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You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION 
       [0001]    The present invention relates tools and techniques to radially expand a downhole tubular in a well. More particularly, this invention relates to a liner hanger expander with improved tool release features. 
       BACKGROUND OF THE INVENTION 
       [0002]    Various types of liner hanger have been proposed for hanging a liner from a casing string in a well. Many liner hangers are set with slips activated by the liner hanger running tool. Liner hangers with multiple parts pose a significant liability when one or more of the parts become loose in the well, thereby disrupting the setting operation and making retrieval difficult. Other liner hangers and running tools cannot perform conventional cementing operations through the running tool before setting the liner hanger in the well. 
         [0003]    Conventional liner hangers have problems supporting heavy liners with the weight of one million pounds or more. Some liner hangers successfully support the liner weight, but do not reliably seal with the casing string. Other liner hangers are not able to obtain burst and/or collapse characteristics equal to that of the casing. A preferred liner hanger maintains a collapse and burst strength at least substantially equal to that of both the casing and the liner. 
         [0004]    Another significant problem with some liner hangers is that the running tool cannot be reliably disengaged from the set liner hanger for retrieval to the surface. This problem with liner hangers becomes more involved with the desirability to rotate the liner with the work string in the well, e.g., for a liner drilling operation, wherein the operator desires to disengage the work string and tool when the liner hanger has been set, thereby allowing the running tool and the work string to be retrieved from the well. 
         [0005]    Publication 2001/0020532A1 discloses a tool for hanging a liner by pipe expansion. U.S. Pat. No. 3,948,321 discloses a reinforcing swage which remains downhole when the tool is retrieved to the surface. U.S. Pat. No. 6,705,395 discloses a radially expanded liner hanger which uses an axially movable annular piston to expand a tubular member. U.S. Pat. Nos. 7,225,880 and 7,278,492 disclose an expandable liner hanger system and method. 
         [0006]    The disadvantages of the prior art are overcome by the present invention, and an improved liner hanger system and method of releasing the liner hanger are hereinafter disclosed. 
       SUMMARY OF THE INVENTION 
       [0007]    An expandable liner hanger system and method achieves positioning, suspension, sealing and optional cementing of a liner in a subterranean well. In an exemplary application, the method involves expansion of a high strength steel tubular hanger body having slips and packing elements positioned about its outer circumference for contact with the inner surface of a casing string, which has a larger internal diameter than the initial external diameter of the liner and liner hanger when run in the well through the casing string. 
         [0008]    The present invention preferably uses a tubular expander to expand the hanger body, and the tubular expander remains inside the expanded hanger body for support at its final expanded diameter, thus sandwiching the expanded plastically deformed hanger body between the outer casing and the tubular expander. This method provides improved sealing and gripping capability, and requires shorter lengths of expandable tubular liner hanger, typically in the range of from one to five feet. 
         [0009]    In the preferred embodiment, three different mechanisms for release of the tool from the liner hanger may be used. In the first technique, a retainer is secured to the tool mandrel, and the downward movement of the work string and thus the mandrel and the retainer releases collet fingers connecting the tool mandrel to the tubular hanger, thereby releasing the tool so that it may be retrieved to the surface. The tool is also provided with hydraulic piston supported on the mandrel to selectively engage and disengage a clutch rotatably connecting the tool mandrel and a housing supporting latching members. When the clutch is engaged, rotation of the work string rotates the mandrel and a bit at the lower end of the liner. The latching members rotatably connect the tubular hanger and a supporting housing, such that when the clutch is disengaged, rotation of the mandrel arm will unthread the retainer which is rotatably connected to the tubular hanger, thereby providing a separate release mechanism to retrieve the tool to the surface. A safety joint is threadably connected to the tool mandrel and an upper collet retainer, such that left-hand rotation of the mandrel releases an upper portion of the mandrel from the clutch, thereby providing a third release mechanism. 
         [0010]    These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  illustrates in cross-section an upper portion of the tool positioned within a casing. 
           [0012]      FIG. 2  illustrates a lower portion of the tool, including portions of a hydraulic actuator. 
           [0013]      FIG. 3  illustrates an intermediate portion of the tool, and specifically shows the safety release joint. 
           [0014]      FIG. 4  illustrates a lower portion of the tool with a collet mechanism and dogs rotatably engaging the tool and the liner. 
           [0015]      FIG. 5  illustrates a lower portion of the tool with a ball seat. 
           [0016]      FIG. 6  illustrates a cementing plug on a still lower portion of the tool. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0017]    A liner may be conveyed into the well to the desired setting or suspension depth by a drill pipe or work string connected to a multi-stage, double action hydraulic setting and releasing tool (running tool) that furnishes the necessary forces to expand the liner hanger assembly into engagement with the casing. The running tool may be constructed of sufficiently high strength steel to support the weight of the liner as it is run into the well and to provide the necessary force to expand the liner hanger assembly. Additionally, the running tool preferably has a sufficiently large internal bore in its central mandrel to enable passage and displacement of cement for cementing the liner within the well bore. 
