Abstract:
A cementing adaptor includes a cylindrical carrier carrying a casing seal, a middle interval and a lower end separated by an annular rib, and a cylindrical swivel element disposed around and coaxially rotatable relative to the middle interval. A cylindrical connector has an upper end rotatably disposed around the carrier&#39;s lower end and non-rotatably connected to the swivel element, plus a lower end connectable to an inner tubular string. With the carrier&#39;s upper end connected to a casing running tool (CRT), this assembly can be disposed within a casing string with the casing seal engaging the casing and preventing fluid flow into the casing annulus below the seal when cement is pumped down the inner string, such that the cement is urged into the wellbore annulus. The swivel connection limits torque transfer that might otherwise overload the CRT or its connection to the cementing adaptor.

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates in general to apparatus and methods for introducing fluids into a casing string or other tubular element during well construction operations, and for removing fluids from the casing string. In particular, the disclosure relates to apparatus and methods for introducing a fluid such as drilling mud or cement slurry into a casing string at a selected depth by means of a tubular inner string. 
     BACKGROUND 
     Typical construction of an oil or gas well includes the operations of assembling a casing string, inserting the casing string into a wellbore, and cementing the casing in place in the wellbore. Casing assembly involves connecting multiple individual lengths of pipe (or “joints”) to form an elongate casing string. Threaded connections are usually used to join the individual lengths of pipe, requiring the application of torque to “make up” the connections, or to “break out” the connections should the string need to be disassembled. After a wellbore has been drilled to a desired depth into a subsurface formation, by means of a rotating drill bit mounted to the end of a drill string, the drill string is withdrawn and the casing string is then inserted essentially coaxially within the wellbore. 
     In the alternative method known as casing drilling (or “drilling with casing”), the wellbore is drilled with a drill bit mounted to the bottom of the casing string, eliminating the need for a separate drill string. After the well is drilled, the casing remains in the wellbore. As used in this patent document, the term “drill string” is to be understood, in the context of the drilling phase, as referring to the casing string for purposes of well construction operations using casing drilling methods. 
     During the drilling phase of well construction, a selected drilling fluid (commonly called “drilling mud”) is pumped under pressure downward from the surface through the drill string, out through ports in the drill bit into the wellbore, and then upward back to the surface through the annular space that forms between the drill string and the wellbore (due to the fact that the drill bit diameter is larger than the drill string diameter). The drilling fluid, which may be water-based or oil-based, carries wellbore cuttings to the surface, and can serve other beneficial functions including drill bit cooling, and formation of a protective cake to stabilize and seal the wellbore wall. 
     Once the well has been drilled to a desired depth and the casing is in place within the wellbore, the casing is cemented into place by introducing a cement slurry (commonly referred to simply as “cement”) into the wellbore annulus. This is typically done by introducing an appropriate volume of cement into the casing string (i.e., a volume corresponding to the volume of the wellbore annulus), and then introducing a second and lighter fluid (such as drilling mud or water) into the casing under pressure, such that the second fluid will displace the cement downward and force it out and around the bottom of the casing, and up into the wellbore annulus. In the typical case, this operation is continued until the cement has risen within the wellbore annulus up to the top of the casing. Once thus cemented, the casing acts to structurally line the wellbore and provide hydraulic isolation of formation fluids from each other and from wellbore fluids. 
     In some applications it is desirable to introduce cement into the casing through a tubular “inner string” inserted into the casing bore and arranged to extend from the proximal (i.e., upper) end of the casing string to a selected depth, typically near the distal (i.e., lower) end of the casing string or near what is referred to as the “casing shoe”. The inner annulus between the inner string and casing is left fluid-filled and sealed near the proximal end of the casing so that cement pumped through the inner string is then introduced into the casing near the shoe. The fluid filling the inner annulus tends to prevent cement flow up the inside of the casing and instead the cement is urged to immediately enter the casing wellbore annulus during pumping. This is known in the art as an “inner string cement job” and typically requires an adaptor nubbin, sealingly connecting between the casing and the inner string. On top-drive-equipped rigs, the adaptor nubbin also connects to the top drive, facilitating the functions of rotation and reciprocation during cementing to further promote distribution of the cement in the casing to the wellbore annulus. 
