Patent Abstract:
An assembly that is usable in a subterranean well includes a valve, a sleeve and an index mechanism. The valve is adapted to selectively isolate a region of the well, and the sleeve is adapted to be moved by a downhole tool to cause the valve to transition from a first state to a second state. The index mechanism prevents the valve from transitioning from the first state to the second state until after a position of the sleeve follows a predefined pattern.

Full Description:
Pursuant to 35 U.S.C. §119, this application claims the benefit of U.S. Provisional Application Serial No. 60/250,754, entitled FORMATION ISOLATION VALVE,” filed on Dec. 1, 2000. 
    
    
     BACKGROUND 
     The invention generally relates to a formation isolation valve. 
     A formation isolation valve may be located downhole to form a sealed access to a particular formation. In this manner, the formation isolation valve may be opened or run open so that a tubular string may be run downhole through the valve to permit the string to perform one or more downhole functions below the formation isolation valve. After these functions are complete, the string may be retrieved. After the end of the string passes through the valve during the retrieval of the string, the valve may then be operated to seal off the formation below the valve. In this manner, a shifting tool may be located at the end of the tool to physically engage the valve to cause the valve to close. The shifting tool may also be used to open the valve. 
     As an example, the string may include a gravel packing tool to route gravel into an annular region that surrounds a screened portion of a production tubing of the well. In this manner, the gravel travels down a central passageway of the string and through radial ports of the gravel packing tool into the annular region. The gravel may include sand that falls between the interior opening of the formation isolation valve and the outside of the string to create friction between the string and the valve. Unfortunately, the friction between the string and valve may cause the string to unintentionally physically engage the valve to cause the valve to prematurely close on the string. Thus, such a scenario may cause the string to become wedged in the valve. 
     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 assembly that is usable in a subterranean well includes a valve, a sleeve and an index mechanism. The valve is adapted to selectively isolate a region of the well, and the sleeve is adapted to be moved by a downhole tool to cause the valve to transition from a first state to a second state. The index mechanism prevents the valve from transitioning from the first state to the second state until after a position of the sleeve follows a predefined pattern. 
    
    
     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 formation isolation valve assembly according to an embodiment of the invention. 
     FIGS. 2,  3 ,  4 ,  6 ,  7  and  8  are more detailed schematic diagrams of sections of the formation isolation valve assembly according to an embodiment of the invention. 
     FIGS. 5 and 9 are schematic diagrams of flattened portions of the formation isolation valve assembly depicting J-slots according to different embodiments of the invention. 
     FIG. 10 is a schematic diagram of a portion of a production tubing according to an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, an embodiment  10  of a formation isolation valve assembly in accordance with the invention controls access to a region of a well below the valve  10 . In this manner, the valve assembly  10  permits a string, such as a string  30 , to pass through the valve assembly  10  to the region beneath the valve assembly  10  when the valve assembly  10  is in an open state (as depicted in FIG.  1 ), and when the valve assembly  10  is in a closed state, the valve assembly  10  seals off communication with the region beneath the valve assembly  10 . An annular region, or annulus  11 , that is located between an exterior surface of the valve assembly  10  and a production tubing  9  of the well may be sealed off by a packer (not shown). 
     More specifically, in some embodiments of the invention, the valve assembly  10  includes a ball valve  22  that assumes an open state to permit the string  30  to pass through the valve assembly  10  and assumes a closed state to seal off the region below the valve assembly  10  when the string  30  no longer extends through the ball valve  22 . 
     In some embodiments of the invention, when the formation isolation valve assembly  10  is first set in place downhole, the ball valve  22  may be opened (or run into the well bore open) to permit the string  30  to pass through. Alternatively, the formation isolation valve assembly  10  may be run with the string  30  already included through the ball valve  22 . The string  30  may include a gravel packing tool to perform gravel packing operations downhole. After the gravel packing operations are complete, the string  30  may be withdrawn from the well bore. 