         [0018]    Referring to  FIG. 1 , the upper end of the running tool  10  may include a hydraulic actuator assembly  12 , which is shown in greater detail in  FIG. 2 . A top connector  14  is structurally connected by threads  16  to a work string (not shown), and to the running tool inner mandrel  34 . One or more seals  24  provide dynamic sealing of connector  14  and outer sleeve  22 , and threads  26  connect  14  and mandrel  34 . A throughport  31  in the mandrel  34  allows fluid pressure within the interior of the running tool to act on the outer piston  28 , which as shown includes conventional seals  33  for static sealing with the outer sleeve  22  and seals  32  for dynamic sealing with the mandrel  34 . Threads  30  structurally connect the outer piston  28  to outer sleeve  22 . A predetermined amount of fluid pressure within the running tool acting on the outer piston  28  will thus provide downward movement of the outer sleeve  22 . 
         [0019]    Shear ring  18  engages shoulder  17  on connector  14 , and is threaded to outer sleeve  22  and rotatably pinned to outer sleeve  22  by one or more pins  20 ,  21 . Shear ring  18  prevents activation of the tool until a predetermined amount of pressure is applied to generate force sufficient to break the reduced wall section  19  and thereby allow upward movement of connector  14  and mandrel  34  relative to the outer sleeve  22 . Pins  20 ,  21  slide within slots  23  to provide non-rotational interconnection between the outer sleeve  22  and the mandrel  34 . 
         [0020]    Referring now to  FIG. 2 , an inner piston  40  is threadably connected to the mandrel  34  by threads  42 . Ports  36  in the mandrel allow for passage of fluid between the inner piston  40  and a lower outer piston  28 . The inner piston  40  includes one or more static seals for sealing engagement with the mandrel, and includes one or more dynamic seals  38  for dynamic sealing engagement with the outer sleeve  22 . Outer piston  28  in turn includes static seals for sealing with the outer sleeve  22 , and dynamic seals  32  for sealing engagement with the mandrel  34 . Ports similar to  36  may be provided at various locations in the mandrel to provide for the reliable actuation of the inner and outer pistons.  FIG. 2  also depicts another lower inner piston  40  threaded to the mandrel  34  and also containing static seals for sealing with the mandrel, and dynamic seals for sealing with the outer sleeve  22 . A lower sealing block  42  is threadably connected by threads  44  to outer sleeve  22 , and similarly contains outer static seals for sealing with outer sleeve  22  and inner dynamic seals for sealing engagement with the mandrel  34 . 
         [0021]    The lower end of the sealing block  42  includes threads  48  for threaded engagement with sleeve  50 , which as shown in  FIG. 3 , contains a retainer  52  threaded at  54  to sleeve  50 , and including one or more shear pins and shear sleeve  58  for engaging the shoulder  59  on tubular expander  60 .  FIG. 2  depicts the upper end  56  of the expander body show more clearly in  FIG. 3 . Expander  60  preferably includes a plurality of annular radially outer bumps  62  and a lower tapered portion  74  for increasing the diameter of the tubular hanger when moved downward relative to the liner hanger. The lower end of the mandrel  34  is threaded at  64  to upper connector  66 , which is threaded at  68  to lower connector  70 . Threads  72  secure the lower connector to the lower portion of the mandrel  34 . 
         [0022]    As shown in  FIGS. 3 and 4 , the tubing hanger  90  includes an upper hanger body  80  with a plurality of vertically spaced slips  76  and packing or other sealing elements  78 . Collet mechanism  86  includes lower collets which are threaded at  88  to the body of the tubing hanger  90 . Nut  92  is threaded at  94  to the mandrel  34 . Upward movement of the nut relative to the mandrel is prevented by sleeve retainer  84  which is threaded at  85  to the mandrel  34 . 
         [0023]    The lower end of the mandrel  34  in  FIG. 4  is threaded at  102  to the upper clutch body  96 , which includes a downwardly extending member  106  which fits within a suitable receptacle  104  provided in the lower clutch body  112 . Circumferentially spaced dogs or similar blocks  107  are outwardly biased by respective springs  108  for engaging an axial spline in the liner body  100 , thereby rotatably interconnecting the block  112  and the liner. Conventional static seals  110  are also provided. The dogs  107  rotatably connect the liner to the block  112  thereby allowing rotation at the liner and a bit at the lower end of the liner when the mandrel  34  and the clutch formed by engagement of  104  and  106 . Ports  162  in mandrel extension  105  allow pressure to act on the smaller diameter seal to force block  112  downward, thereby disengaging the clutch. Mandrel  105  as shown in  FIG. 5  thus rotates within the block  112 . 
         [0024]      FIG. 5  shows the lower end of the liner connected to the liner body  100  connected to the liner L by threads  114 . Ball seat  120  is also shown in  FIG. 5 , and is initially retained in an upper position with respect to sleeve  116  by a plurality of pins  124 . The sleeve  120  moves downward relative to sleeve  116  and when pins  124  shear, thereby opening ports  125  to fluid internal of the mandrel. The lower end of the sleeve  116  is threaded at  122  to lower mandrel extension  126 . 
