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This application claims the priority of U.S. Provisional Patent Application Ser. No. 60/700,555 filed Jul. 19, 2005. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates generally to devices and methods for conducting liner drilling and subsequent completion of the drilled section by securing the liner into place by anchoring and cementing. 
   2. Description of the Related Art 
   In its basic form, a wellbore is drilled using a drill bit that is attached to a drill string fashioned of drill pipe. When the wellbore is drilled to an original desired depth, the drill string and bit are removed from the hole. Then steel casing is inserted into the borehole and cemented in place as a protective tubular sheath to prevent collapse of the borehole wall. The term “casing,” as used herein will refer to those protective sheaths that extend along a portion of the wellbore all the way to the surface. The well can then be drilled to deeper depths in successively smaller diameter intervals below the original depth. These lower intervals are then lined with wellbore liners. As used herein, the term “liner” will refer to those protective sheaths that extend along a portion of the wellbore, but do not extend all the way to the surface. 
   In addition to traditional drilling using drill strings made up of drill pipe, techniques have been developed recently for casing drilling and liner drilling. In casing drilling, the bottom hole assembly containing the drill bit is threaded to a section of casing and, after drilling, the casing is hung at the top of the wellbore. Liner drilling is a similar concept. In liner drilling, the liner to be cemented in serves as a part of the drilling string while traditional drill pipe usually forms the upper part of the drill string. The bit can be attached to the liner and the liner then rotated within the borehole. Alternatively, a mud motor is attached to liner and the mud motor is used to turn the bit while the liner remains stationary. When liner drilling is completed, the drill pipe portion of the drill string is detached from the liner and withdrawn from the wellbore. The liner portion of the drilling string remains in the borehole, set on the bottom of the hole and is later cemented into place. The bit and mud motor are also left in the hole. 
   A significant problem with this conventional liner drilling process is that the liner can deform by bending or corkscrewing under its own weight when set down on bottom. This is especially true of very long liners. If the liner is cemented in this condition, it will be permanently deformed and perhaps be unusable for passing large diameter tools through. For this reason, a number of “one-trip” liner drilling arrangements have been developed that incorporate liner hangers into the drilling string on the upper end of the liner so that the liner can be anchored to the pre-existing casing after cementing. An example of a “one-trip” liner drilling system is described in U.S. Pat. No. 5,497,840, issued to Hudson. 
   A major problem with “one trip” liner drilling systems is their ability to return drill cuttings to the surface of the wellbore. The liner portion of the drill string has a much greater diameter than traditional drill pipe. As a result, the annulus surrounding the liner portion is quite small, leaving little room for pumped down drilling mud and generated cuttings to return to the surface of the well. While this problem is inherent to the process of liner drilling, it is made substantially worse by the presence of any exterior components that extend outwardly into the annulus beyond the diameter of the liner. Thus, externally mounted hangers or packers, that might be used to hang the liner in tension from the casing or liner above could not be run in with the liner during the drilling operation without destroying the ability to drill and remove cuttings effectively during drilling. Thus, there is a need to be able to conduct liner drilling with minimal exterior components to allow annular bypass of returning drilling mud and cuttings. 
   The present invention addresses the problems of the prior art. 
   SUMMARY OF THE INVENTION 
   The invention provides improved methods and systems for conducting liner drilling and subsequent completion of the drilled section by cementing and anchoring the liner into place. The methods and systems of the present invention prevent the liner from being cemented in in a bent or corkscrewed configuration. Additionally, the systems and methods of the present invention minimize the number of exterior components associated with the liner during drilling so as to allow relatively unrestricted return of drilling mud and cuttings. 
