Patent Abstract:
A method and apparatus for a drilling with casing includes therewith a drill shoe configured for later drilling through thereof in situ, with cutters retainable thereon in response to the forces encountered during borehole drilling, yet moveable from the envelope through which the later drill shoe will pass when cutting through the in situ drill shoe. The drill shoe includes one or more profiles thereon, into which blades carrying the formation drilling cutters are disposed. The profiles include at least one projection thereon, which is received within a mating slot in the blades. The blades also may be configured to have opposed sections which are configured with respect to one another to have an included angle of less than ninety degrees.

Full Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims benefit of co-pending U.S. Provisional Patent Application Ser. No. 60/450,432, filed on Feb. 27, 2003, which application is herein incorporated by reference in its entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    Embodiments of the present invention generally relate to the field of well drilling, particularly to the field of well drilling for the extraction of hydrocarbons from sub-surface formations, wherein the drill string is used as the well casing.  
           [0004]    2. Description of the Related Art  
           [0005]    The drilling of wells to recover hydrocarbons from subsurface formations is typically accomplished by directing a rotatable drilling element, such as a drill bit, into the earth on the end of tubing known as a “drill string” through which drilling mud is directed to cool and clean the drilling face of the drill bit and remove drilled material or cuttings from the borehole as it is drilled. After the borehole has been drilled or bored to its desired depth and location, the borehole is typically cased, i.e., metal tubing is located along the length of the borehole and cemented in place to isolate the borehole from the surrounding earth, prevent the formation from caving into the borehole, and to isolate the earth formations from one another. The casing is then perforated at specific locations where hydrocarbons are expected to be found, to enable their recovery through the borehole.  
           [0006]    It is known to use casing as the drill string, and, when drilling is completed to a desired depth, to cement the casing in place and thereby eliminate the need to remove the drill string from the borehole. However, when casing is used in place of the drill string, any equipment or tooling used in the drilling of the well must be removed from the interior of the casing to allow an additional, smaller diameter casing and drill bit to drill the borehole further into the earth. Thus, the drill bit or drill shoe located at the end of the drill string must be eliminated as an obstacle, without pulling the casing from the borehole. Removal of the drill shoe is typically accomplished by drilling through the drill shoe with a second drill shoe or drill bit extended into the previously cemented casing, and thence into the earth beyond the just drilled drill shoe. Thus the drill shoe needs to be configured of a drillable material, which limits the loading which can be placed on the drill shoe during drilling and thus limits the efficiency of drilling with the drillable drill shoe. Typically a “drillable” drill shoe is configured of a relatively soft metal, such as aluminum, with relatively hard inserts of materials such as synthetic diamond located thereon to serve as the cutting material. Additionally, although the main body of the drillable drill shoe is configured of a readily drilled material, the hard cutters of the drill shoe tend to cause rapid wear and physical damage to the drill shoe being used to drill through the previous drill shoe, thus reducing the life of the drill bit, and thus the depth of formation the drill shoe can penetrate before it too must be drilled through by an additional drill shoe directed through the casing.  
           [0007]    It is also known to provide a drill shoe having a relatively soft metal body, within which a plurality of stronger metal blades are received, upon which blades are supplied the cutters for cutting into the earth as the borehole progresses and which blades may be moved out of the area through which the drill shoe is drilled and subsequent casing penetrates, as is disclosed in U.S. Pat. No. 6,443,247, assigned to the assignee of the present invention and incorporated by reference herein in its entirety. This drill shoe includes an integral piston assembly therein, which, upon actuation by a drilling operator, pushes through the drill shoe and physically presses the harder metal blades, with the cutters thereon, into the annular area and/or the adjacent formation and out of the area through which the next drill shoe will pass. Thereafter, an additional drill shoe is passed down the existing casing to remove the remaining, relatively soft, metal mass of the drill shoe, and into the formation beyond the just drilled through drill shoe. Although this drill shoe configuration solves the problem encountered when the drill shoe would otherwise need to engage and grind up hard metal parts, the drill shoes still suffer from limited lifetimes because the blades will extrude or otherwise become separated from the relatively soft metal body of the drill shoe if the loading thereon exceeds a certain threshold. Thus, although this style of drill shoe has gained a high degree of commercial acceptance, the capability of the drill shoe remains limited.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention generally provides methods and apparatus for drilling of boreholes, wherein the drill string is used as the casing for the borehole, wherein the drill shoe used for drilling the borehole includes an integral displacement element whereby the cutting elements of the drill shoe are displaceable into the formation surrounding the drill shoe when the well is completed. The drill shoe includes one or more blades having cutters thereon, and each of the blades includes an engagement profile for secure engagement with the body of the drill shoe during drilling operation yet is readily deformed to be embedded into the formation adjacent the drill shoe when drilling is completed.  
