Patent Publication Number: US-2015060086-A1

Title: Running Tool with Retractable Collet for Liner String Installation in a Wellbore

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119 of the filing date of International Application No. PCT/US2013/058056, filed Sep. 4, 2013. 
    
    
     TECHNICAL FIELD OF THE DISCLOSURE 
     This disclosure relates, in general, to equipment utilized in conjunction with operations performed in relation to subterranean wells and, in particular, to liner running tool having a retractable collet assembly for installing a liner string in a wellbore. 
     BACKGROUND 
     Without limiting the scope of the present invention, its background is described with reference to constructing a subterranean well, as an example. 
     In conventional practice, the drilling of an oil or gas well involves creating a wellbore that traverses numerous subterranean formations. For a variety reasons, each of the formations through which the well passes is preferably sealed. For example, it is important to avoid an undesirable passage of formation fluids, gases or materials out of a formation and into the wellbore or for wellbore fluids to enter a formation. In addition, it is commonly desired to isolate producing formations from one another and from nonproducing formations. 
     Accordingly, conventional well architecture typically includes the installation of casing within the wellbore. In addition to providing the sealing function, the casing also provides wellbore stability to counteract the geomechanics of the formation such as compaction forces, seismic forces and tectonic forces, thereby preventing the collapse of the wellbore wall. The casings are generally fixed within the wellbore by a cement layer between the outer wall of the casing and the wall of the wellbore. During the drilling of the wellbore, annuli are provided between the outer surfaces of the casings and the wellbore wall. When a casing string is located in its desired position in the well, a cement slurry is pumped via the interior of the casing, around the lower end of the casing and upwards into the annulus. As soon as the annulus around the casing is sufficiently filled with the cement slurry, the cement slurry is allowed to harden. The cement sets up in the annulus, supporting and positioning the casing and forming a substantially impermeable barrier. 
     In one approach, each casing string extends downhole from the surface such that only a lower section of each casing string is adjacent to the wellbore wall. Alternatively, the wellbore casings may include one or more liner strings, which do not extend to the surface of the wellbore, but instead typically extend from near the bottom end of a previously installed casing downward into the uncased portion of the wellbore. In such installations, the liner string may be set or suspended from a liner hanger. As yet another alternative, in some wellbore installations, a liner string may be installed in an uncased portion of the wellbore without being set or suspended from a liner hanger. Liner strings are typically lowered downhole on a work string that may include a running tool that attaches to the liner string. It has been found, that in certain wellbores such as deviated wellbores, horizontal wellbores, multilateral wellbores and the like, significant force may be required to work the liner string to the bottom of the wellbore. In addition, it has been found, that following liner string installation in such wellbores, it is sometimes difficult to retrieve the running tool out of the wellbore due to certain components of the running tool, such as collet assemblies, hanging up on profiles of the installed liner string. 
     Accordingly, a need has arisen for a running tool that is operable to deliver the required force to work the liner string to the bottom of the wellbore. In addition, a need has arisen for such a running tool that is operable to be retrieved out of the wellbore without hanging up on profiles of the installed liner string. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the features and advantages of the present disclosure, reference is now made to the detailed description along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which: 
         FIG. 1  is a schematic illustration of an offshore oil and gas platform installing a liner string in a subterranean wellbore according to an embodiment of the present disclosure; 
         FIG. 2A  is a side view of a portion of a running tool in its running configuration for installing a liner string in a subterranean wellbore according to an embodiment of the present disclosure; 
         FIG. 2B  is a quarter sectional view of a portion of a running tool in its running configuration positioned in a liner string according to an embodiment of the present disclosure; 
         FIG. 3A  is a side view of a portion of a running tool in its retrieval configuration after installing a liner string in a subterranean wellbore according to an embodiment of the present disclosure; 
         FIG. 3B  is a quarter sectional view of a portion of a running tool in its retrieval configuration after disengaging from a liner string according to an embodiment of the present disclosure; and 
         FIGS. 4A-4B  are cross sectional views of a collet assembly for use in a running tool according to an embodiment of the present disclosure in its flexed and relaxed states, respectively. 
