Abstract:
A locking door assembly, blowout preventer and method are provided. The blowout preventer is for sealing about a tubular extending from a wellbore of a wellsite. The blowout preventer includes a housing having a bore and a channel therethrough. The tubular is positionable through the bore and engageable therein. The blowout preventer also includes a door assembly including a door slidably positionable along an axis of the channel and providing selective access to the channel, and a lock. The lock includes at least one locking member having at least one raised portion extending along the door assembly in a direction transverse to the axis of the channel. The locking member is extendable into at least one corresponding receptacle of the housing and movable therealong between an unlocked and a locked position whereby the door assembly is selectively retractable from the housing.

Description:
BACKGROUND 
     This present disclosure relates generally to techniques for performing wellsite operations. More specifically, the present disclosure relates to techniques for preventing blowouts involving, for example, a blowout preventer, ram assembly, a door assembly, and/or a lock. 
     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 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 have selectively actuatable rams or ram bonnets, such as pipe rams or shear rams, that may be activated to seal and/or sever a tubular in a wellbore. Some examples of BOPs are provided in U.S. Patent/Application Nos. 20110000670; 7,814,979; and 7,367,396. 
     It may be desirable to provide BOPs with various features, such as seals, ram blocks, doors and/or lock mechanisms, etc., for use in wellsite operations. Examples of BOPs and/or features may be provided in U.S. patent application Ser. Nos.13/018,217 (not yet published at the time of filing), US 2010/0243926, US2011/0012311, U.S.Pat. Nos.5,897,094; 7,044, 430; 7,051,989, 5,575,452, WO 2012/012192, WO 2012/012193, U.S. Pat. Nos. 7,195,224 and 7,798,466. 
     SUMMARY 
     In at least one aspect, the disclosure relates to a door assembly for accessing a blowout preventer of a wellsite. The blowout preventer is for sealing about a tubular extending from a wellbore of the wellsite, and includes a housing having a bore and a channel therethrough. The tubular is positionable through the bore and severable therein. The door assembly includes a door slidably positionable along an axis of the channel and providing selective access to the channel, and a lock. The lock includes at least one locking member having at least one raised portion extending along the door assembly in a direction transverse to the axis of the channel. The locking member is extendable into at least one corresponding receptacle of the housing and movable therealong between an unlocked and a locked position whereby the door assembly is selectively retractable from the housing. 
     The locking member may include at least one locking plate having a plurality teeth, the teeth including a plurality of door teeth and a plurality of housing teeth on opposite sides thereof. The door teeth are engageable with the door. The housing teeth are engageable with the housing. The teeth may be distributed in discrete rows. The discrete rows may have trenches therebetween. The locking member is slidably movable between the locked position with the teeth of the locking member in non-alignment with the trenches of the housing or the door assembly and the unlocked position with the teeth of the locking member in alignment with the trenches of the teeth of the housing or door assembly. 
     The number of teeth of the housing and a number of teeth of the locking member may be the same or different. The teeth may have a polygonal shape, triangular shape, trapezoidal shape, and/or a round shape. The teeth may be at an acute angle to the axis of the channel. The locking member may include a pair of locking members on opposite sides of the door. The lock may also include a pair of lock supports operatively connecting the pair of lock plates about the door assembly. The locking member may include a locking ball. 
     In another aspect the disclosure relates to a blowout preventer for sealing about a tubular extending from a wellbore of the wellsite. The blowout preventer includes a housing having a bore and a channel therethrough, the tubular positionable through the bore and severable therein, and the door assembly positionable about an opening of the channel of the housing. 
     The blowout preventer may also include a ram block with a ram shaft extended therefrom through the door assembly and into a ram cylinder. The ram block may be slidably movable through the channel of the housing and sealingly engageable with the tubular. The blowout preventer may also include an actuator operatively connectable to the ram cylinder. 
     In yet another aspect, the disclosure relates to a method of accessing the blowout preventer of a wellsite. The method involves providing the door assembly about the blowout preventer, selectively retracting the door assembly from the housing by movably positioning the at least one raised portion along the at least one corresponding receptacle of the housing between the locked and unlocked position. 
