Patent Publication Number: US-7909095-B2

Title: Valve device and associated methods of selectively communicating between an interior and an exterior of a tubular string

Description:
BACKGROUND 
     The present disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a valve device and associated methods of selectively communicating between an interior and an exterior of a tubular string. 
     In certain well operations, it is desirable to provide for selective fluid communication between the interior and exterior of a tubular string. For example, in a single trip multi-zone gravel packing operation, several packers in a tubular string may be set in a wellbore. Selective communication between the interior and exterior of the tubular string is desirable in this operation to provide for testing of the packers prior to gravel packing. 
     In the past, this packer testing function has been accomplished by opening ports in the packers themselves or in the tubular string between the packers. Unfortunately, these techniques have also involved either opening ports which cannot be re-closed, or manipulating another service string within the tubular string. 
     It will be appreciated that a permanently open port in the tubular string is highly detrimental if its associated packer is leaking (e.g., requiring that the tubular string be retrieved from the well), and that intervening into the tubular string with another service string (or wireline, etc.) is time-consuming and hazardous. 
     Therefore, it may be seen that improvements are needed in the art of providing selective communication between the interior and exterior of a tubular string. Such improvements would be useful in packer testing as discussed above, and also in other operations such as circulating, cementing, acidizing, fracturing, producing, injecting, conformance, etc. 
     SUMMARY 
     In the present specification, a valve device and associated methods are provided which solve at least one problem in the art. One example is described below in which the valve device provides for selective fluid communication between the interior and exterior of a tubular string. Another example is described below in which such fluid communication results only if an associated annular seal leaks, in which case the valve device can be re-closed without intervening into the tubular string. 
     In one aspect, a valve device is provided which includes an openable and closable flowpath for selectively permitting and preventing flow between an interior and an exterior of the valve device. A lock assembly prevents the flowpath from being cycled from closed to open greater than a predetermined number of times. 
     In another aspect, a method of testing at least one annular seal in an annulus formed between a tubular string and a wellbore wall is provided which includes the steps of: sealingly engaging the annular seal to thereby prevent flow through the annulus across the annular seal; and applying a pressure differential across the annular seal to thereby test the annular seal, the pressure differential being applied via a valve device interconnected in the tubular string. The pressure differential applying step may include transmitting pressure between an interior flow passage of the tubular string and the annulus via the valve device without permitting fluid communication between the annulus and the flow passage. The method may include the step of, after the pressure differential applying step, closing the valve device interconnected in the tubular string, thereby preventing fluid communication through the valve device between the annulus and an interior flow passage of the tubular string. The closing step may be performed without manipulating the tubular string and without intervening into the tubular string. 
     In yet another aspect, a test system for a well having an annulus formed between a tubular string and a wall of a wellbore includes multiple sets of annular seals for sealing the annulus at longitudinally spaced apart locations, with each of the sets including at least two annular seals. Multiple valve devices are openable and closable in response to variation of pressure in an interior flow passage of the tubular string. Each of the valve devices thereby selectively permits and prevents fluid communication between the interior flow passage and the annulus longitudinally between the annular seals of a respective one of the sets of annular seals. 
     In a further aspect, an annular seal assembly is provided which includes at least two annular seals and a valve device with an openable and closable flowpath for selectively permitting and preventing flow between an interior of the seal assembly and an exterior of the seal assembly longitudinally between the annular seals. The valve device also includes a lock assembly which prevents the flowpath from being cycled from closed to open greater than a predetermined number of times, with the flowpath being cyclable from closed to open at least one time. 
     These and other features, advantages, benefits and objects will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments hereinbelow and the accompanying drawings, in which similar elements are indicated in the various figures using the same reference numbers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic partially cross-sectional view of a test system and associated method embodying principles of the present disclosure; 
         FIGS. 2 &amp; 3  are enlarged scale schematic quarter-sectional views of an annular seal assembly usable in the test system; 
         FIGS. 4-8  are schematic quarter-sectional views of another configuration of a valve device usable in the annular seal assembly; 
         FIG. 9  is a schematic quarter-sectional view of another configuration of the valve device; 
         FIG. 10  is a schematic quarter-sectional view of another configuration of the annular seal assembly; 
         FIGS. 11-15  are schematic cross-sectional views of another configuration of the valve device; 
         FIG. 16  is a schematic partially cross-sectional view of another test system and associated method embodying principles of the present disclosure; and 
         FIG. 17  is a schematic partially cross-sectional view of another method of using the valve device. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the various embodiments described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present disclosure. The embodiments are described merely as examples of useful applications of the principles of the disclosure, which are not limited to any specific details of these embodiments. 
