Abstract:
The disclosure relates to a seal assembly for a ram of a blowout preventer for sealing a wellbore penetrating a subterranean formation. The wellbore has a tubular to pass fluid therefrom. The rams are positionable about the tubular. The seal assembly includes a compound seal carried by the ram. The compound seal includes a face seal having a sealing surface sealingly engageable about the tubular and a support seal positionable adjacent to the face seal a distance from the sealing surface. The sealing surface extends along a front face thereof engageable with at least one of the tubular and the face seal of another ram. The support seal is non-engageable with the tubular during sealing and is more deformable than the face seal whereby the compound seal is supported during sealing.

Description:
BACKGROUND 
     The present disclosure relates generally to techniques for performing wellsite operations. More specifically, the present disclosure relates to techniques for preventing blowouts, such as blowout preventers and/or seals. 
     Oilfield operations may be performed to locate and gather valuable downhole fluids. Oil rigs are positioned at wellsites, and downhole tools, such as drilling tools, are deployed into the ground to reach subsurface reservoirs. Once the downhole tools form a wellbore to reach a desired reservoir, casings may be cemented into place within the wellbore, and the wellbore completed to initiate production of fluids from the reservoir. Downhole tubular devices, such as pipes, certain downhole tools, casings, drill pipe, liner, coiled tubing, production tubing, wireline, slickline, or other tubular members positioned in the wellbore, and associated components, such as drill collars, tool joints, drill bits, logging tools, packers, and the like, (referred to as ‘tubulars’ or ‘tubular strings’) may be positioned in the wellbore to enable the passage of subsurface fluids to the surface. 
     Leakage of subsurface fluids may pose an environmental threat if released from the wellbore. Equipment, such as blow out preventers (BOPs), may be positioned about the wellbore to form a seal about a tubular therein to prevent leakage of fluid as it is brought to the surface. BOPs may be annular or ram BOPs with mechanism, such as rams or fingers, with seals to seal a tubular in a wellbore. Examples of BOPs are provided in U.S. Patent/Application Nos. 2012/0227987; 2011/0226475; 2011/0000670; 2010/0243926; U.S. Pat. Nos. 7,814,979; and 7,367,396, the entire contents of which are hereby incorporated by reference herein. 
     SUMMARY 
     In at least one aspect, the disclosure relates to a seal assembly for a ram of a blowout preventer for sealing a wellbore penetrating a subterranean formation. The wellbore has a tubular to pass fluid therefrom. The ram is positionable about the tubular. The seal assembly includes a compound seal carried by the ram. The compound seal includes a face seal having a sealing surface sealing engageable about the tubular, and a support seal positionable adjacent to the face seal a distance from the sealing surface. The sealing surface extending along a front face thereof engageable with at least one of the tubular and the face seal of another ram. The support seal is non-engageable with the tubular during sealing, and is more deformable than the face seal whereby the compound seal is supported during sealing. 
     The seal assembly may also include an array of inserts with the face seal molded thereabout. The face seal may have a lip extending between upper and lower portions of the array of inserts. The seal assembly may also include supports on opposite sides of the array. The face seal may have contact regions about the supports. The contact regions may define a flat face along the sealing surface. The face seal may have a support surface away from the sealing surface. The support seal is positionable along the support surface. Both the face seal and the support seal each may have a pair of linear portions with an arcuate portion therebetween. 
     The face seal and support seal each comprise a deformable material. 
     In another aspect, the disclosure relates to a blowout preventer for sealing a wellbore penetrating a subterranean formation. The wellbore has a tubular to pass fluid from the wellbore. The blowout preventer includes a housing positionable about the wellbore, rams positionable about the passage, and a seal assembly carried by each of the rams. The housing has a passage to receive the tubular therethrough. The seal assembly includes a compound seal. The compound seal includes a face seal having a sealing surface sealing engageable about the tubular, and a support seal positionable adjacent to the face seal a distance from the sealing surface. The sealing surface extending along a front face thereof engageable with at least one of the tubular and the face seal of another ram. The support seal is non-engageable with the tubular and is more deformable than the face seal whereby the compound seal is supported during sealing. 
     The blowout preventer may also include a housing seal carried by the ram. Each of the rams may have a sealing face. The sealing surface of the seal assembly may be positioned about the sealing face. Each ram may have a seal cavity therein, and the seal assembly may be receivable in the seal cavity. Each ram may have a seal cavity extending into a sealing face thereof, and the seal assembly may be receivable in the seal cavity such that the sealing surface is positioned about the sealing face. Each of the rams may have at least one keys and at least one keyway about a sealing face thereof. The keys and keyways may be interlockingly engageable with a corresponding at least one key and at least one keyway of an adjacent ram. The blowout preventer may also include an actuator to selectively extend and retract the rams. 