     The raised portion may include a plurality of teeth and the selectively retracting may involve slidably moving the plurality of teeth of the locking member between the locked position in non-alignment with the trenches of the plurality of teeth of the housing and the unlocked position in alignment with trenches in the housing. The method may also involve slidably positioning a ram assembly in the channel of the housing. The ram assembly includes a ram block with a ram shaft extended therefrom through the door assembly and into a ram cylinder. The method also involves accessing the ram assembly by retracting the door assembly. The method may also involve slidingly moving the ram block slidably through the channel of the housing and in sealing engagement with the tubular. 
     The disclosure may also relate to a blowout preventer for sealing about a tubular. The blowout preventer includes a housing and a door assembly. The housing has a bore and a channel therethrough, the tubular positionable through the bore. The door assembly is positionable about an opening of the housing and provides selective access to the channel therein. The door assembly includes a plurality of teeth extendable into the housing and lockingly engageable therewith. 
     The disclosure may also relate to a method of sealing a tubular. The method involves positioning the blowout preventer about a wellbore, positioning the tubular through the bore of the housing, and positioning the door assembly about the opening of the housing such that the teeth extend into the housing and lockingly engage therewith. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the above recited features and advantages of the present disclosure can be understood in detail, 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 only typical 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 a ram assembly and a locking door assembly. 
         FIGS. 2A-2B  depict vertical cross-sectional views of a BOP with a ram assembly in a sealed and an unsealed position, respectively. 
         FIG. 3  depicts a horizontal cross-sectional view of a BOP with a ram assembly in the unsealed position. 
         FIGS. 4A-4B  depict perspective views of a BOP with a door assembly in a locked and an unlocked position, respectively. 
         FIGS. 5A-5B  depict top and bottom views, respectively, of locking members of the door assembly of  FIG. 4B . 
         FIGS. 6A-6E  depict vertical cross-sectional views of a portion of a BOP with various lock configurations. 
     
    
    
     DETAILED DESCRIPTION 
     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 tubular to provide a seal therewith, for example, during a blowout. To access portions of the BOP and/or components therein, the BOP may be provided with a door assembly to provide selective access thereto. Due to, for example, high pressures and temperatures in operating conditions, the door assembly may be provided with a lock that provides selective access and maintains the door assembly in a sealed, closed position during operation of the BOP. The lock may be in the form of a pair of lock plates with a plurality of teeth slidably positionable in selective locking engagement with a housing of the BOP. 
       FIG. 1  depicts an offshore wellsite  100  having a subsea system  104  and a surface system  102 . The surface system  102  may be used to facilitate oilfield operations at the offshore wellsite  100 . The surface system  102  may include a rig  105 , a platform  106  (or vessel) and a controller  108 . 
     The subsea system  104  includes a conduit (e.g., riser)  110  extending from the platform  106  to a sea floor  112 . The subsea system further includes a wellhead  114  with a tubular  116  extending into a wellbore  118 , a BOP  120  and a controller  108 . The BOP  120  has various BOP components, such as a ram assembly  124  for shearing the tubular  116  and sealing the wellbore  118 . The ram assembly  124  is engageable with the tubular  116  to form a seal about the tubular and/or to sever or cut the tubular  116 . The BOP  120  also has a door assembly  125  with a lock for providing selective access into the BOP as will be described more fully herein. 
     The surface system  102  and subsea system  104  may be provided with one or more controllers  108  located at various locations to control the surface system  102  and/or the subsea systems  104 . Communication links  126  may be provided for communication between the controllers  108  and various parts of the wellsite  100 . 
     Although the BOP  120  is described herein as being used in subsea operations, it will be appreciated that the wellsite  100  may be land or water based, and the BOP  120  and/or door assembly  125  may be used in any wellsite environment. The BOP  120  may sever and/or seal a tubular device, such as tubular  116 . ‘Tubular devices’ as used herein refers to tubular members or 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’). 