     In the following description of the representative embodiments of the disclosure, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. In general, “above”, “upper”, “upward” and similar terms refer to a direction toward the earth&#39;s surface along a wellbore, and “below”, “lower”, “downward” and similar terms refer to a direction away from the earth&#39;s surface along the wellbore. 
     Representatively illustrated in  FIG. 1  is a test system  10  which embodies principles of the present disclosure. The test system  10  in this example is part of an overall well system  12  in which a multi-zone gravel packing operation is to be performed, and in which it is desired to pressure test multiple packers or annular seals  14 ,  16  prior to the gravel packing operation. 
     However, it should be clearly understood that the principles of this disclosure are not limited to use in testing annular seals for gravel packing operations, or in any particular testing operation. Instead, the principles described herein may be used in a wide variety of different techniques, operations and configurations. 
     As depicted in  FIG. 1 , the annular seals  14 ,  16  are part of an annular seal assembly  18  interconnected in a tubular string  20  positioned in a wellbore  22 . In this example, the wellbore  22  is provided with protective casing  24  defining an inner wall  26  for the wellbore, but in other examples the wellbore could be uncased or open, in which case the inner wall would be defined by the wellbore itself. 
     The annular seal assembly  18  is used to prevent flow longitudinally through an annulus  28  formed radially between the tubular string  20  and the inner wall  26 . In this manner, the seals  14 ,  16  provide for isolation in the wellbore  22  between two formation zones  30   a,b  intersected by the wellbore, thereby allowing the zones to be independently stimulated, gravel packed, produced, isolated, etc. 
     The tubular string  20  also includes various other equipment, such as screens  32   a  and  32   b , gravel packing tools  34   a  and  34   b  (e.g., flow control devices, seals crossovers, etc.). Of course, any number, combination, configuration and/or arrangement of this or any other equipment may be used in keeping with the principles of this disclosure. 
     The annular seal assembly  18  also includes a valve device  36  which selectively permits and prevents fluid communication between the annulus  28  and an interior flow passage of the tubular string  20 . In this manner, the sealing integrity of each of the annular seals  14 ,  16  may be tested after the seals have been engaged to seal the annulus  28  between the tubular string  20  and the inner wall  26 . 
     For example, if the seals  14 ,  16  are set by pressure or mechanical force, then the valve device  36  may be opened after the seals  14 ,  16  are set. Pressure may then be applied to the annulus  28  longitudinally between the seals  14 ,  16  via the open valve device  36  from the interior flow passage of the tubular string  20  to test the sealing integrity of the seals. Note that, during this testing operation, fluid communication radially through the screens  32   a,b  is preferably not permitted (e.g., by closing sliding sleeve valves (not shown) or other flow control devices for the screens). 
     Several unique features of the valve device  36  allow the testing operation to be performed without intervening into the tubular string  20 , without manipulation of the tubular string, and/or with the ability to re-close the valve device even if one or both of the seals  14 ,  16  should leak. These and other features of the valve device  36  are described below in detail for several configurations of the valve device. However, it should be clearly understood that the principles of this disclosure are not limited in any way to any particular features or combination of features described for the valve device configurations below. 
     Referring additionally now to  FIG. 2 , the test system  10  is representatively illustrated within the casing  24 , but apart from the remainder of the well system  12 , for illustrative clarity. Note that the interior flow passage  38  of the tubular string  20  extends longitudinally through the test system  10 , including the annular seals  14 ,  16  and the valve device  36 . The annulus  28  is exterior to the seals  14 ,  16  and the valve device  36 . 
     In this configuration, the upper seal  14  is part of a hydraulically set packer  40 , and the valve device  36  is incorporated with the packer, so that the packer and valve device are a single well tool for interconnection in the tubular string  20 . In contrast, the lower seal  16  is part of another hydraulically set packer  42  which is preferably of conventional construction. 
