. The housing includes a bore through which an upper portion of a pulling mandrel passes. The bore of the housing includes a plurality of annular cylinders defined by radially inwardly extending and spaced apart annular stops. The pulling mandrel has a bore and a plurality of radially outwardly extending annular pistons that are reciprocatably received within the annular cylinders defined within the bore of the housing. This axially aligned arrangement of hydraulic cylinders is known in the art. 
     The rack retainer is coupled to the slip cage which is coupled to the distal end of the housing. The rack retainer includes a bore through which a portion of the pulling mandrel passes. The rack retainer movably secures the self-adjusting reaction assembly to the slip cage and to the housing. The rack retainer threadably cooperates with the ratcheting component to permit uni-directional movement of the ratcheting component from a retracted position, proximal to the slip cage and the housing, to an extended position that is distal to the slip cage and the housing to vary (increase) the distance from the ratcheting component, which is connected to the proximal end of the expandable liner, to the slip cage and housing during the expansion process. The reaction assembly of the expansion tool of the present invention includes an elongate ratchet rack having a threaded exterior and a bore through which the lower portion of the pulling mandrel passes. The reaction assembly further includes a ratcheting component having a ratchet ring housed within a ring housing. The ratchet ring includes a radially interior threaded portion and a longitudinal slot that is spring biased to engage the interior threaded portion with the threaded exterior portion of the ratchet rack. The ring housing includes an interior chamber that accommodates cyclic expansion and contraction of the ratchet ring therewithin, and that surrounds the spring-biased ratchet ring. The ratchet housing is secured to the proximal end of the expandable liner using, for example, threaded fasteners. The ratchet ring includes a bore with buttress threads adapted to cooperate with the buttress threads along the exterior of the elongate ratchet rack to resist movement of the ratchet rack in a distal direction relative to the ratcheting component and the expandable liner connected thereto, but to allow movement of the ratchet rack in a proximal direction relative to the ratcheting component and the expandable liner connected thereto. The ratcheting component may comprise an exterior surface adapted for being releasably engaged with the unexpanded proximal end of the bore of the liner. For example, the ring housing of the ratcheting component may include external threads or other surface gripping structures and/or bonding agents. In one embodiment, the ring housing of the ratcheting component is secured to the unexpanded proximal end of the expandable liner with threaded and headless fasteners, as illustrated in the appended drawings. The uni-directional movement of the ratchet rack within and relative to the ratcheting component (including the ratchet ring and the ring housing that surrounds the ratchet ring) can, in one embodiment, be provided by the use of buttress threads disposed along the ratchet rack and cooperating buttress threads disposed within the bore of the slotted ratchet ring. The slot of the ratchet ring resiliently opens (expands) and closes (contracts) to allow the ratchet rack to move within the ratchet ring and the ring housing in the proximal direction (relative movement), but to prevent movement of the ratchet rack within the ratchet ring and the ring housing in the distal direction (relative movement). It will be understood that cooperative sets of buttress teeth can provide for this ratcheting function. These features are discussed in more detail below and illustrated in the appended drawings. 
     The self-adjusting reaction assembly of embodiments of the expansion tool of the present invention allows the housing and the hydraulic annular cylinders formed therein, along with the slip cage and the slips movably captured therein, to be repositioned further uphole between each stage of hydraulically assisted liner expansion without disengaging the reaction assembly from the proximal end of the liner. At the onset and during the earlier stages of the liner expansion process, the pulling mandrel is hydraulically displaced proximally within the bore of the housing and the slip cage to first set the slips to secure the expansion tool within the casing, and then to pull the expander through a portion or an interval of the bore of the expandable liner. The ratcheting component reacts against the proximal end of the liner to oppose any shifting or movement of the liner within the casing due to the axial component of the force applied to the liner by the expander. During an expansion stroke of the pulling mandrel and the expander connected thereto, the ratcheting component may move in a distal direction relative to the ratchet rack to compensate for axial shrinkage of the expandable liner occurring during radial expansion by the expander. It will be understood by persons knowledgeable in metallurgy that the expansion of a slender tubular member generally results in a corresponding reduction in the length, or shrinkage, of the tubular member to compensate for radial expansion which reduces wall thickness. 
     The expansion tool of the present invention includes slips to grip the bore of the casing and to secure the housing, the slip cage, the rack retainer, and the reaction assembly in a position within the casing. As explained above, the reaction assembly prevents axial movement of the liner, except for the capacity of the reaction assembly to accommodate liner shrinkage. Hydraulic pressurization of the bore of the pulling mandrel results in axial displacement of the pulling mandrel relative to the housing. At the very onset of hydraulic pressurization of the hydraulic section of the expansion tool, the pulling mandrel may move in a proximal direction while the housing may move in a distal direction. That is, until the slips are set within the casing, the housing may also be slightly movable upon pressurization of the tubular string, probably less than about one inch (2.54 cm), in a downhole direction opposite to the initial movement of the pulling mandrel. However, once the slip actuator engages and displaces the slips radially outwardly through windows of the slip cage to engage a gripping face of each of the slips with the interior bore of the casing, the slip cage and the housing coupled to the slip cage become secured in position in the casing. Further movement of the pulling mandrel in the proximal direction pulls the expander through a distal portion of the bore of the expandable liner, which is secured against movement in the proximal direction by the reaction assembly, slips and slip cage. 
     After completion of an expansion stroke, the annular pistons on the pulling mandrel are hydraulically displaced in a proximal direction to proximal ends of the annular cylinders formed within the housing. The expander on the distal end of the pulling mandrel is sized so that when it is drawn through a portion of the bore of the expandable liner, it remains lodged at the end of a stroke within a freshly expanded portion of the expandable liner which is, in turn, lodged in the bore of the casing in which the expandable liner is to be expanded. The pressure of the fluid in the bore of the pulling mandrel and in the portions of the annular cylinders distal to the annular pistons is relieved. The draw works on the rig at the surface then pulls the tubular string that is connected at its distal end to the housing of the liner expansion tool and, through the housing, it also pulls the slip cage in a proximal direction, or uphole, to unseat the slips. The draw works on the rig is then used to pull the housing further in an uphole direction to reposition the housing, the annular cylinders therein and the rack retainer in a proximal direction, or uphole, to restore each of the annular pistons on the lodged pulling mandrel to their original “cocked” positions at the distal ends of each of the annular cylinders of the housing. This process uses the frictional resistance to movement of the lodged expander, the expanded portion of the expandable liner disposed around the expander and the pulling mandrel to which the expander is connected to re-cock the hydraulic section of the housing by moving the housing relative to the pulling mandrel. 
     The pulling mandrel is again hydraulically actuated by fluid pressurization of the bore of the tubular string to again deploy the slips to grip the bore of the casing at a position spaced uphole from the first gripping position, and further to displace the expander in a proximal direction, relative to the housing and the slip cage, through a second portion of the expandable liner. The expander is again lodged within the freshly expanded portion of the expandable liner which is, in turn, lodged within the casing in which the liner is being expanded. The process is repeated and the expandable liner is stepwise expanded, interval by interval, with each expanded interval of the liner being generally equal in length to the stroke of a plurality of annular pistons on the pulling mandrel within the corresponding plurality of annular cylinders of the housing. This stepwise expansion process continues until the entire length of the expandable liner is expanded and the reaction assembly is disconnected from the proximal end of the expandable liner. 
     The bore of the pulling mandrel includes a plurality of strategically positioned apertures immediately distal to each of the annular pistons on the pulling mandrel. Pressurization of the fluid in the bore of the tubular string that is used to position the expandable liner expansion tool in the well and of the bore of the pulling mandrel in fluid communication with the work string provides fluid pressure through the apertures into adjacent annular cylinders of the housing. The fluid pressure provides the power to fluidically displace the annular pistons on the pulling mandrel in a proximal direction within the annular cylinders of the housing. Similarly, there are vents in the housing at the proximal end of each of the annular cylinders that allow fluid to be displaced from the annular cylinders as the annular pistons on the pulling mandrel are hydraulically displaced by the pressure in the distal portion of each annular cylinder. 
