Abstract:
In an embodiment of the invention, an apparatus for use in a subterranean well includes a tubular member, a hydraulically set packer, a control line and a valve. The tubular member has an internal passageway, and the hydraulically set packer circumscribes the tubular member and is adapted to be set in response to a difference between first pressure that is exerted by a first fluid in a passageway of the tubular member and a second pressure that is exerted by a second fluid in an annular region that surrounds the packer. The control line is adapted to communicate an indication of the first pressure to the packer, and the valve is adapted to selectively block the communication of the indication to prevent unintentional setting of the packer.

Description:
BACKGROUND 
     The invention relates to a completion valve assembly for use in a subterranean well. 
     In a subterranean well, a packer may be used to form a seal between the outside of a tubing (a production tubing, for example) and the inside of a well casing. This seal may be useful for testing or production purposes to ensure that well fluid below the packer travels through a central passageway of the tubing. 
     The packer typically includes a resilient elastomer member that surrounds the tubing. When the packer is set, compression sleeves of the packer compress the member to cause the member to radially expand between the tubing and the well casing to form the seal. For purposes of maintaining compression on the member, stingers of the packer typically extend in a radially outward direction when the packer is set to grasp the well casing to lock the positions of the compression sleeves. 
     To establish the force that is necessary to set the packer, two techniques are commonly used. A weight set packer uses the weight of a tubular string that is located above the packer and possibly the weight of associated weight collars to derive a force that is sufficient to compress the elastomer member to set the packer. 
     In contrast to the weight set packer, a hydraulically set packer uses a pressure differential that exists between the fluids of the central passageway of the tubing and the annular region outside of the tubing (called the “annulus”) to establish a force that is sufficient to set the packer. More specifically, the hydraulically set packer typically is set by pressurizing fluid that is present in the central passageway of the tubing. However, before this pressurization occurs, the tubing must be sealed, a requirement that means the central passageway of the tubing must be sealed off below the packer for purposes of forming a column of fluid inside the tubing that can be pressurized. The seal may be formed by a plug. 
     In addition to using the plug to set a hydraulically set packer, plugs may be used for other downhole purposes, such as pressure testing the tubing. If pressure testing is conducted, it is important to ensure that none of the downhole tools, including any hydraulically set packers, are prematurely activated by the pressure testing. 
     After the hydraulically set packer is set, the plug may be removed by running a tool downhole to remove the plug or by pressurizing the interior of the tubing to a level that is sufficient to dislodge the plug from the bottom of the tubing. A wireline or slickline run is risky, particularly in deep water or sea water wells. Also, the rig time is expensive when two runs are required. Thus, interventionless operation is desired. 
     For purposes of filling the tubing with a fluid, a fill tube may be placed in the central passageway. Another technique to fill the tubing uses a tubing fill valve. In this manner, the tubing fill valve controls fluid communication between the annulus and the central passageway of the tubing. Typically, the tubing fill valve is open when the tubing is run downhole for purposes of permitting a formation kill fluid (already present inside the casing) to fill the central passageway of the tubing in case the plug seals or valves leak. Because the hydraulically set packer is set in response to the pressure differential exceeding a predetermined differential threshold, it is possible for this threshold to be exceeded before the packer has reached the desired depth. Therefore, the packer may be unintentionally set at the wrong depth. 
     Thus, there is a continuing need for an arrangement that addresses one or more of the problems that are stated above. 
     SUMMARY 
     In an embodiment of the invention, an apparatus for use in a subterranean well includes a tubular member, a hydraulically set packer, a control line and a valve. The tubular member has an internal passageway, and the hydraulically set packer circumscribes the tubular member and is adapted to be set in response to a difference between a first pressure that is exerted by a first fluid in a passageway of the tubular member and a second pressure that is exerted by a second fluid in an annular region that surrounds the packer. The control line is adapted to communicate an indication of the first pressure to the packer, and the valve is adapted to selectively block the communication of the indication to prevent unintentional setting of the packer. 
     In another embodiment of the invention, an apparatus for use with a subterranean well includes a tubular member and a valve. The tubular member has a longitudinal passageway and at least one port for establishing communication between the passageway and an annular region that surrounds the tubular member. The valve is adapted to open and close the port and lock the valve closed after the valve closes more than a predetermined number of times. 