     Finally, in another aspect, the disclosure relates to a method of sealing a wellbore penetrating a subterranean formation. The wellbore has a tubular to pass fluid from the wellbore. The method involves positioning a blowout preventer about the wellbore with the tubing through a passage of the blowout preventer, converging rams of the blowout preventer about the tubular, and sealingly engaging compound seals of the rams by sealingly engaging a sealing surface of a face seal of each of the compound seals about the tubular while supporting the face seal with a support seal, the sealing surface extending along a front face thereof engageable with at least one of the tubular and the face seal of another ram, the support seal positioned adjacent to the face seal a distance from the sealing surface such that the support seal is non-engageable with the tubular during the sealingly engaging, the support seal being more deformable than the face seal. 
     The may also include supporting an array of inserts with the face seal. The sealingly engaging may involve advancing an array of inserts towards the tubular with the face seal, flowing material of the compound seal towards the tubular, flowing contact regions of the compound seal towards an arcuate region of the compound seal between the contact regions, flowing material of the arcuate region of the compound seal towards the inserts, and/or flowing material of the compound seal towards along the sealing surface. The converging may involve advancing the rams towards the tubular. The sealingly engaging may involve deforming the compound seal with the rams, deforming the face seal against the tubular and deforming the face seal with the support seal, and/or deforming the face seal against the face seal of another ram. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more particular description of the disclosure, briefly summarized above, may be had by reference to the embodiments thereof that are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate example embodiments and are, therefore, not to be considered limiting of its scope. The figures are not necessarily to scale and certain features, and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness. 
         FIG. 1  depicts a schematic view of an offshore wellsite having a blowout preventer (BOP) with rams and BOP seal assemblies having compound BOP seals. 
         FIG. 2  is a vertical cross-sectional view of a BOP having the BOP seal assemblies with the compound BOP seals. 
         FIGS. 3A and 3B  are perspective and exploded views, respectively, of a ram block having the BOP seal assembly with the compound BOP seal. 
         FIGS. 4A and 4B  are perspective and exploded views, respectively, of the BOP seal assembly with the compound BOP seal including a face seal and a support seal. 
         FIGS. 5A and 5B  are front and rear perspective views, respectively, of the BOP seal assembly with the support seal removed. 
         FIGS. 6A-6C  are top, front, and rear views, respectively, of the face seal of the compound BOP seal. 
         FIGS. 7A-7C  are top, front, and rear views, respectively, of a support seal of the compound BOP seal. 
         FIGS. 8A and 8B  are perspective and top views of the BOP seal assembly in an undeformed and deformed position, respectively. 
         FIG. 9  is a schematic view of the BOP seal assembly showing flow of the compound BOP seal during sealing. 
         FIGS. 10A and 10B  are flow charts depicting methods of sealing a wellbore. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The description that follows includes exemplary apparatus, methods, techniques, and/or instruction sequences that embody techniques of the present subject matter. However, it is understood that the described embodiments may be practiced without these specific details. 
     Blowout preventers (BOPS) may be positioned about a wellsite and provided with rams having BOP seal assemblies. The BOP seal assemblies have compound BOP seals to form a seal about the wellbore, for example, during a blowout. The compound BOP seal may include multiple seals, such as a face seal and a support seal to selectively engage during sealing. The face seal may have a sealing surface for contact with another ram and/or a wellbore tubular to form a seal therewith. The support seal may support the face seal as the ram block is advanced and the face seal is deformed during sealing. 
     The face seal and the support seal may be made of an elastomeric or other deformable (non-rigid) material (e.g., rubber). The face seal may be made of a harder (e.g., stronger, stiffer, more rigid, and less deformable) material than the support seal, and/or be made of a different material. The material of the face seal may be the same as or different from the support seal, with the face seal being less deformable than the support seal. The material may be of any material and of any compressibility (deformability) such that the support seal is more deformable than the face seal. By way of non-limiting example, the support seal may have compressibility that is about 1% or more greater (e.g., from about 10 to about 20%) than the face seal. 