     In some embodiments of the invention, after the gravel packing operation is complete, the ball valve  22  is closed. In this manner, the string  30  may include a shifting tool  16  (near a lower end of the string  30 ) to physically close the ball valve  22 . More specifically, after lower end of the string  30  is retracted above the ball valve  22 , a profiled section  17  of the shifting tool  16  engages (as described below) the valve assembly  10  and is operated in a manner (described below) to cause the ball valve  22  to close. 
     After the string  30  is withdrawn from the well bore and the gravel packing operations are complete, pressure tests may be conducted downhole. At the conclusion of the pressure tests, a pressure may be used (as described below) to reopen the ball valve  22 . 
     For purposes of preventing unintentional opening and closing of the ball valve  22 , the valve assembly  10  includes two index mechanisms  15  and  20 , in some embodiments of the invention. The index mechanism  15  is pressure actuated and prevents the unintentional opening of the ball valve  22  without the occurrence of a predetermined number of pressurization/de-pressurization cycles, as described below. The index mechanism  20  is actuated via physical contact between the shifting tool  16  and the valve assembly  10  and prevents the unintentional closing of the ball valve  22  without a predetermined pattern of engagement, described below. Without the index mechanism  20 , movement of the shifting tool  16  or movement of the string  30  itself may unintentionally engage the closing mechanism of the valve assembly  10  to cause the ball valve assembly  10  to attempt to prematurely close, a condition that may cause the string  30  to become jammed in the ball valve  22 , thereby preventing the removal of the string  30  from the well. 
     More particularly, in some embodiments of the invention, the valve assembly  10  includes an operator mandrel  12  that moves up in response to applied tubing pressure (in the central passageway of the assembly  10 ) and moves down when the pressure is released. The downward travel of the mandrel  12  is limited by the index mechanism  15  until a predetermined number of cycles occur in which the tubing pressure increases and then decreases. After the predetermined number of cycles, the index mechanism  15  permits the mandrel  12  to travel downward to contact a collet actuator  13  that is engaged with a ball valve operator mandrel  14  that, in turn, operates the ball valve  22 . In this manner, the downward movement of mandrel  12  causes the mandrel  14  to move in a downward direction to open the ball valve  22 . 
     In some embodiments of the invention, to close the ball valve  22  via the shifting tool  16 , the profile  17  of the shifting tool  16  engages (as described below) the collet actuator  13  to force the collet actuator  13  up and down. On each upward stroke, the collet actuator  13  disengages from the mandrel  14 , as described below. 
     When the mandrel  14  moves up by a sufficient distance, the mandrel  14  closes the ball valve  22 . However, the upward travel of the mandrel  14  is limited by the index mechanism  20  until the shifting tool  16  forces the collet actuator  13  up and down for a predetermined number of cycles. After the cycles occur, the mandrel  14  engages with the collet actuator  13  on the downstoke on the sleeve  13  and remains engaged with the collet actuator  13  on the upstroke of the collet actuator  13 , thereby permitting the shifting tool  16  to lift the mandrel  14  up for a sufficient distance to close the ball valve  22 . 
     Referring to the formation isolation valve assembly  10  in more detail, FIGS. 2,  3  and  4  depict sections  10 A,  10 B and  10 C that form a section (of the valve assembly  10 ) that houses the index mechanism  15  and the mandrel  12 . The upper part of this section is formed from an upper housing section  44   a  that mates with a lower housing section  44   b . In this manner, the lower end of the housing section  44   a  is received into a bore in the upper end of the housing section  44   b . Both housing sections  44   a  and  44   b  are generally cylindrical and circumscribe a longitudinal axis of the valve assembly  10 . 
     The mandrel  12  moves up in response to applied tubing pressure in a central passageway  40  of the valve assembly  10 , and moves down in response to the pressure exerted by a nitrogen gas chamber  47  (FIG.  3 ). The nitrogen gas chamber  47 , in some embodiments of the invention, is formed from an annularly recessed cavity located between the housing section  44   a  and the mandrel  12 . The nitrogen gas chamber  47 , in other embodiments of the invention, may be replaced by a coil spring or another type of spring, as examples. 
