Abstract:
An improved liner hanger comprises a mandrel having a piston housing and a plurality of spring slots disposed on the outer wall surface of the mandrel. Each spring slot having at least one spring disposed therein. The liner hanger also has a slip housing having a plurality of slips operatively associated therewith, a spring adjustment sleeve, and an adjustment sleeve ring. The location of the spring slots on the outer wall surface of the mandrel permits an increase in the number of springs utilized for setting the liner hanger. The spring adjustment sleeve and adjustment sleeve ring permit easy and safe assembly and disassembly of the liner hanger. Additionally, when actuated to move from its run-in position to its set position, springs, slip housing, and slips all move upward.

Description:
BACKGROUND 
   1. Field of Invention 
   The invention is directed to anchoring slip assemblies and, in particular, liner hanger devices used for suspending a liner within a wellbore. 
   2. Description of Art 
   A liner is a tubular member that is usually run inside of wellbore casing of an oil or gas well and suspended within the wellbore casing. Liners are typically secured within a wellbore by toothed slips that are located on liner hangers. The slips are set by axially translating them with respect to the liner hanger mandrel or housing. As the slips are translated axially, they are cammed radially outwardly by a ramped surface that is fashioned into the mandrel. As the slips move radially outwardly, the toothed surfaces of the slip will bitingly engage the inner wall surface of the wellbore casing. This type of arrangement is shown, for example, in U.S. Pat. No. 4,497,368 in which slips that are radially expanded by riding up over cone elements disposed into the tubular body of the central mandrel. 
   Actuation systems for such slips in the past employed full circumference hydraulically actuated pistons to move the slips. These designs presented a pressure rating problem in that the full circumference piston frequently had a maximum working pressure significantly lower than the mandrel which it surrounded. Thus, this type of design limited the maximum working pressure in the string to the rating of the cylindrical piston housing assembly. For example, it was not unusual in prior designs to have mandrels rated for 12,000 PSI while the surrounding cylinder housing for the cylindrical piston to only have a rating of approximately 3,000 PSI. 
   In an effort to improve the shortcoming of this design, another design illustrated in U.S. Pat. No. 5,417,288 was developed. In this design the mandrel body received a pair of bores straddling each of the slips. A piston assembly was mounted in each of the bores with all of the necessary seals. The application of hydraulic pressure in the mandrel into all the piston bores actuated the pistons on either side of each slip through a common sleeve to which all the slips were attached. This design, however, was expensive to manufacture, had many potential leak paths in the form of the ring seals on each of the pistons wherein each slip required two pistons. 
   On the other hand, this design provided for a higher pressure rating for the liner hanger body and also used the hydraulic pressure directly to actuate the slips. Necessarily it did not include a locking feature against premature slip movements due to inadvertently applied pressures. The design in U.S. Pat. No. 5,417,288 also did not provide for flexibility for changed conditions downhole which could require additional force to set the slips. In essence, each application was designed for a pre-existing set of conditions with field variability not included as a feature of that prior art design. 
   Additionally, the design of the liner hanger needs to accommodate circulation of mud and cement. The foregoing prior designs, particularly those using a cylindrical piston, obstructed the passages that could have been used for circulating cement and mud. 
   Slip assemblies in the past also have been configured in a variety of ways. In one configuration, when the slips are actuated, the load is passed through the slips circumferentially through their guides or retainers and transmission of the load to the underlying mandrel is avoided. In other more traditional designs, the slips are driven along tapered surfaces of a supporting cone and the loading is placed on the supporting mandrel is in a radial direction toward its center, thus tending to deform the mandrel when setting the slips. Typical of such applications are U.S. Pat. Nos. 4,762,177, 4,711,326 and 5,086,845. 
   In another prior attempt, illustrated in U.S. Pat. No. 6,431,277, the slips are designed to move in two directions upon being actuated. The slips initially move in the direction of the actuating piston, but reverse direction through the movement of one or more springs energized to expand in the direction opposite of the actuating piston. The liner hanger in this patent is also designed with a separate spring housing that restricts the total number of springs that can be used and is difficult to assemble. 