   In accordance with preferred embodiments of the invention, a liner is drilled into a wellbore below original depth using a running tool. A liner setting sleeve having a substantially smooth exterior is affixed to the top of the liner, thereby permitting substantially unrestricted annular bypass and minimal exterior mechanical complexity during drilling. Once the target depth has been reached, the liner is set on the bottom of the hole and the liner setting tool is released from the liner. The running string is then withdrawn from the hole. Next, a liner hanger/packer assembly is run into the hole. The liner hanger/packer assembly has a latch-in seal assembly to latch into the liner setting sleeve. Once, latched, the liner is lifted off the bottom of the hole. A liner packer is then set to hang the liner in tension. Thereafter, the liner may be anchored to the casing above and cemented into place within the wellbore in a substantially straight and true condition. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein: 
       FIG. 1  is a schematic side, cross-sectional view of an exemplary borehole being drilled from the original depth to a lower interval using liner drilling. 
       FIG. 2  is a schematic side, cross-sectional view of the borehole shown in  FIG. 1  now with the running tool being removed. 
       FIG. 3  is a schematic side, cross-sectional view of the borehole of  FIGS. 1 and 2  now with a liner hanger/packer assembly being latched into the liner setting sleeve. 
       FIG. 4  is a schematic side, cross-sectional view of the borehole of  FIGS. 1-3  now with the liner being picked up off the bottom of the borehole. 
       FIG. 5  depicts the setting of a liner packer to hang the liner in tension. 
       FIG. 6  depicts a cementing operation to secure the liner in place. 
       FIG. 7  is an enlarged, cross-sectional side view of the liner setting sleeve. 
       FIG. 8  is an enlarged, cross-sectional side view depicting the running tool attached to the liner setting sleeve. 
       FIG. 9  is an enlarged, partial cross-sectional side view showing the liner hanger/packer latched into the liner setting sleeve. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  depicts an exemplary wellbore  10  that has been drilled from the surface  12  through the earth  14  to an original depth  16 . Metallic casing  18  has been cemented in the wellbore  10  from the surface  12  down near the original depth  16 . A liner drilling system  20  has been inserted into the wellbore  10  from a drilling rig  22  at the surface  12 . In  FIG. 1 , the liner drilling system  20  is drilling a deeper interval portion  24  of the wellbore  10 . The liner drilling system  20  includes a bottom hole assembly  26  with a drill bit  28  thereupon. The bottom hole assembly  26  is attached by a landing collar  30  to a section of liner  32 . The liner section  32  is of a length that approximates the length of the deeper interval portion  24  to be drilled. Secured to the upper end of the liner section  32  is a liner setting sleeve  34 . The liner setting sleeve  34  is shown in greater detail in  FIG. 7 . It is noted that the liner setting sleeve  34  has a smooth external radial surface  36  and is affixed by a threaded connection  38  to the upper end of the liner section  32 . It is noted that, although the liner setting sleeve  34  is depicted as having a greater outer diameter than the liner  32 , the diametrical increase is, in actuality, very small, and presents no obstacle to the passage of drilling mud and cuttings. The liner setting sleeve  34  defines a latching groove  39  within. A suitable liner setting sleeve is the HRD™ Liner Setting Sleeve, which is available commercially from Baker Oil Tools of Houston, Tex. A short PBR (polished bore receptacle)  40  is secured to the upper end of the liner setting sleeve  34 . 
   The liner drilling system  20  also includes a length of running string formed of drill pipe  42  that extends downwardly from the drilling rig  22  and is secured to the liner setting sleeve  34  and PBR  40  at its lower end.  FIG. 8  illustrates an exemplary releasable interconnection between the drill pipe running string  42  and the liner section  32 . A packoff  44  is disposed within the PBR  40  to secure the two components together. A hydraulic releasing tool  46  is also disposed within the PBR  40  and setting sleeve  34 . Suitable commercially available devices for use as the packoff  44 , setting sleeve  34 , and hydraulic releasing tool  46  are those within a standard HRD™ Hydraulic Release Setting Tool, which is available commercially from Baker Oil Tools of Houston, Tex. With further reference to  FIG. 8 , it is noted that the drill pipe running string  42  defines a central flowbore  48  for passage of drilling mud downwardly to the drill bit  28 . During drilling, drilling mud is pumped downwardly through the central flowbore  48  and drilling mud and drill cuttings are circulated upwardly through the annulus  50  to the surface  12 . Because there are no external packers or hangers on the drilling system  20 , the cuttings and mud have a substantially unrestricted return path through the annulus  50 . 