     The responsiveness of the mandrel  12  to the tubing pressure and the pressure that is exerted by the gas in the chamber  47  is attributable to an upper annular surface  50  (of the mandrel  12 ) that is in contact with the nitrogen gas in the nitrogen gas chamber  47  and a lower annular surface  51  of the mandrel  14  that is in contact with the fluid in the central passageway  40 . Therefore, when the fluid in the central passageway  40  exerts a force (on the lower annular surface  51 ) that is sufficient to overcome the force that the gas in the chamber  47  exerts on the upper annular surface  50 , a net upward force is established on the mandrel  12 . Otherwise, a net downward force is exerted on the mandrel  12  to force the ball valve operator mandrel  14  down. 
     Referring to FIG. 4, the index mechanism  15  limits the upward and downward travel of the mandrel  12 . More particularly, the index mechanism  15  confines the lower travel limit of the mandrel  12  until the mandrel  12  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  12  moving from a limited (set by the index mechanism  15 ) down position to a limited up position (set by the index mechanism  15 ) 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  40  is increased and then after testing is completed, released. 
     After the mandrel  12  transitions through the predetermined number of up/down cycles, the index mechanism  15  no longer confines the downward travel of the mandrel  12 . Therefore, when the central passageway  18  is pressurized again, the mandrel  12  is free to travel down to contact the mandrel  14  to open the valve  22 . 
     Referring to FIG. 3, the mandrel  12  includes an exterior annular notch to hold O-rings  53  to seal off the bottom of the gas chamber  47 . O-rings  39  are also located in an interior annular notch of the housing section  44   a  (see FIG. 3) to form a seal between the housing section  44   a  and the mandrel  12  to seal off the nitrogen gas chamber  47 . O-rings  38  form a seal between the housing sections  44   a  and  44   b.    
     Referring back to FIG. 4, in some embodiments of the invention, the index mechanism  15  includes an index sleeve  94  that is coaxial with the longitudinal axis of the valve assembly  10 , circumscribes the mandrel  12  and is circumscribed by the housing section  44   c . The index sleeve  94  includes a generally cylindrical body  97  that is coaxial with the longitudinal axis of the valve assembly  10  and is closely circumscribed by the housing section  44   c . The index sleeve  94  includes protruding splines, or members  104  (one being shown in FIG.  4 ), that radially extend from the body  97  toward the mandrel  12  to serve as a stop to limit the downward travel of the mandrel  12  until the mandrel  12  moves through the predetermined number of up/down cycles. 
     More specifically, the protruding members  104  are radially spaced apart around the longitudinal axis of the valve assembly  10  so that when the index sleeve  94  is rotated to the appropriate position after the predetermined number of up/down cycles, radially spaced protruding members  102  (two being shown in FIG. 4) of the mandrel  12  that radially extend from the mandrel  12  toward the index sleeve  94  pass between the protruding members  104  of the index sleeve  94 . Otherwise, the protruding members  104  limit the downward travel of the mandrel  12 , as the protruding members  102  and  104  contact each other. 
     Each up/down cycle of the mandrel  12  rotates the index sleeve  94  about the longitudinal axis of the valve assembly  10  by a predetermined angular displacement. After the predetermined number of up/down cycles, the protruding members  102  of the mandrel  12  are completely misaligned with the protruding members  104  of the index sleeve  94 , thereby allowing the mandrel  12  to pass through. 