     It is increasingly common in the drilling industry to use top-drive-equipped drilling rigs instead of traditional rotary table rigs, and to install casing (an operation commonly referred to as “casing running”) and/or to drill with casing directly using the top drive. Casing running tools (CRTs), such as the “Gripping Tool” described in U.S. Pat. No. 7,909,120, connect to the top drive quill and support these well construction operations by engaging the upper end of the tubular string (i.e., drill string or casing string, as the case may be) so as to allow transfer of axial and torsional loads between the tubular string and the top drive, and to allow the flow of fluids (such as drilling mud and cement) into or out of the casing string through a central passage or bore in the tool. Such tools thus enable the top drive to be used for make-up and break-out of connections between joints of pipe, hoisting and rotation of tubular strings, casing fill-up, circulation of drilling mud, and cementing of casing. 
     BRIEF SUMMARY 
     The present disclosure teaches embodiments of cementing adaptor tools for sealingly connecting an inner string to the distal (lower) end of a CRT while also facilitating the functions of reciprocation and rotation, so that the CRT can be used to replace the function of the adaptor nubbin without the need to engage with the casing threads, thus providing a sealed flow path for cement into the inner string and thereby enabling the CRT to be used perform an “inner string cement job”. This has the advantages of exploiting the existing capacity of the CRT to grip and seal with the casing, obviating the need for an adaptor nubbin customized to the casing thread (and thus removing the risk of damage to the casing thread), and eliminating the need to rig down the CRT after running the casing to replace it with the adaptor nubbin, thus saving time and reducing risk of damage. 
     Cementing adaptors in accordance with the disclosure are provided with a swivel connection for limiting torque that will typically arise during rotation of the inner string casing assembly as a result of frictional interaction between the inner string and the casing as they are rotated in wellbores having at least some deviation from vertical, thus inducing lateral loading between the casing&#39;s inner surface and tubular inner string&#39;s outer surface. It will be apparent to persons skilled in the art that right-hand rotation of the casing relative to the wellbore will tend to cause left-hand torque to build toward the proximal (upper) end of the inner string, which torque tends to back off the connections between the joints comprising the inner string (which are normally provided as right-hand-threaded connections). 
     The swivel connection further limits the torque that might otherwise overload the CRT or the connection between the cementing adaptor and the CRT. It will be apparent to persons skilled in the art that the swivel may take various forms and use various means to transfer loads from the inner string to the CRT while minimizing friction in the connection. Such alternative means may include (without being limited to) plain bushings, rolling element bearings, and pressurized fluid chambers. 
     To provide further protection for the CRT and the cementing adaptor against the risk of overload from bending loads that might arise from lateral gravity loads on the inner string in applications such as slant drilling (or other operations tending to displace the inner string away from substantially concentric alignment with the casing), suitable centralizers can be mounted to the inner string elements to act between the tubular inner string and the inside of the casing at selected locations along the length of the inner string to adequately support the inner string to a depth sufficient to prevent excess bending at the attachment point to the CRT or at any point in the inner string. It will be apparent to persons skilled in the art that the length and lateral stiffness of the inner string elements connecting the centralizers to the cementing adaptor can be selected to minimize bending loads at the attachment point. 
     Cementing adaptors in accordance with the present disclosure also provide means for sealing the annular space between the outer surface of the inner string and the inner surface of the casing, to prevent fluid in this annular space from being displaced out of the casing when cement is being pumped down the inner string, such that the cement is urged into the annular space between the outer surface of the casing and the wellbore. 