     Advantages and other features of the invention will become apparent from the following description, drawing and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic diagram of a completion valve assembly according to an embodiment of the invention. 
     FIGS. 2,  3 ,  4 ,  5 ,  7  and  8  are more detailed schematic diagrams of sections of the completion valve according to an embodiment of the invention. 
     FIG. 6 is a schematic diagram of a flattened portion of a mandrel of the completion valve assembly depicting a J-slot according to an embodiment of the invention. 
     FIG. 9 is a schematic diagram of a tubing fill valve according to an embodiment of the invention. 
     FIG. 10 is a schematic diagram of a ratchet mechanism of the tubing fill valve according to an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, an embodiment  10  of a completion valve assembly in accordance with the invention include a hydraulically set packer  14  that is constructed to be run downhole as part of a tubular string. Besides the packer  14 , the completion valve assembly  10  includes a tubing fill valve  35 , a packer isolation valve  22  and a formation isolation valve  31 . As described below, due to the construction of these tools, several downhole operations may be performed without requiring physical intervention with the completion valve assembly  10 , such as a physical intervention that includes running a wireline tool downhole to change a state of the tool. For example, in some embodiments of the invention, the following operations may be performed without requiring physical intervention with the completion valve assembly  10 : the tubing fill valve  35  may be selectively opened and closed at any depth so that pressure tests may be performed when described; the packer  14  may be set with the tubing pressure without exceeding a final tubing pressure; the packer  14  may be isolated (via the packer isolation valve  22 ) from the internal tubing pressure while running the completion valve assembly  10  downhole or while pressure testing to avoid unintentionally setting the packer  14 ; and the formation isolation valve  31  may automatically open  31  (as described below) after the packer  14  is set. 
     More specifically, in some embodiments of the invention, the packer isolation valve  22  operates to selectively isolate a central passageway  18  (that extends along a longitudinal axis  11  of the completion valve assembly  10 ) from a control line  16  that extends to the packer  14 . In this manner, the control line  16  communicates pressure from the central passageway  18  to the packer  14  so that the packer  14  may be set when a pressure differential between the central passageway  18  and a region  9  (called the annulus) that surrounds the completion valve assembly  10  exceeds a predetermined differential pressure threshold. It may be possible in conventional tools for this predetermined differential pressure threshold to unintentionally be reached while the packer being run downhole, thereby causing the unintentional setting of the packer. For example, pressure tests of the tubing may be performed at various depths before the setting depth is reached, and these pressure tests, in turn, may unintentionally set the packer. However, unlike these conventional arrangements, the completion valve assembly  10  includes the packer isolation valve  22  that includes a cylindrical sleeve  20  to block communication between the control line  16  and the central passageway  18  until the packer  14  is ready to be set. 
     To accomplish this, in some embodiments of the invention, the sleeve  20  is coaxial with and circumscribes the longitudinal axis  11  of the completion valve assembly  10 . The sleeve  20  is circumscribed by a housing section  15  (of the completion valve assembly  10 ) that include ports for establishing communication between the control line  16  and the central passageway  18 . Before the packer  14  is set, the sleeve  20  is held in place in a lower position by a detent ring (not shown in FIG. 1) that resides in a corresponding annular slot (not shown in FIG. 1) that is formed in the housing section  15 . In the lower position, the sleeve  20  covers the radial port to block communication between the control line  16  and the central passageway  18 . O-rings  23  that are located in corresponding annular slots of the sleeve  20  form corresponding seals between the sleeve  20  and the housing section  15 . When the packer  14  is to be set, a mandrel  24  may be operated (as described below) to dislodge the sleeve  20  and move the sleeve  20  to an upper position to open communication between the control line  16  and the central passageway  18 . The sleeve  20  is held in place in its new upper position by the detent ring that resides in another corresponding annular slot (not shown in FIG. 1) of the housing section  15 . 
