Patent Publication Number: US-8540017-B2

Title: Method and system for sealing a wellbore

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     Applicant has also filed U.S. Non-Provisional application Ser. No. 12/838,701 entitled SYSTEM AND METHOD FOR SEALING A WELLBORE contemporaneously herewith. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to techniques for performing wellsite operations. More specifically, the present invention relates to techniques, such as blowout preventers (BOPs) and/or ram blocks, for sealing wellbores. 
     2. Background of the Related Art 
     Oilfield operations are typically 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. Tubing or pipes are typically positioned in the wellbore to enable the passage of subsurface fluids to the surface. 
     Leakage of subsurface fluids may pose a significant environmental threat if released from the wellbore. Equipment, such as blow out preventers (BOPs), are often positioned about the wellbore to form a seal about pipes therein to prevent leakage of fluid as it is brought to the surface. In some cases, the BOPs employ rams and/or ram blocks that seal the wellbore. Some examples of ram BOPs and/or ram blocks are provided in U.S. Pat. Nos. 4,647,002, 6,173,770, 5,025,708, 7,051,989, 5,575,452, 6,374,925, 2008/0265188, 5,735,502, 5,897,094, 7,234,530 and 2009/0056132. 
     Despite the development of techniques involving ram BOPs and/or ram blocks, there remains a need to provide advanced techniques for preventing leakage of subsurface fluids from wellbores. It may be desirable to provide techniques that provide more effective sealing and/or failure resistance. It may be further desirable to provide techniques that provide positive locking of seals. Preferably, such techniques involve one or more of the following, among others: adaptability to wellsite equipment (e.g., various pipe diameters), enhanced sealing, performance under deflection and/or wellsite equipment failures, distribution and/or absorption of loads, enhanced manufacturing capabilities (e.g., wider tolerances), balanced pressures, and increased capacity (e.g., load, pressure, etc.) The present invention is directed to fulfilling these needs in the art. 
     SUMMARY OF THE INVENTION 
     In at least one aspect, the present invention relates to a seal assembly for sealing a wellbore. The wellbore has a pipe therein for the passage of fluid therethrough and a blowout preventer (BOP) positionable about the pipe. The seal assembly has a plurality of blocks positionable within the BOP, each of the blocks having an opening extending into a cavity therein; at least one actuator for selectively moving the blocks to a contact position surrounding the pipe of the wellbore; and a plurality of pipe seals carried by the blocks for creating a seal about the pipe of the wellbore. The pipe seals being positionable in the cavities of the blocks and flowable through the opening thereof whereby at least a portion of a pressure applied to the pipe seals is released from the blocks. 
     In another aspect, the present invention relates to a system for sealing a wellbore. The wellbore has a pipe therein for the passage of fluid therethrough. The system has a BOP positionable about the pipe, and at least one seal assembly positionable about the BOP. Each of the seal assemblies have a plurality of blocks positionable within the BOP, each of the plurality of blocks having an opening extending into a cavity therein; at least one actuator for selectively moving the plurality of blocks to a contact position surrounding the pipe of the wellbore; and a plurality of pipe seals carried by the blocks for creating a seal about the pipe of the wellbore. The pipe seals being positionable in the cavities of the blocks and flowable through the opening thereof whereby at least a portion of a pressure applied to the pipe seals is released from the blocks. 
     Finally, in at least one aspect, the present invention relates to a method for sealing a wellbore. The wellbore has a pipe therein for the passage of fluid therethrough. The method involves positioning a BOP about the pipe, the BOP having a seal assembly therein comprising a plurality of blocks, each of the blocks having an opening extending into a cavity therein and a pipe seal in each cavity; pressing the pipe seals into sealing engagement with the pipe by selectively moving the blocks therein to a contact position surrounding the pipe of the wellbore; and permitting at least a portion of the pipe seals to flow through the opening of the blocks such that at least a portion of a pressure applied to the pipe seals is released from the blocks. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the above recited features and advantages of the present invention can be understood in detail, a more particular description of the invention, 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 of this invention and are, therefore, not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 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  shows a schematic view of an offshore wellsite having a BOP with a seal assembly therein according to the present invention. 
         FIG. 2  shows a schematic view of the BOP of  FIG. 1 . 
         FIGS. 3A-C  show longitudinal cross-sectional views of the BOP of  FIG. 2  taken along line  3 - 3 . In  FIGS. 3A-C , the seal assembly is a dynamic seal assembly depicted in a first, second and third position, respectively, the dynamic seal assembly comprising ram blocks with dynamic pipe seals therein. 
         FIGS. 4A-C  show horizontal cross-sectional views of the BOP of  FIG. 2  taken along line  4 - 4 . In  FIGS. 4A-C , the seal assembly is a dynamic seal assembly depicted in a first, second and third position, respectively, the dynamic seal assembly comprising ram blocks with dynamic pipe seals therein. 
         FIGS. 5A-5C  show top, side and end views, respectively, of the ram blocks of  FIG. 4C  with the dynamic pipe seals removed. 
         FIGS. 6A-6B  are detailed views of one of the ram blocks of  FIG. 5A .  FIG. 6A  is an inner end view of the one of the ram blocks of  FIG. 5A .  FIG. 6B  is a cross-sectional view of the ram block of  FIG. 6A  taken along line  6 - 6 , with one of the dynamic pipe seals therein. 
         FIG. 7  shows a detailed, schematic view of one of the dynamic pipe seals of  FIG. 4A , the dynamic pipe seal having segments. 
         FIGS. 8A-C  are various schematic views of one of the segments of  FIG. 7 . 