     Alternative embodiments of cementing adaptor tools in accordance with the present disclosure may also be adapted for use in conjunction with a plug-dropping manifold tool. A plug-dropping manifold tool, as is known to the art, has means to provide a swivel fluid entry to an inner string bore or tool bore, plus means for releasing one or more plugs (which may be ball plugs, wiper plugs or other similar devices), and include means for positively indicating the dropping of such plugs, while facilitating the functions of reciprocation and rotation by providing means for transferring axial and torsion loads from a top drive to the various tubulars used in oil well drilling and construction. In such embodiments, the cementing adaptor is attached to the distal (lower) end of a CRT mounted to the distal end of the plug-dropping manifold tool. The bores of the CRT and the inner string cementing tool are sized and aligned so that plugs released from the plug-dropping manifold tool will pass through the cementing adaptor and the inner string to provide functions including:
         separation of displacing fluids from displaced fluids;   positive wiping of the inner surfaces of the casing to further enhance complete fluid displacement; and   engagement with their intended targets located downhole from the inner string.       

     Downhole targets may include devices such as cement staging tools or subsea cementing wiper plug launchers where the casing wiper plug is carried at the distal end of the cementing string and launched when a dropped ball or dart is pumped down and into engagement with the device in a manner known in the art of well cementing. Cementing adaptor tools adapted for use with plug-dropping manifold tools provide the advantage of not having to rig out the CRT to launch plugs or to perform ball drops, and also facilitate side-entry fluid injection (mud or cement), which is desirable in cases where operators prefer not to have certain fluids or slurries (such as cement) run through the top drive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments in accordance with the present disclosure will now be described with reference to the accompanying Figures, in which numerical references denote like parts, and in which: 
         FIG. 1  is a cross-sectional view of an embodiment of a cementing adaptor tool in accordance with the present disclosure, shown fitted with a stab guide/thread protector to allow for normal casing running operations with the cementing adaptor attached. 
         FIG. 2  is a cross-sectional view of the cementing adaptor tool in  FIG. 1 , shown as it would appear disposed between and attached to a casing running tool and an inner string. 
         FIG. 3  is a cross-sectional view of the assembly in  FIG. 2 , disposed within a tubular casing string with the casing running tool grippingly engaging the casing string. 
         FIG. 4  is a cross-sectional view of an assembly generally as in  FIG. 2 , but with an inner string centralizing pup mounted between the inner string and the lower end of the cementing adaptor tool. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 through 4  illustrate embodiments of a cementing adaptor tool  100  in accordance with the present disclosure. Cementing adaptor  100  is of an elongate and generally cylindrical configuration, with a proximal (upper) end  101  that can be rigidly attached to a casing running tool (CRT) and a distal (lower) end  103  that can be rigidly attached to a tubular inner string. Cementing adaptor  100  is provided with an internal flow path FP and configured such that flow path FP will be continuous with and sealed to an internal flow path in the CRT after cementing adaptor  100  has been mounted to the CRT. This internal flow path FP generally runs the length of the tool and allows for flow of fluid from the CRT through the cementing adaptor from the proximal end to the distal end. 
     Disposed between the proximal and distal ends of cementing adaptor  100  is a swivel element which allows an inner string attached to the distal end of cementing adaptor  100  to rotate independently of the CRT, and to minimize torque build-up within the inner string and thus minimize torque transfer from the inner string to the CRT. The distal end of cementing adaptor  100  typically will incorporate the male end of a shouldering threaded connection designed to threadingly and sealingly engage the female (or box end) of an inner string (which typically will be made up from oilfield drill pipe). Cementing adaptor  100  further incorporates a casing seal assembly designed to seal the annular space between cementing adaptor  100  and a casing string. 