     Referring both to FIG.  4  and FIG. 5 (that depicts a flattened portion  12 A of the mandrel  12 ), in some embodiments of the invention, a J-slot  105  may be formed in the mandrel  12  to establish the indexed rotation of the index sleeve  94 . In this J-slot arrangement, one end of an index pin  92  (see FIG. 4) is connected to the index sleeve  94 . The index pin  92  extends through a particular protruding member  104  in a radially inward direction from the index sleeve  94  toward the mandrel  12  so that the other end of the index pin  92  resides in the J-slot  105 . As described below, for purposes of preventing rotation of the mandrel  12 , a pin  90  radially extends from the housing section  44   c  into a groove (of mandrel  12 ) that confines movement of the mandrel  12  to translational movement along the longitudinal axis of the valve assembly  10 , as described below. 
     As depicted in FIG. 5, the J-slot  105  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  105 . All of the grooves  108  and  106  are aligned with the longitudinal axis of the valve assembly  10 . 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  12  causes the index pin  92  to move from the upper end of one of the upper grooves  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  105  during one up/down cycle. In this manner, before the mandrel  12  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  12  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  12 , a movement that, combined with the produced rotation of the index sleeve  94 , guides the index pin  92  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  12  has moved to its farther upper point of travel. The downstroke of the mandrel  12  causes further rotation of the index sleeve  94 . This rotation is attributable to the downward translational movement of the mandrel  12  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  12  completes the predefined angular displacement of the index sleeve  94  that is associated with one up/down cycle of the mandrel  12 . 
     At the end of the predetermined number of up/down cycles of the mandrel  12 , the index pin  92  rests near an upper end  119  of the upper groove  108   c . In this manner, on the next up stroke, the index pin  92  moves across one of the diagonal grooves  107  down into the lower end  116  of a lower groove  110 . The resulting rotation of the index sleeve  94  causes the protruding members  102  of the mandrel  12  to become completely misaligned with the protruding members  104  of the index sleeve  94 . Therefore, on the subsequent downstroke, the index pin  92  effectively travels up into the upper groove  112  as the mandrel  14  travels in a downward direction to open the packer isolation valve. 
     The index pin  90  (see also FIG. 4) always travels in the upper groove  112 . Because the index pin  90  is secured to the housing section  19 , this arrangement keeps the mandrel  12  from rotating during the rotation of the index sleeve  94 . 
     FIGS. 6 and 7 depict sections  10 D and  10 E (of the valve assembly  10 ) that include the collet actuator  13 , the ball valve operator mandrel  14  and the index mechanism  20 . The sections  10 D and  10 E are formed by the housing sections  44   c ,  44   d  and  44   e , each of which circumscribes the longitudinal axis of the valve  20 . In this manner, the lower end of the housing section  44   c  is received by a bore located in the upper end of the housing section  44   d . The housing sections  44   c  and  44   d  are sealed together via O-rings  213  that are located in an exterior annular notch of the housing section  44   c . The lower end of the housing section  44   d  is received by a bore located in the upper end of the housing section  44   d . The housing sections  44   d  and  44   e  are sealed together via O-rings  321  that are located in an exterior annular notch of the housing section  44   d.    
     In some embodiments of the invention, when the shifting tool  16  closes the ball valve  22  (after gravel packing operations, for example), the collet actuator  13  is engaged with the mandrel  14  and has a higher position than depicted in FIGS. 6 and 7. In this higher position, the mandrel  14  closes the ball valve  22  and subsequent action by the mandrel  12  is required to open the ball valve  22 . More specifically, a collet sleeve  206  is mounted to the collet actuator  13  to lock the collet actuator  13  and mandrel  14  (that is at this point engaged with the mandrel  14 ) into a position that keeps the ball valve  22  closed until the mandrel  12  forces the collet actuator  13  and mandrel  14  in a downward direction at the end of pressure testing operations, as described above. 