     In other examples, the valve device  36  could be incorporated into a single well tool with the lower packer  42 , the valve device could be incorporated into a single well tool with both of the upper and lower packers  40 ,  42 , or each of these devices could be separate well tools. Thus, it will be appreciated that any combination or arrangement of the devices described herein may be used in keeping with the principles of this disclosure. 
     Since the lower packer  42  in the example of  FIG. 2  is preferably of conventional construction, it will not be described further herein, except to note that it preferably includes slips for gripping the inner wall  26 . The upper packer  40  in this example preferably does not include slips for gripping the inner wall  26 , and so the lower packer  42  is preferably set first, followed by setting of the upper packer. This is accomplished by applying increased pressure to the flow passage  38  to set the lower packer  42 , and then further increasing the pressure in the flow passage to set the upper packer  40 . 
     At a predetermined level of pressure in the flow passage  38 , a burst disk  44  in the upper packer  40  will rupture, thereby admitting the pressure into a chamber  46 . Pressure in the chamber  46  greater than pressure in the annulus  28  will cause a piston  48  to displace upwardly and longitudinally compress the annular seal  14 , thereby radially outwardly extending the seal into sealing engagement with the inner wall  26 . A slip or ratchet mechanism  50  prevents the piston  48  from displacing downwardly if the pressure in the chamber  46  decreases. 
     Note that there are many different ways of sealingly engaging a seal, and that the hydraulically set packer  40  is just one example. Other ways include mechanically displacing the seal, swelling the seal, inflating the seal, etc. Thus, it will be appreciated that the principles of this disclosure are not limited to use with hydraulically set packers. 
     Referring additionally now to  FIG. 3 , the test system  10  is representatively illustrated after the upper packer  40  has been set. The upper seal  14  is now sealingly engaged between the tubular string  20  and the inner wall  26 , with the lower seal  16  having previously been sealingly engaged between the tubular string and the inner wall, as described above. A section of the annulus  28  longitudinally between the seals  14 ,  16  is now isolated from the remainder of the annulus. 
     Pressure in the flow passage  38  has been further increased to another predetermined level to thereby rupture another bust disk  52  which initially isolated the chamber  46  from the annulus  28 . After the disk  52  is ruptured, fluid communication is permitted between the flow passage  38  and the annulus  28 . 
     The seals  14 ,  16  can now be pressure tested, for example, by applying pressure to the flow passage  38 , which pressure will be communicated to the annulus  28  between the seals  14 ,  16 . If either of the seals  14 ,  16  leaks, then fluid loss and/or pressure decrease will be detected in the flow passage  38 . 
     Additional equipment (such as sensors, etc.) may be used if desired to determine which of the seals  14 ,  16  is leaking. If neither of the seals  14 ,  16  is leaking, then the gravel packing operations may proceed. If only one of the seals  14 ,  16  is leaking, then a decision may be made whether or not to proceed with the gravel packing operations, or whether to retrieve the tubular string  20  and replace any of the packers  40 ,  42  and/or seals  14 ,  16 . 
     Referring additionally now to  FIGS. 4-8 , another configuration of the valve device  36  is representatively illustrated. In this configuration, the seals  14 ,  16  can be pressure tested without necessarily opening a flowpath to fluid communication between the flow passage  38  and the annulus  28 . Instead, the flowpath opens only if one or both of the seals  14 ,  16  leaks. Once opened, the flowpath can be re-closed, in order to again isolate the annulus  28  from the flow passage  38  at the valve device  36 . 
     In  FIG. 4 , the test system  10  is depicted prior to setting the upper packer  40 . Note that the lower packer  42  is not illustrated in  FIGS. 4-8 , but its operation would preferably be the same as, or at least similar to, that described above for  FIGS. 2 &amp; 3 . 
     Preferably, the lower packer  42  would be set (prior to setting the upper packer  40 ) by increasing pressure in the flow passage  38  to a predetermined level. Pressure in the flow passage  38  would then be increased further to another predetermined level to set the upper packer  40 . 