     The compound BOP seal may be configured to flow during sealing and/or to balance movement of the BOP seal assembly (e.g., inserts) with strength needed to maintain seal under wellbore pressures. The selected configuration may be provided to achieve desired strength to perform at any temperature, to bridge minor extrusion gaps between portions of the BOP seal assembly (e.g., inserts), to provide flexibility to seal over a wide sealing range, to resist wear, etc. 
       FIG. 1  depicts an offshore wellsite  100  including a surface system  102  and a subsea system  104 . The surface system  102  may include a rig  106 , a platform  108  (or vessel), and a surface unit  110 . The surface unit  110  may include one or more units, tools, controllers, processors, databases, etc., located at the platform  108 , on a separate vessel, and/or near to or remote from the wellsite  100 . While an offshore wellsite is depicted, the wellsite may be land based. 
     The subsea system  104  includes a conduit  112  extending from the platform  108  to a sea floor  114 . The subsea system  104  further includes a wellhead  116  with a tubular  118  extending into a wellbore  120 , a BOP  122  and a subsea unit  124 . The BOP  122  has a ram assembly  125  with rams  126  for shearing and/or sealing to seal the wellbore  120 . The rams  126  each include a BOP seal assembly  130  with a compound BOP seal  132 . 
     The surface system  102  and subsea system  104  may be provided with one or more control units, such as the surface unit  110  and/or the subsea unit  124 , located at various locations to control the surface system  102  and/or the subsea systems  104 . Communication links  128  may be provided for communication between the units and various parts of the wellsite  100 . 
     The BOP  122  may be coupled to a BOP monitoring system  101  to monitor BOP operations. The BOP monitoring system  101  may be coupled to the BOP  122  and/or other portions of the wellsite  100  and/or offshore locations to collect data, communicate with various locations, measure parameters, analyze results, generate reports and/or adjust operations. The BOP monitoring system  101  may be in communication with the BOP  122 , for example, via the units  110 ,  124  and/or communication links  128 . 
     The BOP monitoring system  101  may be located on or off the wellsite  100 . While the BOP monitoring system  101  is depicted as being coupled to the BOP  122  via communication link  128 , the BOP monitoring system  101  may be incorporated into one or more of the control units  110 ,  124 , the surface system  102 , the downhole system  104 , and/or other locations. Sensors may optionally be provided as part of the BOP monitoring system  101  or be coupled thereto for providing information. 
       FIG. 2  depicts an example BOP  222  usable as the BOP  122  of  FIG. 1 . The BOP  222  includes a housing  229  with multiple rams  226  movably positionable therein by actuators  234 . The actuators  234  may include a ram rod  233  and cylinder  235  for selectively extending and retracting the rams  226 . The pipe  118  extends through the housing  229 . The rams  226  are positionable in passage  236  of the housing  229  and selectively movable into engagement with the pipe  118  for sealing and/or severing the pipe  118 . The actuators  234  may be selectively activated by units (e.g.,  110 ,  124  of  FIG. 1 ). The rams  226  may extend for engagement within the BOP  222  with or without contact with the pipe  118  to form a seal about the wellbore. 
     The rams  226  have BOP seal assemblies  230  with compound BOP seals  232  therein for forming a seal. The BOP seal assemblies  230  and compound BOP seals  232  are carried by the rams  226  and move relative to the pipe  118 . The seal assemblies  230  of adjacent rams  226  may converge and move into sealing engagement about the tubular  118 . The seal assemblies  230  may seal with the seal assembly  230  of an adjacent ram and/or with the tubular  118 . 
       FIGS. 3A and 3B  show perspective and exploded views, respectively, of the ram  226  and the BOP seal assembly  230 . The ram  226  includes a ram block  334  with a seal cavity  336  to receive the BOP seal assembly  230 . The ram  226  also has a sealing face  333  with the seal cavity  336  extending therein, and an inlet  335  shaped to receive the tubular  118 . The ram  226  may also include other features, such as a housing seal  338 , keys  340 , and keyways  342 . 
     The BOP seal assembly  230  includes the compound BOP seal  232 . The compound BOP seal  232  has a sealing surface  337  extending along the sealing face  333  and inlet  335  of the ram  226 . The sealing surface  337  of the compound BOP seal  232  is sealingly engageable with a compound BOP seal  232  of an adjacent ram and/or with the tubular  118 . 
       FIGS. 4-5B  show various aspects of the BOP seal assembly  230 .  FIGS. 4A and 4B  show perspective and exploded views, respectively, of the BOP seal assembly  230 . FIGS.  5 A and  5 B show front and rear perspective views, respectively, of a portion of the BOP seal assembly  230 . 