     In some embodiments of the invention, the mandrel  24  moves up in response to applied tubing pressure in the central passageway  18  and moves down in response to the pressure exerted by a nitrogen gas chamber  26 . The nitrogen gas chamber  26 , in other embodiments of the invention, may be replaced by a coil spring or another type of spring, as examples. This operation of the mandrel  24  is attributable to an upper annular surface  37  (of the mandrel  24 ) that is in contact with the nitrogen gas in the nitrogen gas chamber  26  and a lower annular surface  29  of the mandrel  24  that is in contact with the fluid in the central passageway  18 . Therefore, when the fluid in the central passageway  18  exerts a force (on the lower annular surface  29 ) that is sufficient to overcome the force that the gas in the chamber  26  exerts on the upper annular surface  37 , a net upward force is established on the mandrel  24 . Otherwise, a net downward force is exerted on the mandrel  24 . As described below, the mandrel  24  moves down to force a ball valve operator mandrel  33  down to open a ball valve  31  after the packer  14  is set. However, as described below, the upward and downward travel of the mandrel  24  may be limited by an index mechanism  28  that controls when the mandrel  24  opens the packer isolation valve  22  and when the mandrel  24  opens the ball valve  3   1 . 
     In this manner, the completion valve assembly  10 , in some embodiments of the invention, includes an index mechanism  28  that limits the upward and downward travel of the mandrel  24 . More particularly, the index mechanism  28  confines the upper and lower travel limits of the mandrel  24  until the mandrel  24  has made a predetermined number (eight or ten, as examples) of up/down cycles. In this context, an up/down cycle is defined as the mandrel  24  moving from a limited (by the index mechanism  28 ) down position to a limited (by the index mechanism  28 ) up position and then back down to the limited down position. A particular up/down cycle may be attributable to a pressure test in which the pressure in the central passageway  18  is increased and then after testing is completed, released. 
     After the mandrel  24  transitions through the predetermined number of up/down cycles, the index mechanism  28  no longer confines the upper travel of the mandrel  24 . Therefore, when the central passageway  18  is pressurized again to overcome the predetermined pressure threshold, the mandrel  24  moves upward beyond the travel limit that was imposed by the index mechanism  28 ; contacts the sleeve  20  of the packer isolation valve  22 ; dislodges the sleeve  20 ; and moves the sleeve  20  in an upward direction to open the packer isolation valve  22 . At this point, the central passageway  18  may be further pressurized to the appropriate level to set the packer  14 . After pressure is released below the predetermined pressure threshold, the mandrel  24  travels back down. However, on this down cycle, the index mechanism  28  does not set a limit on the lower travel of the mandrel  24 . Instead, the mandrel  24  travels down; contacts the ball valve operator mandrel  33 ; and moves the ball valve operator mandrel  33  down to open the ball valve  31 . Thus, after some predetermined pattern of movement of the mandrel  24 , the mandrel  24  may on its upstroke actuate one tool, such as the packer isolation valve  22 , and may on its downstroke actuate another tool, such as the ball valve  31 . Other tools, such as different types of valves (as examples), may be actuated by the mandrel  24  after a predetermined movement in a similar manner, and these other tools are also within the scope of the appended claims. 
     The tubing fill valve  35  selectively opens and closes communication between the annulus and the central passageway  18 . More particularly, the tubing fill valve  35  includes a mandrel  32  that is coaxial with and circumscribes the longitudinal axis  11  and is circumscribed by a housing section  13 . When the tubing fill valve  35  is open, radial ports  43  in the mandrel  32  align with corresponding radial ports  34  in the housing section  13 . The mandrel  32  is biased open by a compression spring  38  that resides an annular cavity that exists between the mandrel  32  and the housing section  13 . This cavity is in communication with the fluid in the annulus via radial ports  36 . The upper end of the compression spring  38  contacts an annular shoulder  41  of the housing section  13 , and the lower end of the compression spring  38  contacts an upper annular surface  47  of a piston head  49  of the mandrel  32 . A lower annular surface  45  of the piston head  49  is in contact with the fluid in the central passageway  18 . 
     Therefore, due to the above-described arrangement, the tubing fill valve  35  operates in the following manner. When a pressure differential between the fluids in the central passageway  18  and the annulus is below a predetermined differential pressure threshold, the compression spring  38  forces the mandrel  32  down to keep the tubing fill valve  35  open. To close the tubing fill valve  35  (to perform tubing pressure tests or to set the packer  14 , as examples), fluid is circulated at a certain flow rate through the radial ports  34  and  43  until the pressure differential between the fluids in the central passageway  18  and the annulus surpasses the predetermined differential pressure threshold. At this point, a net upward force is established to move the mandrel  32  upward to close off the radial ports  34  and thus, close the tubing fill valve  35 . 