         FIGS. 9A and 9B  show longitudinal cross-sectional views of the BOP of  FIG. 2  taken along line  9 - 9 . In  FIGS. 9A-B , the seal assembly is a static seal assembly, with a BOP adapter, depicted in a first and second position, respectively, the static seal assembly comprising ram blocks with static pipe seals therein. 
         FIGS. 10A and 10B  show horizontal cross-sectional views of the BOP of  FIG. 2  taken along line  10 - 10 . In  FIGS. 10A-B , the seal assembly is a static seal assembly, with a BOP adapter, depicted in a first and second position, respectively, the static seal assembly comprising ram blocks with static pipe seals therein. 
         FIGS. 11A-11C  show top, side and end views, respectively, of the ram blocks of  FIG. 10B . 
         FIGS. 12A-12B  are detailed views of one of the ram blocks of  FIG. 11A .  FIG. 12A  is an inner end view of the one of the ram blocks of  FIG. 11A .  FIG. 12B  is a cross-sectional view of the ram block of  FIG. 12A  taken along line  12 - 12 . 
         FIG. 13  shows an exploded view of one of the static seal assemblies of  FIG. 9A . 
         FIG. 14  shows a schematic view of an alternate BOP of  FIG. 1 . 
         FIGS. 15A-15C  show longitudinal cross-sectional views of the BOP of  FIG. 14  taken along line  15 - 15 . In  FIGS. 15A-C , the seal assembly is a static seal assembly depicted in a first, second and third position, respectively, the static seal assembly comprising ram blocks with static pipe seals therein. 
         FIGS. 16A-16C  show horizontal cross-sectional views of the BOP of  FIG. 14  taken along line  16 - 16 . In  FIGS. 16A-C , the seal assembly is a static seal assembly depicted in a first, second and third position, respectively, the static seal assembly comprising ram blocks with static pipe seals therein. 
         FIGS. 17A-17C  show top, side and end views, respectively, of the ram blocks of  FIG. 16C . 
         FIGS. 18A-18B  are detailed views of one of the ram blocks of  FIG. 17A .  FIG. 18A  is an inner end view of the one of the ram blocks of  FIG. 17A .  FIG. 18B  is a cross-sectional view of the ram block of  FIG. 18A  taken along line  18 - 18 . 
         FIG. 19  is a flow chart depicting a method of sealing a wellbore. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The description that follows includes exemplary apparatuses, methods, techniques, and instruction sequences that embody techniques of the present inventive subject matter. However, it is understood that the described embodiments may be practiced without these specific details. 
       FIG. 1  depicts an offshore wellsite  100  having a seal assembly  102  configured to seal a wellbore  105  extending into a seabed  107 . As shown, the seal assembly  102  is positioned in a blowout preventer (BOP)  108  that is part of a subsea system  106  positioned on the seabed  107 . The subsea system  106  may also comprise a pipe (or tubular)  104  extending from the wellbore  105 , a wellhead  110  about the wellbore  105 , a conduit  112  extending from the wellbore  105  and other subsea devices, such as a stripper and a conveyance delivery system (not shown). While the wellsite  100  is depicted as a subsea operation, it will be appreciated that the wellsite  100  may be land or water based, and the seal assembly  102  may be used in any wellsite environment. 
     A surface system  120  may be used to facilitate operations at the offshore wellsite  100 . The surface system  120  may comprise a rig  122 , a platform  124  (or vessel) and a surface controller  126 . Further, there may be one or more subsea controllers  128 . While the surface controller  126  is shown as part of the surface system  120  at a surface location and the subsea controller  128  is shown part of the subsea system  106  in a subsea location, it will be appreciated that one or more controllers may be located at various locations to control the surface and/or subsea systems. 
     To operate one or more seal assemblies  102  and/or other devices associated with the wellsite  100 , the surface controller  126  and/or the subsea controller  128  may be placed in communication therewith. The surface controller  126 , the subsea controller  128 , and/or any devices at the wellsite  100  may communicate via one or more communication links  134 . The communication links  134  may be any suitable communication means, such as hydraulic lines, pneumatic lines, wiring, fiber optics, telemetry, acoustics, wireless communication, any combination thereof, and the like. The seal assembly  102 , BOP  108  and/or other devices at the wellsite  100  may be automatically, manually and/or selectively operated via the controllers  126  and/or  128 . 
       FIG. 2  shows a detailed, schematic view of a BOP  108  that may be used as the BOP  108  of  FIG. 1 . The BOP  108  is depicted as a cuboid-shaped device having a hole  220  therethrough for receiving the pipe  104 . The BOP  108  is also provided with a channel  222  therethrough for receiving the seal assembly  102 . While the BOP  108  is depicted as having a specific configuration, it will be appreciated that the BOP  108  may have a variety of shapes, and be provided with other devices, such as sensors (not shown). An example of a BOP that may be used is described in U.S. Pat. No. 5,735,502, the entire contents of which is hereby incorporated by reference. Another BOP that may be used is depicted in  FIG. 14  as will be described further herein. 
       FIGS. 3A-C  depict a dynamic seal assembly  102   a  usable as the seal assembly  102  of  FIGS. 1 and 2 .  FIGS. 3A-3C  are longitudinal, cross-sectional views of the BOP  108  and dynamic seal assembly  102   a  of  FIG. 2  taken along line  3 - 3 .  FIGS. 4A-4C  are horizontal, cross-sectional views of the BOP  108  and the dynamic seal assembly  102  of  FIG. 2  taken along line  4 - 4 . The seal assembly  102   a  comprises a pair of blocks (or ram blocks)  326 , each block having a dynamic pipe seal  328  therein. 