     In  FIG. 5 , the system  10  is depicted after the upper packer  40  has been set. The burst disk  44  has been ruptured, and the piston  48  has displaced upward to compress and radially outwardly extend the seal  14  into sealing engagement with the inner wall  26 . 
     Note that, instead of or in addition to the burst disk  44 , one or more shear screws  54  may be used to restrain the piston  48  until the predetermined pressure differential from the flow passage  38  to the annulus  28  has been achieved. Thus, it will be appreciated that various different configurations of the packer  40  can be used in keeping with the principles of this disclosure. 
     In  FIG. 6 , the system  10  is depicted after the pressure in the flow passage  38  has been further increased to rupture the burst disk  52 . However, note that there is no fluid communication between the flow passage  38  and the annulus  28  at this point. 
     Instead, a floating piston  56  continues to provide fluid isolation between the flow passage  38  and the annulus  28 . As pressure in the flow passage  38  is increased or decreased, the piston  56  may displace respectively downwardly or upwardly (depending on the pressure differential between the flow passage and the annulus  28  at any given time), but unless at least one of the seals  14 ,  16  leaks, there will be no fluid communication between the flow passage and the annulus. 
     As depicted in  FIG. 6 , the piston  56  has displaced downward somewhat (as compared to its position as viewed in  FIG. 5 ) due to the pressure differential from the flow passage  38  to the annulus  28 . Once pressures in the flow passage  38  and annulus  28  between the seals  14 ,  16  are equalized, the piston  56  will stop displacing, and this will indicate that neither of the seals  14 ,  16  is leaking. Thus, a successful pressure test will be accomplished without the need to open a flowpath which permits fluid communication between the interior and exterior of the tubular string  20 . The flowpath  58  is opened by rupturing the disks  44  and  52 , but as long as neither of the seals  14 ,  16  is leaking, there will be no fluid communication between the passage  38  and annulus  28  via the flowpath  58 . 
     In  FIG. 7 , the system  10  is depicted in the case where one or both of the seals  14 ,  16  is leaking. The pressure differential from the flow passage  38  to the annulus  28  does not equalize in this case, and the piston  56  displaces downwardly past an opening  60 . 
     Thus, the flowpath  58  is opened to allow fluid communication between the flow passage  38  and the annulus  28 . The flowpath  58  in this example extends from the passage  38 , through the burst disk  44 , through the burst disk  52 , through the opening  60  and to the annulus  28 . A decrease in pressure and/or loss of fluid in the passage  38  will indicate that one or both of the seals  14 ,  16  is leaking. 
     If the pressure differential from the passage  38  to the annulus  28  is subsequently relieved, a biasing device  62  (such as a compression spring, compressed gas chamber, etc.) may be used to upwardly displace the piston  56  past the opening  60 . Thus, the flowpath  58  can be re-closed (to thereby again prevent fluid communication between the passage  38  and the annulus  28 ) after having been opened. 
     In  FIG. 8 , the system  10  is depicted after the pressure differential from the passage  38  to the annulus  28  has been relieved. The biasing device  62  has upwardly displaced the piston  56  past the opening  60 , so that fluid communication is again prevented between the passage  38  and the annulus  28  via the flowpath  58 . 
     In addition, the packer  40  has been unset in preparation for retrieving the tubular string  20  from the well. To unset the packer  40 , an upwardly directed force is applied to the tubular string  20  to shear one or more shear screws  64 . This allows the piston  48  to displace downwardly and uncompress the seal  14 , thereby disengaging the seal from the inner wall  26 . 
     Referring additionally now to  FIG. 9 , another configuration of the packer  40  and valve device  36  is representatively illustrated. In this view, the packer  40  and valve device  36  are configured similar to that depicted in  FIG. 10  (e.g., after the disks  44 ,  52  have been ruptured, the flowpath  58  is closed, and the tubular string  20  is to be retrieved from the well). 
     However, the mechanism for unsetting the packer  40  is somewhat different in the configuration of  FIG. 9 , in that shearing of the shear screws  64  allows an inner mandrel  66  to displace upwardly relative to an outer housing  68  which is rigidly connected to the tubular string  20  below the packer  40  and valve device  36 , thereby uncompressing the seal  14 . A slip or ratchet mechanism  70  prevents subsequent downward displacement of the inner mandrel  66  relative to the outer housing  68 . 