           [0009]    In one embodiment, the blades include an outer axial section, a transverse section, and a generally axial base section that are received in a continuous slot formed within the body of the drill shoe. The slot and the blade include complementary profiles for maintaining the blades in position against the loading of the blades caused by the engagement thereof with the formation being drilled, while allowing the blades to be displaced into the formation after drilling is completed.  
           [0010]    To enable displacement of the blades into the formation, the drill shoe preferably includes a passageway therein through which the drilling mud is flowed, and which is selectively blocked while the drilling mud is continued to be pumped into the drill string. The blocking of the mud passages completes a piston structure, which is actuated through the drill shoe and thereby pushes the blades into the adjacent formation.  
           [0011]    In another aspect, the present invention provides an earth removal apparatus comprising a first body portion and a second body portion at least partially receivable within the first body portion. A profile is formed on an outer surface of the second body portion and a cutting member is engaged with the profile, wherein the profile is adapted to maintain the cuffing member on the profile during operation.  
           [0012]    In another aspect, the present invention provides an earth removal apparatus comprising a drillable body portion and at least one profile formed on an outer surface of the drillable body portion. The at least one profile including at least two intersecting faces, wherein one of the faces includes a projection thereon. A blade is matingly engageable with the at least one profile.  
           [0013]    In another aspect, the present invention provides a drill bit comprising a first body portion and a drillable second body portion. At least one profile is formed integral with at least one of the first body portion and the drillable second body portion, the at least one profile having at least two opposed segments having a discernable orientation. A cutting member is received in the at least one profile and having the discernable orientation and the discernable orientation including an included angle between the opposed segments of less than ninety degrees.  
           [0014]    In another aspect, the present invention provides a method of drilling with casing, wherein a drillable drill bit is provided, comprising providing a drill bit support at a lower end of the casing, locating a drillable body portion within the drill bit support, and providing a blade receiving member integral with at least one of the drill bit support and the body portion. The receiving member including a profile. The method also includes positioning a blade having a mating profile on the receiving member and using the drill bit to form a wellbore, wherein the profile is adapted to substantially maintain the blade on the blade receiving member during drilling.  
           [0015]    In another aspect, the present invention provides a method of completing a wellbore comprising providing an earth removal apparatus at a lower of a drill string. The earth removal apparatus having a first body portion and a drillable portion disposed in the first body portion, the drillable portion including a bore. The method also includes forming the wellbore, blocking the bore from fluid communication, moving the drillable portion relative the first sleeve portion, and re-establishing fluid communication between an inner portion of the earth removal apparatus and the wellbore.  
           [0016]    In another aspect, the present invention provides a downhole valve comprising a first body portion, a bore disposed through the first body portion, and an obstruction member retainer at least partially disposed in the bore, wherein the obstruction member retainer is adapted to cooperate with an obstruction member to provide selective fluid communication through the bore. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.  