     
    
    
     DETAILED DESCRIPTION 
     While various system, method and other embodiments are discussed in detail below, it should be appreciated that the present disclosure provides many applicable inventive concepts, which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative, and do not delimit the scope of the present disclosure. 
     The present disclosure is directed to a running tool that is operable to deliver the required force to work a liner string to the bottom of a wellbore. In addition, the running tool that of the present disclosure is operable to be retrieved out of the wellbore without hanging up on profiles of the installed liner string. 
     In a first aspect, the present disclosure is directed to a running tool for installing a liner string having a profile in a wellbore. The running tool includes a mandrel, a prop assembly positioned about the mandrel and a collet assembly slidably positioned on the mandrel. The collet assembly has a generally cylindrical collet collar with a plurality of collet fingers extending therefrom each having a collet head on a distal end thereof. In a first position of the collet assembly relative to the mandrel, the prop assembly radially outwardly flexes the collet fingers such that the collet heads engage the profile of the liner string and are operable to apply a force in the downhole direction to the liner string. In a second position of the collet assembly relative to the mandrel, the collet assembly is remote from the prop assembly such that the collet fingers radially inwardly contract disengaging the collet heads from the profile of the liner string, thereby enabling removal of the running tool from the liner string. 
     In one embodiment of the running tool, in the second position of the collet assembly relative to the mandrel, an inner surface of the collet heads is proximate the mandrel forming clearance gaps therebetween. In another embodiment, in the second position of the collet assembly relative to the mandrel, an inner surface of the collet heads contacts the mandrel. In certain embodiments of the running tool, in the second position of the collet assembly relative to the mandrel, the collet fingers are angled toward the mandrel from the collet collar to the collet heads. In such embodiments, collet fingers may be angled between about 2 degrees and about 6 degrees or the collet fingers may be angled at least 3 degrees. In some embodiments of the running tool, in the first position of the collet assembly relative to the mandrel, the collet fingers are in a first radially outwardly flexed state and in the second position of the collet assembly relative to the mandrel, the collet fingers are in a second radially outwardly flexed state that is less than the first radially outwardly flexed state. In other embodiments of the running tool, in the first position of the collet assembly relative to the mandrel, the collet fingers are in the radially outwardly flexed state and in the second position of the collet assembly relative to the mandrel, the collet fingers are in a radially relaxed state. In these embodiments, in the second position of the collet assembly relative to the mandrel, the collet fingers may be operable to be radially inwardly flexed to contact an inner surface of the collet heads with the mandrel. 
     In a second aspect, the present disclosure is directed to a method for installing a liner string with a profile in a wellbore. The method includes lowering the liner string into the wellbore on a running tool, the running tool including a mandrel, a prop assembly positioned about the mandrel and a collet assembly slidably positioned on the mandrel, the collet assembly having a generally cylindrical collet collar with a plurality of collet fingers extending therefrom each having a collet head on a distal end thereof; engaging the collet heads in the profile of the liner string by radially outwardly flexing the collet fingers with the prop assembly; applying a force in the downhole direction to the liner string with the collet assembly; positioning the liner string at a desired location in the wellbore; disengaging the collet heads from the profile of the liner string by unpropping the collet assembly such that the collet fingers radially inwardly contract; and removing the running tool from the liner string. 
     The method may also include lowering the running tool downhole into the liner string, locating an inner surface of the collet heads proximate to the mandrel forming clearance gaps therebetween, contacting an inner surface of the collet heads with the mandrel; positioning the collet fingers at an angle toward the mandrel from the collet collar to the collet heads; placing the collet fingers in a reduced radially outwardly flexed state; placing the collet fingers in a radially relaxed state; and/or radially inwardly flexing the collet fingers to contact an inner surface of the collet heads with the mandrel. 