         [0025]    Referring now to  FIG. 6 , mandrel sleeve  126  passes through guide block  140 , which includes seal  134  and retainer  136  for sealing with sleeve  126 , and seal  132  and guide ring  128  for sealing with liner body  100 . Cementing plug  142  is also shown in  FIG. 6 , including inner sleeve  150  and port  157 . Ball seat  144  is pinned at  148  to lower wiper body  146 , which is threaded at  152  to sleeve  150 . 
         [0026]    The liner may be run to setting depth on drill pipe and cemented in a conventional manner. The cement may be displaced from the drill pipe and liner and into the well bore/liner annulus using cement wiper plugs as is customary in the art. Once the plugs have displaced the cement and seated near the bottom of the liner, pressure may be applied to fluid within the work string and consequently through the pressure ports of the mandrel and into the pressure chambers formed between upward moving pistons and downward moving pistons. Pressure may be increased until the force created is sufficient to cause the expander to move downward, forcing the expander into the upward facing receptacle of the liner hanger body. Forcing the expander downward causes the liner hanger body to expand radially outward, forcing slips and sealing elements into engagement with the inside surface of the casing, thus sealing and supporting the liner hanger within the casing. 
         [0027]    If pressure within the drill pipe and liner cannot be increased after landing the wiper plugs, a setting ball may be dropped into the drill pipe and permitted to gravitate until the ball engages the seat at the lower end of the running tool. Pressure may then be increased to operate the setting tool. 
         [0028]    As disclosed herein, the tubular expander is positioned at least partially within the hanger body, thereby radially expanding at least part of the liner hanger body. In other cases, all or substantially all of the tubular expander will be within the liner hanger body when the assembly is set. Complete insertion of the tubular expander within the liner hanger body is not required, however, for all applications. 
         [0029]    One technique for releasing the tool from the liner involves axial movement of the work string, i.e., use of the set down weight to release the tool from the liner. This technique allows the work string and thus the retainer or nut  92  threaded to the mandrel to move downward, while the collet mechanism  86  remains engaged with the tubing hanger  90 . This downward movement thus allows the collet fingers to be released in the retainer  92 , so the entire tool may be retrieved to the surface by subsequently pulling the work string. While this operation is relatively simple and reliable, it does require that the work string be moveable downward relative to the liner, which may not be possible if the hydraulic pistons have stroked the expander  60  to a downward position to expand the hanger body  80 . 
         [0030]    Another technique for releasing the tool from the liner involves the use of hydraulic fluid to pass through the ports  162  as shown in  FIG. 4 , thereby pressurizing the lower clutch body  112 , which acts as a piston. This action disengages the downward extending member  106  from the receptacle  104 , which allows the work string and thus the mandrel  34  to be rotated while the dogs  107  maintain the tubing hanger  90  stationary. This rotation will thus lower the retainer  92  with respect to the mandrel, and continued rotation of the work string effectively disengages the retainer or nut  92  from the collet mechanism  86 , thereby allowing the collets to collapse so that tool may be retrieved to the surface. While this operation is also reliable, it does require that fluid pressure be applied to disengage the clutch, and there may be applications wherein sufficient fluid pressure cannot be obtained downhole to accomplish the release of the tool by this mechanism. 
         [0031]    Yet another mechanism for releasing the tool to be retrieved to surface involves rotation of the work string and thus the mandrel  34 , such that the thread  68  begins to unthread, hereby moving a lower portion of the mandrel  34  downward, and thus moving the retainer  92  downward and disengaging the retainer from the collet mechanism  86 . The thread  68  as shown in  FIG. 3  may be used with one or more ball members  67  to ride within unfilled thread cavities  69  in the lower connector  70 . Once the threads  68  on the exterior of the upper connector  66  engage the ball members  67 , no further unthreading of the connection occurs, so that the upper connector  66  remains engaged with the lower connector  70 , although the lower connector  70  and the mandrel  34  beneath the upper connector  66  have moved downward axially relative to the upper connector. 
         [0032]    According to the present invention, one technique for releasing the tool from the liner involves axial movement (set down) of the work string, while another technique involves a combination of hydraulic fluid pressure and rotation of the work string, while the third technique involves left-hand rotation of the work stream. 
         [0033]    Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.

Summary:
A liner hanger ( 10 ) is provided for supporting a liner in a well. An expandable tubular hanger ( 90 ) is positioned within the well and a running tool with a tool mandrel ( 34 ) passes fluid through the running tool. An actuator ( 12 ) forcibly moves the tubular expander to an expanded position. Release of the running tool from the liner may be accomplished with a retainer ( 84 ) and downward movement of the mandrel, with fluid pressure acting on a hydraulic piston ( 28 ) coupled with rotation of the mandrel, or by safety joint ( 68 ) along the tubular mandrel.