         [0018]    [0018]FIG. 1 is a perspective view of a drill shoe of the present invention;  
         [0019]    [0019]FIG. 2 is a sectional view of the drill shoe of FIG. 1 in a downhole location;  
         [0020]    [0020]FIG. 3 is a sectional view of the drill shoe of FIG. 2, after the drill shoe has reached total depth and the drill shoe is prepared to be drilled through;  
         [0021]    [0021]FIG. 4 is a perspective view of a blade portion of the drill shoe of FIG. 1;  
         [0022]    [0022]FIG. 5 is a sectional view of the blade portion disposed on the notch of the drill shoe;  
         [0023]    [0023]FIG. 6 is a further sectional view of the blade portion disposed on the notch of the drill shoe;  
         [0024]    [0024]FIG. 7 is a sectional view of the drill shoe as shown in FIG. 2, after having been drilled through  
         [0025]    [0025]FIG. 8 shows another embodiment of a drill shoe according to aspects of the present invention;  
         [0026]    [0026]FIG. 9 shows yet another embodiment of a drill shoe according to aspects of the present invention; and  
         [0027]    [0027]FIG. 10 shows the drill shoe of FIG. 9 after the ball has extruded though the ball seat to re-establish circulation. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]    Referring initially to FIG. 1, there is shown in perspective an earth removal apparatus such as a drill shoe  10  of the present invention, for placement on the end of a string of casing for drilling a borehole into the earth, primarily for the recovery or potential recovery of hydrocarbons from sub-surface locations. The drill shoe  10  generally includes a support, such as a sleeve portion  20 , into which is received a drillable member, such as a body portion  30 , and over which are secured a plurality of cutting members or blades  26  (only four of a total of six to be so located) in notches  70  formed on the exterior of the drill shoe  10 . The drill shoe  10  is specifically configured to enable the drilling of a borehole with the drill shoe  10 , with subsequent cementing of the casing into the borehole, and then subsequent drilling through of the drill shoe  10  with a subsequent drill shoe  10 .  
         [0029]    Referring now to FIGS. 2 and 3, there is shown, in cross section, the drill shoe  10  of the present invention, suspended upon casing  12  located within a borehole  14 , which casing  12  is rotated by a drilling table, top drive, or similar apparatus (not shown) at the earth&#39;s surface to enable the drill shoe  10  to drill or cut into the formations encountered thereby and thus form the borehole  14 . The drill shoe  10  generally includes an outer, tubular sleeve  20  upon which a plurality of blades  26  are secured, and within which is positioned a body portion  30  of a drillable material, such as aluminum. In operation, the body portion  30  provides rigidity to prevent deformation of the sleeve  20  and maintain the drill shoe  10  on a threaded connection on the lower most extension of the casing in the wellbore as drilling operations are carried out, and also provides an extrusion element which may be pushed through the sleeve  20  and thereby push the blades  26  into the adjacent formation in the annular area and/or sides of the borehole  14  to enable drilling through of the drill shoe  10  during subsequent operations in the borehole  14 .  
         [0030]    Sleeve  20  is generally configured as a tubular or cylindrical element, and includes a first, threaded end  22  for threaded receipt upon the lowermost extension of the casing  12 , an outer, cylindrical face  24  upon which a plurality of blades  26  (preferably 6) are disposed, and a lower open end  28 . The inner cylindrical face of sleeve  20  includes a first, major diameter bore  34  extending from first end  22 , and a second smaller diameter bore  36  extending from a ledge  38  formed at the intersection of these two, collinear, bores. Within sleeve  20  is received the body portion  30  of a drillable material, such as aluminum, which forms a mass within the sleeve to maintain the shape of sleeve  20  as the drill shoe  10  is pushed against the bottom  16  of the borehole  14  and rotated. Sleeve  20  further includes a plurality of mud vents  37 , disposed radially through the sleeve  20  at the major diameter bore  34 .  