     In a third aspect, the present disclosure is directed to a collet assembly for releasably engaging a profile of a downhole tubular. The collet assembly includes a generally cylindrical collet collar having a central axis and a plurality of collet fingers extending from the collet collar each having a collet head on a distal end thereof. In a first configuration, the collet fingers are in a radially outwardly flexed state such that the collet fingers extend substantially parallel with the central axis of the collet collar. In a second configuration, the collet fingers are in a radially relaxed state such that the collet fingers extend from the collet collar to the collet heads at an angle toward the central axis of the collet collar. 
     In certain embodiments of the second configuration, the collet fingers are angled between about 2 degrees and about 6 degrees toward the central axis of the collet collar when the collet fingers are in the radially relaxed state. In some embodiments of the second configuration, the collet fingers are angled at least 3 degrees toward the central axis of the collet collar when the collet fingers are in the radially relaxed state. In one embodiment of the second configuration, the collet fingers are operable to be radially inwardly flexed when the collet fingers are in the radially relaxed state. 
     Referring initially to  FIG. 1 , a running tool for installing a liner string in a subterranean wellbore is being deployed from an offshore oil or gas platform that is schematically illustrated and generally designated  10 . A semi-submersible platform  12  is centered over submerged oil and gas formation  14  located below sea floor  16 . A subsea conduit  18  extends from deck  20  of platform  12  to wellhead installation  22 , including blowout preventers  24 . Platform  12  has a hoisting apparatus  26 , a derrick  28 , a travel block  30 , a hook  32  and a swivel  34  for raising and lowering pipe strings, such as a liner string  36 . 
     A main wellbore  38  has been drilled through the various earth strata including formation  14 . The terms “parent” and “main” wellbore are used herein to designate a wellbore from which another wellbore is drilled. It is to be noted, however, that a parent or main wellbore does not necessarily extend directly to the earth&#39;s surface, but could instead be a branch of yet another wellbore. A casing string  40  is secured within main wellbore  38  by cement  42 . The term “casing” is used herein to designate a tubular string used in a wellbore or to line a wellbore. The casing may be of the type known to those skilled in the art as a “liner” and may be made of any material, such as steel or a composite material and may be segmented or continuous, such as coiled tubing. 
     Casing string  38  includes a window joint  44  interconnected therein. In addition, casing string  38  includes a latch coupling  46 . Latch coupling  46  has a latch profile that is operably engagable with latch keys of a latch assembly  48  such that latch assembly  48  may be axially anchored and rotationally oriented in latch coupling  46 . In the illustrated embodiment, when the primary latch key of latch assembly  48  has operably engaged the latch profile of latch coupling  46 , a deflection assembly depicted as whipstock  50  is positioned in a desired circumferential orientation relative to window joint  44  such that a window can be milled, drilled or otherwise formed in window joint  44  in the desired circumferential direction. As illustrated, a branch or lateral wellbore  52  has been drilled from window joint  44  of main wellbore  38 . The terms “branch” and “lateral” wellbore are used herein to designate a wellbore that is drilled outwardly from its intersection with another wellbore, such as a parent or main wellbore. A branch or lateral wellbore may have another branch or lateral wellbore drilled outwardly therefrom. 
     Liner string  36  is being lowered downhole on a work string  54  that includes a running tool  56  that attaches work string  54  to liner string  36 . As shown, liner string  36  is being positioned in lateral wellbore  52  that is generally horizontal. Due to friction between liner string  36  and the surface of lateral wellbore  52 , significant force may be required to push liner string  36  to the bottom or toe of lateral wellbore  52 . This is achieved by applying a force in the downhole direction to liner string  36  with a collet assembly of running tool  56  that engages a profile within liner string  36 . After liner string  36  is positioned at a desired location in wellbore  52 , the collet assembly disengages from the profile, which enables running tool  56  to be retrieved to the surface with work string  54 . 