     As shown in  FIGS. 3A-3C  and  4 A- 4 C, the blocks  326  are slidably movable within the BOP  108  between a non-contact position as shown in  FIGS. 3A and 4A , and a face-to-face contact position as shown in  FIGS. 3B-3C  and  4 B- 4 C. As also shown in  FIGS. 3A-3C  and  4 A- 4 C, the dynamic pipe seals  328  are slidably movable between a retracted position as shown in  FIGS. 3A-3B  and  4 A- 4 B, and an extended position as shown in  FIGS. 3C and 4C . 
     One or more actuators  329  may be provided for selectively activating one or more of the blocks  326  and/or pipe seals  328 . The actuator(s)  329  may be positioned in and/or about the BOP  108  for selective actuation as desired. The actuators  329  may be controlled by the controller(s)  126  and/or  128  ( FIG. 1 ). The actuator(s)  329  may be, for example, hydraulic cylinders that move the blocks  326  together (or closes the blocks) by pushing them from behind towards each other. Preferably, the actuator(s)  329  selectively move the blocks  326  to the contact position and the pipe seals  328  to the extended position for sealing engagement about the pipe  104 . During well control situations, the actuators  329  are typically actuated shut, which pushes the blocks  326  together to create a seal about pipe  104 . When the situation is over, the actuators  329  may retract the blocks  326  into the BOP to ready for the next use. The actuator(s)  329  may be activated based on predefined criteria (e.g., timing, sensors, data, events, etc.) and/or as desired. 
     The blocks  326  are shown in greater detail in  FIGS. 5A-5C  (also shown in  FIGS. 3A-3C  and  4 A- 4 C).  FIGS. 5A-5C  show top, plan and outer side views, respectively, of the blocks  326  in the face-to-face contact position. As shown in the top view of  FIG. 5A , a pair of blocks  326  with a rectangular shape, an inlet  528  therethrough and a channel  530   a  therein is preferably provided. However, it will be appreciated that two or more blocks with a variety of shapes movable within the BOP  108  may be utilized. 
     In the contact position as shown in  FIGS. 3B-3C ,  4 B- 4 C and  5 A- 5 C, the inlets  528  of the blocks  326  form a hole configured to receive the pipe  104  ( FIGS. 1 and 2 ). Also in the contact position as shown, the channels  530   a  of the blocks  326  form a continuous (and in this case circular) channel therebetween along a top surface  531  of the blocks  326 . A surface seal  535   a  is positionable in the channel  530   a . The surface seals  535   a  form a seal with the BOP  108  to prevent fluid from passing between the blocks  326  and the BOP  108  adjacent thereto (see, e.g.,  FIGS. 5A-5C ). A vent or eye hole  537  is provided in each block  326  as will be described further herein. 
     The blocks  326  each have a contact surface  532  that is preferably flat for face-to-face engagement therebetween. The inlet  528  extends through each contact surface  532  on each block  326 . This configuration provides positive touching of the blocks  326  along contact surfaces  532  of adjacent blocks  326 . As shown, the contact surfaces  532  preferably meet and are pressed against each other. In this position, the blocks  326  surround and form a seal about the pipe  104  which is positioned in the inlets  528 . 
     As shown in  FIG. 5B , apertures  533   a  extend into side  529  of each of the blocks  326 . As shown in  FIG. 5C , apertures  533   b  extend into the outer end  545  of each block  326 . The apertures  533   a  and  533   b  are configured to receive portions of the dynamic pipe seal  328  as will be described further herein. 
       FIGS. 6A and 6B  are detailed views of one of the blocks  326  (also shown in  FIGS. 3A-3C  and  4 A- 4 C).  FIG. 6A  shows a plan view of the contact surface  532  of the block  326  with the pipe seal  328  removed. The contact surface  532  has the inlet  528  extending therethrough. Also, channel  530   b  extends from the top surface  531  and continues along the contact surface  532  on either side of the inlet  528 . A cavity  634  extends through the contact surface  532  and into the block  326 . The cavity  634  joins portions of channel  530   b  on either side of the inlet  528  to form a continuous channel along the contact surface  532 . The cavity  634  also preferably extends through block  326  for communication with aperture  533   b . Cavity  634  is configured to receive the dynamic pipe seal  328 . The dynamic pipe seal  328  is slidably movable within the cavity  634 . The dynamic pipe seal  328  is preferably positionable adjacent the static pipe seal  535  bin cavity  634  and the surface seal  535   b  in channel  530   b  to form a continuous seal along contact surface  532  and for sealing engagement therebetween to seal the BOP  108  (see, e.g.,  FIGS. 3B-C  and  4 B-C). 
       FIG. 6B  is a cross-sectional view of block  326  of  FIG. 6A  taken along line  6 - 6  with the dynamic pipe seal  328  of  FIG. 7  taken along line  7 - 7  therein. This view shows the dynamic pipe seal  328  in the block  326  in the retracted position of  FIGS. 3A-B  and  4 A-B. In the retracted position as shown, the pipe seal  328  is positionable such that a seal end  636  is positioned behind the contact surface  532  of block  326  to prevent damage thereto as the blocks  326  are moved to the contact position as shown in  FIGS. 3B and 4B . 
     Vent hole  537  is shown as extending into aperture  533   b . Cavity  634  is preferably in fluid communication with vent hole  537  for passage of fluid, such as air therebetween. The vent hole  537  may release pressure from the blocks  326  as the dynamic pipe seal  328  reciprocates within the block  326 . Channel  530   a  with surface seal  535   a  therein is also depicted. 
     Referring to  FIGS. 6B and 7 , the dynamic pipe seal  328  is shown in greater detail (also shown in  FIGS. 3A-3C  and  4 A- 4 C). The pipe seal  328  comprises a seal  640 , a base  642  and a ram or drive shaft  644 . The seal  640  is supported on base  642  and extends a distance therefrom. The drive shaft  644  is positioned adjacent base  642  on an opposite side from the seal  640 . The drive shaft  644  may be connected to the base  642  for operation therewith. The seal  640 , base  642  and drive shaft  644  are selectively movable within the block  326 . Actuator  329  ( FIG. 3A ) may be used to move the dynamic pipe seal  328 . 