     It will be understood that the bore of the pulling mandrel is open as the expansion tool is run into the well and positioned within the casing at the targeted liner expansion location. The open bore of the pulling mandrel enables the operator of the well to maintain well control at all times during running and positioning of the expansion tool. The bore of the pulling mandrel can be closed to enable the bore of the pulling mandrel, and the annular pistons in fluid communication with the bore of the pulling mandrel, to be pressurized in order to stroke the expansion tool and displace the pulling mandrel and expander relative to the housing. The pulling mandrel includes a ball seat disposed intermediate the plurality of apertures that provide fluid pressure to the annular cylinders of the housing and the expander at the distal end of the pulling mandrel. The ball seat is adapted to receive a ball introduced into the tubular string and pumped through the tubular string and the bore of the pulling mandrel to engage and seal with the ball seat. The ball is deployed from the rig through the tubular string and into the bore of the pulling mandrel after the expansion tool and the liner are favorably positioned in the casing. Once the ball engages and seals with the ball seat, pressurized fluid pumped through the work string and into the bore of the pulling mandrel communicates through the apertures to the annular cylinders to apply fluid pressure against the distal face of the annular pistons on the pulling mandrel. 
     After the expansion tool is stroked to draw the expander into the bore of the expandable liner to expand an initial and distal portion of the expandable liner, the fluid pressure within the tubular string and the bore of the pulling mandrel is relieved. Relieving the pressure in the bore of the pulling mandrel relieves the pressure urging the slips into the gripping position with the bore of the casing. The draw works of the rig is used to pull the tubular string and the housing of the expansion tool connected to the tubular string towards the surface end of the well as the lodged expander, pulling mandrel and partially expanded liner remain in place in the casing. The slips are thereby unseated and retract to allow the housing, slip cage and the rack retainer coupled thereto to be repositioned uphole. Repositioning of the housing, slip cage and rack retainer, with the pulling mandrel and expander remaining in place in the casing, re-cocks the expansion tool and positions the pulling mandrel for another stroke to further expand an additional interval of the liner. During the re-cocking process, the housing and the annular chambers formed therein move in a proximal direction relative to the stationary annular pistons that remain in place with the lodged expander, the partially expanded liner and the pulling mandrel to which the expander is connected. Once the expander is drawn into the bore of the expandable liner, the expander remains lodged in an interference fit with the expanded portion of the expandable liner, and the expanded portion of the liner is circumferentially trapped between the exterior of the expander and the bore of the casing in which the expandable liner is being installed. The interference fit advantageously lodges the expander, the pulling mandrel, the annular pistons on the pulling mandrel and the partially expanded liner in position within the bore of the casing as the housing, slip cage and rack retainer are moved in a proximal direction with the tubular string. The ratcheting component, however, remains engaged with the proximal end of the expandable liner and it ratchets in a distal direction along the ratchet rack as the housing, the annular chambers and the ratchet rack are pulled uphole during the re-cocking step. 
     After re-cocking of the expansion tool in preparation for another expansion stroke, the expansion tool is again capable of being hydraulically stroked by pressurizing the work string and the bore of the pulling mandrel to hydraulically displace the pulling mandrel and the expander through another expansion stroke to expand another interval of the expandable liner. Upon hydraulic pressurization of the bore of the work string and the bore of the pulling mandrel, the slips are initially set to grip the bore of the casing to secure the housing and the rack retainer in place within the casing. The expander is then drawn through another interval of the bore of the expandable liner as the ratcheting component remains engaged with the proximal end of the expandable liner to resist movement of the partially expanded liner in a proximal direction relative to the ratchet rack. The ratcheting component thereby provides a reaction force against the expandable liner to prevent unwanted axial shifting or movement of the partially expanded liner during each expansion stroke. 
     In one embodiment, a reaction assembly, meaning at least one of the ratcheting component and the ratchet rack, may include one or more spring elements that bias one or more dogs into engagement with a series of buttress threads disposed along the other of the ratcheting component and ratchet rack. Spring biased elements may be disposed circumferentially within the ratcheting component. In other embodiments, the ratcheting component may comprise a circumferentially expandable slotted ratchet ring with a threaded bore. The longitudinal slot of the ratchet ring allows the threaded bore of the ratchet ring to elastically expand in response to an applied expanding force. The ratchet rack includes an exterior having cooperating threads. In a preferred embodiment, the threads along the exterior surface of the ratchet rack are buttress threads on which the proximal side of each thread is ramped and the distal side of each thread is steep, and the buttress threads of the interior bore of the cooperating slotted ratchet ring are ramped on the distal side and steep on the proximal side. This arrangement of cooperating buttress threads on the bore of the ratchet ring and the exterior surface of the ratchet rack allows the ratchet ring to ratchet in a distal direction along the ratchet rack as the ramped sides of the mating threads slidably engage to elastically and circumferentially expand the bore of the ratchet ring. Expansion of the slot of the ratchet ring allows the threads of the internal bore of the ratchet ring to skip over and slide past threads of the ratchet rack and to move, or ratchet, in a distal direction along the ratchet rack. This ratcheting movement of the ratchet ring occurs as the housing, the slip cage and the ratchet rack are pulled in a proximal direction as the ratchet ring remains secured to the proximal end of the partially expanded liner to re-cock the hydraulic section of the expansion tool. At the onset of the subsequent expansion stroke, the axial force applied by the expander to the liner forces the liner and the ratchet ring coupled to the proximal end of the liner in a proximal direction relative to the ratchet rack, and into binding engagement with the ratchet rack as the steep sides of the cooperating threads engage to oppose expansion and movement of the ratchet ring. It will be understood that at some point during the staged expansion process, the expanded portion of the expandable liner will be sufficiently long so that the frictional engagement between the expanded portion of the expandable liner and the casing becomes sufficient to prevent movement of the expandable liner in response to further movement of the expander through the bore of the expandable liner. At this juncture, the operator may choose to use the draw works on the rig to pull the expansion tool to finish expanding the expandable liner. 
     In embodiments of the liner expansion tool of the present invention, an expansion stroke initially causes the ratchet rack to be displaced, along with the ratchet ring and relative to the housing and the work string, until the slip actuator is moved relative to the slips to displace the slips radially outwardly through the windows in the slip cage to engage with the bore of the casing to prevent movement of the housing, the slip cage and the ratchet rack. Once the slips are firmly engaged with the bore of the casing, further displacement of the pulling mandrel within the housing and the slip cage causes the expander to be pulled through an interval of the expandable liner to radially expand the liner within the casing bore. 
     In addition to enabling the liner expansion tool to be re-cocked, the ratcheting component, which includes the ratchet ring and ring housing, can also move in a distal direction relative to and along the ratchet rack to compensate for the axial shrinkage in the expandable liner that occurs as a result of the radial expansion of the expandable liner resulting from movement of the expander. Each time the expansion tool is re-cocked, the ratcheting component remains engaged with the proximal end of the partially expanded liner as the ratchet rack moves in a proximal direction relative to the ratcheting component to re-cock the expansion tool. The ratcheting component, which includes the ratchet ring and ratchet housing, therefore serves the dual functions of enabling the tool to be re-cocked between expansion strokes and also compensating for axial shrinkage of the expandable liner occurring during an expansion stroke. 