     Referring now to  FIG. 1 , cementing adaptor  100  with a proximal (upper) end  101 , a middle interval  102 , and a distal (lower) end  103  is shown in cross-sectional view with a stab guide  110  attached to distal end  103 . Cementing adaptor  100  comprises an elongate and generally cylindrical carrier  120 , a generally cylindrical swivel element  140 , a generally cylindrical connector  160 , and a generally cylindrical casing seal assembly  180 . Carrier  120  extends between proximal end  101  and middle interval  102  of cementing adaptor  100  and has an upper end  121 , a middle interval  122 , and a lower end  123 , with middle interval  122  and lower end  123  being separated or demarcated by an annular shoulder rib  127  extending radially outward from carrier  120 . Swivel  140  is coaxially and rotatably disposed about middle interval  122  of carrier  120 , above shoulder rib  127 . A load thread  124  and a seal  125  are provided at upper end  121  of carrier  120 . A plurality of seal grooves  126  are disposed along the outside surface of middle interval  122 . Annular shoulder rib  127  defines an upward facing shoulder  128  and a downward facing shoulder  129 . Lower end  123  is formed with a plurality of seal grooves  130 . 
     In the illustrated embodiment, casing seal assembly  180  includes a packer cup  181  of a type common to many oilfield casing seal assemblies. Casing seal assembly  180  is coaxially carried by carrier  120 , and sealingly engaged with one or more of seal grooves  126  on middle interval  122  of carrier  120 . It is understood that the performance criteria for seal assembly  180  will vary depending on casing weights and pressure requirements and may be changed from job to job as required. It is also to be understood that various options exist for alternative casing seal arrangements, and that cementing adaptors in accordance with the present disclosure are not limited to the use of the illustrated casing seal arrangement or any other particular casing seal arrangement. 
     In the illustrated embodiment, swivel element  140  has an upper end  141 , a lower end  142  with a lower end face  147 , and an internal surface  143  defining a downward-facing annular shoulder  144  near upper end  141 . Threads  145  are provided in a lower region of internal surface  143 , and pins  146  are provided through openings in the cylindrical wall of swivel  140  below threads  145 . Upper end  141  of swivel  140  sealingly engages a seal groove  126  on carrier  120  above shoulder rib  127 . Downward-facing shoulder  144  is parallel and adjacent to upward facing shoulder  128  on shoulder rib  127 , Shoulders  128  and  144  are separated by and mutually abutted by a friction-reducing bushing  150 . Connector  160  has an upper end  161 , a lower end  162 , an inside cylindrical surface  167  and an annular upper face  168  at upper end  161 , and an outer surface  163 , with threads  164  on an upper region of outer surface  163  for mating engagement with threads  145  on swivel  140 . A plurality of pockets  165  are formed into outer surface  163  for engagement with pins  146 . Tapered threads  166  are provided on outer surface  163  at lower end  162 . 
     It to be is understood that cementing adaptors in accordance with the present disclosure are not limited to embodiments incorporating the illustrated shouldering threaded connection. Depending on the application, this style of connection to the inner string may be modified either by providing a different connector or by providing a crossover to adapt the tool to a different size or style of connection. 
     Inside surface  167  at upper end  161  of connector  160  sealingly engages seals  132  disposed in seal grooves  130  on lower end  123  of carrier  120 , while thread  164  engages thread  145  on swivel  140  and pins  146  engage pockets  165  to prevent thread disengagement and to react any torque generated through friction on shoulder  144 . Upper face  168  of connector  160  abuts downward-facing shoulder  129  of carrier  120 . Stab guide  110 , with lower tapered face  111 , upper shoulder  112 , tapered internal thread  113 , and locking pins  114 , loosely threadingly engages tapered thread  166  on connector  160 . Locking pins  114  engage pockets  169  on lower end  162  of connector  160  to prevent thread disengagement and to react any incidental torque. 
     With reference now to  FIG. 2 , cementing adaptor  100  is shown disposed between and rigidly attached to the lower end  201  of a casing running tool (CRT)  200  (such as, by way of example only, a “Gripping Tool” as described in U.S. Pat. No. 7,909,120) and the upper end  301  of an inner string  300 . Carrier  120  of cementing adaptor  100  is rigidly attached to and in sealing engagement with the inside surface  202  on the lower end of CRT  200 . In this embodiment, the attachment method is a threaded and pinned arrangement wherein axial load is carried by thread  124  on carrier  120  and the mating thread on CRT  200 , and torque is reacted in shear through a plurality of cap screws  203  in holes  133  on carrier  120 . A seal  125  engages a seal face  204  on CRT  200  to provide a continuous sealed bore through the CRT  200  and adaptor  100 . Still referring to  FIG. 2 , tapered and shouldered thread  166  of connector  160  is shown engaged with a female tapered shouldering thread  302  on the upper end  301  of an inner string  300 , providing rigid attachment and sealing engagement. 