     The seal  640  preferably has an arcuate shaped face seal or portion  638  adapted to receive a rounded (or near rounded) pipe  104  ( FIGS. 1 and 2 ). The face seal  638  is preferably integral with the seal  640 . The base  642  may be shaped to support the seal  640 . As shown, the seal  640  may be provided with seal supports (or petals or segments)  641  for providing support to the face seal  638 . The seal supports  641  may be positioned adjacent the face seal  638  in an interlocking formation for supporting the face seal  638  as it is pressed against pipe  104 . While the seal supports  641  are depicted as discrete petals, it will be appreciated that the supports may be continuous, discrete, separate from and/or integral with the seal  640 . 
     One of the seal supports  641  is shown in greater detail in  FIGS. 8A-8C . As shown in these figures, each of the seal supports  641  has a body  876  with a channel  870  therethrough. The seal supports  641  are preferably provided with keys  872 , and keyways  874  for receiving the keys  872 . The keys  872 , keyways  874  and other portions of the segments may be provided for interlocking positioning of the seal supports  641 . A bonding agent or other materials may be placed about the seal supports  641  for adhesion of the seal supports  641  to the seal  640 . While the seal supports  641  as shown have interlocking bodies of a certain shape, the seal supports  641  may be in the form of a unitary ring or other shape as desired to support the seal  640  to achieve the desired sealing engagement with pipe  104 . 
     Preferably the seal  640  and the face seal  638  are made of an elastomeric or other material capable of sealing engagement with the pipe  104  (see, e.g.,  FIGS. 3C and 4C ). The seal supports  641  may be made of elastomeric, plastic or other material, preferably more sturdy than the face seal  640  to provide support thereto. One or more gaskets or other sealing items may also be provided as desired for sealing within the BOP  108 . 
     Referring back to  FIGS. 6B and 7 , the drive shaft  644  is positionable in aperture  533   b  of the blocks  326  and slidably movable therein. Preferably, the drive shaft  644  is snugly positionable within the aperture  533   b  such that the pipe seal  328  is maintained in balance therein during actuation. Base  642  is also preferably snugly fit within cavity  634  to provide further support and balance thereto. 
     As shown in FIGS.  7  and  4 A- 4 C, locking arms (or dogs)  746  are preferably provided for operative interaction with the drive shaft  644 . An actuator, such as actuator  329 , may be used to activate the drive shaft  644  and/or the locking arms  746 . The locking arms  746  are slidably positionable in apertures  533   a  in the blocks  326 . The drive shaft  644  has recesses  748  on opposite sides thereof for receiving the locking arms  746 . 
     Preferably the locking arms  746  are capable of securing the drive shaft  644  in a desired position and/or selectively preventing the drive shaft  644  from extension/retraction. The BOP  108  may be provided with pockets  751  for receiving the locking arms  746 . The locking arms are movable between a locked position in the pockets  751  as shown in  FIG. 4C , and an unlocked position a distance therefrom as shown in  FIGS. 4A and 4B . The locking arms  746  and/or pockets  751  may be configured with angled surfaces  749  to facilitate movement of the locking arms  746  relative to the pockets  751 . 
     The locking arms  746  are preferably configured to move into the locked position when the blocks  326  are moved to the contact position and the pipe seals  328  are moved to the seal position as shown in  FIG. 4C . In the unlocked position of  FIG. 4A-4B , the locking arms  746  are retracted to a position adjacent drive shaft  644 , and the dynamic seal  328  is permitted to slidably move within the cavity  634 . With the blocks  326  (with the seal assembly  102   a  therein) advanced to the face-to-face contact position of  FIG. 4B , the locking arms  746  are positioned adjacent the pockets  751 . The locking arms  746  are then permitted to move to the locked position extending into the pockets  751  and the pipe seal  328  may be activated to move to the extended or sealed position adjacent pipe  104  as indicated by the arrows. 
     Once the locking arms  746  extend into the pockets  751  as shown in  FIG. 4C , the blocks  326  are preferably maintained in the face-to-face contact position and prevented from retracting. The actuator  329  may be used to activate the blocks  326 , pipe seal  328 , locking arms  746  and/or other components of the seal assembly  102   a  to achieve the desired movement. The actuator  329  may also be used to continue to apply force, maintain a given level of force, or discontinue applying force as desired. Seals  535   b  of each block  326  are also preferably pressed together for sealing engagement therebetween. As force is applied to advance the pipe seal  328 , the force may also be used to provide continued motion of the drive shaft  644  to urge the pipe seal  328  against the pipe  104 . 
     The seal assembly  102   a  is preferably configured to prevent damage to the seal  640  and/or face seal  638 . Preferably, the blocks  326  are activated to move from the retracted position of  FIGS. 3A and 4A  to the face-to-face contact position of  FIGS. 3B and 4B  with the pipe seal  328  in the retracted position as shown herein. Once the blocks  326  are moved to the contact position, and preferably locked in place with locking arms  746 , the pipe seal  328  may be moved to the seal position of  FIGS. 3C and 4C . 
     In order to prevent damage to seals  638 ,  639 ,  640  or other seal components, it is further preferable that the pipe seal  328  remain recessed within cavity  634  until the blocks  326  are moved to the contact position. As shown in  FIGS. 3A and 4A , the pipe seal  328  remains in a retracted position in the cavity  634  until the blocks  326  move to the contact position of  FIGS. 3B and 4B . Once the blocks are moved to the contact position, the pipe seals  328  may be extended for sealing engagement with pipe  104 . This configuration and/or activation preferably prevents the pipe seal  328  from being extended between the blocks  326  and potentially causing damage to the blocks  326  and/or pipe seals  328  as the blocks  326  move to the contact position. 