     The collet sleeve  206  is attached to the collet actuator  13  via a pin  200 , circumscribes a portion of the collet actuator  13 , and is located between the collet actuator  13  and the housing section  44   c . When the collet actuator  13  is in its upper position in which the ball valve  22  is closed, the ends of upper fingers  215  of the collet sleeve  206  are located in an annular notch  214  that is formed in an interior surface of the housing section  44   c . However, when the collet actuator  13  is forced in a downward direction, the beveled profile of the notch  214  causes the upper fingers  215  to be forced out of the notch  214  and extend through openings  208  of the collet actuator  13 , thereby permitting the collet actuator  13  and mandrel  14  to travel down. 
     However, before the mandrel  14  may move freely to close the ball valve  22  after gravel packing operations are complete, the index mechanism  20  is engaged to prevent unintentional closing of the ball valve  22  on the string  30 . A predetermined number of up and down cycles of the collet actuator  13  disengages the index mechanism  20  so that the mechanism  20  no longer restricts travel of the mandrel  14 . 
     Referring to FIG. 7, thus, when the index mechanism  20  is engaged and the ball valve  22  is open, the index mechanism&#39;s restriction on the upward travel of the mandrel  14  causes the collet actuator  13  to disengage, or separate, from the mandrel  14  on upstrokes until the collet  13  cycles through the predetermined number of up/down cycles. 
     To regulate the closing of the ball valve  22 , the index mechanism  20  includes an index sleeve  294 . The index sleeve  294  is coaxial with the longitudinal axis of the valve assembly  10 , circumscribes the collet actuator  13  and is circumscribed by the housing section  44   d . The index sleeve  294  is prevented from upward and downward movement via a lower shoulder  217  (see FIG. 6) of the housing section  44   c  and a shoulder  305  (see FIG. 7) of the housing section  44   d . The index sleeve  294  includes a generally cylindrical body  297  that is coaxial with the longitudinal axis of the valve assembly  10  and is closely circumscribed by the housing section  44   d . The index sleeve  294  includes protruding splines, or members  302  (one being shown in FIG.  7 ), that radially extend inwardly from the body  297  to serve as a stop to limit the upward travel of the mandrel  14  until the shifting tool  16  moves the collet actuator  13  up and down a predetermined number of times. The downward travel of the mandrel  14  is limited by the shoulder  305  of the housing section  44   d.    
     More specifically, the protruding members  302  are radially spaced apart so that when the index sleeve  294  is rotated to the appropriate position, radially spaced protruding members  304  (of the mandrel  14 ) that extend radially outwardly from the mandrel  14  toward the index sleeve  294  pass between the protruding members  302  of the index sleeve  294 . When the mandrel  14  is pulled up with the collet actuator  13  to close the ball valve  22 , the index sleeve  294  is positioned to allow the protruding members  304  to pass between the protruding members  302 , as described below. In one embodiment, the protruding members  302 ,  304  remain thus aligned to allow the subsequent axial movement of mandrel  14 . 
     Each time the shifting tool  16  moves the collet actuator  13  up or down, the index sleeve  294  rotates about the longitudinal axis of the valve assembly  10  by a predetermined angular displacement. After the predetermined number of up and down movements by the collet actuator  13 , the protruding members  304  of the mandrel  14  are completely misaligned with the protruding members  302  of the index sleeve  294 , thereby allowing the mandrel  14  to pass through to move in an upward direction to close the ball valve  22 . 
     In some embodiments of the invention, a J-slot  404  (see also FIG. 9 that depicts a flattened portion  314  of the collet actuator  13 ) may be formed in the collet actuator  13  to establish the indexed rotation of the index sleeve  294 . In this J-slot arrangement, one end of an index pin  292  (see FIG. 7) is connected to the index sleeve  294 . The index pin  292  extends radially inwardly so that the other end of the index pin  292  resides in the J-slot  404  in the collet actuator  13 . For purposes of preventing rotation of the collet actuator  13 , a pin  291  radially extends from the housing section  44   d  into a longitudinal groove of the mandrel  14 , and a pin  298  radially extends inwardly from the mandrel  14  into a longitudinal groove of the collet actuator  13 . Thus, the pin  291  confines movement of the mandrel  14  to translational movement along the longitudinal axis of the valve assembly  10 , and the pin  298  confines movement of the collet actuator  13  to the translational movement along the longitudinal axis of the valve assembly  10 . 