       FIGS. 2A ,  2 B and  3  depict various views of a BOP  220  with a ram assembly and a door assembly with a lock.  FIGS. 2A ,  2 B depict longitudinal cross-sectional views of a BOP  220  in a sealed and an unsealed position, respectively.  FIG. 3  depicts a longitudinal, cross-sectional view of a portion of a BOP depicting the door and lock assemblies in greater detail. 
     The BOP  220  includes a housing  228  with a bore  230  and a channel  232  therethrough. The BOP also includes a ram assembly  224  and a door assembly  225 . The ram assembly  224  includes a ram block  234 , a ram shaft  236  a ram cylinder  238  and an actuator  240 . The ram shaft  236  extends through the ram channel  232 . The BOP of  FIGS. 2A and 2B  is depicted with two opposing ram assemblies  224 , but any number may be provided in any direction. The ram block  234  may seal with and/or sever a tubular  216 . An example of a ram assembly usable with the BOP is described in U.S. Pat. No. 5,735,502. 
     The door assembly  225  includes a door  242  that provides access to the channel  232  and the components of the BOP  220 . The ram shaft  236  extends through the door  242  and to the ram cylinder  238  external thereto. The door assembly  225  is also provided with a lock  244  with teeth  246  for locking engagement with the housing  228 . The lock  244  as shown includes a pair of locking members (or plates)  248  positioned between the door  242  and the housing  228  for interlocking engagement therewith. The lock  244  may optionally be integral with the door  242  or housing  228 . 
       FIGS. 4A and 4B  depict perspective views of a portion of the BOP  220  of  FIGS. 2A and 2B  in a locked and unlocked position, respectively. These figures show the operation of the door assembly  225  in greater detail. The lock  244  includes upper and lower locking members  248  positioned on opposite sides of the door  242 . A pair of lock supports  450  are positioned on each end of the pair of locking members  248  and secures them in position about the door  242 . Bolts and/or other fasteners  451  may optionally be provided to secure the locking members  248  in a desired position. 
     The locking members  248  are depicted as being parallel to each other and having identical configurations. Each locking member  248  has a plurality of teeth  246  on a housing surface  452  positionable adjacent to the housing  228 . The teeth  246  are positioned along the housing surface  452  in rows with lock trenches  454  therebetween. The teeth  246  are lockingly engageable with corresponding slots  456  and teeth  457  in the housing  220 . 
     The housing  220  may also be provided with housing trenches  458  corresponding to the rows and lock trenches  454  of the locking member  248 . The slots  456  matingly engage with the teeth  246 . In some versions, the slots  456  may be defined between teeth  457  in the housing  228 . The teeth  457  in the housing  228  may be of the same shape as the teeth  246  for mating engagement therebetween. 
     When positioned with the teeth  246  and slots  456  interlocked as shown in  FIG. 4A , the door  242  is maintained in a closed position. When the lock  244  is moved along the door  242  in either direction as indicated by the dual arrows (e.g., in a direction perpendicular to the travel of the ram assembly) to a disengaged position where the teeth  246  align with the housing trenches  458 , the door  242  is released and moveable to a retracted position as shown in  FIG. 4B . The teeth  246  and the lock trenches  454  are shaped to correspond with slots  456  and housing trenches  458  such that when the locking member  248  is in a lock position, the teeth  246  are in locking engagement with the slots  456  to prevent release of the door  242 . 
     When the locking member  248  is moved to an unlocked position, the teeth  246  are moved into alignment with the housing trenches  458  of the housing and the teeth  457  of the housing are moved into alignment with the lock trenches  454 . In this position, the teeth  246  and  457  are free to move and the locking member may slide relative thereto. The door  242  is thereby released to move to an open position. In this manner, the lock  244  moves between the locked and unlocked position by traveling along the door  242  in a direction as indicated by the dual arrow, which is transverse to a retraction direction D of travel of the ram assembly as indicated by the unidirectional arrow. 
     The locking members  248  may be configured for selective movement between the door assembly  225  and the BOP housing  220 . In some cases, the locking members  248  may be made integral with one or the other of the door assembly  225  and the BOP housing  220 . In some cases, the locking member  248  may be affixed to or made integrally with one or the other of the door assembly  225  and the BOP housing  220 . For example, portions of the door assembly  225  may have teeth engageable with teeth of the BOP housing  220 , or portions of the BOP housing  220  may be provided with teeth engageable with teeth of the door assembly  225 . 