     Even though  FIG. 1  depicts a liner string being installed in a horizontal wellbore, it should be understood by those skilled in the art that the present running tool is equally well suited for use in wellbores having other orientations including vertical wellbores, slanted wellbores, deviated wellbores or the like. Accordingly, it should be understood by those skilled in the art that the use of directional terms such as above, below, upper, lower, upward, downward, uphole, downhole and the like are used in relation to the illustrative embodiments as they are depicted in the figures, the upward direction being toward the top of the corresponding figure and the downward direction being toward the bottom of the corresponding figure, the uphole direction being toward the surface of the well, the downhole direction being toward the toe of the well. Also, even though  FIG. 1  depicts an offshore operation, it should be understood by those skilled in the art that the present running tool is equally well suited for use in onshore operations. 
     Referring next to  FIGS. 2A-2B , therein is depicted a section of a running tool  100  for installing a liner string in a subterranean wellbore. As best seen in  FIG. 2B , a liner string  102  may include any number of substantially tubular sections that are preferably formed from jointed tubulars that are threadably coupled together at the surface. In the illustrated section, liner string  102  includes an upper liner tubular  104  and an intermediate liner tubular  106  that are threadably coupled together at threaded connection  108 . In the illustrated embodiment, liner string  102  defines a profile  110  between an upper shoulder  112  of intermediate liner tubular  106  and a lower shoulder  114  of upper liner tubular  104 . Running tool  100  is positioned at least partially within liner string  102  and is operable to transport, apply downward force on and set liner string  102  in the wellbore. Running tool  100  includes a plurality of substantially tubular members that may be referred to as a generally tubular mandrel  116  that cooperate together to form a central bore  118  extending throughout. In the illustrated section, tubular mandrel  116  includes an upper mandrel tubular  120  that may be threadably and sealingly coupled to or operably associated with other components of the work string at its upper end. Upper mandrel tubular  120  is threadably coupled on it lower end to an intermediate mandrel tubular  122 . Upper mandrel tubular  120  has a radially expanded lower section  124  that defines an upper shoulder  126 . Upper mandrel tubular  120  also has a radially reduced channel  128 . 
     A prop assembly  130  including a prop extension  132  is disposed around upper mandrel tubular  120 . A snap ring  134  prevents axial movement of prop assembly  130  beyond predetermined limits along upper mandrel tubular  120 . A collet assembly  136  is slidably positioned around upper mandrel tubular  120 . Collet assembly  136  includes a generally cylindrical collet collar  138  having a plurality of collet fingers  140  extending therefrom each having a collet head  142  on a distal end thereof. Collet heads  142  include lower shoulders  144  that form a mating surface with upper shoulder  112  of intermediate liner tubular  106 . In addition, collet heads  142  include upper shoulders  146  that form a mating surface with lower shoulder  114  of upper liner tubular  104 . Collet collar  138  has a lower shoulder  148 . 
     In operation and additionally referencing  FIGS. 3A-3B , running tool  100  is used to install liner string  102  in a wellbore. In the illustrated embodiment, as liner string  102  is being run downhole via work string  54 , significant force may be required to push liner string  102  to its desired location, particularly in deviated, horizontal or multilateral wellbores. The force from the surface is applied through work string  54  to upper mandrel tubular  120 . In the running configuration of running tool  100 , upper mandrel tubular  120  applies the downward force to intermediate liner tubular  106  via collet assembly  136 . Specifically, as best seen in  FIG. 2B , prop assembly  130  radially outwardly flexes collet fingers  140  such that collet heads  142  engage profile  110  of liner string  102 . In this configuration, the downward force from upper mandrel tubular  120  is applied to upper shoulder  112  of intermediate liner tubular  106  by lower shoulders  144  of collet heads  142 . 
