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BACKGROUND  
         [0001]    The present invention relates generally to operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a method whereby a latch profile is installed in a tubular string.  
           [0002]    It is common practice to set a packer (or another anchoring device, such as a liner hanger or hanger/packer) in a casing string in a parent wellbore prior to drilling a branch wellbore. The packer provides a secure platform to which a whipstock may be attached during the processes of milling through the casing and drilling the branch wellbore. The packer also seals against the casing, which may be used to provide pressure isolation for a zone of the parent wellbore below the intersection with the branch wellbore, or which may aid in preventing debris from falling down in the parent wellbore.  
           [0003]    Various types of packers have been used for this purpose—permanent packers, retrievable packers, hydraulically set packers, mechanically set packers, etc. Nevertheless, all of these various types of packers share a common disadvantage in that they restrict access and flow through the parent wellbore. If full bore access to the parent wellbore below the branch wellbore intersection is desired after the branch wellbore is drilled, the packer must be unset and retrieved from the well (which is many times quite difficult to accomplish), or the packer must be milled through or washed over (which is quite time-consuming).  
           [0004]    Because of this wellbore restriction due to the use of packers in multilateral wellbore drilling, multilateral wells are typically constructed from bottom up. That is, a first branch wellbore is drilled from a parent wellbore, then a second branch wellbore is drilled from the parent wellbore at a location above the intersection between the parent and first branch wellbores, then a third branch wellbore is drilled from the parent wellbore at a location above the intersection between the parent and second branch wellbores, etc. This situation unnecessarily limits the options available to the operator, such as to drill the branch wellbores in another, more advantageous, sequence or to drill a previously unplanned branch wellbore below another branch wellbore, etc.  
           [0005]    In addition, a packer relies on a gripping engagement with the casing using slips. This gripping engagement may fail due to the severe forces generated in the milling and drilling operations. Such gripping engagement also provides limited radial orientation of the packer relative to the casing, so if the gripping engagement is ever relieved (such as, by unsetting the packer), any subsequent radial orientation relative to the casing (for example, to re-enter the branch wellbore) will not be able to benefit from the original orientation of the packer.  
         SUMMARY  
         [0006]    In carrying out the principles of the present invention, in accordance with an embodiment thereof, a method is provided in which a latch profile is installed in a tubular string after the tubular string is positioned in a well. The method permits an apparatus such as a whipstock to be secured in the tubular string. The latch profile may provide for radial orientation of the apparatus.  
           [0007]    In one aspect of the invention, the latch profile is formed on an expandable latch structure which is conveyed into the tubular string. The latch structure is then expanded outward, thereby securing the latch profile to the tubular string. For example, the latch structure may deform the tubular string when it is expanded outward, thereby recessing the latch structure into an interior surface of the tubular string and leaving full bore access through the tubular string. Bonding agents, such as adhesives and sealants may be used to bond the latch structure to the tubular string.  
           [0008]    In another aspect of the invention, the latch profile may be formed on the interior surface of the tubular string by creating recesses on the interior surface. The recesses may be formed in a predetermined pattern, so that an apparatus engaged therewith will be secured relative to the tubular string and radially oriented relative to the tubular string.  
           [0009]    In yet another aspect of the invention, the latch profile may be formed on the interior surface of the tubular string by cutting into the interior surface to create the recesses. For example, cutting tools such as drills or mills may be used. If the recesses extend through a sidewall of the tubular string, thereby forming openings through the sidewall, sealant may be injected into the openings to prevent fluid flow therethrough.  
           [0010]    In still another aspect of the invention, the latch profile may be installed in the tubular string using any of the methods summarized above, and then an apparatus may be operatively engaged with the profile in a single trip into the well. This may be accomplished by attaching the apparatus to a latch profile installation assembly and conveying these together into the well.  