       FIGS. 5A and 5B  show top and bottom views of the locking members  248 . As shown in these views, the teeth  246  are disposed about the housing surface  452  in rows of parallel teeth  246  with lock trenches  454  therebetween. In this version, the plate  248  need only travel a portion of the distance of the length of the plate to provide separation from the adjacent BOP housing. 
     As shown in  FIG. 5B , a plurality of teeth  559  are depicted on a door side  560  of the locking member  248  and extend along the entire length thereof. The teeth  559  on the door side  560  of the locking member  248  may be used to provide locking engagement between the locking member  248  and the door  242 . In this version, the plate  248  must travel the entire length of the adjacent door before separation may occur. 
     While a specific configuration of teeth  246  is shown, a variety of configurations may be provided that permits selective interlocking engagement between the door  242  and the housing  228 . For example, the teeth  246  may have trenches  454  as shown in  FIG. 5A  to facilitate selective opening of the lock as shown in  FIG. 5B , or prevent opening. Other configurations may be provided to selectively separate the locking member  248  from the door and or BOP housing. 
       FIGS. 6A-6E  show cross-sectional views of various configurations of door assemblies usable as the door assembly  225 . As shown in each of these views, the lock may be of various configurations for providing locking engagement between the door  242  and the BOP housing  228 . The shape of the lock and/or teeth  246  may have a variety of shapes, such as polygonal, triangular, trapezoidal, round, etc. 
       FIG. 6A  shows the lock  244  of  FIGS. 4A-5B  in greater detail. As shown in this view, the locking teeth  246  on the housing surface  452  of the locking member  248  are triangular in shape with a slanted side of the triangle at an acute angle  0  to a horizontal axis X of the ram door  242 , and a vertical side of the triangle perpendicular to the horizontal axis X of the ram door  242 . This buttress configuration of the teeth  246  resists movement of the door  242  in the retraction direction D of travel for the door  242 . 
     As also shown in this view, the slots  456  receivingly engage the teeth  246 . The slots  456  define teeth  457  in the buttress configuration to provide a corresponding, interlocking configuration between the locking member  248  and the BOP housing  228 . The teeth  559  along the door surface  560  of the locking member  248  may also be provided with various shapes, such as those described with respect to the teeth  246 . The door  242  is provided with slots  660  and/or corresponding teeth  662  for receiving the teeth  559 . 
     Various numbers of teeth may be provided along the BOP housing, door and/or locking member(s) to achieve the desired resistance to movement. For example, as shown in  FIG. 6B , the lock  244   a  may have a locking member (or ball)  248   a , and the housing  228   a  and the door  242   a  may have slots  456   a  and  660   a  shaped to receive the lock  244   a . In this case, there is a single slot in each of the housing  228   a  and the door  242   a . In the version in  FIG. 6C , the lock  244   b  includes a locking member  248   b  has rectangular teeth  246   b  on the housing surface  452   b  of the housing  228   b  and rectangular teeth  559   b  on the door surface  560   b  of the door  242   b . The locking member  248   b  has an asymmetrical configuration with a different number of teeth on each side thereof. 
     In the version of  FIG. 6D  the lock  244   c  includes a locking member  248   c  with rectangular teeth  246   c  on the housing surface  452   c  of the lock  248   c  for engaging the housing  228   c  and a single rectangular tooth  559   c  on the door surface  560   c  of the door  242   c . The locking member  248   c  has an asymmetrical configuration with more teeth  246   c  on the housing surface  452   c  than on the door surface  560   c . In the version of  FIG. 6E , the lock  244   d  includes multiple locking members  248   d  or teeth  246   d  provided between the door  242   d  and the housing  228   d . Each of the locks  244   d  are symmetrical and have a rectangular cross-section. 
     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 locks with one or more teeth on either side thereof and in various configurations may be positioned about the door and/or housing, and be made integral therewith or independent therefrom. 
     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.