     The setting of the slips of the expansion tool of the present invention to grip the interior wall of a casing occurs at the onset of an expansion stroke. At the onset of a stroke of the hydraulic section of the liner expansion tool, the slip actuators, coupled to the housing, are moved in a proximal direction relative to the slips and the slip housing in which the slips are axially captured. The slip actuators slidably engage and radially outwardly deploy the slips to engage and grip the interior bore of the casing. The slip cage is coupled to the ratchet rack, and the ratchet rack is thereby secured within the casing by deployment of the slips to the gripping position. The limited amount of relative movement between the housing, coupled to the slip actuators, and the ratchet rack, coupled to the slips, is enabled by a collet assembly having a collet, with a bore therethrough, that is releasably seated within a collet cage, which also has a bore to receive the collet. The collet cage retains the collet within a limited range of axial movement within the collet cage. In one embodiment, the collet includes at least one radially inwardly directed protrusion, or a series of radially inwardly directed protrusions, that is releasably seated within at least one corresponding radially outwardly extending notch, or a series of radially outwardly directed notches, in the exterior of the pulling mandrel that passes through the bore of the collet. The collet is in a seated position within the collet cage when the radially inwardly directed notch of the collet is engaged with the radially outwardly directed notch in the pulling mandrel. The collet cage is coupled to the slip cage and to the ratchet rack. Upon pressurization of the bore of the pulling mandrel, the collet can be moved only a limited distance within the collet cage and then forcibly disengaged from the pulling mandrel by application of a sufficient force applied through the ratchet rack to cause the at least one radially inwardly directed protrusion on the collet to unseat from the corresponding at least one notch in the exterior of the pulling mandrel. The application of force to the collet is provided upon stroking of the hydraulic section of the expansion tool to pull the expander on the distal end of the pulling mandrel against the distal end of the expandable liner which, in turn, bears against the ratcheting component engaged with the proximal end of the expandable liner to lock the ratcheting component on the ratchet rack due to the ratcheting component being forced in a proximal direction along the ratchet rack. The ratcheting component resists movement in a proximal direction along the ratchet rack due to the unidirectional ratchet ring and, therefore, transfers the force applied by the expander to the expandable liner through the ratcheting component to the ratchet rack, urging the ratchet rack in the proximal direction against the collet. The ratchet rack bears against the collet which bears against the slips to set the slips by urging them up and radially outward of the slip actuator. Once the slips are set, the collet is held in place and the force applied to the pulling mandrel becomes sufficient to unseat the pulling mandrel from the collet, and the pulling mandrel then continues to move in a proximal direction relative to the housing and the slips to pull the expander through an interval of the expandable liner. 
     The drawings that are appended to this application illustrate one embodiment of the expansion tool and method of the present invention. It will be understood that other embodiments may also be within the scope of the present invention, which is limited only by the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional elevation view of a proximal end of an embodiment of the liner expansion tool of the present invention in a run-in configuration. The distal end of the tubular string used to run and position the liner expansion tool in the well is not shown in  FIG. 1 . 
         FIG. 2  is the view of  FIG. 1  after the proximal end of the pulling mandrel is hydraulically displaced by an expansion stroke to a position that is closer to the proximal end of the housing of the liner expansion tool. 
         FIG. 3  is a sectional elevation view of a portion of the hydraulic section of the liner expansion tool of  FIG. 1  illustrating an annular piston on the pulling mandrel disposed adjacent to an annular stop of the housing forming an end of an annular chamber in which an annular piston is movable.  FIG. 3 , like  FIG. 1 , illustrates the run-in configuration of the liner expansion tool. 
         FIG. 4  is a sectional view of a gripping portion of an embodiment of the liner expansion tool that includes a plurality of slip actuators coupled to the housing and a plurality of slips coupled to a ratchet retainer and displaced by initial movement of the pulling mandrel relative to the housing at the onset of an expansion stroke. A reaction assembly of the liner expansion tool (including a rack retainer, a ratchet rack and a ratcheting component) is illustrated as being disposed below the slips to react against the liner at the onset of liner expansion. 
         FIG. 4A  is an enlarged view of a radially inwardly disposed protrusion of the collet at the location of interaction with a radially outwardly disposed notch of the pulling mandrel. 
         FIG. 5  is an enlarged view of a portion of a ratcheting component threadedly engaged with the exterior surface of a ratchet rack to enable relative movement of the ratchet rack only in a proximal direction relative to the ratcheting component. 
         FIG. 5A  is a sectional view of the ratcheting component of the liner expansion tool illustrated in  FIG. 5  with the ratchet ring in the radially inwardly collapsed or contracted mode to prevent movement of the ratchet rack in a distal direction relative to the ratcheting component. 
         FIG. 5B  is the sectional view of the portion of the expansion tool of  FIG. 5A  with the ratchet ring in the circumferentially expanded mode to permit movement of the ratchet rack in a proximal direction relative the ratcheting component. 
         FIG. 6  is a sectional elevation view of a portion of the embodiment of the expansion tool of the present invention including slip actuators positioned for being moved under or radially within the adjacent slips to secure the housing within the casing in which the expandable liner is to be expanded. 
         FIG. 7  is a sectional elevation view of the distal end of an embodiment of a liner expansion tool of the present invention illustrating the distal portion of the expandable liner, a ball seat within the bore of the pulling mandrel, the expander coupled to the pulling mandrel. The bore of the pulling mandrel can be isolated for pressurization using a ball to engage the ball seat. 
         FIG. 8  is the lower portion of the view of  FIG. 7  illustrating a ball being received in the ball seat to isolate the bore of the pulling mandrel to enable the expansion tool to be hydraulically stroked, causing the expander to enter and expand the bore of the expandable liner. 
         FIG. 9  is a sectional elevation view of a portion of the hydraulic section of the liner expansion tool of the present invention illustrating the initial separation of an annular piston on the pulling mandrel from an adjacent annular stop of the housing that occurs at the onset of a hydraulic stroke the liner expansion tool. 
         FIG. 10  is a sectional elevation view of the gripping section of the liner expansion tool of the present invention with the slip actuator coupled to the housing and the slips in a deployed configuration to engage and grip the casing.  FIG. 10  corresponds to the position of the annular piston and adjacent annular stop of  FIG. 9 . 
         FIG. 11  is a sectional elevation view of a portion of the gripping section of the liner expansion tool in the gripping configuration of  FIG. 10  and illustrates the coupling between the expandable liner, the ratcheting component, the ratchet rack, the rack retainer and the slips are intercoupled to deploy the gripping section of the expansion tool at the onset of an expansion stroke of the expansion tool. 
         FIG. 12  is a high-level flowchart illustrating the steps of a method of expanding a liner within a targeted interval of a casing using an embodiment of a liner expansion tool. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a sectional view of a proximal end  12  of an embodiment of the liner expansion tool  10  of the present invention disposed within a casing  99 .  FIG. 1  illustrates a threaded connector  15  that used to secure the housing  11  of the liner expansion tool  10  to a correspondingly threaded distal end of a tubular string (not shown) extended stepwise from a rig (not shown) into a casing  99  of a well. The proximal end of the tubular string is conventionally coupled to a draw works on the rig to enable positioning of the liner expansion tool  10  in the casing  99 . 
       FIG. 1  illustrates the position of a proximal end  42  of a pulling mandrel  40  that is reciprocatably and slidably disposed within the bore  14  of the housing  11  of the liner expansion tool  10 . In  FIG. 1 , the proximal end  42  of the pulling mandrel  40  is at a distance  16  from the proximal end  12  of the housing  11 .  FIG. 1  further illustrates a bore  44  of the pulling mandrel  40  and a seal  19  between an annular stop  18  extending radially inwardly from the bore  14  of the housing  11  and the exterior surface  41  of the pulling mandrel  40 . The seal  19  prevents fluid pressure introduced into the proximal end  12  of the housing  11  from being communicated to the bore  14  of the housing  11  below the seal  19 , and the seal  19  re-directs fluid pressure that is introduced through the tubular string (not shown) and into the proximal end  12  of the housing  11  into the bore  44  of the pulling mandrel  40 . Hydraulic stroking of the pulling mandrel  40  within the bore  14  of the housing  11  from the position illustrated in  FIG. 1  to the position illustrated in  FIG. 2  results in movement of the pulling mandrel  40  within the bore  14  of the housing  11  in the direction of arrow  39  to the position illustrated in  FIG. 2 . 