         [0031]    Body portion  30  is a generally right circular mass of drillable material, having features formed therein such as by machining, to provide a mass of material to back up the relatively thin wall of the sleeve  20  during drilling, to enable the extrusion of the body portion  30  through any potentially borehole interfering sections of the sleeve  20  and the blades  26  when the drilling is completed with the drill shoe  10 , and to provide a readily drillable material for removal of the mass from the borehole  14 . Body portion  30  generally includes a main counterbore  40  extending inwardly of the first end  42  thereof, and ending at a generally conically concave base  44  from which a mud bore  46  extends inwardly of the backup portion of body portion forming backup mass to limit the deformation of the sleeve  20  and the blades  26  during drilling operations. Mud bore  46  splits into a plurality of mud passages  50 , which terminate at the lower surface of the body portion  30 . Mud bore  46  also includes a tapered seat portion  52 , into which a ball  51  (FIG. 2) may be seated, as will be further described herein. The outer surface of body portion  30  includes a generally right circular outer face  54 , and an end portion  56  which is profiled and machined to receive a portion of the blades  26  therein, as will be described further herein. Outer face  54  includes, at the opening of the counterbore  40 , a outwardly extending lip  58  which sealingly, or at least is substantially closely, fits to the inner face of major diameter bore  34 , as well as at least one axial slot  60 , extending along the outer face  54  from the end portion  56 . A pin  62  is secured within sleeve  20  and extends into slot  60 , and serves to prevent rotation of the body portion  30  within sleeve  20  when a different drill bit introduced down the casing interior drills the body portion  30  out.  
         [0032]    To retain the body portion  30  within sleeve  20 , the sleeve  20  includes a retainer ring  64 , located within major diameter bore  34  generally above the body portion  30  and secured thereto with pins or the like, which prevents retraction of the body portion  30  from the sleeve  20 , and an inwardly projecting lip  66 , extending inwardly at the lower open end thereof, which is received into an annular recess  68  machined or cast into the face of body portion  30  about its perimeter (best shown in FIG. 3). Lip  66  may be a continuous inward projection on the end of the sleeve  20 , or may be a separate retainer ring which is affixed at its inboard end to the end of sleeve  20 .  
         [0033]    Referring again to FIG. 1, a general overview of the structure of the blades  26 , as well as their attachment to the drill shoe  10 , is shown. Generally, the blades  26  are received within a profile which extends along the outer surface of the sleeve  20  and the base of body portion  30 . An exemplary profile is a notch  70  configured to interact with the blade  26  to keep the blade  26  in position on the sleeve  20  during drilling operation. Each blade  26  is formed of a single length of steel, or similar material having both relatively high strength, rigidity and ductility, bent to form opposed first and second linear sections  72 ,  74 , which are interconnected by curved shoulder segment  76 . A plurality of cutters  78  are located on the outer face of the blades  26 , to be engaged with, and cut into, the formation as the borehole extends therein. Although six blades  6  are shown in the Figures, it is contemplated that any suitable number of blades  26  may be disposed on the drill shoe  10 . For example, the drill shoe  10  may include four blades or five blades.  
         [0034]    The interface and interconnection of the blade  26  and notch  70  is shown in detail in FIGS. 5 and 6, wherein the blade  26  is generally rectangular in cross section, and includes a multifaceted base  80  which contacts a multifaceted first face  82  of the notch  70 , and a sidewall  84  which abuts against a second face  86  of the notch  70 . Multifaceted base  80  includes a centrally located, generally rectangular, slot  88  extending therein over the length thereof, into which a mating rectangular projection  90  of the notch  70  extends, along the entire length of the blade  26 . Projection  90 , being generally rectangular in cross section, forms in conjunction with multifaceted first face  82  a first compression face  104  extended upwardly on projection  90 , and first and second lower compression faces  106 ,  108 , disposed to either side of first compression face  104 , an anti-rotation flank  100  in facing relationship to second face  86  of notch  70 , and a secondary abutment face  93 , on the opposed flank of the projection from anti rotation flank  100  and generally parallel thereto and to second face  86  of the notch  70 .  