     Therefore, due to the above-described arrangement, each time the collet actuator  13  moves in a downward direction, the index sleeve  294  rotates by a predetermined angular displacement, and each time the collet actuator  13  moves in an upward direction, the index sleeve  294  rotates by a predetermined displacement. Eventually, the index sleeve  294  does not restrict the upward travel of the mandrel  14  and permits the mandrel  14  to be pulled up enough to close the ball valve  22 . 
     Referring to FIG. 6, for purposes of allowing the shifting tool  16  to engage the collet actuator  13  to move the collet actuator  13  up and down, the collet actuator  13  has an interior annular upper groove  250  and an interior annular lower groove  252  that each have beveled cross-sections. The upper groove  250  has the openings  208  (two being depicted in FIG. 6) through which the end of the upper fingers  215  of the collet sleeve  206  extend to catch the shifting tool  16  to permit the tool  16  to lift the collet actuator  13  to the height that is allowed by the index pin  292 . When the collet actuator  13  travels in an upward direction, the upper fingers  215  are received by an upper annular groove  214  formed on the interior surface of the housing section  44   c . When received by the groove  214 , the upper fingers  215  retract to release the grip on the shifting tool  16 . The lower groove  252  has openings  209  (two being depicted in FIG. 6) through which the ends of lower fingers  211  of the collet sleeve  206  extend to catch the shifting tool  16  to permit the tool  16  to shift the collet actuator  13  back down. When the collet actuator  13  travels in a downward direction, the lower fingers  211  are received by an annular groove  212  that is formed in the interior surface of the housing section  44   c . When received by the groove  212 , the lower fingers  211  retract to release their grip on the shifting tool  16 . 
     Referring to FIGS. 7 and 8, in some embodiments of the invention, the collet actuator  13  includes fingers, such as a finger  324  that is depicted in FIG. 7, that includes an exterior annular ridge  320  that is received by a corresponding beveled interior annular notch  322  of the mandrel  14 . Thus, as long as the index sleeve  294  restricts the upward travel of the mandrel  14 , the upward force that is applied on the collet actuator  13  by the shifting tool  16  dislodges the collet actuator  13  from the mandrel  14  and allows the collet actuator  13  to proceed upwardly by itself. When the collet actuator  13  is one again moved downwardly by the shifting tool  16 , the exterior annular ridge  320  is once again received by the annular notch  322 . As depicted in FIG. 8, the mandrel  14  extends to operate the ball valve  22  that is housed in a lower section  10 F of the valve assembly  10 . 
     Once the index pin  292  enters the final, longitudinal groove  407  (see FIG. 9) of the J-slot  404 , the index sleeve  294  no longer restricts the upward travel of the mandrel  14 . Thus, the ridge  320 /notch  322  connection will not disengage when the collet actuator  13  is moved upward (or downward), and the upward movement of the collet actuator  13  also results in the upward movement of mandrel  14 . Based on the now “fixed” connection between the mandrel  14  and collet actuator  13 , the shifting tool  16  may be used to close the ball valve  22  by pulling the collet actuator  13  up and open the ball valve by shifting the collet actuator  13  down, as the index mechanism  20  is effectively disabled after cycling once through the above-described sequence. It is noted that the J-slot  404  may be designed to require any number of up/down cycles by the collet actuator  13  before releasing the mandrel  14 , as can be appreciated by those skilled in the art. 