     Referring additionally now to  FIG. 10 , another configuration of the annular seal assembly  18  is representatively illustrated. In this configuration, both of the upper and lower packers  40 ,  42  are conventional hydraulically set packers, and the valve device  36  is interconnected between the packers. 
     Operation of the valve device  36  is similar to that described above for the configuration of  FIGS. 4-8 , except that the burst disk  52  is exposed to the pressure differential between the passage  38  and the annulus  28  without the need to first rupture the burst disk  44 . However, in the configuration of  FIG. 10  it is still preferred that the burst disk  52  not rupture until both of the packers  40 ,  42  have been set. 
     Referring additionally now to  FIGS. 11-15 , another configuration of the valve device  36  is representatively illustrated. This configuration is similar to that described above for the configuration of  FIG. 10  (in that the valve device  36  is a separate component and the burst disk  52  is exposed to the pressure differential between the passage  38  and the annulus  28  without first rupturing the burst disk  44 ) and its operation is similar to that described above for the configuration of  FIGS. 4-8 . 
     However, instead of displacing past the opening  60  to open the flowpath  58  in the event that either of the seals  14 ,  16  leaks, the piston  56  displaces out of a bore  72 , and the valve device  36  of  FIGS. 11-15  includes a lock assembly  74  to lock the valve closed after it has been opened a predetermined number of times. 
     In  FIG. 11 , the valve device  36  is depicted prior to the burst disk  52  being ruptured. The piston  56  is received in the bore  72 . Thus, the flowpath  58  between the burst disk  52  and the piston  56  is isolated from both the passage  38  and the annulus  28 . 
     In  FIG. 12 , the burst disk  52  has been ruptured by increasing pressure in the passage  38  to a predetermined level. The piston  56  has displaced downwardly somewhat, as would be the case if neither of the seals  14 ,  16  is leaking. As in the other configurations described above, the piston  56  displaces downward until pressures in the passage  38  and annulus  28  are balanced, if neither of the seals  14 ,  16  is leaking. 
     In  FIG. 13 , the valve device  36  is depicted in the event that one or both of the seals  14 ,  16  does leak. The piston  56  has displaced out of the bore  72 , and fluid communication is now permitted between the passage  38  and the annulus  28  via the flowpath  58 . 
     Note that the piston  56  has also contacted and downwardly displaced an outer housing  76  of the lock assembly  74 , and has thereby compressed the biasing device  62 . A lug  78  projects inwardly from the housing  76  into engagement with a profile  80  formed externally on an inner mandrel  82  of the lock assembly  74 . 
     The profile  80  may be of the type known to those skilled in the art as a “J-slot” profile. When the housing  76  and lug  78  displace longitudinally relative to the mandrel  82  and profile  80 , the engagement between the lug and profile causes relative rotation between the housing and the mandrel, and the lug enters different portions of the profile. 
     In  FIG. 14 , the pressure differential from the passage  38  to the annulus  28  has been relieved, and the biasing device  62  has upwardly displaced the piston  56  so that it is again received in the bore  72 . This closes the flowpath  58  and prevents fluid communication between the passage  38  and the annulus  28 . 
     Note that inwardly projecting pins  84  carried on the outer housing  76  engage a shoulder  86  on the inner mandrel  82  to limit the upward displacement of the outer housing. However, the shoulder  86  has slots  88  formed in it which allow the pins  84  to displace upwardly past the shoulder to thereby allow the outer housing  76  to displace further upwardly relative to the inner mandrel  82  when the pins are aligned with the slots. 
     This alignment between the pins  84  and the slots is controlled by the engagement between the lug  78  and the profile  80 . That is, as the lug  78  displaces to successive different portions of the profile  80 , the outer housing  76  rotates about the inner mandrel  82 , until eventually the pins  84  are aligned with the slots. At that point, the outer housing  76  can displace upwardly a greater distance. 