       FIGS. 9A-13  depict a static seal assembly  102   b  usable as the seal assembly  102  of  FIGS. 1 and 2 .  FIGS. 9A and 9B  are longitudinal, cross-sectional views of the BOP  108  and static seal assembly  102   b  of  FIG. 2  taken along line  9 - 9 .  FIGS. 10A and 10B  are horizontal, cross-sectional views of the BOP  108  and the static seal assembly  102   b  of  FIG. 2  taken along line  10 - 10 .  FIG. 10A-C  are detailed views of the static seal assembly  102   b  depicting the components thereof. The static seal assembly  102   b  comprises a BOP adapter  950  and a pair of blocks (or ram blocks)  926 , each block having a static pipe seal  928  therein. 
     As shown in  FIGS. 9A-9B  and  10 A- 10 B, the blocks  926  are slidably movable within the BOP  108  between a non-contact position as shown in  FIGS. 9A and 10A , and a face-to-face contact position as shown in  FIGS. 9B and 10B . The static pipe seal  928  is positioned in the blocks  926  and carried thereby. One or more actuators  329  may be provided for selectively activating the blocks  926  in the same manner as the blocks  326  and/or  1526  as described herein. 
     The BOP adapter  950  is preferably a tubular member positioned in the BOP  108 . As shown, the BOP  108  may be modified to receive the BOP adapter  950 , for example by machining a recess  951  therein adapted to receive the BOP adapter  950 . The BOP adapter  950  is positioned in the BOP  108  and is engaged by the blocks  926  during operation. The blocks  926  are adapted to receive the BOP adapter  950  and preferably engage the BOP adapter  950  when in the face-to-face contact position. A surface seal  952  may be provided in each block  926  for sealing with the BOP adapter  950 . 
     The blocks  926  are shown in greater detail in  FIGS. 11A-11C  (also shown in  FIGS. 9A-9B  and  10 A- 10 B).  FIGS. 11A-11C  show top, plan and outer side views, respectively, of the blocks  926  in the face-to-face contact position. As shown in the top view of  FIG. 11A , the pair of blocks  926  preferably have a rectangular shape, with an inlet  929  and a depression  930  therein. However, it will be appreciated that two or more blocks  926  may be provided with a variety of shapes movable within the BOP  108 . 
     The blocks  926  each have a contact surface  932  that is preferably flat for face-to-face engagement therebetween. The inlet  929  extends through each contact surface  932  on each block  926 . This configuration provides positive touching of the blocks  926  along contact surfaces  932  of adjacent blocks  926 . As shown in  FIGS. 11A and 11B , the contact surfaces  932  preferably meet and are pressed against each other. In this position, the blocks  926  surround the pipe  104  which is positioned in the inlets  929  (see  FIGS. 1 and 2 ). 
     In the contact position as shown, the inlets  929  of the blocks  926  form a hole configured to receive the pipe  104  (see  FIGS. 1 and 2 ). Also in the contact position as shown, the depressions  930  of the blocks  926  form a continuous (and in this case circular) depression therebetween along a top surface  931  of the blocks  926 . The surface seal  952  is positionable in the depression  930 . The depressions  930  are preferably configured for receiving the surface seal  952 , and for receiving the BOP adapter  950  when in the contact position. The surface seal  952  as shown is a semi-oval member positionable in the depression  930  for sealing engagement with the BOP adapter  950  and the BOP  108 . As shown in  FIGS. 9A and 9B , the surface seal  952  is positionable in the depression  930  to form a seal with the BOP  108  and the BOP adapter  950  to prevent fluid from passing between the blocks  926  and the BOP  108  adjacent thereto. 
       FIGS. 12A and 12B  are detailed views of one of the blocks  926  (also shown in  FIGS. 9A-9C ,  10 A- 10 C and  11 A- 11 C).  FIG. 12A  shows a plan view of the contact surface  932  of the block  926  with the surface seal  952  and the pipe seal  928  therein.  FIG. 12B  is a cross-sectional view of block  926  of  FIG. 12A  taken along line  12 - 12 . The contact surface  932  has the inlet  929  extending therethrough. A cavity  1234  extends through the contact surface  932  and into the block  926  about inlet  929 . The cavity  1234  also extends through a bottom surface  935 . Cavity  1234  is configured to receive the static pipe seal  928 . The static pipe seal  928  is preferably positionable in the cavity  1234  for sealing engagement with the pipe  104  when the blocks  926  are in the contact position as will be described further herein. 
     The static pipe seal  928  is positioned in cavity  1234  for sealing engagement with pipe  104  (see, e.g.,  FIGS. 9B and 10B ). As shown, the static pipe seal  928  is positioned in a top portion of cavity  1234  and does not fill the entire cavity  1234 . While the static pipe seal  928  may be sized to fill cavity  1234 , cavity  1234  is preferably defined (in this case semi-circularly) to receive pipe seal  928  with additional space to permit deformation of the pipe seal  928  within the cavity  1234 . The cavity  1234  is preferably open through the bottom surface  935  to permit the static pipe seal  928  to flow therethrough when pipe  104  is pressed against the pipe seal  928 . 
     As shown in  FIGS. 12A and 12B , an anti-extrusion ring  953  is provided in static pipe seal  928 . The anti-extrusion ring  953  preferably prevents the static pipe seal  928  from flowing into the inlet  929  adjacent contact surface  932 . The static pipe seal  928  is permitted to flow from cavity  934  and out opening  955  therein as the blocks  926  are moved into the contact position of  FIGS. 9B and 10B . An anti-extrusion plate  937  may also be provided to further prevent the seal from flowing between the blocks  926 . 