     In the proceeding description, the completion valve assembly  10  is described in more detail, including discussion of the above referenced tubing fill valve  35 ; packer isolation valve  35 ; and index mechanism  28 . In this manner, sections  10 A (FIG.  2 ),  10 B (FIG.  3 ),  10 C (FIG.  4 ),  10 D (FIG.  5 ),  10 E (FIG. 7) and  10 F (FIG. 8) of the completion valve assembly  10  are described below. 
     Referring to FIG. 2, the uppermost section  10 A of the completion valve assembly  10  includes a cylindrical tubular section  12  that is circumscribed by the packer  14 . The tubular section  12  is coaxial with the longitudinal axis  11 , and the central passageway of the section  12  forms part of the central passageway  18 . The upper end of the section  12  may include a connector assembly (not shown) for connecting the completion valve assembly  10  to a tubular string. 
     The tubular section  12  is received by a bore of the tubular housing section  13  that is coaxial with the longitudinal axis  11  and also forms part of the central passageway  18 . As an example, the tubular section  12  may include a threaded section that mates with a corresponding threaded section that is formed inside the receiving bore of the housing section  13 . The end (of the tubular section  12 ) that mates with the housing section  13  rests on a protrusion  52  (of the housing section  13 ) that extends radially inward. The protrusion  52  also forms a stop to limit the upward travel of the mandrel  32  of the tubing fill valve  35 . An annular cavity  54  in the housing section  13  contains the compression spring  38 . The mandrel  32  includes annular O-rings notches above and below the radial ports  43 . These O-rings notches hold corresponding O-rings  50 . 
     Referring to FIG. 3, in the section  10 B of the completion valve assembly  10 , the mandrel  32  includes an exterior annular notch to hold O-rings  58  to seal off the bottom of the chamber  54 . The housing section  13  has a bore that receives a lower housing section  15  that is concentric with the longitudinal axis  11  and forms part of the central passageway  18 . The two housing sections  13  and  15  may be mated by a threaded connection, for example. Near its upper end, the housing section  15  includes an annular notch  64  on its interior surface that has a profile for purposes of mating with a detent ring  60  when the packer isolation valve  22  is open. The detent ring  60  rests in an annular notch  63  that is formed on the interior of the sleeve  20  near the sleeve&#39;s upper end. When the packer isolation valve  22  is closed, the detent ring  60  rests in the annular notch  62  that is formed in the interior surface of the housing section  15  below the annular notch  64 . When the packer isolation valve  22  is opened and the sleeve  20  moves to its upper position, the detent ring  60  leaves the annular notch  62  and is received into the annular notch  64  to lock the sleeve  20  in the opened position. O-rings seals  70  may be located in an exterior annular notch of the housing section  15  to seal the two housing sections  13  and  15  together. O-rings seals  72  may also be located in corresponding exterior annular notches in the sleeve  20  to seal off a radial port  74  (in the housing section  15 ) that is communication with the control line  16 . 
     Referring to FIG. 4, the section  10 C of the completion valve assembly  10  includes a generally cylindrical housing section  17  that is coaxial with the longitudinal axis  11  and includes a housing bore (see also FIG. 3) for receiving an end of the housing section  15 . O-rings  82  reside in a corresponding exterior annular notch of the housing section  17  to seal the two housing sections  15  and  17  together. O-rings  84  are also located in a corresponding interior annular notch to form a seal between the housing section  15  and the mandrel  24  to seal off the nitrogen gas chamber  26 . In this manner, the nitrogen gas chamber  26  is formed below the lower end of the housing section  15  and above an annular shoulder  80  of the housing section  17 . An O-rings  86  resides in a corresponding exterior annular notch of the mandrel  24  to seal off the nitrogen gas chamber  26 . 
     Referring to FIG. 5, in the section  10 D of the completion valve assembly  10 , the lower end of the housing section  17  is received into a bore of an upper end of a housing section  19 . The housing section  19  is coaxial with and circumscribes the longitudinal axis  11 . O-rings  91  reside in a corresponding exterior annular notch of the housing section  17  to seal the housing sections  17  and  19  together. 