         [0035]    Referring again to FIG. 1, to create the multifaceted notch  70 , a continuous groove (not shown) is cut into the outer face of both the sleeve  20  and body  30 , into which preforms  112  and  114 , having the specific geometry of the notch  70  provided therein, are inserted and welded into place. Alternatively, the preform  114  in body portion  30  may be created by directly molding a boss into the body portion  30  when the body portion  30  is initially configured such as by aluminum casting, and then machining the specific geometry of the notch  70  therein. Alternatively still, the preforms  112 ,  114  may be formed into both the sleeve  20  and the body portion  30  by machining. Additionally, the outer surface of the sleeve  20  includes stabilizers or standoffs  132 , positioned at the uppermost terminus of the notch  70 , having a height corresponding generally to the height of the cutters  78  on the first linear section  72  of the blades  26 , to center or stabilize the drill shoe  10  in the borehole  14 .  
         [0036]    Referring now to FIGS. 5 and 6, the blade  26  includes geometry complimentary to the notch  70 , such that slot  88  projecting into multifaceted base  80  creates a multi level engagement surface, including a recessed face  91  and two extended faces  92 ,  94 , generally parallel thereto and extended therefrom by the depth of the slot  88 , as well as first projecting face  96  and second projecting face  98 , formed as the flanks of the slot in a facing, generally parallel relationship to one another and to the sidewall  84 . The depth of slot  88  is variable, such that the slot  88  is deeper, and thus the area of faces  96  and  98  are greater, in second linear section  74  of the blade  26  which, in use, is located within the notch  70  received in the body portion  30  of the drill shoe  10 . Likewise, as shown in FIG. 5, the height of sidewall  84  is increased to maintain a larger area for full depth contact between sidewall  84  and second face  86 . As it is specifically contemplated that the body portion  30  is configured from an easily drillable material, which will likely have a lower shear or yield resistance than the material used for the sleeve  20 , this larger area of the faces (and correspondingly of sidewall  84 ) helps distribute the load in the notch  70  over a greater area in the body portion  30  as compared to the sleeve  20 , and thereby reduce the likelihood of plastic failure of the notch  70  as it extends in the body portion  30  under drilling conditions. As shown in FIGS. 5 and 6, the aspect ratio of the slot  88  (and correspondingly in the mating surfaces of the notch  70 ), and likewise of the projection  90 , defined as the height of the projection (or depth of slot) to its width, ranges in the embodiment shown from slightly over 1:1 at the first linear section  72  of the blade  26 , to approximately 2:1 at the second linear section  74  of the blade  26 . It is contemplated that higher aspect ratios are appropriate, for example, where the blade is very large in width, i.e., the circumferential direction of the sleeve  20 , for example on the order of 5 inches wide, a slot depth of only 0.010 inches may be appropriate, resulting in an aspect ratio of 0.002:1. Likewise, were the blade made relatively tall, a high aspect ratio on the order of 500:1 may be appropriate.  
         [0037]    Received upon the outer surface of the blade  26  are a plurality of cutters  78 , typically hardened synthetic diamond compacts, which are attached thereto using welding, high strength adhesives, threaded engagement into bores in the blade  26 , or the like. To secure the blade  26  and fill the gaps or clearances between the blade  26  in the notch  70 , adhesive or filler, such as Tubelok available from Weatherford Corporation of Houston, Tex., is applied to the blade  26  and notch  70 , and the blade  26  pushed therein. It is specifically contemplated that the fit of the blade  26  in the notch  70  not be an interference fit at ambient temperatures, and that a clearance on the order of a few thousands of an inch between the slot  88  and projection  90  is allowable as long as the fit is snug.  
         [0038]    During drilling operation, the drill shoe  10  rotates generally about axis  120  (FIG. 2) such that, as shown in FIG. 5, the blade  26  moves in the direction of arrow  122  into engagement with the formation. As a result, force will be imparted against the blade  26  as shown by arrow  124 , tending to cause the blade  26  to rotate (or load in the notch  70 ) as shown by arrow  126 . The configuration of the blade  26  and notch  70  are specifically provided to prevent such motion. Thus, as this loading occurs, sidewall  84  is pushed against second face  86  of the groove, and first projecting face  96  bears against secondary abutment face  93  of groove, to provide lateral or direct support against the primary load of the formation, simultaneously, second projecting face  98  is coupled, by the moment caused by the loading of the blade  26  at the cutters  78 , against anti-rotation flank  100 , and each of the faces  91 ,  92  and  94  of the blade  26  are loaded by the moment against their respective compression faces  104 ,  106  and  108 , thereby preventing significant movement of the blade  26  in the notch  70 . Thus, as force is imparted against the blade  26  in the direction of the arrow  126 , any tipping or rotation of the blade  26  will be absorbed by the notch  70 . To secure the blade  26  on the sleeve  20 , the blade  26  is welded thereto at one or more locations along its length.  