     In  FIG. 15 , the outer housing  76  has been displaced upwardly and downwardly relative to the inner mandrel  82  a sufficient number of times that the pins  84  have been aligned with the slots  88  and, upon relieving the pressure differential from the passage  38  to the annulus  28 , the biasing device  62  displaces the outer housing and piston  56  upward. The outer housing  76  is displaced further upward relative to the inner mandrel  82  than previously, due to the alignment of the pins  84  with the slots  88 . 
     This further upward displacement of the outer housing  76  allows a snap ring  90  to extend outward and prevent subsequent downward displacement of the outer housing sufficient to permit the piston  56  to displace out of the bore  72 . Thus, the flowpath  58  is closed and fluid communication cannot again be permitted between the passage  38  and the annulus  28  through the flowpath. 
     It will be readily appreciated that the lock assembly  74  can be configured to permit the flowpath  58  to be opened and closed any number of times before the lock assembly prevents subsequent opening of the flowpath. For example, the profile  80  can be changed and/or the azimuthal relationship between the pins  84  and the slots  88  can be changed to thereby change the number of times the piston  56  displaces the outer housing  76  downward prior to the pins being aligned with the slots. 
     However, in the example of  FIGS. 11-15 , the outer housing  76  is not displaced downwardly by the piston  56  unless the flowpath  58  is opened at least one time due to at least one of the seals  14 ,  16  leaking. Thus, if one of the seals  14 ,  16  does not leak, then the flowpath  58  is not opened at all, and the lock assembly  74  is not operated at all. 
     Referring additionally now to  FIG. 16 , another configuration of the test system  10  is representatively illustrated in which multiple annular seal assemblies  18   a - e  are used to isolate multiple corresponding sections  28   a - d  of the annulus  28  in a multi-zone gravel packing operation. In this example, the seal assemblies  18   a - e  utilize the valve device  36  configuration of  FIGS. 11-15  in order to permit determination of which of the seal assemblies  18   a - e  is leaking in a pressure test. 
     The annulus sections  28   a - d  correspond to formation zones  30   a - d . Screens  32   a - d  and gravel packing tools  34   a - d  are interconnected in the tubular string  20  for gravel packing the zones  30   a - d.    
     The annular seal assemblies  18   a - e  straddle the zones  30   a - d , so that each of the zones can be independently stimulated, gravel packed, produced, isolated, etc. The seal assemblies  18   a - e  include respective annular seals  14   a - e , annular seals  16   a - e  and valve devices  36   a - e.    
     As noted above, the valve devices  36   a - e  are preferably of the configuration depicted in  FIGS. 11-15  and described above. However, the lock assemblies  74  of the valve devices  36   a - e  are individually configured to permit the valve devices to be opened and closed a different number of times before being locked closed. 
     Preferably, each successive one of the valve devices  36   a - e  is configured to lock closed in response to a correspondingly increased number of pressure increases and then decreases in the flow passage  38  to open and close the flowpaths  58  of the valve devices. For example, valve device  36   a  is configured to lock closed upon being opened and then closed once, valve device  36   b  is configured to lock closed upon being opened and then closed twice, valve device  36   c  is configured to lock closed upon being opened and then closed three times, valve device  36   d  is configured to lock closed upon being opened and then closed four times, and valve device  36   e  is configured to lock closed upon being opened and then closed five times. However, as described above for the configuration of  FIGS. 11-15 , none of the valve devices  36   a - e  will open unless at least one of the seals  14   a - e  or  16   a - e  leaks during a pressure test. 
     In operation, the test system  10  of  FIG. 16  would function as follows: The seals  14   a - e  and  16   a - e  would be sealingly engaged with the inner wall  26  to thereby seal off the annulus  28  into separate isolated sections  28   a - d . Preferably, this would be accomplished by increasing pressure in the interior of the tubular string  20  to a predetermined level to set packers associated with the seals  14   a - e  and  16   a - e  as described above, although other means of sealingly engaging the seals may be used if desired. 
     Pressure in the interior of the tubular string  20  would then be further increased to another predetermined level at which the burst disks  52  of the valve devices  36   a - e  will rupture. If none of the seals  14   a - e  or  16   a - e  leaks, then no fluid communication between the interior and exterior of the tubular string  20  (i.e., between the passage  38  and the annulus  28  longitudinally between the respective seals) will be permitted, and this will be an indication that all of the seals have passed the pressure test. In that case, the gravel packing operation can proceed. 
