Abstract:
A method of anchoring tubing in a bore comprising: providing tubing having a section with outer surface portions defining a tubing profile, and configured to describe an outer diameter less than a first diameter. The tubing is located within a bore having an internal diameter equal to the first diameter and defining a bore profile. The tubing is then reconfigured such that the tubing profile engages with the bore profile, anchoring the tubing within the bore.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    A recent development in the oil and gas exploration and production industry has been the adoption of expandable bore-lining tubing. This involves running tubing into an open section of bore and then expanding at least a portion of the tubing to a larger diameter. Typically, the upper end of the tubing will overlap the lower end of existing bore-lining casing or liner. In a number of proposals, the upper end of the tubing is expanded initially to create a tubing hanger which serves to fix the tubing in the bore so that the tubing may be disengaged from the running string used to carry the tubing into the bore. Other operations, such as cementing the tubing, or expanding other portions of the tubing, may then take place.  
           [0002]    The present applicant has identified that there are certain difficulties involved in creating the initial anchor, particularly in previously cemented tubing. A number of existing proposals suggest the use of radially extendable members for radially extending circumferentially spaced portions of the tubing, to bring the outer surfaces of these portions into engagement with the surrounding casing. However, in any such deformation of metallic tubing, there is a degree of elastic recovery of the tubing once the deforming force has been removed. Thus, the desired degree of engagement between the tubing and the casing may not be achieved.  
         Field of the Invention  
         [0003]    This invention relates to tubing anchors. In particular the invention relates to an apparatus and method of anchoring one tubing within another, most particularly at a downhole location.  
         SUMMARY OF THE INVENTION  
         [0004]    According to a first aspect of the present invention there is provided a method of anchoring tubing in a bore, the method comprising:  
           [0005]    providing tubing having a section having outer surface portions defining a tubing profile, the outer surface portions configured to describe an outer diameter less than a first diameter;  
           [0006]    locating the tubing within a bore having an internal diameter equal to the first diameter, and defining a bore profile; and  
           [0007]    reconfiguring the tubing section such that the tubing profile engages with the bore profile.  
           [0008]    Preferably, the tubing profile defines a radially extending surface and the bore profile defines a cooperating radially extending surface. The tubing profile may be a radial projection and the bore profile a radial recess.  
           [0009]    Preferably, the tubing profile is defined by a plurality of radial projections and the bore profile a one or more of radial recesses. Alternatively, the tubing profile may be a circumferential rib.  
           [0010]    In an alternative embodiment the bore profile may be defined by one or more radial projections and the tubing profile by one or more radial recesses. Conveniently, the bore profile may be a circumferential rib and the tubing profile a circumferential channel.  
           [0011]    When the tubing section is reconfigured, the outer surface portions are moved radially outwardly such that the tubing profile may engage with the bore profile, securing the tubing in the bore. Further reconfiguration of the tubing section may bring further parts of the outer surface portions into contact with the bore, which will further assist in securing the tubing in the bore.  
           [0012]    The method of the invention thus provides a convenient method of creating a coupling between a tubing and a surrounding bore wall, which coupling may be utilised to fix the tubing relative to the bore, both axially and rotationally, to facilitate subsequent operations, such as further reconfiguration or deformation of the tubing, or cementation of the tubing in the bore. The outer surface portions of the tubing may be circumferentially spaced, and most preferably are regularly spaced around the circumference of the tubing. Alternatively, the outer surface portions may be defined by a substantially continuous arc or segment. The tubing may initially be circular and in this initial form preferably has an outer diameter at least as large as the first diameter. Portions of the initially circular tubing wall may be reconfigured to a generally planar form such that the tubing is then substantially polygonal, most preferably defining a pentagon or hexagon. The tubing may then be further reconfigured such that the planar tubing wall portions become convex, and are located between the outer surface portions, which describe the tubing maximum diameter, which is less than said first diameter. The tubing may then be passed into the bore. Alternatively, one or more indents may be formed in the tubing wall, to create one or more convex wall portions such that the tubing defines an outer diameter less than said first diameter. Of course the tubing may be initially created in this form, if desired.  
           [0013]    If a radially outwardly directed force is then applied to the one or more convex wall portions, which will typically describe the tubing section minimum diameter, the outer surface portions are urged radially outwards to assume a configuration in which at least the tubing profile and the bore profile can engage.  