     FIG. 2  shows the wellbore  10  now drilled to the deeper interval portion  24 . The drill pipe running string  42  has been released from the liner portion  32  by actuation of the hydraulic releasing tool  46  and is being removed from the wellbore  10 . At this point, the liner portion  32 , bottom hole assembly  26  and bit  28  are resting on the bottom  52  of the drilled deeper interval portion  24  of the wellbore  10 . The liner portion  32  may become deformed in this condition by bending, buckling, or corkscrewing. 
     FIG. 3  illustrates the next step in the liner drilling process wherein a latching liner hanger assembly  54  is run into the wellbore  10  on a drill pipe running string  55  to be secured to the upper end of the liner portion  32  by latching engagement.  FIG. 9  illustrates the latching arrangement and the latching liner hanger assembly  54  in greater detail. The latching liner hanger assembly  54  includes a liner packer  56  having an elastomeric sealing element  58  that is set by axial movement upon ramped surface  60 . The packer  56  is preferably actuated hydraulically, in a manner that is known in the art. The hanger assembly  54  also includes a set of anchoring slips  62  that are moveable radially outwardly to form a biting engagement with a surrounding tubular member. The slips  62 , like the packer  56 , are preferably hydraulically actuated. In addition, the hanger assembly  54  includes a latching sub  64  at its lower end. The latching sub  64  includes a set of collets  66  with radially outward projections  68  that are shaped and sized to reside within the groove  39  of the liner setting sleeve  34 . 
     FIG. 4  shows the subsequent step of lifting the liner  32  off the bottom  52  so that the liner  32  is hanging in tension. Because the liner  32  is hanging in tension, the deformations from corkscrewing or bending are undone. At this point, the hanger assembly  54  is actuated to urge the slips  62  and sealing element  58  of the packer  56  radially outwardly and into engagement with the casing  18 . This ties the liner  32  in with the casing  18  above. In  FIG. 5 , the liner packer  56  and slips  62  are now in the set position. 
     FIG. 6  illustrates the step of cementing in the liner  32 . Conventional cementing techniques are used to circulate cement down through the flowbore of the drill pipe running tool  55 , as depicted by arrows  70 . The cement then passes through the liner  32  and the bit  28  to be deposited at the bottom  52  of the wellbore  10 . From there, placed cement  72  will rise to fill in the annular space  74  between the liner  32  and the sidewalls of the extended length portion  24  of wellbore  10 . The interior of the drill string running tool  55  and the liner  32  are then cleaned using wiper darts of a type known in the art. As the techniques of cementing in liners are well known to those of skill in the art, they will not be described in further detail herein. 
   After the completion of cementing, the drill string running tool  55  is then removed from the latching liner hanger assembly  54 . This is usually accomplished by rotating the drill string running tool  55  to unthread the hanger assembly  54  and then withdrawing the running tool  55  from the wellbore  10 . 
   Those of skill in the art will recognize that the methods and systems of the present invention provide a number of advantages over conventional liner drilling and placing systems. First, they help ensure that the liner  32  will not be deformed from compression bending or corkscrewing at the time that it is cemented in or anchored to the casing  18 . As a result, there will be fewer subsequent problems with running large diameter tools through the liner  32  at a later point in development of the wellbore  10 . Additionally, the liner drilling process is made more effective because there is a minimum complication of the annulus  50  during the drilling phase. There are no external packers or slips associated with the liner  32  during the drilling phase, and therefore, the cuttings and mud can more easily reach the surface  12 . 
   Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.

Summary:
Methods and systems for conducting liner drilling and subsequent completion of the drilled section by cementing and anchoring the liner into place. The methods and systems prevent the liner from being cemented in in a bent or corkscrewed configuration. Additionally, there are no exterior components associated with the liner during drilling so as to allow relatively unrestricted return of drilling mud and cuttings.