     The index mechanism  28  includes an index sleeve  94  that is coaxial with the longitudinal axis of the tool assembly  10 , circumscribes the mandrel  24  and is circumscribed by the housing section  19 . The index sleeve  94  includes a generally cylindrical body  97  that is coaxial with the longitudinal axis of the tool assembly  20  and is closely circumscribed by the housing section  19 . The index sleeve  94  includes upper  98  and lower  96  protruding members that radially extend from the body  97  toward the mandrel  24  to serve as stops to limit the travel of the mandrel  24  until the mandrel  24  moves through the predetermined number of up/down cycles. The upper  98  and lower  96  protruding members are spaced apart. 
     More specifically, the mandrel  24  includes protruding members  102 . Each protruding member  102  extends in a radially outward direction from the mandrel  24  and is spaced apart from its adjacent protruding member  102  so that the protruding member  102  shuttles between the upper  98  and lower  96  protruding members. Before the mandrel  24  transitions through the predetermined number of up/down cycles, each protruding member  102  is confined between one of the upper  98  and one of the lower  96  protruding members of the index sleeve  94 . In this manner, the upper protruding members  98 , when aligned or partially aligned with the protruding members  102 , prevent the mandrel  24  from traveling to its farthest up position to open the packer isolation valve  20 . The lower protruding members  96 , when aligned with the protruding members  102 , prevent the mandrel  24  from traveling to its farthest down to position to open the ball valve  31 . 
     Each up/down cycle of the mandrel  24  rotates the index sleeve  94  about the longitudinal axis  11  by a predetermined angular displacement. After the predetermined number of up/down cycles, the protruding members  102  of the mandrel  24  are completely misaligned with the upper protruding members  98  of the index sleeve  94 . However, at this point, the protruding members  102  of the mandrel  24  are partially aligned with the lower protruding members  96  of the index sleeve  94  to prevent the mandrel  24  from opening the ball valve  31 . At this stage, the mandrel  24  moves up to open the packer isolation valve  20 . The upper travel limit of the mandrel  24  is established by a lower end, or shoulder  100 , of the housing section  17 . The mandrel  24  remains in this far up position until the packer  14  is set. In this manner, after the packer  14  is set, the pressure inside the central passageway  18  is released, an event that causes the mandrel  24  to travel down. However, at this point the protruding members  102  of the mandrel  24  are no longer aligned with the lower protruding members  96 , as the latest up/down cycle rotated the index sleeve  94  by another predetermined angular displacement. Therefore, the mandrel  24  is free to move down to open the ball valve  31 , and the downward travel of the mandrel  24  is limited only by an annular shoulder  103  of the housing section  19 . 
     In some embodiments of the invention, a J-slot  104  (see also FIG. 6) may be formed in the mandrel  24  to establish the indexed rotation of the index sleeve  94 . FIG. 6 depicts a flattened portion  24 A of the mandrel  24 . In this J-slot arrangement, one end of an index pin  92  (see FIG. 5) is connected to the index sleeve  94 . The index pin  92  extends in a radially inward direction from the index sleeve  94  toward the mandrel  24  so that the other end of the index pin  92  resides in the J-slot  104 . As described below, for purposes of preventing rotation of the mandrel  24 , a pin  90  radially extends from the housing section  17  into a groove (of mandrel  24 ) that confines movement of the mandrel  24  to translational movement along the longitudinal axis  11 , as described below. 
     As depicted in FIG. 6, the J-slot  104  includes upper grooves  108  (grooves  108   a ,  108   b  and  108   c , as examples) that are located above and are peripherally offset from lower grooves  106  (groove  106   a , as an example) of the J-slot  104 . All of the grooves  108  and  106  are aligned with the longitudinal axis  11 . The upper  108  and lower  106  grooves are connected by diagonal grooves  107  and  109 . Due to this arrangement, each up/down cycle of the mandrel  24  causes the index pin  92  to move from the upper end of one of the upper grooves a  108 , through the corresponding diagonal groove  107 , to the lower end of one of the lower grooves  106  and then return along the corresponding diagonal groove  109  to the upper end of another one of the upper grooves  108 . The traversal of the path by the index pin  90  causes the index sleeve  94  to rotate by a predetermined angular displacement. 