     Referring to  FIGS. 12B and 13 , the static seal assembly  102   b  is shown in greater detail (also shown in  FIGS. 9A-9B  and  10 A- 10 B).  FIG. 13  provides an exploded view of the seal assembly  102   b . In this view, the surface seal  952 , static pipe seals  928  and arcuate-shaped depression  930  and cavity  1234  are depicted. Also, the BOP adapter  950  is depicted as a tubular member. Preferably, the static pipe seal  928 , the surface seal  952  and any gaskets used therewith are made of an elastomeric or other material capable of sealing engagement. Supports, such as seal supports  641  as used with the dynamic pipe seal  328  of  FIGS. 3A-8C  may be used with the static pipe seal  928  and/or the surface seal  952 . 
     In operation, the blocks  926  (with the static pipe seal  928  therein) advance to the face-to-face contact position of  FIGS. 9B and 10B , and the blocks  326  are pressed together. As the blocks  926  are advanced, the force applied to the blocks preferably provides continued motion to press the blocks  926  together and to urge the seals  928  against the pipe  104 . Also, as the blocks  926  advance, surface seals  952  are also pressed against BOP adapter  950  for sealing engagement therewith. The actuator  329  may be used to activate the blocks  926  and/or other components of the seal assembly  102   b  to achieve the desired movement. The actuator  329  may also be used to continue to apply force, maintain a given level of force, or discontinue applying force as desired. Seals  928  and  952  of each block  926  are also preferably pressed together for sealing engagement therebetween. 
     The seal assembly  102   b  is preferably configured to prevent damage to the surface seal  952  and/or static pipe seal  928 . Preferably, the blocks  926  are activated to move from the retracted position of  FIGS. 9A and 10A  to the face-to-face contact position of  FIGS. 9B and 9B  with the static pipe seal  928  in the retracted position as shown herein. In order to prevent damage to surface seals  952  and static pipe seal  928 , it is further preferable that such seals remain recessed within depression  930  and cavity  1234 , respectively, until the blocks  926  are moved to the contact position. Once moved, the seals  952 , 928  may flow in cavity  1234  (and out the bottom of block  926  if needed) and about the blocks  926  and/or pipe  104  as they are compressed. 
     As shown in  FIGS. 9A and 9B  (and also seen in  FIGS. 12A and 12B ), the pipe seal  928  are positioned in the cavity  1234  as the blocks  926  move to the contact position of FIGS.  9 B and  10 B. This unconfined configuration and/or activation preferably permits the seals  928  to flow out of the blocks  926  as pressure is applied thereto. As the blocks are pressed together, the static pipe seal  928  is preferably prevented from flowing between the blocks  926 , but is permitted to flow out cavity  1234 . This unconfined configuration also allows the blocks  926  to receive a boost force applied thereto during activation, and also preferably reduces the pressure on the seals  928  and the strain on the blocks  926 . 
     As shown, the static pipe seal  928  is positioned in a top portion of cavity  1234  and does not fill the entire cavity. While the static pipe seal  928  may be sized to fill cavity  1234 , cavity  1234  is preferably defined to receive pipe seal  928  with additional space to permit deformation of the pipe seal  928  within the cavity  1234 . The cavity  1234  is preferably open through a bottom surface  935  of blocks  926  to permit the static pipe seal  928  to flow therethrough when pipe  104  is pressed against the pipe seal  928 . 
     The actuator  329  and wellbore pressure outside the blocks  926  apply a force to the blocks  926  as they are pressed together. In the face-to-face contact position of  FIGS. 9B and 10B , the blocks  926  are permitted to press together to distribute force therebetween. To permit the face-to-face contact position, it is preferable that the pipe seals  928  are prevented from extending between the blocks  926 . By allowing the pipe seals  928  to flow out the cavity  1234 , forces applied to the pipe seal  928  are permitted to exit the blocks  926 . Preferably, the pipe seals  928  are permitted to flow out of the blocks  926  to prevent forces applied to the blocks  926  from remaining in the blocks and potentially causing damage thereto. 
     Preferably, the pipe seal is configured to withstand ultra high pressure of about 30,000 psi (206.84 MPa) or more of wellbore pressure, as well as lower pressures. For the static seal assembly  102   b , the rubber of the seals therein is preferably allowed to flow where it needs to, and is not fully confined. This configuration is provided to reduce the rubber pressure which reduces the stress in the block that contains the rubber. The rubber pressure may be around, for example, the pressure of the wellbore fluid. 
       FIG. 14  shows a detailed, schematic view of an alternate BOP  108 ′ that may be used as the BOP  108  of  FIG. 1 . The BOP  108 ′ is depicted as having a hole  220 ′ therethrough for receiving the pipe  104 . The BOP  108  is also provided with two channels  222 ′ therethrough for receiving the seal assembly (or assemblies)  102 . While the BOP  108 ′ is depicted as having a specific configuration, it will be appreciated that the BOP  108  may have a variety of shapes, and be provided with other devices, such as sensors (not shown). An example of a BOP that may be used is depicted in U.S. Pat. No. 5,735,502, previously incorporated by reference herein. Also, the BOP of  FIG. 2  may also be employed. 