     Referring now to  FIG. 3 , cementing adaptor  100  is shown disposed between and rigidly attached to lower end  201  of CRT  200  and upper end  301  of inner string  300 . CRT  200  is shown engaged with and gripping a casing string  400 . Packer cup  181  is shown engaged with the inner surface  401  of casing string  400 , sealing off the annular space below packer cup  181  between cementing adaptor  100  and inner surface  401  of casing string  400  from the annular space above packer cup  181  between CRT  200  and inner surface  401  of casing string  400 . As thus arranged, CRT  200  is able to hoist, rotate, and reciprocate the casing, with any incidental relative rotation as a result of the tumbling action of inner string  300  within casing  400  (such as in a deviated wellbore) being relieved through the action of swivel  140 . This arrangement thus facilitates and enables the functions required for running an inner string cementing job, including rotation and reciprocation of the casing string, taking into consideration the hoisting and torque capacities of both the system as a whole and its individual components. 
     Referring now to  FIG. 4 , cementing adaptor  100  is shown disposed between and rigidly attached to lower end  201  of CRT  200  and upper end  301  of inner string  300 , with CRT  200  engaging and gripping casing string  400 , generally as seen in  FIG. 3 . In this arrangement, however, an inner string pup  500  with a centralizing flange  501  is disposed between and attached to connector  160  and inner string  300 , and a side load bushing flange  190  is disposed between upward-facing shoulder  168  on connector  160  and lower end face  147  of swivel  140 . Both the outer diameter of bushing flange  190  and centralizing flange  501  are selected to be close to the minimum allowable casing diameter (or “drift”). The arrangement of these centralizing flanges prevents side loads induced by slant-drilling operations (or other forces tending to displace the inner string eccentric from substantially coaxial alignment with the casing) from overloading carrier  120  in bending, which would typically occur in the region of minimum section near upper end  121  of carrier  120 . It to be is understood that when significant side load is anticipated during an inner string cementing job, the axial spacing of these flanges can be selected in consideration of the compliance of both the cementing adaptor and the inner string, and in consideration of the clearance between the outer diameter of the flanges and the inner diameter of casing  400 , to prevent excessive bending stresses in cementing adaptor  100  and CRT  200 . 
     It will be readily appreciated by those skilled in the art that various modifications of cementing adaptor tools in accordance with the present disclosure may be devised without departing from the scope and teaching of the present disclosure, including modifications which may use equivalent structures or materials hereafter conceived or developed. It is to be especially understood that the disclosure is not intended to be limited to any described or illustrated embodiment, and that the substitution of a variant of a claimed element or feature, without any substantial resultant change in function or operation, will not constitute a departure from the scope of the disclosure. It is also to be appreciated that the different teachings of the embodiments described and discussed herein may be employed separately or in any suitable combination to produce desired results. 
     In this patent document, any form of the word “comprise” is to be understood in its non-limiting sense to mean that any item following such word is included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one such element. 
     Any use of any form of the terms “connect”, “engage”, “attach”, “mount”, or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the subject elements, and may also include indirect interaction between the elements such as through secondary or intermediary structure. 
     Relational terms such as “parallel”, “concentric”, and “coaxial” are not intended to denote or require absolute mathematical or geometrical precision. Accordingly, such terms are to be understood as denoting or requiring general or substantial precision only (e.g., “generally parallel” or “substantially parallel”) unless the context clearly requires otherwise. 
     Wherever used in this document, the terms “typical” and “typically” are to be interpreted in the sense of representative or common usage or practice, and are not to be understood as implying invariability or essentiality.