       FIG. 2  is the sectional view of the proximal end of the embodiment of the liner expansion tool  10  of  FIG. 1  after the pulling mandrel  40  has been hydraulically displaced within the bore  14  of the housing  11  towards the proximal end  12  of the housing  11  by hydraulically stroking of the liner expansion tool  10 .  FIG. 2  illustrates the upwardly repositioned proximal end  42  of the pulling mandrel  40  within the bore  14  of the housing  11  from the distance  16  from the threaded connector  15  illustrated on  FIG. 1  to lesser distance  26  illustrated on  FIG. 2 . As will be explained in detail below, the distance of the displacement of the pulling mandrel  40  during a stroke is illustrated by the distance  16  of  FIG. 1  less the distance  26  in  FIG. 2 , and that difference is related to the interval of an expandable liner  62  (not shown) that can be expanded by a single hydraulic stroke of the liner expansion tool  10 , after which the liner expansion tool  10  must be re-cocked in order to subsequently further expand additional intervals of the expandable liner  62 . It will be understood, however, that at some point during the stepwise liner expansion process, the remaining portion of the expandable liner  62 , or some portions of the expandable liner  62 , can be expanded by merely pulling the liner expansion tool  10  using the draw works on the rig. 
     Stroking of the expansion tool  10  from the run-in configuration or cocked configuration, illustrated in  FIG. 1 , to the stroked configuration or un-cocked configuration, illustrated in  FIG. 2 , is enabled by hydraulic pressurization of the tubular string (not shown) and the bore  44  of the pulling mandrel  40 .  FIG. 2  illustrates a first annular piston  48  extending radially outwardly from an exterior surface  41  of the pulling mandrel  40  to slidably and sealably engage the bore  14  of the housing  11 . A seal  49  on the first annular piston  48  engages the bore  14  of the housing  11 .  FIG. 2  further illustrates a first annular stop  18  extending radially inwardly from the bore  14  of the housing  11  to sealably and slidably engage the exterior surface  41  of the pulling mandrel  40  at the seal  19 . The first annular piston  48  on the pulling mandrel  40  appears in  FIG. 2 , and not in  FIG. 1 , because  FIG. 2  illustrates the position of the pulling mandrel  40  after upward displacement of the pulling mandrel  40  in the proximal direction (in the direction of arrow  39  on  FIG. 1 ) within the bore  14  of the housing  11  to bring the first annular piston  48  proximal to the first annular stop  18  and into the same view as the proximal end  12  of the housing  11 . Fluid pressure introduced into the tubular string (not shown) and into the proximal end  12  of the housing  11  is isolated by the seal  19  on the first annular stop  18  and thereby redirected into the bore  44  of the pulling mandrel  40 . The pressure is communicated from the bore  44  of the pulling mandrel  40  through aperture  77  in the pulling mandrel  40  to a first annular chamber  78  formed radially between the exterior surface  41  of the pulling mandrel  40  and the bore  14  of the housing  11  and formed axially between the first annular stop  18  of the housing  11  and a second annular stop  118  (not shown in  FIG. 2 —see  FIG. 3 ) of the housing  11  that is below and spaced apart from the first annular stop  18 . More specifically, it will be noted that the aperture  77  is disposed distal to the first annular piston  48  so that fluid pressure introduced into the first annular chamber  78  bears against the first annular piston  48  to displace the first annular piston  48  in the proximal direction (of arrow  39  in  FIG. 1 ) during a hydraulic stroke of the liner expansion tool  10 . 
       FIG. 3  is a sectional view of a lower portion of the expansion tool  10  of  FIG. 1  illustrating a first annular piston  48  on the pulling mandrel  40  adjacent and proximal to a second annular stop  118  of the housing  11 . Fluid pressure introduced into the bore  44  of the pulling mandrel  40  is communicated from the bore  44  of the pulling mandrel  40  through the aperture  77  to a distal portion  81  of the annular cylinder  78 , distal to the first annular piston  48  and between the first annular piston  48  and the second annular stop  118 . The distal portion  81  of the annular cylinder  78  appears very small in  FIG. 3  because the liner expansion tool  10  is in the run-in configuration or the cocked configuration, meaning that the liner expansion tool  10  in the configuration in  FIG. 3  is cocked and ready for being hydraulically stroked. The fluid pressure introduced into the distal portion  81  of the annular cylinder  78  will displace the first annular piston  48  and the pulling mandrel  40  in an upward or proximal direction (in the direction of the arrow  39 ). Fluid residing in the remaining or proximal portion of the first annular cylinder  78 , that is, between the first annular piston  48  and the first annular stop  18  (see  FIG. 2 ), is displaced from the liner expansion tool  10  through exhaust aperture  79  (not shown in  FIG. 3 —see  FIGS. 1 and 2 ) in the housing  11  as the first annular piston  48  and pulling mandrel  40  are moved within the housing  11 . It will be understood that the distal end of the first annular piston  48  is exposed to the elevated fluid pressure provided through the bore  44  of the pulling mandrel  40  and through the aperture  77  in the pulling mandrel  40  during a hydraulic stroking of the liner expansion tool  10 . 
     The second annular stop  118  shown in  FIG. 3  forms a distal end of a first annular cylinder  78  in which the annular piston  48  on the pulling mandrel  40  is movable. The portion of the liner expansion tool  10  illustrated in  FIG. 3  is distal to the portion of the liner expansion tool  10  illustrated in  FIGS. 1 and 2 .  FIG. 3  illustrates the first annular cylinder  78  axially intermediate a first annular stop  18  (not shown in  FIG. 3 —see  FIGS. 1 and 2 ) extending radially inwardly from the interior surface  34  of the housing  11  and a second annular stop  118  also extending radially inwardly from the interior surface  34  of the housing  11 . The first annular stop  18  of  FIG. 1  and the second annular stop  118  of  FIG. 2  are spaced apart one from the other within the housing  11  to define the first annular cylinder  78  axially therebetween, and both of the first annular stop  18  and the second annular stop  118  sealably engage the exterior surface  41  of the pulling mandrel  40  at seals  19  and  35 , respectively. A first annular piston  48  moves within the first annular cylinder  78  and is depicted in  FIG. 3  immediately adjacent to the second annular stop  118  of the housing  11 , thereby indicating that the liner expansion tool  10  is in the cocked configuration in  FIG. 3 . The seal  35  on the second annular stop  118  and the seal  19  on the first annular stop  18  (see  FIG. 1 ) engage the exterior surface  41  of the pulling mandrel  40  to isolate the first annular cylinder  78  so that fluid pressure introduced into the distal portion  81  of the first annular cylinder  78  through the aperture  77  will exert a displacing force against the first annular piston  48  to move it within the first annular cylinder  78  as fluid is displaced from the first annular cylinder  78  through exhaust apertures  79  shown on  FIGS. 1-3 . 
       FIG. 3  illustrates the aperture  77  in the pulling mandrel  40  positioned to axially coincide with the distal portion  81  of the first annular cylinder  78  shown in  FIG. 3  intermediate the first annular piston  48  of the pulling mandrel  40  and the second annular stop  118  of the housing  11 . Pressurization of fluid within the tubular string (not shown in  FIG. 3 ) is communicated through the proximal end  12  of the housing  11  (see  FIG. 1 ), into the bore  44  of the pulling mandrel  40  and through the aperture  77  in the pulling mandrel  40  to the portion of the annular chamber  78  at the distal end  81  to hydraulically urge the first annular piston  48  and the pulling mandrel  40  to move in the proximal direction as indicated by arrow  39 . It will be understood that hydraulic displacement of the first annular piston  48  of  FIG. 3  in a proximal direction and away from the second annular stop  118  of the housing  11  and towards the first annular stop  18  of the housing  11  (shown on  FIG. 1 ) to increase the distal portion  81  will move the pulling mandrel  40  to the “stroked” or un-cocked position corresponding to  FIG. 2 . 