         [0039]    The blade geometry, in addition to the blade profile helps maintain the blade  26  on the sleeve  20 . During drilling operations, it is unlikely that the entire length of a blade  26  will be simultaneously engaged against the formation. Furthermore, the presence of standoffs  132  on the sidewall of the sleeve  20  limits the penetration of the cutters  78  on the first linear section  72  of the blade  26 . Thus, when the drill shoe  10  is pushing against the bottom of the borehole  14 , the second linear section  74  of the blade  26  will be engaged with the formation, whereas the other portions may not. Thus, force will be imparted against the second linear section  74  of the blade  26 , tending to cause it to tip or rotate in the notch  70  in the direction of arrow  126  (FIG. 5). However, it can be seen from FIG. 4 that the geometry of the blade  26  results in the first linear section  72  and curved segment  76  being levers, with respect to the second linear section  74 , and the placement of these portions of the blade  26  within the notch  70  will cause these portions of the blade  26 , along with the structural rigidity of the blade  26 , to help the blade  26  resist rotating out of the notch  70 . Additionally, the included angle  136  between the two linear sections  72 ,  74 , is preferably maintained below 90 degrees, which further enhances the likelihood of maintaining the blade  26  in the notch  70 . As the outer face  138  of the blade  26  is preferably parallel with the recessed face  91  and two extended faces  92 ,  94  of the blade  26  which rest at compression faces  104 ,  106  and  108  of the notch  70 , the included angle  136  is repeated between these faces as well.  
         [0040]    Referring again to FIGS. 2 and 3, the operation of the drill shoe  10  for using the casing  12  as drill string is shown. Specifically, when the borehole  14  has reached total depth for the specific drill shoe  10  in use, which is a function of the wear of the drill shoe  10 , the casing  12  is pulled upwardly in the borehole  14 , to leave a space between the drill shoe  10  and the bottom of the hole  14  as shown in FIG. 2. In this position, drilling mud continues to flow down the middle of the casing  12 , and thence outwardly through the mud passages  50  in the drill shoe  10  and thence to the surface through the space between the drill shoe  10  and casing  12  and the borehole  14 .  
         [0041]    To begin the operation ultimately leading to the elimination of the drill shoe  10  as an obstacle in the borehole  14 , a ball  51  is dropped through the casing  12  into the mud bore  52  from a remote location, which can include the earth&#39;s surface. When the ball  51  enters the mud bore  52 , it seals the mud bore  52  causing the mud to press down upon the body portion  30 , and causes the body portion  30  to slide within sleeve  20  from the position of FIG. 2 and FIG. 3. As the body portion  30  begins to slide, it deforms the base of sleeve  20  outwardly, and also deforms the second section  74  about the angled portion  76  of the blade  26  such that the blades  26  are bent into a generally linear condition as shown in FIG. 3. In one embodiment, the second section  74  may be embedded within the walls of the borehole along with the likewise deformed base of the sleeve  20 . In another embodiment, it may that a clearance exists between the wall of the borehole and the second section  74 . Movement of the body portion  30  within the sleeve  20  to the position shown in FIG. 3 also exposes the mud vents  37  to the drilling mud, thereby providing a new path for mud flow to re-establish circulation. In this respect, the new path may be used to introduce cement into the borehole to cement the casing  10 . In one embodiment, cement may be supplied through the mud vents  37  to cement at least a portion of the casing  10  into place. Additionally, re-establishing the new path also causes a pressure drop in the mud column, which indicates to the operator that the body portion  30  successfully moved within the sleeve  20  to bend the blades  26  outwardly. Thereafter, a subsequent drill bit or drill shoe is passed down the casing  12 , and is engaged into body portion  30  to drill through body portion and continue the drilling of the borehole  14  to further depth as shown in FIG. 7.  
