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BACKGROUND 
       [0001]    Selectively openable ports are used in the downhole drilling and completions industry for enabling fluid communication between tubulars, annuli, etc., in a variety of applications. Some systems use one or more slidable sleeves for providing the selective control of the ports. One way of increasing the pressure rating of the system is to increase the wall thickness of the components of the system. However, this can become very expensive and result in the need for a larger borehole or an unnecessarily large usage of radial space. As a result, the industry always well receives new port control systems having improved pressure ratings. 
       BRIEF DESCRIPTION 
       [0002]    A system for selectively enabling fluid communication between two volumes, including a tubular having a port housing with at least one port; a member disposed with the tubular and movable between a closed position in which the port is closed and an open position in which the port is open; a lock element positively engaged with both the member and the tubular for maintaining the member in the closed position; and an actuator in keyed engagement with the lock element for biasing the lock element, wherein actuation of the actuator releases the lock element to resiliently spring into engagement with solely one of the member or the tubular for enabling the member to move relative to the tubular to the open position for opening the port. 
         [0003]    A method of selectively enabling fluid communication between two volumes, including running a system having a member radially disposed with a tubular, the tubular having at least one port, the port closed when the member is in a closed position and open when the member is in an open position; maintaining the member in the closed position with a lock element positively engaged with both the member and the tubular, the lock element in keyed engagement with an actuator for biasing the lock element; pressurizing the system for actuating the actuator for releasing the lock element to resiliently spring into engagement with solely one of the member or the tubular for enabling relative movement between the member and the tubular; and depressurizing the system for moving the member to the open position to open the port. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0005]      FIG. 1  is a cross-sectional view of a system for enabling selective fluid communication between opposite radial sides of a tubular in an initial run-in position; 
           [0006]      FIG. 2  is an enlarged view of the area encircled in  FIG. 1 ; 
           [0007]      FIG. 3  is a cross-sectional view of a locking assembly of the system of  FIG. 1  taken generally along line  3 - 3 ; 
           [0008]      FIG. 4  is a cross-sectional view of the system of  FIG. 1  under high tubing pressure for actuating a piston to release the locking assembly of  FIG. 3 ; 
           [0009]      FIG. 5  is a cross-sectional view of the system of  FIG. 4  after tubing pressure has been dropped for enabling actuation of an outer sleeve and fluid communication between an inner passage and outer volume via a set of ports; 
           [0010]      FIG. 6  is a cross-sectional view of the system of  FIG. 5  in which an inner sleeve is shifted for selectively opening the ports after the outer sleeve has been actuated; and 
           [0011]      FIG. 7  is a cross-sectional view of a balanced piston embodiment requiring an isolation device to be set before ports can be opened. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
         [0013]    Referring now to  FIG. 1 , a system  10  is shown including a tubular  12  formed, e.g., from a first sub  12   a  and a second sub  12   b . The system  10  as illustrated in  FIG. 1  is arranged for being initially run in a borehole or the like. In one embodiment, the first sub  12   a  is an upper sub and the second sub  12   b  is a lower sub. The system  10  includes a port housing  14  that is secured between the subs  12   a  and  12   b . The housing  14  includes at least one opening or port  16  therein. An inner sleeve  18  is radially disposed within the tubular  12 , having at least one opening or port  20  initially aligned with the port  16  in the coupling  14 . 
         [0014]    Initially, as shown in  FIG. 1 , the alignment of the ports  16  and  20  enable fluid communication between an interior passage  22  of the tubular  12  and a chamber  24  formed by an outer sleeve  26 . As described in more detail below, the sleeve  26  is actuatable to release the ports  16  and  20  from the chamber  24  in order to enable fluid communication between the interior passage  22  and an outer volume  28  (e.g., a casing annulus) located radially outwardly of the system  10 . Of course, other actuatable members such as valve mechanisms, rods, pistons, etc. could be used in lieu of the sleeves as disclosed herein for selectively opening ports. The ports  16  and  20  and the sleeve  26  are arranged, for example, to selectively enable fluid communication between a tubing and casing annulus in a downhole completion for providing fluid circulation therebetween, for providing high pressure fluid for fracturing a formation wall, etc. Also, for example, it is to be appreciated that the sleeve  26  could be any other actuatable member for opening a port or opening. 
         [0015]    A retainer  30  is included affixed to the tubular  12  between the tubular  12  and the sleeve  26  for retaining a spring  32 . The spring  32  urges a ring  34  of the sleeve  26  in a direction opposite the retainer  30 . However, the sleeve  26  is initially locked by a locking assembly  36 . The locking assembly includes a snap ring  38  disposed in both a groove  40  formed in the sub  12   a  and a groove  42  formed in the sleeve  26 , as shown in more detail in  FIG. 2 . As shown in  FIG. 3 , a rod piston  44  includes a key member  46  engaged with both ends of the snap ring  38 , which is formed as a substantially c-shaped ring. Locking both ends of the snap ring  38  with the key member  46  biases the snap ring  38  radially inwardly, as the snap ring  38  is arranged to expand radially outwardly or spring open in order to return to its neutral position. The snap ring  38  could take forms of other elements for providing a similar selective positive locking of the tubular  12  and sleeve  26 , e.g., a leaf spring or other resilient or spring-like member, disposed in the grooves  40  and  42  and springing or expanding out of the groove  40  upon release from the key member  46 . Further, the grooves  40  and  42  could be formed as notches or any other feature for enabling positive engagement of the snap ring  38  with the sleeve  26  and/or the tubular  12 . Relative movement of the sleeve  26  with respect to the tubular  12  is prevented while the snap ring  38  is disposed in both the grooves  40  and  42 , as the snap ring  38  causes positive interference between these components. 