     In summary, in some embodiments of the invention, the valve assembly  10  may be run downhole with the ball valve  22  in the open state, with a string  30 , including a shifting tool  16 , disposed through the ball valve  22 . The string  30  is used to conduct an operation (like gravel packing) below the ball valve  22 . When the operation is completed, the string  30  is pulled up and the shifting tool  16  engages the collet actuator  13 . Due to the presence of the index mechanism  20 , movement of the mandrel  14  is initially restricted. In order to move mandrel  14  to close the ball valve  22 , the shifting tool  16  must be used to move the collet actuator  13  up and down the predetermined number of times until the index mechanism  20  is disengaged. Once the index mechanism  20  is disengaged, the shifting tool  16  pulls the collet actuator  13  and mandrel  14  upward closing the ball valve  22 . The string  30  is then removed from the wellbore. By requiring the predetermined number of times, the index mechanism  20  prevents the inadvertent and/or premature closure of the ball valve  22 . 
     At this point, index mechanism  20  is disengaged (with index pin  292  always subsequently riding in groove  407 ) and the mandrel  14  can be forced down by the mandrel  12 . The operator may at this point wish to pressure test the tubing string above the ball valve  22  or perform other pressure-responsive operations. Due to the presence of index mechanism  15 , movement of the mandrel  12  is initially restricted. As such, the pressure cycles will not act to open the ball valve  22  until after the predetermined number of pressure cycles have been performed. After the last of the predetermined pressure cycles, the index mechanism  15  disengages, allowing mandrel  12  to move downward, act on collet actuator  13 , and move collet actuator  13  and mandrel  14  (since index mechanism  20  is also disengaged) to open ball valve  22 . Once both index mechanisms  15 ,  20  are disengaged, the ball valve  22  may be opened or closed through the engagement between shifting tool  16  and collet actuator  13 . At this point, one shift down will normally open ball valve  22 , and one shift up will normally close ball valve  22 . 
     Although the use of the mandrel  12  and the predetermined number of pressurization/de-pressurization cycles are described above for opening the ball valve  22  after the pressure tests, the ball valve  22  may also be opened via the shifting tool  16 . In some embodiments of the invention, the index mechanisms  15  and  20  may be disengaged in a reverse order to that described above. In this manner, in some embodiments of the invention, the pressurization/de-pressurization cycles may be used to open and/or close the ball valve  22  before the shifting tool  16  is used in connection with the up and downstrokes of the collet actuator  13 . Other variations are possible. 
     Referring to FIG. 10, in some embodiments of the invention, the valve assembly  10  may be located inside a production tubing  600 . As shown, the valve assembly  10  is located closer to the surface of the well than a port closure sleeve  602  (of the production tubing  600 ) that is located downhole from the valve assembly  10 . For the vertical arrangement depicted in FIG. 10, the valve assembly  10  is located above, or uphole from, the sleeve  602 . 
     This relationship between the valve assembly  10  and sleeve  602  may be particularly advantageous for use with gravel packing operations. In this manner, the port closure sleeve  602  includes radial ports that may be opened for purposes of a gravel packing operation, an operation in which a gravel packing tool (not shown) may be extended through the valve assembly  10  and positioned near the port closure sleeve  602  so that gravel may be introduced around the exterior of the production tubing  600 . After the completion of the gravel packing operation, the gravel packing tool may then be withdrawn through the valve assembly  10 . 
     It is possible that the introduction of gravel through the radial ports of the sleeve  602  may compromise the seal integrity of sleeve  602 . For example, when the sleeve  602  is supposed to be closed to seal off the internal passageway of the production tubing  600  from receiving fluid from outside of the tubing  600 , debris that is introduced by the gravel packing operation may keep the sleeve  602  from forming a tight seal when closed. 
     However, because the valve assembly  10  is located between the sleeve  602  and the surface of the well, the valve assembly  10  may be closed to perfect the seal that may otherwise not be provided by the sleeve  602 . Thus, the location of the valve assembly  10  above the sleeve  602  circumvents potential sealing problems that may occur with the use of the sleeve  602 . 
     In the preceding description, directional terms, such as “upper,” “lower,” “vertical,” “horizontal,” etc., may have been used for reasons of convenience to describe the isolation valve 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.

Technology Classification (CPC): 4