       FIG. 3  also illustrates a second annular piston  148  on the pulling mandrel  40  that is spaced apart on the pulling mandrel  40  from the first annular piston  48 . The second annular piston  148  is movable within a second annular chamber  178  formed axially between the second annular stop  118  of the housing  11  and a third annular piston  218  (not shown in  FIG. 3 ) and radially between the exterior surface  41  of the pulling mandrel  40  and the interior surface  34  of the housing  11 . The alternating arrangement of annular stops and annular pistons illustrated in  FIGS. 1 and 3  can be extended to provide an aligned series of stacked annular cylinders, each reciprocatably receiving annular pistons to thereby multiply the amount of force that can be hydraulically applied to the pulling mandrel  40  to displace the pulling mandrel  40  within the bore  14  of the housing  11  during a stroke of the liner expansion tool  10 . 
       FIG. 4  is a sectional view of a portion of the embodiment of the liner expansion tool  10  of  FIGS. 1-3  that is below the hydraulic section of the liner expansion tool  10  illustrated in  FIGS. 1-3 . The portion of the liner expansion tool  10  illustrated in  FIG. 4  includes a plurality of slips  47  linked to a rack retainer  52  that is secured to a collet cage  20  that, in turn, surrounds a collet  21 . Turning to  FIG. 4A , the collet  21  is releasably coupled to the pulling mandrel  40  using one or more radially outwardly disposed notches  28  on the pulling mandrel  40  that releasably receive one or more radially inwardly protruding ridges  27  on the collet  21 . The collet cage  20  includes an interior channel  22  that surrounds the collet  21  and allows a limited amount of movement of the collet  21  within the collet cage  20 . Returning to  FIG. 4 , the collet cage  20  is coupled to the ratchet rack  55 . The ratchet rack  55  is a tubular member having a bore  54  and a buttress-threaded exterior  56  to cooperate with a ratcheting component  150  that is movable in the direction of arrow  69  along the ratchet rack  55 . It will be understood that the ratcheting component  150  may move in the direction of arrow  69  along a stationary ratchet rack  55  or the ratchet rack  55  is movable in the direction of arrow  39  within a stationary ratcheting component  150 , which is the same relative direction of movement of one component relative to the other. This unidirectional movement is permitted by the buttress-threaded exterior  56  of the ratchet rack  55  and the corresponding buttress-threaded interior bore of the ratchet ring  57 . The ratcheting component  150  includes the ratchet ring  57  captured within a shaped chamber  159  (see  FIGS. 5 and 5A ) of a ring housing  50 . The ratchet ring  57  is illustrated in  FIG. 5  in the collapsed or contracted position to lock the ratcheting component  150  in position relative to the ratchet rack  55  and to thereby prevent movement of the proximal end  62  of the expandable liner  62  relative to the ratchet rack  55 . It will be understood that this condition may leave a small amount of space within the chamber  159  radially outwardly of the ratchet ring  57 . The ratchet ring  57  may include radially outwardly extending exterior threads  59  for engaging the correspondingly shaped chamber  159  of the ring housing  50  upon expansion of the ratchet ring  57 . The ratchet ring  57  of  FIG. 5  further includes radially inwardly extending interior buttress threads  58  that cooperate with correspondingly shaped buttress threads along the threaded exterior  56  of the ratchet rack  55 . In  FIG. 5 , these interior buttress threads  58  of the ratchet ring  57  are shown engaged with the correspondingly shaped threaded exterior  56  of the ratchet rack  55  of the liner expansion tool  10 . 
     Returning to  FIG. 4 , the reaction assembly of the liner expansion tool  10  of the embodiment of the present invention illustrated in the appended drawings includes the rack retainer  52 , the collet cage  20 , the collet  21 , the ratchet rack  55  and the ratcheting component  150  which includes a ratchet ring  57  and a ratchet housing  50 . The ratchet ring  57  includes a longitudinal slot to allow expansion and contraction of the ratchet ring  57  within the ratchet housing  50  as one of the ratcheting component  150  and the ratchet rack  50  moves relative to the other of the ratcheting component  150  and the ratchet rack  50 . Turning again to  FIG. 5 , the ratchet ring  57  is specially threaded to enable uni-directional movement along the ratchet rack  55  relative to the ratcheting component  150  by circumferentially expanding, along the slot of the ratchet ring  57 , within the chamber  159  of the ring housing  50  to a size large enough to allow the radially inwardly disposed buttress threads  58  of the ratchet ring  57  to index or to skip over the corresponding radially outwardly extending buttress threads  56  on the exterior of the ratchet rack  55  for relative movement of the ratchet ring  57  and ring housing  50  in the direction of arrow  157  or, conversely, for relative movement of the ratchet rack  55  relative to the ratchet ring  57 , and relative to the ring housing  50  in which the ratchet ring  57  is expandably captured, in the direction of arrow  155 . It will be understood that each buttress thread of the various buttress-threaded surfaces each include a ramped side and a steep side, and that the inwardly extending buttress-threads  58  on the ratchet ring  57  and the outwardly extending buttress-threads on the ratchet rack  55 , respectively, are together arranged for movement in the direction of the ramped side of the buttress threads. The reaction assembly is adapted to accommodate both axial liner shrinkage due to radial expansion and re-cocking of the expansion tool  10 , as will be discussed below. 
       FIG. 5A  is a sectioned view of the portion of the liner expansion tool  10  illustrated in  FIG. 5  with the section line taken through the ratchet ring  57  and the ring housing  50  in which the ratchet ring  57  is expandably captured.  FIG. 5A  shows the pulling mandrel  40 , which is movably received within the bore  54  of the ratchet rack  55 , which is movably received within the ratchet ring  57  which is expandably captured within the ring housing  50 . The sectional view of  FIG. 5A  illustrates the contracted or locked position of the ratchet ring  57  and only a small amount of the inwardly extending buttress threads  58  of the ratchet ring  57  can be seen in  FIG. 5A  because they are locked and engaged with the corresponding buttress threads  56  of the ratchet rack  55 . The outwardly extending threads  59  of the ratchet ring  57  are visible in  FIG. 5A  between the ratchet ring  57  and the ring housing  50 . This position corresponds to the condition of the reaction assembly that resists movement of the ratchet ring  57  and ring housing  50  along the ratchet rack  55 , such as when the expandable liner  62  is first being expanded within the well casing  99  and requires that the reaction assembly hold it in position within the well casing  99 . It will be noted that in  FIG. 5A , which corresponds to the contracted position of the ratchet ring  57 , there is either no gap or a small gap  57 A formed at the slot of the ratchet ring  57  which is in its circumferentially contracted configuration. It will be further noted that the expandable liner  62  is not in the sectioned view of  FIG. 5A , which is above the expandable liner  62 . 
       FIG. 5B  is another sectioned view of the portion of the expansion tool  10  illustrated in  FIG. 5  with the section line taken through the ratchet ring  57  and the ring housing  50  in which it is expandably captured.  FIG. 5B  also shows the pulling mandrel  40 , the ratchet rack  55 , the ratchet ring  57  and the ring housing  50 , but the sectional view of  FIG. 5B  illustrates the expanded position of the ratchet ring  57 . It should be noted that the inwardly extending buttress threads  58  of the ratchet ring  57  can be seen in  FIG. 5B  because they are expanded and disengaged from the buttress threads  56  of the ratchet rack  55 . The outwardly extending threads  59  of the ratchet ring  57  are not visible in  FIG. 5B  between the ratchet ring  57  and the ring housing  50  because they are recessed within the shaped chamber  159  of the ring housing  50 . This position corresponds to the condition of the reaction assembly that permits movement of the ratchet ring  57  and ring housing  50  along the ratchet rack  55 , such as when the expandable liner  62  axially contracts while being expanded within the well casing  99 . It will be noted that in FIG.  5 B, which corresponds to the expanded position of the ratchet ring  57 , there is a larger gap  57 B formed in the ratchet ring  57  which is in its circumferentially expanded configuration. 