         [0016]    By increasing the tubing pressure (i.e., pressurizing the interior passage  22 ), the sleeve  26  is urged against a stop  48  of the sub  12   b  due to pressure in the chamber  24 . Simultaneously, a piston chamber  50  for the piston  44  is pressurized via a channel  52 . Pressurizing the passage  22 , and therefore the piston chamber  50 , actuates the piston  44  toward the sub  12   b  as shown in  FIG. 4 . Actuation of the piston  44  moves the key member  46  axially out of engagement with the ends of the snap ring  38 , thereby releasing the snap ring  38  to expand radially outwardly fully into the groove  42  and out of the groove  40 . When released from the key member  46 , the snap ring  38  is thus no longer locked in the groove  40  and accordingly no longer prevents relative movement between the sleeve  26  and the tubular  12 . The groove  40  and snap ring  38  may include complementarily sloped surfaces for assisting in the tubular  12  expanding the snap ring  38  into the groove  42  when relative movement between the sleeve  26  and the tubular  12  begins. A release member  54 , e.g., a set screw, could be included to prevent premature actuation of the piston  44 , i.e., until a predetermined minimum pressure is reached in the chamber  50 . A check valve  55  may also be included to hold the piston  44  in the actuated position once sufficient pressure has been introduced to the chamber  50 . 
         [0017]    When tubing pressure is dropped, as shown in  FIG. 5 , the sleeve  26 , now released from the locking assembly  36  as discussed above, is urged by the spring  32  toward the sub  12   a . The spring  32  shifts the sleeve  26  until the ring  34  travels in the axial direction past a stop  56  of the sub  12   a . The stop  56  receives the spring  32  and prevents further movement of the sleeve  26 . By shifting the sleeve  26 , the ports  16  and  20  have become opened to the volume  28  for enabling fluid communication between the interior passage  22  and the volume  28 . Of course, it is to be appreciated that the above-described components could be radially reversed but following a similar method, i.e., for enabling fluid communication between radially inner and outer volumes, but instead being actuated by the pressure in the outer volume. Further, it is to be noted that the unique arrangement of the currently described embodiments enables a higher pressure rating with respect to prior systems without the need to increase radial size. 
         [0018]    After actuation of the sleeve  26 , the ports  16  and  20  can be selectively opened and closed by shifting the inner sleeve  18 , as shown in  FIG. 6 . For example, the inner sleeve  18  includes a locking profile  58  for enabling shifting of the sleeve  18  by a standard shifting tool and wireline methods and equipment (not shown), which are well known in the art and require no further description. 
         [0019]    Another embodiment is shown partially in  FIG. 7 . Specifically, a system  60  is shown including many of the same components as the system  10 , which components are similarly numbered and included for the reasons discussed above. However, unlike the system  10 , the system  60  is of a balanced piston design. That is, a balanced piston  62 , in lieu of the piston  44 , is associated with a first piston chamber  64  and a second piston chamber  66 , the chambers  64  and  66  disposed at opposite ends of the piston  62 . The piston chamber  64  is in communication with the passage  22  via a channel  68 . The piston chamber  66  is in communication with the passage  22  via the channel  70 . In another embodiment, the channel  70  could be formed axially between the chamber  66  and the chamber  24  (the retainer  30  positioned in the chamber  24  and not dynamically sealed to the sleeve  26 , or including passages therethrough), with the chamber  24  open to the passage  22  via the ports  16  and  20 , for achieving the same results. 
         [0020]    Thus, by merely pressurizing the passage  22 , a differential pressure will not be formed across the piston  62 , as both chambers  64  and  66  are open to tubing pressure. If a differential pressure is not formed across the piston  62 , the piston  62  will not actuate, thereby preventing the sleeve  26  from opening the passage  22  to the volume  28  via the ports  16  and  20 . Accordingly, actuation of the piston  62  is only possible if isolation is first achieved between the chambers  64  and  66 . In  FIG. 7 , an isolation device  72  is shown in the passage  22  for isolating the chambers  64  and  66  from each other. For example, the isolation device  72  could be a service packer sealing opposite ends from each other, a ball, plug, or dart landing in a seat for blocking the passage  22 , or any other suitable means for isolating or sealing the chambers  64  and  66  from each other. 
         [0021]    While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

Summary:
A system and method for selectively enabling fluid communication between two volumes, the system including a tubular having a port housing with at least one port, a member disposed with the tubular and movable between a closed position in which the port is closed and an open position in which the port is open, a lock element positively engaged with both the member and the tubular for maintaining the member in the closed position, and an actuator in keyed engagement with the lock element for biasing the lock element, wherein actuation of the actuator releases the lock element to resiliently spring into engagement with solely one of the member or the tubular for enabling the member to move relative to the tubular to the open position for opening the port.