       FIGS. 15A-17B  depict a static seal assembly  102   b ′ usable as the seal assembly  102  of  FIGS. 1 and 2 .  FIGS. 15A-15C  are longitudinal, cross-sectional views of the BOP  108 ′ of  FIG. 14  taken along line  15 - 15  with the static seal assembly  102   b ′ therein.  FIGS. 16A-16C  are horizontal, cross-sectional views of the BOP  108 ′ and the static seal assembly  102   b ′ of  FIG. 14  taken along line  16 - 16 .  FIGS. 18A-C  are detailed views of the static seal assembly  102   b ′ depicting the components thereof. The seal assembly  102   b ′ comprises a pair of blocks (or ram blocks)  1526 , each block having a static pipe seal  1528  therein. 
     As shown in  FIGS. 15A-15C  and  16 A- 16 C, the blocks  1526  are slidably movable within the BOP  108 ′ between a non-contact position as shown in  FIGS. 15A and 16A , and a face-to-face contact position as shown in  FIGS. 15C and 16C . The static pipe seal  1528  is positioned in the blocks  1526  and carried thereby. In an intermediate position of  FIGS. 15B and 16B , the static pipe seals  1528  of each block meet, and are then pressed together to permit the blocks  1526  to move to the face-to-face contact position of  FIGS. 15C and 16C . One or more actuators  329  may be provided for selectively activating the blocks  1526  in the same manner as the blocks  326  and/or  926  as described herein. 
     A surface seal  1552  may be provided in each block  1526  for sealing with the BOP  108 ′. The blocks  1526  have a cavity  1527  for receiving the surface seal  1552  and preferably engage the BOP  108 ′ to form a seal between the BOP  108 ′ and the blocks  1526 . The surface seal  1552  preferably prevent leakage of fluid from the pipe  104  and between the BOP  108 ′ and a top side of the blocks  1526 . 
     The blocks  1526  are shown in greater detail in  FIGS. 17A-17C  (also shown in  FIGS. 15A-15C  and  16 A- 16 C).  FIGS. 17A-17C  show top, plan and outer side views, respectively, of the blocks  1526  in the face-to-face contact position. As shown in the top view of  FIG. 17A , the pair of blocks  1526  have an octagonal shape when put together, an inlet  1729  therein and a channel  1730  therein is preferably provided. However, it will be appreciated that two or more blocks  1526  may be provided with a variety of shapes movable within the BOP  108 ′. 
     The blocks  1526  each have a contact surface  1732  that is preferably flat for face-to-face engagement therebetween. The inlet  1729  extends through each contact surface  1732  on each block  1526 . This configuration provides positive touching of the blocks  1526  along contact surfaces  1732  of adjacent blocks  1526 . As shown in  FIGS. 17A and 17B , the contact surfaces  1732  preferably meet and are pressed against each other. In this position, the blocks  1526  surround the pipe  104  which is positioned in the inlets  1729  (see, e.g.,  FIGS. 15A-C ). 
     In the contact position as shown, the inlets  1729  of the blocks  1526  form a hole configured to receive the pipe  104  (see  FIGS. 1 and 2 ). Also in the contact position as shown, the channels  1730  of the blocks  1526  form a continuous (and in this case circular) channel therein along a top surface  1731  of the blocks  1526 . The surface seal  1552  is positionable in the channel  1730 . The channels  1730  are preferably configured for receiving the surface seal  1552 . The surface seal  1552  as shown is a semi-oval member positionable in the channel  1730 . As shown, for example, in  FIG. 15C , the surface seal  1552  is positionable in the cavity  1527  to form a seal with the BOP  108 ′ to prevent fluid from passing between the blocks  1526  and the BOP  108  adjacent thereto. 
       FIGS. 18A and 18B  are detailed views of one of the blocks  1526  (also shown in  FIGS. 15A-15C ,  16 A- 16 C and  17 A- 17 C).  FIG. 18A  shows a plan view of the contact surface  1732  of the blocks  1526  with the surface seal  1552  and the static pipe seal  1528  therein.  FIG. 18B  is a cross-sectional view of block  1526  of  FIG. 18A  taken along line  18 - 18 . The contact surface  1732  has the inlet  1729  extending therethrough. The cavity  1834  extends through the contact surface  1732  and into the block  1526  about inlet  1729 . The cavity  1834  also extends through a bottom surface  1838 . Cavity  1834  is configured to receive the static pipe seal  1528 . The static pipe seal  1528  is preferably positionable in cavity  1834  for sealing engagement with the pipe  104  when the blocks  1526  are in the contact position as shown in  FIGS. 15C and 16C . 
     The static pipe seal  1528  is positioned in cavity  1834  for sealing engagement with pipe  104 . As shown, the static pipe seal  1528  is positioned in a top portion of cavity  1834  and does not fill the entire cavity. While the static pipe seal  1528  may be sized to fill cavity  1834 , cavity  1834  is preferably defined to receive pipe seal  1528  with additional space to permit deformation of the pipe seal  1528  within the cavity  1834 . The cavity  1834  is preferably open through the bottom surface  1838  to permit the static pipe seal  1528  to flow therethrough when pipe  104  is pressed against the pipe seal  1528 . 
     Like the seal assemblies  102   a  and  102   b , the seal assembly  102   b ′ is preferably configured to prevent damage to the surface seal  1552  and/or static pipe seal  1528 . Preferably, the blocks as shown in  FIG. 18B , an anti-extrusion ring  1853  is provided in static pipe seal  1528 . The anti-extrusion ring  1853  preferably prevents the static pipe seal  1528  from flowing into the inlet  1729  adjacent contact surface  1732 . The static pipe seal  1528  is permitted to flow from cavity  1834  and out opening  1855  therein as the blocks  1526  are moved into the contact position of  FIGS. 15C and 16C . An anti-extrusion plate  1837  may also be provided to further prevent the seal from flowing between the blocks  1526 . 