     Returning to  FIG. 5 , a proximal end  61  of an expandable liner  62  is received concentrically onto the elongate ratchet rack  55  prior to connection of the expander  87  (see  FIG. 7 ) to axially capture the expandable liner  62  between the expander  87  and the ratcheting component  150  and to concentrically surround the ratchet rack  55  with the expandable liner  62 . The expandable liner  62  is also axially captured intermediate the ring housing  50  of the ratcheting component  150 , which is engaged with the proximal end  61  of the expandable liner  62 , and the expander  87  (not shown in  FIG. 5 —see  FIGS. 7 and 8 ) connected to a distal end of the pulling mandrel  40  that is reciprocatably received through the bore  54  of the ratchet rack  55 . The proximal end  61  of the expandable liner  62  is illustrated in  FIG. 5  as being disposed around at least a portion of the ring housing  50  and secured to the ring housing  50  by threaded fasteners  71 . The expandable liner  62  is illustrated in  FIG. 5  and in  FIGS. 7 and 8  in position for being radially outwardly expanded by stroking of the pulling mandrel  40  to pull the expander  87  to expand the expandable liner  62  and to engage the expanded liner  62  with the interior wall  98  of the targeted interval of the well casing  99 . 
       FIG. 6  illustrates how the liner expansion tool  10  of the present invention is securable in the well casing  99  in which the expandable liner  62  is to be expanded and installed, as opposed to being securable in the expandable liner  62  itself, as are some other liner expansion tools. The slips  47  of the liner expansion tool  10  are radially outwardly deployable to engage the interior wall  98  of the well casing  99  by initial movement of the pulling mandrel  40  and the expander  87  attached thereto in the direction of the arrow  39  relative to the housing  11  of the liner expansion tool  10 . Movement of the pulling mandrel  40  (and the expander  87  connected thereto and shown in  FIGS. 7 and 8 ) in the direction of the arrow  39  places the expandable liner  62  in axial compression and transfers the axial component of the force applied by the expander  87  to the distal end  64  (not shown in  FIG. 6 —see  FIG. 8 ) of the expandable liner  62  to the ring housing  50  and to the ratchet ring  57  within the ring housing  50  engaged with the proximal end  61  of the expandable liner  62 . The ratchet ring  57  transfers the axial component of the force applied by the expander  87  through the expandable liner  62  to the ratchet rack  55  on which the ratchet ring  57  is threadably engaged, and the ratchet rack  55  transfers the force to the collet cage  20  that surrounds the collet  21 . The collet cage  20  transfers the force to the rack retainer  52  that is connected through the collet cage  20  to the ratchet rack  55 , and the rack retainer  52  transfers the force to the slips  47  and urges the slips  47  in a proximal direction relative to the slip actuator  46 . The slips  47  include sloped interior portions  67  that slide against and cooperate with similarly sloped exterior portions  43  of the slip actuator  46 . As the slips  47  are displaced upwardly in the direction of arrow  39  relative to the slip actuators  46  by the force applied to the slips  47  by the rack retainer  52  during an expansion stroke as described above, the slips  47  are radially outwardly deployed away from the axis  88  of the liner expansion tool  10  to engage and grip the interior wall  98  of the casing  99 . It should be noted that the slips  47  are radially outwardly deployed by a small amount of axial movement of the slips  47  relative to the cooperating slip actuators  46  to engage and grip the casing  99 . It will be understood that the slips  47  may be disposed within a slip cage portion or extension of the tubular housing  11  having openings or “windows” adjacent to the slips  47  to permit the slips  47  to grippingly engage the interior wall  98  of the casing  99  upon deployment to secure the liner expansion tool  10  in position within the casing  99 . The slips  47  may be biased towards the retracted configuration by springs  51 . 
       FIG. 5  is an enlarged view of the specially threaded interface between the ratchet rack  55  and the ratchet ring  57  of the expansion tool  10 . The ratchet ring  57  includes a threaded interior bore  58  having buttress threads such as, for example, buttress threads. The ratchet ring  57  may also include exterior surface features such as, for example, exterior threads  59  for grippingly engaging the interior bore  53  of the proximal end  61  of the expandable liner  62 . The ratchet rack  55 , on which the ratchet ring  57  is uni-directionally movable, also includes a bore  54  through which the pulling mandrel  40  is received. It will be understood that only small portions of the pulling mandrel  40 , the ratchet rack  55  and the ratchet ring  57  are shown in the enlarged view of  FIG. 5 . The threaded exterior surface  56  of the ratchet rack  55  also includes buttress threads  56  such as, for example, buttress threads, that cooperate with the buttress threads on the threaded interior bore  58  of the ratchet ring  57  to provide for movement of the ratchet ring  57  only in the distal direction along the ratchet rack  55 , as indicated by arrow  157  in  FIG. 5  or, stated another way, to provide for movement of the ratchet rack  55  in a proximal direction relative to the ratchet ring  57 , as indicated by arrow  155 . The threads  58  of the ratchet ring  57  and the engaging threads  56  of the ratchet rack  55  cooperate to prevent movement of the ratchet ring  57  in the proximal direction along the ratchet rack  55 . It will be understood that the axially compressing force applied by the expander  87  (see  FIG. 7 ) to the distal end  64  of the liner  62  is transferred to the retainer ring  57  urging it to move along the ratchet rack  55 , and that the threading of the ratchet rack  55  and ratchet ring  57  (see  FIG. 5 ) prevent movement of the ratchet ring  57  in response to the force applied by the expander  87 . This interaction between the ratchet rack  55  and the ratchet ring  57  enables the transfer of the force to the rack retainer  52  and to the slips  47  at the onset of an expansion stroke. 
       FIG. 5A  shows an embodiment of the ratchet ring  57  for use in connection with the liner expansion tool  10  of the present invention that includes a slot  57 A to allow for circumferential elastic expansion and contraction (collapse) of the ratchet ring  57  as it and the ring housing  50  ratchets along the exterior surface  56  of the ratchet rack  55  (in one direction only due to the buttress threads). It will be understood that the ramping side  63  of the buttress threads  58  (see  FIG. 5 ) within the bore of the ratchet ring  57  will slide along the ramping side  68  of the exterior buttress threads  56  on the ratchet rack  55  to impart an expanding force to the ratchet ring  57  that will cause the slot  57 A (see  FIG. 5A ) to open and expand the ratchet ring  57  enough to allow movement of the ratchet ring  57  in a distal direction (in the direction of arrow  157  on  FIG. 5 ) relative to the ratchet rack  55 . The slotted ratchet ring  57  of  FIG. 5A  will elastically return to a contracted configuration after the peaks  83  of the threads  56  and  58  of the ratchet rack  55  and ratchet ring  57  each pass the other and return to the collapsed configuration shown in  FIG. 5 .  FIG. 5B  shows the peaks  83  of the threads  56  of the ratchet rack  55  and the threads  58  of the ratchet ring  57  engaged just before the ratchet ring  57  collapses or retracts back to the configuration shown in  FIG. 5A . It will be noted that in  FIG. 5B  the slot  57 B is at its largest opening. 