     As shown in  FIGS. 4A-5B , the BOP seal assembly  230  also includes inserts  446 , metal supports  448 , lateral pins  450 , and retention washer  452 . As shown, the compound BOP seal  232  includes a face seal  454  and a support seal  456 .  FIGS. 6A-6C  show additional views of the face seal  454 .  FIGS. 7A-7C  show additional views of the support seal  456 . The face seal  454  may be molded together with the inserts  446 , supports  448 , and pins  450 . The support seal  456  is positioned along a rear support surface  458  of the face seal  454  opposite the sealing surface  337  to provide support thereto. 
     The face seal  454  is depicted as having contact region  455  about the supports  448  and an arcuate region  457  about the inserts  446  (see, e.g.,  FIG. 5A ). The front sealing surface  337  has a lateral bead  460  along each of the linear portions about the supports  448 , and a seal bore  462  along the inlet  335 . The front sealing surface  337  of face seal  454  is shaped to contact and sealingly engage another surface and/or the tubular  118 . The support seal  456  is shaped to support the face seal  454 . 
     As shown in  FIGS. 4B and 6A , the face seal  454  may be molded around inserts  446  such that portions of the face seal  454  form holes to receive the inserts  446  therethrough. The seal bore  462  is sandwiched between portions of the inserts  446  such that the seal bore forms a lip deformable against the tubular between portions of the insert  446  above and below the lip. 
     Referring to  FIGS. 4A-5B , the face seal  454  has the front sealing surface  337  positionable in a contact position for sealing with the tubular  118  and/or another BOP seal. The support seal  456  is positionable away from the sealing surface  337  and in a non-contact position relative to the another BOP seal and/or the tubular  118 . In this configuration, the face seal  454  provides contact surfaces for sealing engagement, while the support seal  456  is isolated from, contact with sealed components. Other configurations may be provided where at least a portion of the support seal  456  engages the sealed components. 
     The compound BOP seal  232 , face seal  454 , and/or support seal  456  may be made of one or more materials. The materials may be, for example, an elastomeric material, such as rubber. One or more seals may be used to form the compound BOP seal  232 . The face seal  454  may be made of a harder (less deformable) material (e.g., with a higher compressive modulus) with flow sufficient to provide a seal. The support seal  456  may be made of a softer (more deformable) material (e.g., with a lower compressive modulus) with a reduced strength to provide support to the face seal  454  and increase flow thereabout. 
     In an example, a harder compound may be used with the face seal  454  to resist higher stresses, and a softer compound may be used with the support seal  456  to facilitate actuation of the BOP seal. A softer compound may be used, for example, to increase sealing ranges at low temperatures. A harder compound may be used, for example, to resist wear and/or fatigue. The selected material may also be selected to achieve a desired sealing range at a desired temperature. 
       FIGS. 8A-9  depict the BOP seal assembly  230  during operation.  FIGS. 8A and 8B  show the BOP seal assembly  230  in an undeformed and a deformed position, respectively.  FIG. 9  shows compression of the BOP seal assembly  230  during operation of the BOP  222  ( FIGS. 1 and 2 ) and convergence of the rams  226  about the tubular  118  ( FIG. 2 ). As the rams  222  press against an adjacent ram and/or tubular  118 , the BOP seal  232  is activated to sealingly engage along sealing surface  337 . 
     During sealing engagement, the face seal  454  makes initial contact along the contact regions  455 . The rams  222  continue to advance and moves from the undeformed position of  FIG. 8A  to the deformed position of  FIG. 8B . Under deformation, the compound BOP seal  232  flows and the inserts  446  converge. Contact pressure is transferred through the face seal  454  and to the support seal  456 . The face seal  454  has a harder (less deformable) material to support the seal in sealing engagement with sufficient flow to allow the inserts  446  to move and to allow the face seal  454  form a seal. 
     The face seal  454  may be used, for example, to affect a seal about the wellbore and/or to activate/move the inserts  446  into the deformed position (e.g., pushed against the tubular  118 ). The face seal  454  may facilitate movement of the inserts  446  to prevent extrusion of the face seal  454  between the inserts  446  and the tubular  118 . The inserts  446  may be movable a range of distances to accommodate various wellsite configurations and/or tubular sizes. 
     The support seal  456  provides flexible support for the face seal  454  along the rear surface  458  thereof. As a softer (more deformable) compound, the support seal  456  flows to provide a flexible support between the face seal  454  and the ram  222 . The ram  222  supplies rigid support along a rear surface of the face seal  448 . The BOP seal  230  is confined from the front surface by contact with an adjacent ram. 