     The following is an example of the interaction between the index sleeve  94  and the J-slot  104  during one up/down cycle. In this manner, before the mandrel  24  transitions through any up/down cycles, the index pin  92  resides at a point  114  that is located near the upper end of the upper groove  108   a . Subsequent pressurization of the fluid in the central passageway  18  causes the mandrel  24  to move up and causes the index sleeve  94  to rotate. More specifically, the rotation of the index sleeve  94  is attributable to the translational movement of the index pin  92  with the mandrel  24 , a movement that, combined with the produced rotation of the index sleeve  94 , guides the index pin  92  (that does not rotate) through the upper groove  108   a , along one of the diagonal grooves  107 , into a lower groove  106   a , and into a lower end  115  of the lower groove  106   a  when the mandrel  24  has moved to its farther upper point of travel. The downstroke of the mandrel  24  causes further rotation of the index sleeve  94 . This rotation is attributable to the downward translational movement of the mandrel  24  and the produced rotation of the index sleeve  94  that guide the index pin  92  from the lower groove  106   a , along one of the diagonal grooves  109  and into an upper end  117  of an upper groove  108   b . The rotation of the index sleeve  94  on the downstroke of the mandrel  24  completes the predefined angular displacement of the index sleeve  94  that is associated with one up/down cycle of the mandrel  24 . 
     At the end of the predetermined number of up/down cycles of the mandrel  24 , the index pin  92  rests near an upper end  119  of the upper groove  108   c . In this manner, on the next up cycle, the index pin  92  moves across one of the diagonal grooves  107  down into a lower groove  110  that is longer than the other lower grooves  106 . This movement of the index pin  92  causes the index sleeve  94  to rotate to cause the protruding members  102  of the mandrel  24  to become completely misaligned with the upper protruding members  98  of the index sleeve  94 . As a result, the index pin  92  travels down into the lower groove  110  near the lower end  116  of the lower groove  110  as the mandrel  24  travels in an upward direction to open the packer isolation valve  14 . When the mandrel  24  subsequently travels in a downward direction, the index pin  92  moves across one of the diagonal grooves  109  down into an upper groove  112  that is longer than the other upper grooves  106 . This movement of the index pin  90  causes the index sleeve  92  to rotate to cause the protruding members  102  of the mandrel  24  to become completely misaligned with the lower protruding members  96  of the index sleeve  94 . As a result, the index pin  92  travels up into the upper groove  112  as the mandrel  24  travels in a downward direction to open the packer isolation valve  14 . 
     The index pin  90  (see FIG. 5) always travels in the upper groove  112 . Because the index pin  90  is secured to the housing section  19 , this arrangement keeps the mandrel  24  from rotating during the rotation of the index sleeve  94 . 
     Referring to FIG. 7, in a section  10 E of the completion valve assembly  10 , the lower end of the housing section  19  is received by a bore of a lower housing section  21  that is coaxial with the longitudinal axis  11  and forms part of the central passageway  18 . O-rings are located in an exterior annular notch of the housing section  19  to seal the two housing sections  19  and  21  together. Referring to FIG. 8, the mandrel  33  operates a ball valve element  130  that is depicted in FIG. 8 in its closed position. There are numerous designs for the ball valve  31 , as can be appreciated by those skilled in the art. 
     Other embodiments are within the scope of the following claims. For example, FIG. 9 depicts a tubing fill valve  300  that may be used in place of the tubing fill valve  35 . Unlike the tubing fill valve  35 , the tubing fill valve  300  locks itself permanently in the closed position after a predetermined number of open and close cycles. 
     More particularly, the tubing fill valve  300  includes a mandrel  321  that is coaxial with a longitudinal axis  350  of the tubing fill valve  300  and forms part of a central passageway  318  of the valve  300 . The mandrel  321  includes radial ports  342  that align with corresponding radial ports  340  of an outer tubular housing  302  when the tubing fill valve  300  is open. The mandrel  321  has a piston head  320  that has a lower annular surface  322  that is in contact with fluids inside the central passageway  318 . An upper annular surface  323  of the piston head  320  contacts a compression spring  328 . Therefore, similar to the design of the tubing fill valve  35 , when the fluid is circulated through the ports  340 , the pressure differential between the central passageway  318  and the annulus increases due to the restriction of the flow by the ports  340 . When this flow rate reaches a certain level, this pressure differential exceeds a predetermined threshold and acts against the force that is supplied by the compression spring  328  to move the mandrel  321  upwards to close communication between the annulus and the central passageway  318 . 