           [0014]    The provision of one or more convex wall portions facilitates passage of fluid between the tubing section and the surrounding bore, both before and after reconfiguring the tubing section, and even after the tubing section is restrained in the bore, which may be particularly useful if the first tubing is to be cemented in the bore. If desired, the tubing may subsequently be sealed to the bore wall by, for example, reconfiguring the tubing section to a form corresponding to the bore wall or, most preferably, by configuring another section of the tubing to a form corresponding to the bore wall. Most preferably, sealing the tubing with the bore wall is achieved by expanding a section of the tubing, which section may include a peripheral seal member. Preferably, the expansion is achieved by means of a rotary expander, that is an expander which is rotatable in the tubing and preferably includes at least one rotating member in rolling contact with the tubing inner wall.  
           [0015]    The bore may be a drilled or otherwise formed bore, a section of tubing or pipe, or a combination of both. Preferably, the bore is at least partially defined by downhole bore-lining tubing, such as casing or liner. The bore-lining tubing will typically be unexpandable, for example if the bore-lining tubing has been cemented; the method of the present invention allows the tubing to be located in such bore-lining tubing while avoiding the difficulties that are inherent in locating tubing by expansion within an unexpandable larger tubing. However, in other embodiments of the invention the bore-lining tubing may experience a degree of expansion, elastic, inelastic or both.  
           [0016]    The radially outwardly directed force is preferably created by passing a tubing expander, which may be of conical or tapered form, through the tubing. Preferably, the tubing expander comprises an expansion cone, and most preferably the expander comprises a seal for sealingly engaging the bore wall, such that fluid pressure may be utilised to drive the expander through the tubing section. The expander may have a first configuration in which fluid may pass through or around the expander, and a second configuration in which the expander creates a barrier to fluid flow through the bore. The second configuration may be achieved by locating a ball or plug in a suitable shoe or profile in the expander. The expander may further be adapted to assume a third configuration in which fluid may again flow through or around the expander. The third configuration may be achieved by rupturing a disc, diaphragm or the like, which may be provided in the plug, or by shearing out a ball or plug shoe.  
           [0017]    The tubing may itself serve as a hanger, or may be coupled, by any appropriate means, to a hanger to be set following the reconfiguration of the tubing.  
           [0018]    A further length of tubing, which may or may not be expandable, may be coupled to the tubing.  
           [0019]    The tubing may include a profile for co-operating with a corresponding profile on a running string to allow the string to support the tubing as the tubing is being run into the bore. Preferably, the profile is provided on an upper portion of the tubing, above a notch in the tubing. The area of tubing including the notch may be subject to expansion utilising a rotary expander, which it has been found results in the tubing shearing or otherwise parting at the notch, allowing the portion of tubing defining the profile to be pulled out of the bore, leaving the remainder of the tubing in the bore.  
           [0020]    According to a second aspect of the present invention there is provided apparatus for use in anchoring tubing in a section of a bore having an internal first diameter and defining a bore profile, the apparatus comprising:  
           [0021]    tubing including a section with a non-circular wall, the wall having an outer surface portion defining a tubing profile, the wall configured such that the outer surface portion describes an outer diameter less than the first diameter;  
           [0022]    means for engaging a running tool for running the tubing into the bore; and  
           [0023]    a first expander for diametrically expanding the tubing section wall such that the tubing profile engages with the bore profile.  
           [0024]    Preferably, the apparatus further comprises a second expander for expanding a section of the tubing into sealing contact with the bore wall.  
           [0025]    According to a further aspect of the present invention there is provided a method of anchoring tubing in a bore, the method comprising:  
           [0026]    providing tubing having a section with outer surface portions defining a profile, the section configured such that the outer surface portions describe an outer diameter less than a first diameter;  
           [0027]    locating the tubing within a bore having an internal surface defining a profile, the bore having an internal diameter corresponding to said first diameter; and  
           [0028]    reconfiguring said section such that said outer surface portions are biased to describe an outer diameter greater than said first diameter but are restrained to said first diameter by said bore, and such that said tubing profile engages the bore profile.  
           [0029]    According to a fourth aspect of the present invention there is provided a method of anchoring tubing in a bore, the bore having an internal first diameter, and defining a bore profile, the method comprising:  
           [0030]    providing tubing having a section with outer surface portions defining a tubing profile, the outer surface portions configured to describe an outer diameter greater than the first diameter, at least one of the tubing and the bore comprising an elastically deformable material; and  
           [0031]    axially translating the tubing relative to the bore to locate the tubing within the bore such that the tubing profile engages with the bore profile.  
           [0032]    Preferably, the tubing comprises elastically deformable material. Alternatively, the bore comprises elastically deformable material.  