           [0011]    These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of a representative embodiment of the invention hereinbelow and the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a schematic cross-sectional view of a first method embodying principles of the present invention;  
         [0013]    [0013]FIG. 2 is a schematic cross-sectional view of the first method of FIG. 1, wherein further steps of the method have been performed;  
         [0014]    [0014]FIG. 3 is a schematic cross-sectional view of a second method embodying principles of the present invention;  
         [0015]    [0015]FIG. 4 is a schematic cross-sectional view of a third method embodying principles of the present invention; and  
         [0016]    [0016]FIGS. 5A &amp; B are schematic cross-sectional views of a fourth method embodying principles of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0017]    Representatively illustrated in FIG. 1 is a method  10  which embodies principles of the present invention. In the following description of the method  10  and other apparatus and methods described herein, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used only for convenience in referring to the accompanying drawings. Additionally, it is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present invention.  
         [0018]    As depicted in FIG. 1, a casing string  12  has been positioned in a parent wellbore  14  and has been cemented therein. The casing string  12  could be any type of tubular string, such as a string of liner, etc., and the parent wellbore  14  could be any type of wellbore, such as a branch wellbore, a vertical, horizontal or deviated wellbore, etc., in keeping with the principles of the invention. In addition, the terms “cemented”, “cement”, “cementing”, etc. as used herein are intended to encompass any means of securing and sealing the casing string  12  in the wellbore  14 . For example, materials such as epoxies, gels, resins, polymers, elastomers, etc., as well as cementitious materials, may be used for this purpose.  
         [0019]    After the casing string  12  has been cemented in the wellbore  14 , a latch profile  16  is installed in the casing. Representatively, the latch profile  16  is used in the method  10  to position a whipstock assembly  18  at a location in the casing string  12  where it is desired to drill a branch wellbore. However, it is to be clearly understood that the latch profile  16  may be used for any of a large variety of purposes other than positioning the whipstock assembly  18 , without departing from the principles of the invention. For example, the latch profile  16  could be used to position a device for re-entering the branch wellbore after it is drilled and the whipstock assembly  18  is retrieved from the well, the latch profile could be used to position a flow control device, such as a plug or valve, to control fluid flow in the parent and/or branch wellbores, etc.  
         [0020]    The whipstock assembly  18  includes a whipstock  20  having an upper deflection surface  22 , a wiper or seal  24  and one or more keys, lugs or dogs  26  for engagement with the latch profile  16 . The deflection surface  22  is used to deflect cutting tools, such as mills and drill bits, to drill the branch wellbore outward from the parent wellbore  14 . The seal  24  is used to prevent debris from fouling the latch profile  16  or from falling down into the parent wellbore  14  therebelow. The keys  26  are complementarily shaped relative to the profile  16  and may be continuously radially outwardly biased, or they may be selectively actuated to extend outward into engagement with the profile when desired.  
         [0021]    As used herein, the term “whipstock” is used to designate any type of deflection device which may be used in a well to deflect an object from one wellbore to another.  
         [0022]    Attached to a lower end of the whipstock assembly  18  is a running tool  28 . The running tool  28  is used to install the latch profile  16  in the casing  12 . Specifically, the running tool  28  is used to outwardly expand a latch structure  30  on which the latch profile  16  is internally formed.  
         [0023]    The latch structure  30  may be a circumferentially continuous generally tubular shaped structure with the latch profile  16  formed on an interior surface thereof. However, it is to be understood that the latch structure  30  could be otherwise shaped and configured. For example, the latch structure  30  could be made up of multiple segments each of which is displaced outward to expand the latch structure. If the latch structure  30  is circumferentially continuous, it may be expanded outward by circumferential stretching.  
         [0024]    Carried externally on the latch structure  30  is a bonding agent  32 . The bonding agent  32  may be an adhesive for securing the latch structure  30  to the casing  12 , or the bonding agent may be a sealant for forming a seal between the latch structure and the casing. Of course, the bonding agent  32  could be an adhesive sealant, and separate adhesive and sealant could also be used. In addition, other means of securing the latch structure  30  to the casing  12  (for example, thermal welding, piercing of the casing, deploying a spear-type device to connect and secure the latch structure to the casing, etc.), and other means of sealing between the latch structure and the casing, may be used without departing from the principles of the invention.  
         [0025]    However, it should be understood that the bonding agent  32  is not necessary in the method  10 , since the latch structure  30  could be secured and/or sealed to the casing  12  by contact therebetween. For example, a metal to metal seal may be formed between the latch structure  30  and the casing  12  when the latch structure is expanded outward into contact with the casing.  
         [0026]    The latch profile  16  is preferably of the type known to those skilled in the art as an orienting profile. That is, once installed in the casing string  12 , the latch profile  16  will serve to radially orient an apparatus engaged therewith relative to the casing string. For example, the whipstock assembly  18  will be radially oriented so that cutting tools are deflected off of the deflection surface  22  in a desired direction to drill the branch wellbore when the whipstock assembly is operatively engaged with the latch profile  16 . Of course, other types of profiles may be used for the latch profile  16  in keeping with the principles of the invention.  
         [0027]    The running tool  28  includes an actuator  34  and a conically-shaped wedge  36 . The actuator  34  is used to displace the wedge  36  through the latch structure  30  to thereby outwardly expand the latch structure. The actuator  34  may be any type of actuator, such as a hydraulic, mechanical, explosive or electrical actuator.  
         [0028]    As depicted in FIG. 1, the whipstock assembly  18  and running tool  28  are conveyed into the casing string  12  on a tubing string  38 . Any form of conveyance may be used in place of the tubing string  38 . For example, a wireline or slickline could be used. Furthermore, note that the tubing string  38  may be a segmented or a continuous tubing string, such as a coiled tubing string.  
         [0029]    Referring additionally now to FIG. 2, the method  10  is representatively illustrated after the latch structure  30  has been expanded outward. Upward displacement of the wedge  36  by the actuator  34  has outwardly expanded the latch structure  30  so that the casing string  12  is plastically deformed, outwardly deforming a sidewall of the casing. The latch profile  16  is thereby secured to the casing string  12 .  
         [0030]    Note that a minimum inner diameter of the latch structure  30  is substantially equal to the minimum inner diameter of the casing string  12 . Thus, the latch structure  30  permits full bore access through the casing string  12 . However, the latch structure  30  could have an inner diameter smaller than the inner diameter of the casing string  12 , without departing from the principles of the invention.  
         [0031]    The bonding agent  32  adheres the latch structure  30  to the casing string  12  and/or forms a seal between the latch structure and the casing string. If the latch structure  30  is made up of individual segments, the bonding agent  32  may prevent the segments from falling inwardly.  
         [0032]    The whipstock assembly  18  has been lowered in the casing string  12 , so that the keys  26  operatively engage the latch profile  16 . This engagement secures the whipstock  20  and radially orients the whipstock relative to the casing string  12 .  
         [0033]    The seal  24  is received in an upper bore of the latch structure  30 . This engagement between the seal  24  and the latch structure  30  may serve to prevent fouling of the latch profile  16  and/or prevent debris from falling into the parent wellbore  14  below the whipstock assembly  18 .  
         [0034]    Note that the latch profile  16  has been installed and the whipstock assembly  18  has been engaged with the latch profile in only a single trip into the casing string  12 . This enhances the economical performance of the method  10 . However, it should be understood that the latch profile  16  could be installed and an apparatus engaged therewith in multiple trips into the casing string  12 , without departing from the principles of the invention.  
         [0035]    Referring additionally now to FIG. 3, another method  40  embodying principles of the present invention is representatively illustrated. In the method  40 , a latch profile  42  made up of multiple spaced apart recesses  44 ,  46  is installed in a casing string  48  after the casing string is positioned in a wellbore  50 . Specifically, the recesses  44 ,  46  are formed in the casing string  48  by plastically deforming the casing string using a forming apparatus  52 .  
         [0036]    The forming apparatus  52  includes dies  54 ,  56  which are outwardly extendable to engage an interior surface of the casing string  48 . On the left hand side of FIG. 3, the dies  54 ,  56  are depicted in retracted positions thereof. On the right hand side of FIG. 3, the dies  54 ,  56  are depicted in extended positions thereof, forming the recesses  44 ,  46  on the interior surface of the casing string  48  by plastically deforming a sidewall of the casing string.  
         [0037]    The dies  54  are circumferentially continuous (i.e., ring-shaped), so that the recesses  44  are also circumferentially continuous. The die  56  is not circumferentially continuous, but produces the discreet recess  46  at a particular desired radial orientation on the casing string  12 . The recesses  44  are used to secure an apparatus (such as the whipstock assembly  18  described above) against axial displacement through the casing string  48 , and the recess  46  is used to radially orient the apparatus relative to the casing string.  
         [0038]    Thus, the recesses  44 ,  46  are arranged in a predetermined pattern, so that an apparatus subsequently engaged therewith will be secured and radially oriented relative to the casing string  48 . For example, the whipstock assembly  18  described above could have keys, dogs or lugs carried thereon in a complementarily shaped pattern to operatively engage the recesses  44 ,  46 . Preferably, the recess  46  would be engaged when the whipstock assembly  18  is properly radially oriented relative to the casing string  48 .  
         [0039]    As depicted in FIG. 3, the forming tool  52  is conveyed into the casing string  48  on a wireline  58 , but any other type of conveyance could be used. The forming tool  52  may be hydraulically, mechanically, explosively or electrically actuated to extend the dies  54 ,  56  outward. However, it should be understood that the forming tool  52  may be actuated in any manner, and may be configured in any manner to produce any desired pattern of recesses, in keeping with the principles of the invention.  
         [0040]    Referring additionally now to FIG. 4, another method  60  embodying principles of the present invention is representatively illustrated. In the method  60 , a cutting apparatus  62  is used to cut into an interior surface of a casing string  64  positioned in a wellbore  66 . Specifically, cutting tools  68  are outwardly extended from the apparatus  62  to form recesses  70  in the interior surface of the casing string  64 .  
         [0041]    On the left hand side of FIG. 4 the cutting tools  68  are depicted in retracted positions thereof, and on the right hand side of FIG. 4 the cutting tools are depicted in extended positions thereof. There may be only one of the cutting tools  68 , which may be used multiple times to cut corresponding multiple recesses  70 , or there may be the same number of cutting tools as recesses to be cut, etc.  
         [0042]    The cutting tools  68  may be drill bits, mills, keyway cutters, or any other type of cutting tool. Alternatively, the cutting tools  68  could be nozzles for a high pressure water jet. In that case, it would not be necessary to outwardly extend the cutting tools  68  from the apparatus  62  in order to cut into the casing  64 . Water jet cutting of the casing  64  may be preferred for cutting a detailed profile into the casing  64 .  
         [0043]    As depicted in FIG. 4, the recesses  70  are preferably cut in a predetermined pattern, so that an apparatus (such as the whipstock assembly  18  described above) subsequently engaged therewith will be secured and radially oriented relative to the casing string  64 . That is, the whipstock assembly  18  or other apparatus may be provided with keys, lugs or dogs arranged in a complementarily shaped pattern to operatively engage the recesses  70 . The pattern of recesses  70  thus make up the latch profile installed by the cutting apparatus  62 . Preferably, the recesses  70  are operatively engaged when the whipstock assembly  18  or other apparatus is radially oriented in a desired direction relative to the casing string  64 .  
         [0044]    The recesses  70  may extend through a sidewall of the casing string  64 , so that they form openings through the casing sidewall. In that case, it may be desired to prevent fluid flow through the openings. A sealant  72  may be injected through the openings  70  for this purpose. For example, the sealant  72  may be an epoxy, polymer, resin, cement, or any other type of sealant.  
         [0045]    As depicted in FIG. 4, the cutting apparatus  62  is conveyed into the casing string  64  by a wireline  74 . However, it is to be understood that any type of conveyance may be used in place of the wireline  74 . For example, a tubing string could be used to convey the apparatus  62 .  
         [0046]    As with the running tool  28  described above, the forming tool  52  and/or the cutting apparatus  62  may be conveyed into a well attached to an apparatus which is to be operatively engaged with the latch profile installed by the forming tool or cutting apparatus. For example, the whipstock assembly  18  could be attached to the forming tool  52  when it is conveyed into the casing string  48 , or the whipstock assembly could be attached to the cutting apparatus  62  when it is conveyed into the casing string  64 . Thus, the latch profiles installed by the forming tool  52  and the cutting apparatus  62  may be operatively engaged by an apparatus, such as the whipstock assembly  18 , in a single trip into the well.  
         [0047]    Referring additionally now to FIGS. 5A &amp; B, another method  80  embodying principles of the invention is representatively illustrated. In the method  80 , an expandable latch structure  82  having a latch profile  84  formed internally thereon is conveyed into a casing string  86 , in a manner similar to that described above for the method  10 . The latch structure  82  is preferably generally tubular and circumferentially continuous, but could be circumferentially segmented if desired.  
         [0048]    The latch structure  82  has a layer of a bonding agent  88  on the external surface of the latch structure. The bonding agent  88  may be similar to the bonding agent  32  in the method  10 . The bonding agent  88  is used to adhere and/or seal the latch structure  82  to the casing string  86 . Suitable materials for the bonding agent  88  may be elastomers, epoxies, other polymer compositions, resins, cements, other sealants, other adhesives, etc.  
         [0049]    However, it should be understood that the bonding agent  88  is not necessary in the method  80 , since the latch structure  82  could be secured and/or sealed to the casing string  86  by contact therebetween. For example, a metal to metal seal may be formed between the latch structure  82  and the casing string  86  when the latch structure is expanded outward into contact with the casing string.  
         [0050]    The profile  84  may be an orienting profile, that is, equipment (such as the whipstock  20  described above) operatively engaged with the profile is rotationally oriented relative to the casing string  86 , as well as being secured axially and rotationally thereto. Alternatively, or in addition, the latch structure  82  may include a laterally inclined upper surface go (known to those skilled in the art as a “muleshoe”) for rotationally orienting and securing the equipment. Preferably, the latch structure  82  is rotationally oriented relative to the casing string  86  prior to expanding the latch structure in the casing string.  
         [0051]    The latch structure  82  is depicted in FIG. 5A in its radially compressed, or unexpanded, configuration. The latch structure  82  is depicted in FIG. 5B in its radially expanded configuration, with the bonding agent  88  contacting and securing and/or sealing the latch structure to the casing string  86 . A conical wedge  92  may be displaced through the latch structure  82  to expand the latch structure radially outward, or other means may be used for this purpose.  
         [0052]    As depicted in FIG. 5B, the latch structure  82  in its expanded configuration has a minimum diameter therethrough which is somewhat less than the inner diameter of the casing string  86 . However, the latch structure  82  may be further radially outwardly expanded to recess the latch structure into the inner wall of the casing string  86  (similar to the manner in which the latch structure  30  is recessed into the casing  12  in the method  10 ) in which case the latch structure  82  could have a minimum diameter substantially equal to, or at least as great as, the casing inner diameter.  
         [0053]    Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to these specific embodiments, and such changes are contemplated by the principles of the present invention. For example, a latch profile may be installed in a casing string using a combination of various forming and cutting methods. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents.

Summary:
A method of installing an internal latch profile in an existing tubular string does not require the use of a packer. In a described embodiment, a method of latch installation includes the step of deforming an interior surface of the tubular string after the tubular string is positioned in a well. In another described embodiment, a method of latch installation includes the step of cutting into the interior surface of the tubular string.