     Alternately, the ratcheting function of the ratchet ring  57 , as it moves in one (the distal) direction only, can also be provided by a conventional spring-biased dog provided on the ratchet ring  57  in lieu of the slot  57 A. The spring-biased dog engages and rides along the thread profile  56  of the ratchet rack  55  with the spring biasing the dog to remain engaged with the threads on the ratchet rack  55 . Each time a force is applied to move the ratchet ring  57  in the distal direction, the dog will be displaced radially outwardly against the spring element and away from the ratchet rack  55  as the dog clears a thread peak  83 . After the dog clears the thread peak  83 , the biasing of the spring element restores the dog into a valley between two adjacent thread peaks to re-engage the dog with the steep side of the thread and to prevent movement of the ratchet ring  57  in the proximal direction. It will be understood that a spring-biased dog is the same apparatus used in many conventional ratcheting apparatuses such as, for example, a ratchet tool and a bumper jack used to lift an automotive vehicle. It will be understood that a large variety of elastically deformable components could be included within a ratchet ring  57  to provide the elastic restoring function of the slotted ratchet ring  57  or the spring-biased ratchet ring described above. 
       FIG. 6  illustrates the positions of the slips  47 , the slip actuator  46 , the rack retainer  52 , the ratchet ring  57 , the ring housing  50  and the ratchet rack  55  on which the ratchet ring  57  is received with the liner expansion tool  10  in the run-in configuration. It can be seen in  FIG. 6  that the pulling mandrel  40  is slidably received through the bore  54  of the ratchet rack  55  and through the slip actuator  46 . The slip actuator  46  includes a plurality of radially outwardly extending lobes  43  that axially and slidably engage and radially outwardly displace a corresponding plurality of lobes  67  of the slips  47  when the slips  47  are displaced, relative to the slip actuator  46 , by the collet  21 , collet cage  20  and the rack retainer  52  engaged thereby. Each of the slips  47  are radially captured between the slip actuator  46  and a retainer spring  51 , and each slip  47  is disposed adjacent a window  13  within the housing  11  through which the slip  47  can engage the interior wall  98  of the casing  99 . The portion of the housing  11  adjacent to the windows  13  and adjacent to the slips  47  may be referred to as a cage portion of the housing  11  because the windows  13  give that portion a cage-like appearance. The application of force by the expander  87  (not shown in  FIG. 6 —see  FIG. 7 ) to the liner  62 , transferred through the ring housing  50 , the ratchet ring  57 , the ratchet rack  55  and the rack retainer  52  to the slips  47 , displaces the slips  47  axially and in the proximal direction of the arrow  39 , onto the slip actuator  46 , and radially outwardly against the spring  51  to engage and grip the casing  99 . Once the slips  47  engage and grip the casing  99 , all further hydraulic displacement of the pulling mandrel  40  relative to the housing  11  results in expansion of a portion of the expandable liner  62 . The collet  21  and collet cage  20  cooperate with the pulling mandrel  40  (see  FIG. 4A ) to set the slips  47  to grip the casing  99  prior to the pulling mandrel  40  disengaging the collet  21 . 
       FIG. 7  is a sectional view of a distal end  73  of the liner expansion tool  10  including the expander  87  and a ball seat  75  within the bore  44  of the pulling mandrel  40 . The ball seat  75  is sized to receive a ball  72  (shown in  FIG. 7  as being en route to the ball seat  75 ) and to thereby isolate the bore  44  of the pulling mandrel  40 . The ball  72  and ball seat  75  enable fluid pressure within the bore  44  to increase to a pressure sufficient to stroke the annular pistons  48  and  148  (not shown in  FIG. 7 —see  FIGS. 2 and 3 ) within the annular cylinders  78  and  178  of the hydraulic section of the liner expansion tool  10 . 
     The ball  72  is introduced into the tubular string (not shown) at the rig, and pumped through the bore  44  of the pulling mandrel  40  and displaced to the distal end  73  of the liner expansion tool  10  to sealably engage the ball seat  75 .  FIG. 7  further illustrates an optional safety joint  29  that allows the liner expansion tool  10  to be rotated free of the expander  87  and ball seat  75  in the event of the liner expansion tool  10  becoming stuck in the casing  99 . The safety joint  29  can be rotated free of the expander  87  and ball seat  75  because the keys  74  (see  FIG. 6 ) slidably engage the grooves  76  in the pulling mandrel  40  to rotatably secure the pulling mandrel to the housing  11  while allowing axial movement of the pulling mandrel  40  relative to the keys  74  and the housing  11 . This arrangement enables torque applied to the proximal end  12  of the housing  11  to be transferred through the keys  74  and grooves  76  to the safety joint  29 . 
       FIG. 8  is the lower portion of  FIG. 7  illustrating the position of the ball  72  after it has been sealably received onto the ball seat  75  to isolate the bore  44  of the pulling mandrel  40  (see  FIG. 7 ) and to enable the liner expansion tool  10  to hydraulically stroke the expander  87  to enter the distal end  64  of the expandable liner  62  and to expand the expandable liner  62 . As the pumping of fluid into the bore  44  of the pulling mandrel  40  continues, the pressure within the bore  44  of the pulling mandrel  40  increases and displaces the annular pistons  48  and  148  and the pulling mandrel  40  to which these annular pistons  48  and  148  are secured in a proximal direction (in the direction of arrow  39  in  FIGS. 1, 3 and 4 ) within the bore  14  of the housing  11 . This relative movement causes the slips  47  to be displaced radially outwardly relative to the slip actuators  46  (see  FIG. 6 ) to grip the casing  99  prior to disengagement of the collet  21  from the pulling mandrel  40  (see  FIG. 4A ) and expansion of the expandable liner  62 . 
       FIG. 9  is a sectional elevation view of a portion of the hydraulic section of the liner expansion tool  10  of the present invention illustrating a small amount of initial separation between the first annular piston  48  of the pulling mandrel  40  from a second annular stop  118  of the housing  11 .  FIG. 9  may be compared to  FIG. 3 , which reflects the condition of the liner expansion tool  10  prior to pressurization of the bore  44  of the pulling mandrel  40 . The small amount of separation illustrated in  FIG. 9  occurs after the ball  72  sealably engages and seats in the ball seat  75  of the pulling mandrel  40  and fluid within the bore  44  of the pulling mandrel  40  is pressurized to stroke the liner expansion tool  10 , and this configuration indicates the initial portion of the stroke of the hydraulic section of the liner expansion tool  10 . The initial separation illustrated in  FIG. 9  may be correlated to the setting of the slips  47 , illustrated in  FIG. 10 , that occurs at the onset of the stroking of the hydraulic section of the liner expansion tool  10  to secure the housing  11  of the liner expansion tool  10  in place within the casing  99 . The small amount of separation between the first annular piston  48  and the second annular stop  118  indicates the condition of the liner expansion tool  10  at the time the slips  47  become engaged to grip the casing  99 . Continued pressurization of the fluid in the bore  44  of the pulling mandrel  40  after the separation indicated by  FIG. 9  causes further movement of the first annular piston  48  within the first annular cylinder  17  (see also  FIG. 3 ) of the housing  11  to draw the expander  87  into the distal end  64  of the expandable liner  62  (see  FIG. 8 ), thereby radially expanding the expandable liner  62  as the expander  87  moves through the expandable liner  62 . 
       FIG. 10  is a sectional elevation view of the slips  47  and slip actuator  46  of the liner expansion tool  10  of the present invention with the slips  47  (also shown in  FIG. 6  as being coupled to the ratchet rack  55 ) displaced from their original position and forced axially onto the slip actuator  46 . The slips  47  are illustrated in  FIG. 10  in a deployed configuration engaging and gripping the interior wall  98  of the casing  99  in which the liner expansion tool  10  is disposed.  FIG. 10  corresponds to the relative positions of the first annular piston  48  and the adjacent second annular stop  118  illustrated in  FIG. 9 .  FIG. 10  illustrates how the slips  47  of the liner expansion tool  10  are deployed at the onset of the pressurization of the bore  44  of the pulling mandrel  40  to secure the housing  11  of the liner expansion tool  10  within the casing  99  before the expander  87  is pulled through a distal portion of the expandable liner  62 . 