   Also, the liner hanger disclosed in U.S. Pat. No. 6,431,277 does not allow the operator to disassemble the liner hanger in the event that the liner hanger is not set within the wellbore. For example, sometimes the liner hanger must be modified, or repaired, prior to installation. In many instances, the modifications or repairs cannot be accomplished while the liner hanger is “energized” for placement within the wellbore. Therefore, the liner hanger is actuated by activating the piston and the spring and, thus, releasing the slips. Accordingly, before the liner hanger can be installed within the wellbore, the entire liner hanger must be reassembled causing increased downtime and costs. 
   Further, the liner hanger disclosed in U.S. Pat. No. 6,431,277 utilized a piston having a passageway disposed longitudinally therethrough. The passageway is used to vent and/or oil the piston within the piston housing. As a result, the mass of the piston was lessened which also lessened the amount of energy the piston was capable of releasing upon actuation. 
   Accordingly, prior to the development of the present invention, there has been no liner hanger that: provides an easy to assemble and disassemble liner hanger; provides a vent port for venting and oiling the piston such that the piston can be solid instead of having a passageway running the length of the piston; and provides an increase in the number of springs use to set the slips of the liner hanger, thereby providing a better initial bite of the slips into the wellbore casing. Therefore, the art has sought a liner hanger that: provides an easy to assemble and disassemble liner hanger; provides a vent port for venting and oiling the piston such that the piston can be solid instead of having a passageway running the length of the piston; and provides an increase in the number of springs use to set the slips of the liner hanger, thereby providing a better initial bite of the slips into the wellbore casing. 
   SUMMARY OF INVENTION 
   Broadly, an improved liner hanger for securing within a wellbore casing is disclosed. The liner hanger includes a mandrel having a piston housing and a plurality of spring slots disposes circumferentially around the outer surface of the mandrel. Each spring slot contains at least one spring that is compressed or “energized” when the liner hanger is in the run-in position. The springs are held in place by a spring adjustment sleeve having a shoulder that abuts up against one end of each spring and compresses or energizes each spring by forcing the other end of each spring against a slip housing circumferentially disposed around the outer surface of the mandrel below the spring slots and the piston housing. 
   The piston housing contains a piston port for receiving a piston. The piston housing preferably includes a vent port disposed along the length of the piston port so that, after a piston is installed within the piston port, the piston port can be vented and/or oiled along the length of the piston port. As a result, a solid piston can be used in the liner hanger. Use of solid piston as opposed to a hollow piston provides a piston that imparts greater energy when actuated due to its greater mass. 
   The slip housing contains a plurality of slips operatively associated therewith. Each slip is designed to slide within a reciprocal slip pocket disposed on the outer surface of the mandrel. In one embodiment, each slip pocket includes at least one groove and the corresponding slip includes a ramp slidingly engaged within the groove. Each slip also includes a gripping profile surface for engaging or biting into the wellbore casing. Each slip is initially disposed within its corresponding slip pocket until the hanger liner is set within the wellbore casing. During setting of the liner hanger within the wellbore casing, each slip moves axially and radially outward to engage or bite into the wellbore casing, thus securing the hanger liner within the wellbore casing. 
   The slip housing includes a key initially held in place by a shear screw. The key maintains a split ring in place until the key is actuated by the piston. Upon actuation of the piston, the piston extends into the key, forcing the key to release the split ring. As a result of the split ring being released by the key, the slip housing is permitted to move axially along the length of the mandrel. Additionally, as a result of the split ring being released by the key, each of the springs in the spring slots are allowed to expand and release their stored energy. Therefore, expansion of the springs forces the slip housing to move upward axially which in turn forces each of the slips in communication with the slip housing to move upward and outward, i.e., radially, until the slips bite into the wellbore casing and the hanger liner becomes set within the wellbore casing. 