           [0033]    The method of the invention thus provides a convenient method of creating a coupling between a tubing and a surrounding bore wall, which coupling may be utilised to fix the tubing relative to the bore, both axially and rotationally, to facilitate subsequent operations, such as further reconfiguration or deformation of the tubing.  
           [0034]    The bore profile may be formed in bore-lining tubing, such as casing or liner. The profile may be formed in the bore-lining tubing prior to the tubing being run into the bore. Alternatively, the profile may be formed after the bore ling tubing is located in the bore. The profile may be formed by any appropriate means, including a rotary profiling tool, as described in application GB 2346909, the disclosure of which is incorporated herein by reference. This permits the profile to be located to suit conditions in the bore.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0035]    These and other aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0036]    [0036]FIG. 1 is a perspective view of an expandable section of tubing incorporating a lip in accordance with an embodiment of the invention;  
         [0037]    [0037]FIG. 2 is a perspective view of an expandable section of tubing incorporating a lip in accordance with an alternative embodiment of the invention; and  
         [0038]    FIGS.  3  to  6  are schematic illustrations of steps in a method of anchoring tubing in a bore, in accordance with an embodiment of a first aspect of the present invention; and  
         [0039]    [0039]FIGS. 3 a ,  4   a  and  6   a  are sectional views on lines  3   a - 3   a ,  4   a - 4   a  and  6   a - 6   a  of FIGS. 3, 4 and  6 , respectively. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0040]    Referring firstly to FIG. 1, this shows a perspective view of an expandable section of bore-lining tubing, generally indicated by reference numeral  100 , incorporating a lip, in accordance with a preferred embodiment of the invention. This section may be part of an otherwise circular section tubing of diameter slightly less than the bore with which the tubing is intended to be located.  
         [0041]    The crinkled, expandable section  100  includes six concave wall portions,  101  to  106 . Between each concave wall portion are lips  111  to  116 , intended for engaging with cooperating recesses in a bore wall (not shown).  
         [0042]    At least this crinkled section of the tubing  100  comprises an elastically deformable material and the lips  111  to  116  describes a diameter slightly greater than the bore internal diameter. The tubing is forced into the bore and the crinkled section  100  deforms to allow the lips  111  to  116  to pass down through the bore. When the lips  111  to  116  reach the complementary profile in the bore, the lips  111  to  116  will spring out to engage with the profile.  
         [0043]    [0043]FIG. 2 shows a perspective view of an expandable section of tubing  120  incorporating a lip, in accordance with an alternative embodiment of the invention. In this case the lip  122  is in the form of a continuous rib, for engaging with a cooperating channel in the bore.  
         [0044]    Reference is now made to FIGS.  3  to  6  of the drawings, which illustrate steps in the method of anchoring tubing, according to a second aspect of the present invention, and subsequently cementing and sealing the tubing. Elements of the method described with reference to FIGS.  3  to  6 , such as for cementing and sealing the tubing, are equally applicable to the method of anchoring described with reference to FIGS. 1 and 2. The tubing is in the form of liner  20 , in the lower end of a drilled bore  22 . In this embodiment the liner  20  describes a diameter less than the bore  22  diameter. In FIG. 3, the liner  20  is shown in the run-in position, with the upper end of the liner  20  overlapping the lower end of existing cemented casing  24 . The remainder of the liner  20  is located in unlined, or open bore.  
         [0045]    The liner  20  is coupled to a running string  26 , formed of drill pipe, by means of co-operating profiles  28 . Below the liner profile  28 , which is located at the upper end of the liner  20 , the liner wall defines a notch  30 , the purpose and function of which will be described in due course.  
         [0046]    Mounted to the lower end of the string  26 , within the liner  20 , is a running tool  31  and a rotary expansion tool  32 . The expansion tool  32  comprises a hollow body  34  in fluid communication with the string  26 , the body  34  accommodating three piston-mounted rollers  36 . As will be described, supplying fluid at elevated pressure to the interior of the body  34  tends to urge the rollers  36  radially outwardly, and by then rotating the tool  32  within the liner  20  the internal and external diameters of the liner may be increased. A cement plug catcher  40  is mounted via shear pins to the lower end of the expansion tool  32 .  