     Unlike the tubing fill valve  35 , the tubing fill valve  300  may only subsequently re-open a predetermined number of times due to a ratchet mechanism. More specifically, this ratchet mechanism includes ratchet keys  314 , ratchet lugs  312  and flat springs  310 . Each ratchet key  314  is located between the mandrel  321  and a housing section  306  and partially circumscribes the mandrel  321  about the longitudinal axis  350 . The ratchet key  314  has annular cavities, each of which houses one of the flat spring  310 . The flat springs  310 , in turn, maintain a force on the ratchet key  314  to push the ratchet key  314  in a radially outward direction toward the housing section  306 . 
     Each ratchet lug  312  is located between an associated ratchet key  314  and the housing section  306 . Referring also to FIG. 10 that depicts a more detailed illustration of the ratchet key  314 , lug  312  and housing section  306 , the ratchet lug  312  has interior profiled teeth  342  and exterior profiled teeth  340 . As an example, each tooth of the interior profiled teeth  342  may include a portion  343  that extends radially between the ratchet lug  312  and the ratchet key  314  and an inclined portion  345  that extends in an upward direction from the ratchet key  314  to the ratchet lug  312 . The ratchet key  314  also has profiled teeth  315  that are complementary to the teeth  342  of the ratchet lug  312 . The exterior profiled teeth  340  of the ratchet lug  312  includes a portion  360  that extends radially between the ratchet lug  312  and the housing section  306  and an inclined portion  362  that extends in an upward direction from the housing section  306  to the ratchet lug  312 . The housing  306  has profiled teeth  308  that are complementary to the teeth  340  of the ratchet lug  312 . 
     Due to this arrangement, the ratchet mechanism operates in the following manner. The tubing fill valve  300  is open when the completion valve assembly  10  is run downhole. Before the tubing fill valve  300  is closed for the first time, the ratchet lugs  312  are positioned near the bottom end of the mandrel  321  and near the bottom end of the teeth  308  of the housing section  306 . When the rate of circulation between the central passageway  318  and the annulus increases to the point that a net upward force moves the mandrel  321  in an upward direction, the ratchet lugs  312  move with the mandrel  321  with respect to the housing section  306 . In this manner, due to the flat springs  310  and the profile of the teeth, the ratchet lugs  312  slide up the housing section  306 . 
     When the tubing fill valve  300  re-opens and the mandrel  321  travels in a downward direction, the ratchet lugs  312  remain stationary with respect to the housing section  306  and slip with respect to the mandrel  321 . The next time the tubing fill valve  300  closes, the ratchet lugs  312  start from higher positions on the housing section  306  than their previous positions from the previous time. Thus, the ratchet lugs  312  effectively move up the housing section  306  due to the opening and closing of the tubing fill valve  35 . 
     Eventually, the ratchet lugs  312  are high enough (such as at the position  312 ′ that is shown in FIG. 9) to serve as a stop to limit the downward travel of the mandrel  321 . In this manner, after the tubing fill valve  300  has closed a predetermined number of times, the lower surface  322  of the piston head  320  contacts the ratchet lugs  312 . Thus, the mandrel  321  is prevented from traveling down to re-open the tubing fill valve  300 , even after the pressure in the central passageway  318  is released. 
     Among the other features of the tubing fill valve  300 , the valve  300  may be formed from a tubular housing that includes the tubular housing section  302 , a tubular housing section  304  and the tubular housing section  306 , all of which are coaxial with the longitudinal axis  350 . The housing section  304  has a housing bore at its upper end that receives the housing section  302 . The two housing sections  302  and  304  may be threadably connected together, for example. The housing section  304  may also have a housing bore at its lower end to receive the upper end of the housing section  306 . The two housing sections  304  and  306  may be threadably connected together, for example. 
     In the preceding description, directional terms, such as “upper,” “lower,” “vertical,” “horizontal,” etc., may have been used for reasons of convenience to describe the completion valve assembly and its associated components. However, such orientations are not needed to practice the invention, and thus, other orientations are possible in other embodiments of the invention. 
     While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of the invention.