     Once liner string  102  is positioned in the desired location in the wellbore, running tool  100  can be decoupled from liner string  102  and retrieved to the surface. This may be accomplished using hydraulic pressure, shear force, string rotation or a combination thereof to decouple a lower collet (not pictured) or other component to allow relative movement between mandrel  116  and liner string  102 . Thereafter, shifting mandrel  116  uphole relative to liner string  102  unprops collet assembly  136  through the interaction of lower shoulder  114  of upper liner tubular  104  with upper shoulders  146  of collet heads  142 . Once collets heads  142  are off of or remote from prop extension  132  of prop assembly  130 , as best seen in  FIG. 3B , collet fingers  140  radially inwardly contract such that an inner surface of collet heads  142  is proximate to the outer surface of upper mandrel tubular  120  forming clearance gaps therebetween or in contact with the outer surface of upper mandrel tubular  120 . In the case of contact between the inner surface of collet heads  142  and the outer surface of upper mandrel tubular  120 , collet fingers  140  go from a first radially outwardly flexed state supported by prop extension  132  to a second radially outwardly flexed state supported by upper mandrel tubular  120 , wherein the first radially outwardly flexed state is greater than the second radially outwardly flexed state. In the case of a proximate relationship between the inner surface of collet heads  142  and the outer surface of upper mandrel tubular  120 , collet fingers  140  go from a radially outwardly flexed state supported by prop extension  132  to radially relaxed state, wherein a radially inwardly directed force could cause collet fingers  140  to be radially inwardly flexed until the inner surface of collet heads  142  contacts upper mandrel tubular  120 . Depending upon the desired relationship between the inner surface of collet heads  142  and the outer surface of upper mandrel tubular  120 , collet fingers  140  may be angled toward upper mandrel tubular  120  from collet collar  138  to collet heads  142  between about 2 degrees and about 6 degrees and preferably at least 3 degrees. 
     In this radially refracted configuration of collet assembly  136 , collet heads  142  have disengaged from mating profile  110 , thereby releasing running tool  100  from liner string  102 . Thereafter, running tool  100  may be withdrawn uphole from liner string  102  and out of the wellbore. Importantly, due to the radially contracted configuration of collet assembly  136 , running tool  100  can be retrieved out of the wellbore without collet heads  140  hanging up on profiles or other radially reduced regions of liner string  102 . In addition, running tool  100  may be lowered further into downhole into liner string  102 , if desired, without collet heads  140  hanging up on profiles or other radially reduced regions of liner string  102 . 
     Referring next to  FIGS. 4A-4B , therein are depicted cross sectional views of a collet assembly in its radially outwardly flexed state and its relaxed state, respectively. Collet assembly  136  includes a generally cylindrical collet collar  138  having a central axis  150 . Collet assembly  136  also includes a plurality of collet fingers  140  that extend from collet collar  138 . Each collet finger  140  has a collet head  142  on a distal end thereof. Collet heads  142  include lower shoulders  144  for mating with upper shoulder  112  of intermediate liner tubular  106 , as described above. In addition, collet heads  142  include upper shoulders  146  for mating with lower shoulder  114  of upper liner tubular  104 , as described above. Collet collar  138  has a lower shoulder  148 . Collet assembly  136  has a first configuration, in which collet fingers  140  are in a radially outwardly flexed state such that collet fingers  140  extend substantially parallel with central axis  150  of collet collar  138 , as best seen in  FIG. 4A . This configuration corresponds to the configuration in  FIG. 2B  wherein collet assembly  136  is engaged in profile  110  of liner string  102 . Collet assembly  136  has a second configuration, in which collet fingers  140  are in a radially relaxed state such that collet fingers  140  extend from collet collar  138  to collet heads  142  at an angle toward central axis  150 , as best seen in  FIG. 4B . This configuration corresponds to the configuration in  FIG. 3B  wherein collet assembly  136  is disengaged from profile  110  of liner string  102 . In this illustrated embodiment, collet fingers  140  are angle toward central axis  150  at about 3 degrees, however, other angles both greater than and less than 3 degrees are also possible and are considered within the scope of the present disclosure including, but not limited to angles between about 2 degrees and about 6 degrees. 
     It should be understood by those skilled in the art that the illustrative embodiments described herein are not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments will be apparent to persons skilled in the art upon reference to this disclosure. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.