     Blocks  1526  are activated to move from the retracted position of  FIGS. 15A and 16A  to the face-to-face contact position of  FIGS. 15C and 16C  with the static pipe seal  928  positioned therein as shown herein. In order to prevent damage to surface seals  1552  and static pipe seal  1528 , it is further preferable that such seals remain recessed within depression  1530  and cavity  1834 , respectively, until the blocks  926  are moved to the contact position. Once moved, the seals  1552 , 1528  may flow in cavity  1834  (and out the bottom of block  1526  if needed) and about the blocks  1526  and/or pipe  104  as they are compressed. 
     As shown in  FIGS. 15A and 16A , the pipe seals  1528  are positioned in the cavity  1834  as the blocks  1526  move to the contact position of  FIGS. 15C and 16C . This unconfined configuration and/or activation preferably permits the seals  1552  and  1528  to flow out of the blocks  1526  as pressure is applied thereto. As the blocks are pressed together, the static pipe seal  1528  is preferably prevented from flowing between the blocks  1526 , but is permitted to flow out opening  1855 . This unconfined configuration allows the blocks  1526  to receive a boost force applied thereto during activation to reduce the pressure on the seals, and also preferably reduces pressure on the seals  1528  and the strain on the blocks  1526 . 
     The actuator  329  and wellbore pressure outside the blocks  1526  apply a force to the blocks  1526  as they are pressed together. In the face-to-face contact position of  FIGS. 15C and 16C , the blocks  1526  are permitted to press together to distribute force therebetween. To permit the face-to-face contact position, it is preferable that the pipe seals  1528  are prevented from extending between the blocks  1526 . By allowing the pipe seals  1528  to flow out the cavity  1834 , forces applied to the pipe seal  1528  are permitted to exit the blocks  1526 . Preferably, the pipe seals  1528  are permitted to flow out of the blocks  1526  to prevent forces applied to the blocks  1526  from damaging the blocks. 
     Preferably, the pipe seal is configured to withstand ultra high pressure of about 30,000 psi (206.84 MPa) or more of wellbore pressure, as well as lower pressures. For the static seal assembly  102   b ′, the rubber of the seals therein is preferably allowed to flow where it needs to, and is not fully confined. This configuration is provided to reduce the rubber pressure which reduces the stress in the block that contains the rubber. The rubber pressure may be around, for example, the pressure of the wellbore fluid. 
     While the seal assemblies  102   a,b  and  102 ′ are depicted in a specific configuration, it will be appreciated that the seal assemblies and/or BOP  108  may be inverted. Additional components, such as gaskets, locking arms or mechanisms and/or dynamic seals, may be used in combination with and/or incorporated into the static seal assembly for operation therewith. Various combinations of features of the static seal assembly and the dynamic seal assembly may be provided. 
       FIG. 19  is a flowchart depicting a method  1900  of sealing a wellbore, such as the wellbore  104  of  FIG. 1 . The method involves positioning  1980  a BOP  108 , 108 ′ about a pipe  104  in a wellbore  105 . The BOP  108 ,  108 ′ has a seal assembly  102  therein also positionable about the pipe  104 . The seal assembly  102  may be a dynamic seal assembly  102   a  comprising blocks  326  with dynamic pipe seals  328  therein. Alternatively, the seal assembly  102  may be a static seal assembly  102   b, b ′ comprising blocks  926 ,  1526  with static pipe seals  928 ,  1528  therein. 
     Actuators are used to selectively move  1982  blocks  326 ,  926 ,  1526  of the seal assembly into the contact position surrounding the pipe of the wellbore. This movement may involve moving the blocks between a non-contact position (see, e.g.,  FIGS. 3A ,  4 A,  9 A,  10 A,  15 A,  16 A) and a face-to-face contact position (see, e.g.,  FIGS. 3B ,  3 C,  4 B,  4 C,  9 B,  10 B,  15 C,  16 C). The actuators may also be used to selectively move  1984  the pipe seals into sealing engagement with the pipe. 
     For dynamic seal assemblies  102   a , a seal is created  1984  about the pipe by selectively extending the pipe seals  328 ,  928 ,  1528  from the blocks and into sealing engagement about the pipe after the plurality of blocks are moved into the contact position such that the plurality of pipe seals is prevented from extending between the plurality of blocks as the plurality of blocks are moved into the contact position. 
     For static seal assemblies  102   b,b ′ the blocks  926 ,  1526  each have an opening extending into a cavity therein and a pipe seal  928 ,  1528  therein. The pipe seals are pressed  1986  into sealing engagement with the pipe by selectively moving the plurality of blocks therein into a contact position surrounding the pipe of the wellbore. When the blocks  926 ,  1526  are in the contact position,  1987  the static pipe seals  928 ,  1528  may be permitted to flow through the opening of the plurality of blocks such that at least a portion of a pressure applied to the plurality of pipe seals is released from the plurality of blocks. 
     The contact surfaces of each of the plurality of blocks are pressed  1988  against each other and the pressing the plurality of pipe seals into sealing engagement with each other after the plurality of blocks are moved into the contact position. The blocks may be retracted  1990 , and the process repeated  1992  as desired. 
     Additional steps may also be performed, such as measuring parameters, such as pressure, force, deflection and other parameters relating to the seal assembly  102 , analyzing data and adjusting wellbore operations based on the measured parameters. 
     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, interne, satellite, etc.) network. 
     While the present disclosure describes specific aspects of the invention, numerous modifications and variations will become apparent to those skilled in the art after studying the disclosure, including use of equivalent functional and/or structural substitutes for elements described herein. For example, aspects of the invention can also be implemented for operation in combination with other known BOPs, rams, actuators and/or seals. All such similar variations apparent to those skilled in the art are deemed to be within the scope of the invention as defined by the appended claims. 
     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.