         [0047]    A drillable cone and seal assembly  48  is initially located within a section of the liner  20   a  below the plug catcher  40 , which liner section  20   a  has been formed to provide a corrugated or crinkled wall profile, as may be seen from FIG. 3 a  of the drawings. In addition the liner includes a radially projecting tubing lip  21 , similar to the lips shown in FIGS. 1 and 2. The casing includes a profile  23 , in the form of a radial recess. Other than the liner section  20   a , the liner  20  is of a circular form and has an outer diameter slightly smaller than the inner diameter of the casing  24 , to provide sufficient clearance for the liner  20  to be run in through the casing  24 . However, the liner section  20   a  has been first shaped into a polygonal form in a forming die and the planar wall portions then further deformed to a concave form such that the outer diameter of the liner section  20   a  is described by six outer surface portions  50 . The minimum inner diameter of the section  20   a  is defined by the midpoints of the concave wall portions  51 .  
         [0048]    The cone and seal assembly  48  comprises a hollow upper cone  52 , and a reduced diameter tubular portion  56  extends from the cone  52  to a larger diameter stabiliser collar  58 . The collar  58  has an external circumferential seal  54  for engaging the inner wall of the liner  20  and defines an internal ball seat  59 . Initially, the assembly  48  is located in the liner  20  as illustrated in FIG. 3, that is with the cone  52  and collar  58  respectively located above and below the crinkled section  20   a , and the tubular portion  56  extending through the section  20   a.    
         [0049]    The lower end of the liner  20  is provided with a drillable cement shoe  60 .  
         [0050]    In use, the liner  20  is run into the bore  22  to the position as illustrated in FIG. 3, with the liner profile  21  lining up with the casing profile  23 . If desired, fluid may be circulated through the liner  20 , and the liner  20  may be rotated within the bore  22  as the liner  20  is run in. Pre-flush fluid may then be pumped from surface down through the running string  26 , followed by a ball  62  (FIG. 4) and a volume of cement  64 . The ball  62  lands on the seat  59  and closes the throughbore defined by the collar  58 . Fluid pressure then acts on the area defined by the seal  54 , and urges the collar  58 , and of course the remainder of the assembly  48 , down through the crinkled section  20   a . The diameter and profile of the cone  52  are selected such that the cone contacts the inner faces of the concave wall portions  51 , which has the effect of moving the outer surface portions  50  radially outwards causing the liner profile  21  to engage with the casing profile  23 . A pressure drop will be evident at surface when the cone  52  clears the lower end of the section  20   a , and further pumping of cement  64  will continue to push the assembly  48  through the liner  20  until the collar  58  engages the shoe  60 .  
         [0051]    The gaps  76  (FIG. 4 a ) that remain between the casing inner wall and the polygonal liner section  20   a  allow for fluid circulation.  
         [0052]    The volume of cement  64  is followed by a wiper plug  66  and water spacer  68 . The plug  66  engages and shears out the plug catcher  40 , which is then pushed through the liner  20  until the catcher  40  engages the cone  52 . Prior to this, a pressure increase will have been applied to shear out the ball seat  59 , such that the seat  59  and ball  62  land out within the float shoe  60 , allowing the cement  64  to circulate into the annulus  70  between the liner  20  and the open bore  22 .  
         [0053]    Weight is then applied to the liner  20  to check the integrity of the thus-formed hanger, before releasing the running tool  31  from the liner  20 .  
         [0054]    Referring to FIG. 5, the expansion tool  32  is then lowered into the liner  20 , which is now axially fixed relative to the casing  24  by the liner profile  21  being engaged with the tubing profile  23 , until the tool  32  is located above the section  20   a  at a liner seal section  20   b . Elevated fluid pressure applied through the string  26  to the tool  32  then acts to extend the rollers  36 , such that rotation of the string  26  and the activated tool  32  will diametrically expand the liner section  20   b  into sealing contact with the casing  24 . Fluid is then pumped through the running string  26  to circulate out cement residue, and the thus-formed hanger is then subject to a pressure test.  
         [0055]    The expansion of the liner  20  is then continued over the notch  30 , and the expansion at the notch causes the liner  20  to separate. The tool  32 , and the short length of liner  20  above the notch  30 , may then be pulled out of the bore on the running string  26 , as shown in FIG. 6.  
         [0056]    In other embodiments of the invention, a profiled liner section may be subject to expansion by a cone and seal assembly or the like while positioned within the lower end of the casing. The outer surface portions of the expanded liner section, if unrestrained by the surrounding casing, would assume a larger diameter. Accordingly, the restraint provided by the casing results in the liner section outer surface portions engaging the casing, allowing the liner to be hung from the casing while providing gaps between the liner and casing to permit fluid circulation.