         [0042]    [0042]FIG. 8 presents another embodiment of the drill shoe according to aspects of the present invention. The drill shoe  10  includes a sleeve  220  having a body portion  230  disposed therein. The body portion  230  comprises a support sleeve  235  and an inner portion  240 . The inner portion  240  may include components such as the ball seat  252  and the inner core  245 . In one embodiment, the ball seat  252  and the inner core  245  may be two separate components, as shown in the Figure. In another embodiment, the inner portion  240 , e.g., the ball seat  252  and the inner core  245 , may be manufactured in one piece, as shown in FIG. 2. Preferably, the inner portion  240  comprises a drillable material such as aluminum, and the support sleeve  235  comprises steel or other composite material of sufficient strength to provide rigidity to the body portion  230 .  
         [0043]    [0043]FIG. 9 presents another embodiment of the drill shoe  10  according to aspects of the present invention. As shown, the drill shoe  10  provides an alternative method of re-establishing circulation. The drill shoe  10  includes a body portion  330  disposed in an outer sleeve  320 . One or more blades are disposed on the outer surface of the outer sleeve  320  and the lower surface of the body portion  330 . The body portion  330  includes a bore  346  which splits into one or more passages for fluid communication with the borehole  14 . The bore  346  may include an obstruction member retainer for retaining an obstruction member. For example, the bore  346  may include a ball seat  352  for receiving a ball  351 . Preferably, the ball seat  352  comprises a flexible material such that the ball  351  may be pumped through the ball seat  352  when a predetermined pressure is reached. The bore  346  also includes a biasing member  360  such as a spring  360  disposed below the ball seat  352 . The spring  360  may be used to bias the ball  351  against the ball seat  352  to act as a valve to regulate fluid flow in the bore  346 . Although a ball seat is disclosed, other types of obstruction member retainer known to a person of ordinary skill in the art are contemplated, for example, an obstruction member retainer having a seating surface for receiving an obstruction member to regulate fluid flow.  
         [0044]    [0044]FIG. 9 shows the drill shoe  10  after drilling has completed and the body portion  330  has deformed the base of the sleeve  320  outwardly. Particularly, a ball  351  landed in the ball seat  352  to allow pressure build up, thereby causing the body portion  330  to slide downward relative to the sleeve  320 . As a result, the second section of the blades is bent into a generally linear condition.  
         [0045]    To re-establish circulation, pressure above the ball  351  is increased further to pump the ball  351  to through the flexible ball seat  352 , as shown in FIG. 10. The ball  351  lands on the spring  360 , which biases the spring  360  against the lower portion of the ball seat  352 , which acts as a second seating surface for the ball  351 . In this respect, a seal is formed between the ball  351  and the ball seat  352 , thereby closing off fluid communication.  
         [0046]    When the pressure of the cement or other fluid in the casing  12  is greater than the biasing force of the spring  360 , the ball  351  may be caused to disengage the ball seat  352 , thereby opening up the bore  346  for fluid communication with the borehole  14 . In this manner, cement may be supplied to cement the casing  12  in the borehole  14 . After the cementing operation is completed, pressure in the casing  12  is relieved. In turn, the spring  360  is again allowed to bias the ball  351  against the ball seat  352 , thereby closing off the bore  346  for fluid communication. In this respect, the ball  351  and the ball seat  352  may act as a check valve to prevent cement or other fluid to re-enter the casing  12 .  
         [0047]    Although the invention has been described herein with respect to a specific embodiment, these embodiments may be modified without affecting the scope of the claims herein. In particular, the groove and slot configuration may be modified. For example, the slot may be positioned in the groove and the blade may include the projection, or alternatively, several slots and mating projections may be provided.  
         [0048]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Technology Classification (CPC): 4