       FIG. 11  is a sectional elevation view of the slips  47  and slip actuator  46  of the liner expansion tool  10  and of the components of the reaction assembly that maintains the position of the expandable liner  62  during expansion.  FIG. 11  illustrates how the expandable liner  62  and the components of the reaction assembly of the liner expansion tool  10  are coupled to deploy the slips  47  upon initial pressurization of the bore  44  of the pulling mandrel  40  for an expansion stroke. Optionally, the expandable liner  62  of  FIG. 11  includes a plurality of elastomeric seals  82  disposed on the expandable liner  62  to engage and seal with the bore  98  of the casing  99  upon expansion of the expandable liner  62 . The expandable liner  62 , upon engagement at the distal end  64  (not shown—see  FIGS. 7 and 8 ) by the expander  87 , is urged against the ring housing  50  that houses the ratchet ring  57 . The ratchet ring  57  cannot move along the ratchet rack  55  in the direction of arrow  39  due to the threaded arrangement (see  FIG. 5 ) and the reaction force applied by the ring housing  50  to the axially compressed liner  62  as the force applied by the expander  87  to the liner  62  is transferred through the ring housing  50  and the ratchet ring  57  housed therein to the ratchet rack  55 . The ratchet rack  55  is coupled to the rack retainer  52  and the force applied by the ratchet ring  57  to the ratchet rack  55  is transferred through the rack retainer  52  to the slips  47 , causing them to move in the axial direction of arrow  39  into the deployed and gripping configuration illustrated in  FIG. 11 . 
     Once the slips  47  engage the casing  99 , the continued introduction of pressurized fluid into the bore of the pulling mandrel causes the pulling mandrel  40  to be displaced in a proximal direction within the bore of the housing  11  and to pull the expander  87  into the bore of the distal end  64  of the liner  62 . The resulting expansion of the expandable liner  62  continues until the stroke of the annular pistons  48  and  148  is completed. At this juncture, the expander  87  is securely lodged within the partially expanded bore of the expandable liner  62  and the exterior surface of the expandable liner  62 , in the portion of the expandable liner  62  that has been expanded, is in engagement with the casing  99 . 
     The remaining unexpanded portion of the expandable liner  62  that has not yet been expanded by movement of the expander  87  through the bore of the distal end  64  of the expandable liner  62  can be expanded by subsequent strokes of the liner expansion tool  10 . Subsequent strokes require that the liner expansion tool  10  be re-cocked to reset the hydraulic section of the liner expansion tool  10 , which means that the pulling mandrel  40  and the annular pistons  48  and  148  thereon must be restored to their original “run-in” positions relative to the housing  11  and the annular chambers defined by the stops  18  and  118  provided within the housing  11  for reciprocal movement of the annular pistons  48  and  148 . 
     The liner expansion tool  10  can be re-cocked by first relieving the fluid pressure within the bore  44  of the pulling mandrel  40  to relieve force applied to each of the annular pistons  48  and  148  disposed on the pulling mandrel  40  by the fluid pressure within each of the annular chambers defined by the stops  18  and  118 . It will be understood that relieving the pressure within the bore  44  of the pulling mandrel  40  requires control of the pumps that pump fluid into the bore  44  of the pulling mandrel  40  by pumping down the tubular string to the housing  11 . With the hydraulic pressure in the bore  44  of the pulling mandrel  40  relieved, and with the expander  87  securely lodged within the partially expanded expandable liner  62 , the expanded portion of which engages the casing  99 , the liner expansion tool  10  can be re-cocked by using the draw works on the rig to pull the tubular string (not shown) and the proximal end  12  of the housing  11  of the liner expansion tool  10  to which it is threadably connected in a proximal direction within the casing  99  to displace the annular pistons  48  and  148  back to their original locations within the annular chambers defined by the annular stops  18  and  118  of the proximally displaced housing  11 . It will be understood that the pulling mandrel  40  and the expander  87  to which it is connected will remain stationary during the re-cocking process, and also that the ball  72  does not disengage the ball seat  75  during this re-cocking step as long as the pressure within the bore  44  of the pulling mandrel  40  does not fall below the pressure within the casing  99 . Once the housing  11  of the liner expansion tool  10  is displaced relative to the pulling mandrel  40  and the expander  87  by using the draw works to pull the proximal end  12  of the housing  11 , the liner expansion tool  10  is re-cocked and ready for being hydraulically stroked to set the slips  47  and then to expand an additional interval of the expandable liner  62 . 
     Subsequent pressurization of the tubular string and of the bore  44  of the pulling mandrel  40  causes the slips  47  to again be engaged to grip the casing  99 , and further pressurization causes the expander  87  to be drawn in a proximal direction further within the bore of the expandable liner  62  to expand another portion of the expandable liner  62 . It will be understood that with each stroke of the liner expansion tool  10 , the axial length of the expanded portion of the expandable liner  62  increases. It will be further understood that since the expanded portion of the expandable liner  62  engages the casing  99 , each stroke of the liner expansion tool  10  increases the overall surface area of frictional engagement between the exterior surface of the expanded portion of the expandable liner  62  and the casing  99  in which the expandable liner  62  is installed. It will be further understood that the expandable liner  62  is initially, during the early stages of expansion of the expandable liner  62 , secured in place by the ratchet ring  57 , the ring housing  50  and the ratchet rack  55 , and by the arrangement of buttress threads within the bore of the ratchet ring  57  and on the exterior surface of the ratchet rack  55 . However, once a sufficient amount of frictional engagement between the expanded portion of the expandable liner  62  and the casing  99  exists, the ratchet ring  57  and cooperating ratchet rack  55  will no longer continue to be loaded during strokes of the expander  87  within the bore of the expandable liner  62  since movement of partially expanded expandable liner  62  within the casing  99  will be prevented by the steadily increasing frictional engagement between the expanded portion of the expandable liner  62  and the casing  99  in which it is expanded. At some point during the expansion of the expandable liner  62 , the use of the hydraulic components (annular pistons  48  and  148 , annular chambers defined by stops  18  and  118 , etc.) and the gripping components (slips  47  and slip actuator  46 ) of the liner expansion tool  10  can be terminated, and the draw works of the rig from which the tubular string is run can be used to pull the liner expansion tool  10  and the expander  87  coupled thereto to expand the remaining unexpanded portion of the partially expanded liner  62 . If the weight on the draw works were to exceed a safe threshold beyond which the draw works or the tubular string may be damaged, the hydraulic components such as the annular pistons  48  and  148  and the annular stops  18  and  118 , and the gripping components of the liner expansion tool  10  such as the slips  47  and the slip actuator  46  can be again engaged to continue expanding the expandable liner  62  one stroke at a time. 
     One embodiment of the method of the present invention includes the step of providing elastomeric seals  82  on the exterior surface  65  of the expandable liner  62  to engage the casing  99  upon expansion of the expandable liner  62 .  FIG. 11  illustrates a plurality of elastomeric seals  82  disposed on the expandable liner  62  near the proximal end  61  of the expandable liner  62 . It will be understood that these seals  82  can be installed at a plurality of locations along the exterior surface  65  of the expandable liner  62  to engage the casing  99  upon expansion of the expandable liner  62  and to thereby provide additional sealing integrity. 
       FIG. 12  is a high level flow chart illustrating the steps of an embodiment of a method  100  of the present invention for installing an expandable liner  62  within a casing  99 . These steps are clearly related to the use of the liner expansion tool  10  illustrated in  FIGS. 1-11  as well as other embodiments of the liner expansion tool  10  of the present invention. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components and/or groups, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The terms “preferably,” “preferred,” “prefer,” “optionally,” “may,” and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention. 
     The corresponding structures, materials, acts, and equivalents of all means or steps plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but it is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.