     As shown in  FIG. 9 , the forces apply to the compound BOP seal  232  as the compound BOP seal  232  flows towards inlet  335 . As the rams  226  are deformed together, a deformation force F C  is applied along sealing surface  337  and compressive force FR is applied along rear surface  458 . The compound BOP seal  232  is confined from the rear to allow the face seal  454  to flow about the inlet  335  in an effort to continue relieving the increasing pressure caused by the force F R  on the ram. 
     A volume of the face seal  454  flows and is transferred along the contact regions  455  and the arcuate region  457  towards the inlet  335  as indicated by the arrows. The harder rubber of the face seal  454  provides a seal with flexibility which flows to allow movement of the inserts, and the softer rubber of the support seal  456  has sufficient flow to permit flexibility between the face seal  454  and the ram  226  while supporting the face seal  454 . The flow displaces a portion of the face seal  454  from the contact region  455  to the arcuate region  457  of the BOP seal assembly  230 . 
     The inserts  446  are displaced with the compound BOP seal  232 , and converge about the tubular  118 . The inserts  446  and/or face seal  454  may engage the tubular  118 . Once in sealing engagement (e.g., in contact with the tubular  118  and/or another BOP seal assembly  230 ), the face seal  454  becomes hydro-locked and the contact pressure P C  of the ram  222  (generated from the force F R ) reaches the desired level to achieve a seal with the compound BOP seal  232 . 
     While a specific configuration of the BOP seal assembly  230  and compound BOP seal  230  are depicted, variations may occur. For example, the compound BOP seal  230  may be made of one or more portions of one or more materials of various geometries. 
       FIG. 10A  depicts a method  1000   a  of sealing a wellbore. The method  1000   a  involves  1060 —providing a blowout preventer about a wellbore. The blowout preventer comprising rams carrying a seal assembly. The seal assembly comprises a face seal and a support seal. The method further involves  1062 —forming a seal about the wellbore by sealingly engaging the seal assemblies of the rams, and  1064 —supporting the face seal with the support seal during the forming. The methods may be performed in any order, or repeated as desired. Various combinations of the methods may also be provided. 
       FIG. 10B  depicts a method  1000   b  of sealing a wellbore. The method  1000   b  involves  1066 —positioning a blowout preventer about the wellbore with the tubing through a passage of the blowout preventer. The method further involves  1068 —converging rams of the blowout preventer about the tubular, and  1070 —sealingly engaging compound seals of the rams by sealingly engaging a sealing surface of a face seal of each of the compound seals about the tubular while supporting the face seal with a support seal positioned adjacent to the face seal a distance from the sealing surface such that the support seal is non-engageable with the tubular, the support seal being more deformable than the face seal. The methods may be performed in any order, or repeated as desired. Various combinations of the methods may also be provided. 
     It will be appreciated by those skilled in the art that the techniques disclosed herein can be implemented for automated/autonomous applications via software configured with algorithms to perform the desired functions. These aspects can be implemented by programming one or more suitable general-purpose computers having appropriate hardware. The programming may be accomplished through the use of one or more program storage devices readable by the processor(s) and encoding one or more programs of instructions executable by the computer for performing the operations described herein. The program storage device may take the form of, e.g., one or more floppy disks; a CD ROM or other optical disk; a read-only memory chip (ROM); and other forms of the kind well known in the art or subsequently developed. The program of instructions may be “object code,” i.e., in binary form that is executable more-or-less directly by the computer; in “source code” that requires compilation or interpretation before execution; or in some intermediate form such as partially compiled code. The precise forms of the program storage device and of the encoding of instructions are immaterial here. Aspects of the invention may also be configured to perform the described functions (via appropriate hardware/software) solely on site and/or remotely controlled via an extended communication (e.g., wireless, internet, satellite, etc.) network. 
     While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible. For example, one or more BOP seals (e.g., face and support) of various shapes may be made of various (same or different) materials having various sealing characteristics (e.g., hardness) for achieving the desired sealing capabilities. 
     Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter. 
     Insofar as the description above and the accompanying drawings disclose any additional subject matter that is not within the scope of the claim(s) herein, the inventions are not dedicated to the public and the right to file one or more applications to claim such additional invention is reserved. Although a very narrow claim may be presented herein, it should be recognized the scope of this invention is much broader than presented by the claim(s). Broader claims may be submitted in an application that claims the benefit of priority from this application.