     If, however, at least one of the seals  14   a - e  or  16   a - e  does leak, then a loss of pressure and/or fluid in the interior of the tubular string  20  will indicate this. It is a unique feature of the system  10  that at this point it may be determined which of the seals  14   a - e  or  16   a - e  is leaking. 
     It is known at this point that at least one of the valve devices  36   a - e  has opened, and that the valve device  36   a  can open only once, the valve device  36   b  can open only twice, the valve device  36   c  can open only three times, the valve device  36   d  can open only four times and the valve device  36   e  can open only five times. Therefore, pressure in the interior of the tubular string  20  can be manipulated in such a way that the leaking seals  14   a - e  or  16   a - e  can be determined. 
     Picking up from the point in the procedure at which a loss of pressure and/or fluid in the tubular string  20  initially indicates that a leak is present, it is known that at least one of the valve devices  36   a - e  has opened. Pressure in the interior of the tubular string  20  can be permitted to decrease (to close any open valve devices), and then can be increased for a second pressure test. If, upon this pressure increase no leaking (loss of pressure and/or fluid from the interior of the tubular string  20 ) is detected, then it can be determined that the previous leaking was that of either of the seals  14   a  or  16   a , because the valve device  36   a  is locked closed (after being opened only once) and none of the other valve devices  36   b - e  has opened. 
     If leaking is detected during the second pressure test, then it must be via fluid communication through one of the open valve devices  36   b - e . Pressure in the interior of the tubular string  20  can be permitted to decrease (to close any open valve devices), and then can be increased for a third pressure test. If, upon this pressure increase no leaking (loss of pressure and/or fluid from the interior of the tubular string  20 ) is detected, then it can be determined that the previous leaking was that of either of the seals  14   b  or  16   b , because the valve device  36   b  is locked closed (after being opened twice) and none of the other valve devices  36   a  or  c - e  has opened. 
     It will be appreciated that, in this manner, a number of pressure tests may be performed to thereby determine which of the valve devices  36   a - e  is opening due to leakage past its associated seals  14   a - e  or  16   a - e . In this example, a lack of leakage during the nth pressure test indicates that the n−1 valve device from the top has been opening. Of course, the valve devices  36   a - e  can be differently configured as desired to permit different procedures for determining which of the seals  14   a - e  or  16   a - e  is leaking. 
     Referring additionally now to  FIG. 17 , another configuration of the well system  12  is representatively illustrated in which the valve device  36  is not used in a gravel packing operation but is instead used to permit selective fluid communication between the passage  38  and the annulus  28 , for example, in cementing, circulating, producing, stimulating, acidizing, fracturing, injecting, or other types of operations. As depicted in  FIG. 17 , fluid  92  is flowed between the interior and the exterior of the tubular string  20  via the open flowpath  58  in the valve device  36 . 
     For example, in a cementing operation, the valve device  36  may be opened after cement has been flowed out of a lower end of the tubular string  20  and upward into the annulus  28 . A dart (not shown) may land in the lower end of the tubular string  20  and an increase in pressure in the interior of the tubular string can cause the valve device  36  to open, thereby allowing the fluid  92  to circulate out any excess cement in the annulus  28  above the valve device. 
     Pressure in the interior of the tubular string  20  can then be decreased to allow the valve device  36  to close. Preferably, the valve device  36  would be locked closed by the lock assembly  74 , so that subsequent opening of the valve device is prevented. 
     It may now be fully appreciated that many advancements in the art of selectively permitting and preventing fluid communication between the interior and exterior of a tubular string are provided by the above disclosure. In particular, these advancements include the valve device  36  in its various configurations described above, which permits testing of annular seals  14 ,  16  in ways not previously economical, convenient or practical. 
     The above disclosure provides a valve device  36  which includes an openable and closable flowpath  58  for selectively permitting and preventing flow between an interior and an exterior of the valve device  36 , and a lock assembly  74  which prevents the flowpath  58  from being cycled from closed to open greater than a predetermined number of times. 
     The flowpath  58  may be locked closed in response to a) the flowpath  58  having been cycled from closed to open the predetermined number of times, and then b) the flowpath  58  being closed. 