   As will be recognized by persons of ordinary skill in the art, the setting of the liner hanger is done through movement of the springs, slip housing, and slips in the same direction. As will also be recognized by persons of ordinary skill in the art, the increase in the number of springs around the outer surface of the mandrel increases the amount of energy and, thus, force that can be released to initially set, or bite, each of the slips into the wellbore casing. Accordingly, the liner hanger can be better secured to the wellbore casing. 
   In one aspect, one or more of the foregoing advantages may be achieved through the a liner hanger for securing to the inner wall of a wellbore casing and having an initial run-in position and a set position. The liner hanger comprises a mandrel having an inner wall surface defining a bore and an outer wall surface, the outer wall surface having at least one slip pocket, a plurality of spring slots, each spring slot having at least one spring disposed therein, and a piston housing, the piston housing having at least one piston disposed therein, wherein the piston is in fluid communication with the bore; and a slip housing disposed below the piston housing and each of the spring slots, the slip housing being slidingly engaged with the outer wall surface of the mandrel and having at least one slip operatively associated therewith, each of the at least one slips being disposed within a corresponding slip pocket, wherein the slip housing is held in the run-in position by the retainer so that each of the slips is disposed within each of the corresponding slip pockets, and wherein actuation of the piston causes the retainer to release the slip housing allowing each of the plurality of springs to move the slip housing upward axially from the run-in position to the set position which causes each of the slips to move upward axially and radially relative to the corresponding slip pockets and the mandrel to engage the inner wall of the wellbore casing. 
   A further feature of the liner hanger is that the mandrel may include a split ring groove and the retainer may be a split ring disposed within the split ring groove, the split ring being operatively associated with a key. Another feature of the liner hanger is that the slip housing may include an inner wall surface having a groove for receiving the split ring and a pocket for receiving the key and wherein the slip housing contacts each of the plurality of springs when the liner hanger is in the run-in position. An additional feature of the liner hanger is that the key may be in contact with the piston when the liner hanger is in the run-in position. Still another feature of the liner hanger is that the key may be held in place by a shear screw when the liner hanger is in the run-in position. A further feature of the liner hanger is that the key may include a body, a pair of opposed surfaces, a tab, and a shear screw hole for receiving the shear screw, the pair of opposed surfaces being matingly engaged with a corresponding pair of opposed shoulders on the split ring when the liner hanger is in the run-in position. Another feature of the liner hanger is that the line hanger may further comprise a spring adjustment sleeve for compressing and maintaining each of the springs within the corresponding spring slots when the liner hanger is in the run-in position. An additional feature of the liner hanger is that the spring adjustment sleeve may include threads on an inner wall surface of the spring adjustment sleeve. Still another feature of the liner hanger is that the liner hanger may further comprise an adjustment sleeve ring for securing the spring adjustment sleeve to the mandrel and wherein the spring adjustment sleeve includes a protrusion slidingly engaged with a slot on the mandrel for aligning the spring adjustment sleeve on the mandrel. A further feature of the liner hanger is that the adjustment sleeve ring may include a set screw for preventing the adjustment sleeve ring from loosening. Another feature of the liner hanger is that the adjustment sleeve ring may include threads for securing the adjustment sleeve ring to the outer wall surface of the mandrel. An additional feature of the liner hanger is that the spring adjustment sleeve may include a shoulder for abutting each of the springs. Still another feature of the liner hanger is that each of the plurality of slips may include a first end having a T-shaped protrusion that matingly engages with a T-slot in the slip housing. A further feature of the liner hanger is that the piston port may include a length and a vent port disposed along the piston port length and in fluid communication with the piston port and an environment outside the mandrel. Another feature of the liner hanger is that each of the springs may include a spring nail. An additional feature of the liner hanger is that each of the plurality of slips may include a gripping wall surface having pyramidal-shaped teeth. 
   In another aspect, one or more of the foregoing advantages may be achieved through an improved liner hanger having a run-in position and a set position. The improvement comprises a plurality of spring slots disposed on an outer wall surface of a mandrel, at least one of the plurality of spring slots having at least one spring disposed therein. 
   A further feature of the improved liner hanger is that each of the at least one springs may be held within the corresponding spring slots by a slip housing and a spring adjustment sleeve disposed on the outer wall surface of the mandrel when the liner hanger is in the run-in position. Another feature of the improved liner hanger is that the spring adjustment sleeve may include a shoulder disposed on an inner wall surface of the spring adjustment sleeve. An additional feature of the improved liner hanger is that the inner wall surface of the spring adjustment sleeve may include threads for securing the spring adjustment sleeve to the outer wall surface of the mandrel. 
   In an additional aspect, one or more of the foregoing advantages may be achieved through a method of setting a liner hanger within the wellbore casing of a well. The method comprises: (a) disposing a liner hanger within a wellbore, the liner hanger having an initial run-in position and a set position and the liner hanger comprising a mandrel having an inner wall surface defining a bore and an outer wall surface, the outer wall surface having at least one slip pocket, a split ring groove, a plurality of spring slots, each spring slot having at least one spring disposed therein, and a piston housing, the piston housing having at least one piston disposed therein, wherein the piston is in fluid communication with the bore, and a slip housing disposed below the piston housing and each of the spring slots, the slip housing being slidingly engaged with the outer wall surface of the mandrel and having at least one slip operatively associated therewith, each of the at least one slips having a gripping wall surface and being slidingly engaged within a corresponding slip pocket, wherein the slip housing is held in the run-in position by a retainer so that each of the slips is disposed within each of the corresponding slip pockets; (b) actuating the piston through an increase in pressure in the bore of the mandrel, wherein the actuation of the piston releases the retainer so that the slip housing is permitted to move axially along the outer wall surface of the mandrel and each of the springs is permitted to expand in an upward direction; and (c) expanding in the upward direction each of the springs sufficiently to move the slip housing axially in the upward direction so that each of the plurality of slips move axially in the upward direction causing each of the slips to move in the upward direction and in an outward direction so that the gripping profile surface of each of the slips bites into an inner wall surface of the wellbore casing. 
   A further feature of the method of setting a liner hanger within the wellbore casing of a well is that each of the slip pockets may include at least one groove for receiving at least one slip ramp disposed on at least one of the slips so that during step (c) movement of each of the slips is guided by the at least one groove. 
   The liner hangers disclosed herein have one or more the advantages of: providing an easy to assemble and disassemble liner hanger; providing a vent port for venting and oiling the piston such that the piston can be solid instead of having a passageway running the length of the piston; and providing an increase in the number of springs use to set the slips of the liner hanger, thereby providing a better initial bite of the slips into the wellbore casing. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1A  is a prospective and exploded view of the mandrel, spring adjustment sleeve, and sleeve adjustment ring of one specific embodiment of the liner hanger disclosed herein. 
       FIG. 1B  is a prospective view of a spring adjustment sleeve for use in another specific embodiment of the liner hanger disclosed herein. 
       FIG. 2A  is a partial cross-sectional view of a top portion of the mandrel of the liner hanger shown in  FIG. 1A . 
       FIG. 2B  is a partial cross-sectional view of a middle portion of the mandrel of the liner hanger shown in  FIG. 1A . 
       FIG. 2C  is a partial cross-sectional view of a bottom portion of the mandrel of the liner hanger shown in  FIG. 1A . 
       FIG. 3A  is a cross-sectional view of one specific embodiment of an assembled liner hanger disclosed herein shown in the run-in position and having the mandrel, spring adjustment sleeve, and sleeve adjustment ring shown in  FIG. 1A  and the mandrel shown in  FIGS. 2A-2C . 
       FIG. 3B  is a detailed cross-sectional view of the slip housing, key, split ring, and shear screw identified by reference number  3 B in the portion of the liner hanger shown in  FIG. 3A . 
       FIG. 3C  is a rotated cross-sectional view of the slip housing, key, and split ring shown in  FIG. 3B . 
       FIG. 3D  is a cross-sectional view of liner hanger shown in  FIG. 3A  shown in the set position. 
       FIG. 4  is an enlarged cross-sectional view of the piston housing identified by the reference number  4  in the portion of the mandrel shown in  FIG. 2B . 
       FIG. 5  is a partial cross-sectional view of the piston housing of the mandrel shown in  FIG. 2B  taken along line  5 - 5 . 
       FIG. 6  is a partial cross-sectional view of the piston housing and the spring slots of the mandrel shown in  FIG. 2B  taken along line  6 - 6 . 
       FIG. 7  is a cross-sectional view of a spring placed within a spring slot of the mandrel shown in  FIG. 1A . 
       FIG. 8  is a perspective view of the slip housing of one specific embodiment of the liner hanger disclosed herein. 
       FIG. 9  is a top view of a slip of one specific embodiment of the liner hanger disclosed herein. 
       FIG. 10  is a cross-sectional view of the slip shown in  FIG. 9  taken along line  10 - 10 . 
       FIG. 11  is a cross-sectional view of a split ring of one specific embodiment of the liner hanger disclosed herein. 
       FIG. 12  is a perspective view of the key of one specific embodiment of the liner hanger disclosed herein. 
       FIG. 13  is a cross-sectional view of the key shown in  FIG. 12  taken along line  13 - 13 . 
   

   While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
   DETAILED DESCRIPTION OF INVENTION 
   Referring now to  FIGS. 1-13 , in one specific embodiment, liner hanger  10  comprises body or mandrel  12  having bore  13 , upper end  14 , and a lower end  16 . Both upper end  14  and lower end  16  are in fluid communication with bore  13  and are adapted to receive additional components of string (not shown). For example, lower end  16  includes threads  18  for matingly engaging another component such as a packer (not shown). As shown in  FIG. 2A , upper end  14  also includes threads  18  for attachment to a blow-out preventer, diverter, Christmas tree, riser, tubing, casing, or other piece of equipment. 
   The outer wall surface  24  of mandrel  12  includes a plurality of slip pockets  26 , a plurality of spring slots  28 , piston housing  30 , and ring threads  32 . As shown in  FIGS. 1A ,  2 B,  3 A,  3 D,  5  and  6 , piston housing  30  is disposed between spring slots  28 . Each slip pocket  26  is designed to receive a slip  70 ; each spring slot  28  is designed to receive a spring  36 ; and ring threads  32  are for securing spring adjustment sleeve  38  by sleeve adjustment ring  40  having threads  41 . 
   Spring adjustment sleeve  38  is a cylindrical housing having an inner diameter that fits snuggly over spring slots  28  and piston housing  30 . On the inner surface of spring adjustment sleeve  38  is shoulder  37  for seating against one end of each spring slot  28  and, thus, one end of each spring  36  disposed in each spring slot  28 . During assembly of liner hanger  10 , after slips  70  and slip housing  60  are installed as discussed in greater detail below, springs  36  (also discussed in greater detail below) are placed in spring slots  28 . In so doing, one end of each spring  36  is held fast by slip housing  60 . Spring adjustment sleeve  38  is then slid over mandrel  12  until each spring  36  abuts shoulder  37  and also face  65  of slip housing  60  ( FIG. 8 ). Sleeve adjustment ring  40  is then slid over mandrel  12  until threads  41  contact with threads  32 . Sleeve adjustment ring  40  is then screwed onto mandrel  12  and spring adjustment sleeve  38  is slowly moved down the length of mandrel  12  causing each spring  36  to be compressed and, thus, energized. Alternatively, as shown in  FIG. 1B , spring adjustment sleeve  38  includes threads  35  or other securing structure on the inner wall surface of spring adjustment sleeve  38  so that sleeve adjustment ring  40  is not needed. 
   Because sleeve adjustment ring  40  and, thus, spring adjustment sleeve  38  can be easily and slowly installed and removed, liner hanger  10  can easily and safely be assembled and disassembled as necessary. Therefore, in situations where liner hanger  10  cannot be installed and cannot be repaired unless one or more of springs  36 , (discussed below), or split ring  80  (discussed below) being actuated or released as in prior liner hangers, in one aspect of the liner hanger  10  disclose herein, liner hanger  10  can be easily disassembled in a controlled and safe manner and without the need for releasing the split ring or actuating the piston. Further, liner hanger  10  can be easily reassembled without the need for fixturing tools that are needed to recompress the springs as in prior liner hangers. 
   In a preferred embodiment, mandrel  12  includes at least one, and preferably two, set screw slots  42  for guiding a protrusion, e.g., screw  39  (shown in  FIGS. 3A and 3D ), on sleeve  38  when spring adjustment sleeve  38  is being secured in place against springs  36  by sleeve adjustment ring  40 . Preferably, sleeve adjustment ring  40  includes set screw  43  (shown in  FIGS. 3A and 3D ) for restricting sleeve adjustment ring  40  from backing-off ring threads  32 . 
   Slip pockets  26  are spaced circumferentially apart from each other and around outer surface  24  of mandrel  12 . Each slip pocket  26  has a shape that is substantially reciprocal to a corresponding slip  70  (described in greater detail below) so that slip  70  is held within slip pocket  26  when liner hanger  10  is in its unset position ( FIG. 3A ) and so that slip  70  will be held fast when liner hanger  10  is placed in its set position ( FIG. 3D ), i.e., with each slip  70  biting into the wellbore casing (not shown). In an alternative embodiment, a portion of outer wall surface  24  has wickers (not shown) or other gripping profile adapted to facilitate gripping the inner wall of the wellbore casing. In other words, in this embodiment, slip pockets  26  and, thus, slips  70  do not completely cover the circumference of outer wall surface  24 . 
   As best shown in  FIGS. 1A ,  3 A and  3 D, each slip pocket  26  includes a length and a width that is smaller than its length and which may vary along its length as shown in  FIG. 1A . Preferably the depth of each slip pocket  26  along its length and its width is constant. Slip pocket  26  also includes slip grooves  27  ( FIGS. 1A ,  2 C, and  3 A) for receiving slip ramps  74  ( FIG. 9 ) which are described in greater detail below in relation to slip  70 . Slip grooves  27  provide a circumferential force component, or loading, of mandrel  12  when slips  70  are moved axially upward and, thus, extended radially into the wellbore casing. 
   Split ring groove  29  ( FIGS. 1A ,  2 B,  3 A, and  3 D) is disposed within outer wall surface  24  for receiving split ring  80  ( FIG. 11 ). Split ring groove  29  is disposed between slip pockets  26  and spring slots  28 /piston housing  30 . As discussed in greater detail below with respect to slip housing  60 , split ring  80  is held in place by key  90  disposed on the inner wall surface of slip housing  60  until piston  45  is actuated, forcing key  90  off of split ring groove  29  to release split ring  80 , causing springs  36  to expand and force slip housing  60  in the direction of the arrow ( FIGS. 3A and 3D ) and, thus, setting slips  70  into the wellbore casing. In this embodiment, split ring  80 , split ring groove  29  and key  90  are considered a retainer for retaining slip housing  60  in the run-in position ( FIG. 3A ). It is to be understood, however, that retainer can be any structural component or components known to persons of ordinary skill in the art for releasably retaining slip housing  60  in the run-in position ( FIG. 3A ). 
   Referring now to  FIGS. 4-5 , piston housing  30  includes piston port  44  that is in fluid communication with bore  13  through communication port  46 . Vent port  48  places piston port  44  in fluid communication with the outside environment so that piston port  44  can be vented and receive oil when piston  45  (shown in  FIG. 3A ) is disposed within piston port  44 . Thus, a solid piston  45  can be used instead of a piston having a longitudinal passageway through which pressure can be vented and oil can be injected. As shown in  FIG. 5 , vent port  48  transverses one or more spring slots  28 . Also, as shown in  FIG. 5 , piston housing  30  preferably includes two screw holes  50  for receiving screws (not shown) to secure the piston (shown in  FIG. 3A ) in piston port  44 . 
   In a preferred embodiment, piston  45  is retained within piston port  44  by a block retainer (not shown) disposed on the outside shoulder of piston housing  30 . The block retainer permits piston  45  to pass through the block retainer, but stops piston  45  from falling out of piston port  44 . Block retainers for pistons are known to persons skilled in the art. 
   Piston  45  can be any appropriately sized piston known by persons of ordinary skill in the art that is capable of actuating upon exposure to a pre-determined pressure and can release split ring  80  for setting slips  70  and, thus, installation of liner hanger  10  within a wellbore. In one embodiment, piston  45  includes rupture disk  47  (shown in  FIG. 3A ). Rupture disk  47  is designed to break-away at a predetermined depth due to hydrostatic pressure of the well fluid or fluid pressures applied by pumps at the surface of the well. Rupture disks  47  are known in the art. 
   As illustrated in  FIG. 6 , mandrel  12  includes a plurality of spring slots  28 . Each spring slot  28  is long and narrow so that each spring slot  28  receives at least one spring  36 . As shown in greater detail in  FIG. 7 , spring  36  preferably includes spring nail  52  having head  54  and shaft  58 . Spring  36  shown in  FIG. 6  is in its compressed or energized position. When released, as discussed in greater detail below, head  54  of spring nail  52  contacts slip housing  60  and moves slip housing  60  upward to set slips  70 . Although spring  36  can be designed to sufficiently move slip housing  60  without the need for spring nail  52 , the increased surface area contacting slip housing  60  by head  54  increases the distribution of force acting on slip housing  60  to better facilitate movement of slip housing  60 . 
   Referring now to  FIG. 8 , slip housing  60  includes slots  61 , preferably includes T-slots  62 , for receiving slips  70  ( FIGS. 9-10 ). As shown in  FIG. 8 , slip housing  60  is formed from three pieces secured together by, for example, screws (not shown) inserted through screw holes  64 . During shipment, slip housing  60  can be secured to outer wall surface  24  of mandrel  12  by fasteners such as a screw (not shown) disposed through hole  63  ( FIG. 8 ) and contacting spot-faced hole  31  ( FIG. 1A ). Prior to running liner hanger  10  into a well, the screw is removed so that slip housing  60  can move from its run-in position ( FIG. 3A ) to its set position ( FIG. 3D ). 
   Slip housing  60  includes split ring groove  66  and key slot  68 . Key slot  68  has shear screw hole  69  for receiving a shear screw  67  (shown in  FIGS. 3A and 3B ) to maintain key  90  (as shown in  FIG. 3A ) in place until piston  45  is actuated. 
   Each slip  70  ( FIGS. 9-10 ) is an elongated member with first end  71 , second end  72 , gripping wall surface  73 , and ramps  74 . Although, first end  71  may include having any design or shape known to persons of ordinary skill in the art to facilitate connection of slip  70  to slip housing  60 , in a preferred embodiment, first end  71  includes a T-shaped extension  75  for matingly engaging T-shaped slots  62  of slip housing  60 . It is to be understood, however, that first end  71 , as well as slip housing slots  61 , can have any shape desired for matingly engaging slip  70  with slip housing  60 . 
   Gripping wall surface  73  may have wickers or any other configuration that facilitates gripping wall surface  73  to grip or bite into the wellbore casing. For example, gripping wall surface  73  includes a plurality of pyramid-shaped “teeth”  78  as illustrated in  FIGS. 9-10 . Alternatively, gripping wall surface  73  may be profiled with grippers formed of carbide or other material, velcro material, ball bearings, or spray-on grit surfaces, or any other material that facilitates increased friction or provides surface penetration of the gripping wall surface  73  into the wellbore casing. In a preferred embodiment, gripping wall surface  73  is curved or convex, having the same curvature as mandrel  12  and wellbore casing (not shown). In one specific embodiment, gripping wall surface  73  is a cam surface causing a camming motion against the wellbore casing to facilitate securing hanger liner  10  to the wellbore casing. Gripping wall surface  73  may also include holes  79  for receiving carbide buttons (not shown) and/or for fixture purposes. 
   Split ring  80  is illustrated in  FIG. 11  as having opposed shoulders  82 ,  84  which are outwardly biased away from each other. In other words, a force is required to squeeze opposed shoulders  82 ,  84  toward one another. 
   Split ring  80  is held in its energized position, i.e., opposed shoulders  82 ,  84  are held close together, by key  90  shown in  FIGS. 12-13 . Key  90  has a body  91 , a pair of opposed surfaces  92 ,  94 , tab  96 , and shear screw hole  98  for receiving shear screw  67  (shown in  FIGS. 3A and 3B ).  FIG. 3C  shows key  90  with split ring  80  held by key  90 .  FIG. 3C  also shows the area through which split ring  80  slides as key  90  is moved by piston  45  to release split ring  80  as discussed in greater detail below. 
   Opposed surfaces  92 ,  94  engage shoulders  82 ,  84 , respectively, to hold the position of split ring  80  to a diameter that can effectively serve as an anchor when fixed in split ring groove  29 . Split ring  80  is held by key  90  within in split ring groove  29  and, thus, within ring groove  66  of slip housing  60 , and key  90  is held within key slot  68  of slip housing  60  by shear screw  67  until liner hanger  10  is actuated, i.e., set within the wellbore casing. 
   In setting liner hanger  10  within wellbore casing, pressure builds up within in bore  13  of the mandrel  12 . After sufficient pressure is reached, the pressure is communicated through communication port  46  to break rupture disk  47  which in turn actuates piston  45 . Piston  45 , which is in communication with tab  96 , forces key  90  upward in the direction of the arrow ( FIGS. 3A and 3D ). As a result, shear screw  67  is broken and key  90  moves in the direction of the arrow in  FIGS. 3A and 3D . As key  90  is pushed upward, opposed shoulders  82 ,  84  of split ring  80  slide out of and way from surfaces  92 ,  94  of key  90  and, as a result, split ring  80  is released from key  90  and expands outwardly to its original shape (shown in  FIG. 11 ) and into split ring groove  66  of slip housing  60 . 
   Due to the release of split ring  80 , slip housing is permitted to move and, therefore, springs  36  are permitted to expand and release their stored energy. Accordingly, each spring  36  expands with head  54  of spring nail  52  pushing slip housing  60  upward in the direction of the arrow in  FIGS. 3A and 3D . As slip housing  60  moves upward, each slip  70  within each slip pocket  26  is moved axially, however, slip ramps  74  slidingly engaged within slip grooves  27  force each slip to expand radially outward from mandrel  12  ( FIG. 3D ). Therefore, as slip housing  60  moves upward, each slip moves upward and outward so that gripping wall surface  73  bites into the inner wall surface of the wellbore casing. Thus, the entire actuation of liner hanger  10  from its initial or run-in position ( FIG. 3A ) to its set position ( FIG. 3D ) occurs in same direction which is believed to allow for setting of the liner hanger  10  with less force from springs  36 . 
   It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. For example, the piston housing and spring slots are shown as being formed from the same piece of material as the mandrel. However, the spring slots and piston housing could be formed by one or more pieces separately from the mandrel that is/are then secured to the outer wall surface of the mandrel. Additionally, actuation of the piston may be done through any device, e.g., rupture disk, or method, e.g., pumping fluid from the surface, known to persons of ordinary skill in the art. Moreover, the size and number of springs may be modified as desired or necessary to increase or decrease the total stored energy of the springs. Moreover, the slips may have any size and shape, and may include any type of gripping profile, desired or necessary to provide axially and radially extension to bite into the inner wall surface of the wellbore casing. Further, more than one piston may be utilized to push the key and release the split ring and one or more key may be utilized to hold the slip housing in place so that a heavier slip housing or heavier slips may be used in larger liner hangers. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.