     The predetermined number of times (greater than which the flowpath  58  is prevented from being cycled from closed to open) may be greater than one. Thus, the flowpath  58  may be opened more than once. 
     The flowpath  58  may open in response to increased pressure in the interior of the valve device  36 , and the flowpath  58  may close in response to decreased pressure in the interior of the valve device  36 . 
     The flowpath  58  may be opened at least one time after having been closed. 
     The flowpath  58  may open in response to a predetermined pressure differential being applied between the interior and exterior of the valve device  36 . The flowpath  58  may close in response to release of the predetermined pressure differential. 
     Also provided by the above disclosure is a method of testing at least one annular seal  14 ,  16  in an annulus  28  formed between a tubular string  20  and a wellbore wall  26 . The method includes the steps of: sealingly engaging the annular seal  14 ,  16  to thereby prevent flow through the annulus  28  across the annular seal  14 ,  16 ; and applying a pressure differential across the annular seal  14 ,  16  to thereby test the annular seal, with the pressure differential being applied via a valve device  36  interconnected in the tubular string  20 . 
     The pressure differential applying step may also include transmitting pressure between an interior flow passage  38  of the tubular string  20  and the annulus  28  via the valve device  36  without permitting fluid communication between the annulus and the flow passage. 
     The method may also include the step of, after the pressure differential applying step, closing the valve device  36  interconnected in the tubular string, thereby preventing fluid communication through the valve device  36  between the annulus  28  and an interior flow passage  38  of the tubular string  20 . The closing step is performed without manipulating the tubular string  20  and without intervening into the tubular string  20 . 
     The closing step may include preventing flow from the annulus  28  into the flow passage  38 . The closing step may include preventing flow from the flow passage  38  into the annulus  28 . 
     The pressure differential applying step may include providing fluid communication between the annulus  28  and the flow passage  38  via the valve device  36 . 
     The fluid communication providing step may include opening the valve device  36  by applying increased pressure to the flow passage  38 . The fluid communication preventing step may include decreasing pressure in the flow passage  38  after the step of applying increased pressure to the flow passage  38 . 
     The above disclosure also provides a test system  10  for a well having an annulus  28  formed between a tubular string  20  and a wall  26  of a wellbore  22 . The system  10  includes multiple sets of annular seals  14   a - e ,  16   a - e  for sealing the annulus  28  at longitudinally spaced apart locations, with each of the sets including at least two annular seals. The system  10  also includes multiple valve devices  36   a - e  which are openable and closable in response to variation of pressure in an interior flow passage  38  of the tubular string  20 . Each of the valve devices  36   a - e  thereby selectively permits and prevents fluid communication between the interior flow passage  38  and the annulus  28  longitudinally between the annular seals of a respective one of the sets of annular seals  14   a - e ,  16   a - e.    
     Each successive one of the valve devices  36   a - e  may be configured to lock closed in response to a correspondingly increased number of pressure manipulations in the flow passage  38 . 
     Each of the valve devices  36   a - e  may open only if a corresponding at least one of the annular seals  14   a - e ,  16   a - e  leaks. The valve devices  36   a - e  may be closable in response to pressure variation in the interior flow passage  38  after the valve devices have been opened. 
     Also provided by the above disclosure is an annular seal assembly  18  which includes at least two annular seals  14 ,  16  and a valve device  36 . The valve device  36  comprises an openable and closable flowpath  58  for selectively permitting and preventing flow between an interior of the seal assembly  18  and an exterior of the seal assembly  18  longitudinally between the annular seals  14 ,  16 , and a lock assembly  74  which prevents the flowpath  58  from being cycled from closed to open greater than a predetermined number of times. The flowpath  58  is cyclable from closed to open at least one time. 
     The flowpath  58  may be closable without manipulating the annular seal assembly  18  and without intervening into the annular seal assembly. The flowpath  58  may be openable by applying increased pressure to the interior of the seal assembly  18 , and the flowpath may be closable by decreasing pressure in the interior of the seal assembly after applying increased pressure to the interior of the seal assembly. 
     Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to these specific embodiments, and such changes are within the scope of the principles of the present disclosure. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents.