Abstract:
A method usable with a subterranean well that includes actuating a downhole tool (a valve assembly, for example). The method also includes applying at least one of an impulse stimulus and a vibration stimulus to the tool during the actuating to enhance operation of the tool.

Description:
BACKGROUND  
       [0001]     The invention relates generally to flow control actuation.  
         [0002]     A subterranean well typically includes flow control valves, such as sliding sleeve valves, ball valves and rotating sleeve valves, as just a few examples. The effective cross-sectional flow area of a flow control valve may be incrementally adjustable for purposes of precisely regulating the flow through the valve when open. Another type of flow control valve has a fixed cross-sectional flow area when open. Thus, this type of flow control valve is either fully closed or opened.  
         [0003]     Regardless of the particular type of flow control valve, the static force that is required to actuate the valve (i.e., the static force needed to change the state of the valve) may increase over the lifetime of the valve, due to the deposition of solids (scale deposits, for example) on the valve. This deposition typically opposes the movement of parts (a sleeve, for example) of the flow control valve and thus, may require the use of more static force to operate the valve as the deposition accumulates over the life of the valve. A typical solution to this problem is to oversize (at least initially) the valve&#39;s actuator so that the actuator produces enough force to overcome an increasing opposing force as more material is deposited on the valve. However, this solution may cause the valve to be undesirably large, expensive and/or complex.  
         [0004]     Thus, there exists a continuing need for an arrangement and/or technique to address one or more of the problems that are set forth above as well as possibly address one or more problems that are not set forth above.  
       SUMMARY  
       [0005]     In an embodiment of the invention, a technique that is usable with a subterranean well includes actuating a downhole tool (a valve, for example) and applying at least one of an impulse stimulus and a vibration stimulus to the tool during the actuating to enhance operation of the tool.  
         [0006]     In another embodiment of the invention, an apparatus that is usable with a subterranean well includes an actuator to apply a force to a downhole tool to operate the tool. The apparatus also includes a generator to apply at least one of an impulse stimulus and a vibration stimulus to the tool during the actuating to enhance operation of the tool.  
         [0007]     Advantages and other features of the invention will become apparent from the following description, drawing and claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a schematic diagram of a well according to an embodiment of the invention.  
         [0009]      FIGS. 2 and 9  are flow diagrams depicting techniques to actuate a flow control valve assembly according to embodiments of the invention.  
         [0010]      FIGS. 3 and 4  are schematic diagrams of flow control valve assemblies according to embodiments of the invention.  
         [0011]      FIGS. 5, 6  and  7  are schematic diagrams of impulse/vibration generators according to different embodiments of the invention.  
         [0012]      FIG. 8  is a cross-sectional view of a flow control valve assembly according to an embodiment of the invention.  
         [0013]      FIG. 10  is a schematic diagram of electronics of the flow control valve assembly according to an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0014]     Referring to  FIG. 1 , an embodiment of a well  10  in accordance with the invention includes a tubing string  14  (a production tubing string, for example) that extends into a vertical wellbore of the well  10 . As shown in  FIG. 1 , in some embodiments of the invention, the well  10  may be cased, and thus, the tubing string  14  may extend through the passageway that is formed by a casing string  12  of the well  10 . Alternatively, in some embodiments of the invention, the well  10  may be uncased, and thus, the tubing string  14  may extend through an uncased borehole of the well  10 .  
         [0015]     Although a vertical wellbore is depicted in  FIG. 1 , it is noted that in some embodiments of the invention, the tubing string  14 , or a similar tubular string, may extend into a lateral wellbore, for example. Thus, many variations are possible and are within the scope of the appended claims.  
         [0016]     The tubing string  14  includes a flow control valve assembly  20  (herein called “valve assembly  20 ”). As a specific example, it is assumed herein that the valve assembly  20  is a linear sliding sleeve valve. However, this is for purposes of example only, as in other embodiments of the invention, other types of valve assemblies may be used.  
         [0017]     For example, the arrangements and techniques described herein may be applied to ball valves, rotating sleeve valves, incrementally-positionable valves, etc. Furthermore, as described below, in some embodiments of the invention, the valve assembly  20  may be an exterior sliding sleeve valve assembly, although in other embodiments of the invention, other types of sliding sleeve valves (an interior sliding sleeve valve, for example) may be used. Additionally, although  FIG. 1  depicts a single valve assembly  20 , it is understood that in other embodiments of the invention, the tubing string  14  may include multiple valve assemblies, each of which may be the same type of valve assembly or different types of valve assemblies (as examples). Furthermore, in some embodiments of the invention, the well  10  may include multiple tubing strings, in addition to the tubing string  14 , for example.  
         [0018]     In other embodiments of the invention, the well  10  may not include a tubular string  14 , such as the tubing string that extends to the surface of the well (as depicted in  FIG. 1 ), but rather, in some embodiments of the invention, a particular tubular section that contains a valve assembly that may be installed downhole and not extend to the surface of the well. Thus, many variations are possible and are within the scope of the appended claims.  
         [0019]     Although techniques for actuating a valve assembly are described herein, it is understood that a valve assembly is just one example of a downhole tool. Thus, the techniques that are disclosed herein may be applied to other downhole tools, in other embodiments of the invention.  
         [0020]     Referring to the specific embodiment that is depicted in  FIG. 1 , the valve assembly  20  may include an exterior sliding sleeve  26  that is operated (i.e., moved by) by a linear actuator  24  of the valve assembly  20  for purposes of opening and closing the valve assembly  20  to the flow of well fluid. For example, the sliding sleeve valve  26  may control communication between an annulus  15  of the well  10  and a central passageway of the tubing string  14 . Here, the phrase “annulus” means the region between the outside of the tubing string  14  and the interior surface of the casing string  12 .  
         [0021]     It is noted that in some embodiments of the invention, the valve assembly  20  may be incrementally-adjustable, in that the sleeve  26  may be controlled to vary the size of the effective cross-sectional area flow path of the valve assembly  20  when the valve assembly  20  is not closed. This particular embodiment is described below. However, in other embodiments of the invention, the valve actuator  20  may operate the sleeve  26  so that the valve assembly  20  is either fully opened or closed (i.e., the valve assembly may have a cross-sectional area flow path whose size is not incrementally-adjustable).  
         [0022]     Over the course of the lifetime of the valve assembly  20 , deposits may accumulate on the surface over which the sleeve  26  moves and introduce resistance to the movement of the sleeve  26 . For example, it is possible that over the course of the lifetime of the valve assembly  20 , scale deposit may build up on the surface over which the sleeve  26  slides. As a result, the scale deposit may significantly resist movement of the sleeve  26  so that the sleeve  26  may not receive enough force (via the linear actuator  24 ) to operate (i.e., move to the desired position), if not for the features of the present invention. To accommodate this scenario, a conventional valve assembly may oversize the linear actuator which means the actuator is designed to exert enough force to accommodate a future scale (or other deposit) build up on the valve assembly  20 , which opposes movement of the sliding sleeve. However, unlike conventional arrangements, in some embodiments of the invention, the linear actuator  24  is not oversized in anticipation of deposit buildup on the valve assembly  20 . Rather, in some embodiments of the invention, the valve assembly  20  applies impulse and/or vibrational energy concurrently with the operation of the valve assembly  20  for purposes of overcoming any opposing forces (to the sleeve&#39;s movement) that are caused by deposition of solids on the valve assembly  20 .  
         [0023]     More specifically, in some embodiments of the invention, the valve assembly  20  includes an impulse/vibration generator  22 , a mechanical and/or electrical device that is actuated during operation of the valve assembly  20  for purposes of producing an impulse stimulus and/or a vibration stimulus that is superimposed on the output force that is generated by the actuator  24  to overcome any scale or other deposit that would otherwise oppose the displacement of the sleeve  24 . In this notation, the “impulse/vibration generator” means either an impulse generator that generates an impulse stimulus; a vibration generator that generates a vibration stimulus; or a combined impulse and vibration generator that generates both impulse and vibration stimuli.  
         [0024]     It is noted that the generator  22  may be actuated both during the opening of the sleeve  26  in a particular direction and also during the closing of the sleeve  26  in the opposite direction.  
         [0025]     In the context of this application, a vibration stimulus is a stimulus (of a long or short duration) that is somewhat periodic in nature in that the vibration stimulus has a frequency that is constant or follows a predefined sweep pattern. The amplitude and frequency of the vibration stimulus is chosen to overcome the resistance to the intended movement of the downhole tool. Thus, the generator  22 , in some embodiments of the invention, generates the vibration stimulus until the resistance to movement is overcome. The vibration stimulus is to be contrasted to the impulse stimulus, a stimulus that may be unique or repeated without a predetermined timing. In some embodiments of the invention, the generator  22  repeats generation of the impulse stimulus after a certain lapse in time only if the resistance remains, with the frequency at which generator  22  repeats the impulses not being instrumental in overcoming the resistance.  
         [0026]     Depending on the particular embodiment of the invention, the generator  22  may generate a vibration stimulus only, impulse stimuli only or a combination of the two. Thus, for example, in some embodiments of the invention, the generator  22  may generate a vibration stimulus and at non-regular intervals generate impulse stimuli (superimposed upon the vibration stimulus) until the resistance to the sleeve&#39;s movement is overcome. Therefore, many variations are possible and are within the scope of the appended claims.  
         [0027]     Still referring to  FIG. 1 , among the other features of the well  10 , in some embodiments of the invention, the well  10  may include, for example, a wellhead  34  that is connected to the surface of the tubing string  14  for purposes of (for example) directing production fluid from the string  14  to a pipeline or well fluid processing equipment. Furthermore, in some embodiments of the invention, the well  10  may include, for example, a mud pump  38  that is connected to an annulus  15  of the well.  
         [0028]     The mud pump  38  may be controlled to, for example, communicate command-encoded fluid pulses through the annulus  15  for purposes of operating the valve assembly  20 . In this regard, in some embodiments of the invention, the tubing string  14  may include, for example, a fluid pressure sensor  30  that is in communication with the annulus  15  for purposes of detecting fluid pressure exerted by the mud pump  38  on the fluid in the annulus. Electronics  21  of the valve assembly  20  use the fluid pressure sensor  30  to extract encoded commands from the fluid and operate the valve assembly  20  accordingly. As depicted in  FIG. 1 , in some embodiments of the invention, a packer  32  may seal off the annulus  15  near (above, for example) the valve assembly  20 .  
         [0029]     Other variations are possible in other embodiments of the invention. For example, many other techniques may be used to communicate with and control the valve assembly  20  in other embodiments of the invention. In this regard, acoustic, and/or electromagnetic communication may be used in other embodiments of the invention to communicate commands to the valve assembly  20  from the surface. Furthermore, in other embodiments of the invention, the central passageway of the tubing string  14  may be used, for example, to communicate command-encoded fluid pulses to the valve assembly  20 . Thus, many variations are possible and are within the scope of the appended claims.  
         [0030]     Referring to  FIG. 2 , in accordance with some embodiments of the invention, a technique  50  may be used for purposes of operating the valve assembly  20 . Pursuant to the technique  50 , the valve assembly  20  is actuated, as depicted in block  52 . More specifically, in accordance with some embodiments of the invention, the actuation of the valve assembly  20  may include, for example, communicating a command downhole to the valve assembly  20  for purposes of changing the cross-sectional flow path (i.e., either decreasing the cross-sectional flow path, increasing the cross-sectional flow path or closing off the cross-sectional flow path.) Regardless of the specific command, the actuation of the valve  52  means that the actuator  24  (see  FIG. 1 ) moves the sleeve  26  (see  FIG. 1 ) in a particular direction. Still referring to  FIG. 2 , pursuant to the technique  50 , impulse stimuli and/or a vibration stimulus is concurrently applied to the valve assembly  20 , during the actuation, to impart vibrational/impulse energy to the valve assembly, as depicted in block  54 . Thus, the technique  50  superimposes vibrational and/or impulse forces with the force that is exerted by the linear actuator  24  for purposes of moving the sleeve  26  in a particular direction to increase or restrict flow through the valve assembly  20 .  
         [0031]     As a more specific example,  FIG. 3  depicts an embodiment of the valve assembly  20  in accordance with the invention. As shown, in some embodiments of the invention, the valve assembly  20  includes the linear actuator  24  and the generator  22  that may be mounted to, for example, a wall  64  of the tubing string  14 .  
         [0032]     As depicted in  FIG. 3 , in some embodiments of the invention, the generator  22  may be coupled to the wall  64  to apply the impulse/vibrational energy directly to the tubing string  14 , as the string  14  may be used as a guide to communicate the impulse/vibrational energy to the sliding sleeve  26 . However, as further described below, impulse/vibrational energy may be applied to the sleeve  26  by other techniques, in other embodiments of the invention.  
         [0033]     As depicted in  FIG. 3 , in some embodiments of the invention, radial ports  74  extend through the wall  64 . When the sleeve  26  is in its very upmost position (a position not depicted in  FIG. 3 ), the valve assembly  20  is fully opened to its least restrictive effective cross-sectional flow path. However, the sliding sleeve  26  may be moved to other positions in which some of the radial ports  74  are blocked by the sleeve  26  and other radial ports  74  are open to allow flow into a central passageway  60  of the tubing string  14 . Thus, the effective flow path through the valve assembly  20  depends on the particular position of the sleeve  26 .  
         [0034]     As also depicted in  FIG. 3 , in some embodiments of the invention, the linear actuator  24  may include a torque and/or force sensor  65  that measures the force/torque that is being applied to the sleeve  26  by the linear actuator  24 . As described further below, by measuring the force that is exerted on the sliding sleeve  26 , a decision may be made (automatically by electronics of the valve assembly  20  or remotely by an operator at the surface of the well, as examples) whether or not to actuate the generator  22  to cause the generator  22  to generate impulse stimuli and/or a vibration stimulus. The decision on what type of stimulis (vibration, impulse or a combination of the two) may be based on the measured force, in some embodiments of the invention.  
         [0035]     In some embodiments of the invention, the generator  22  may be continuously on; and in other embodiments of the invention, the generator  22  may be activated only when movement of the sliding sleeve  26  is required and thus, may only be activated when the linear actuator  24  itself is actuated. Thus, many variations are possible and are within the scope of the appended claims.  
         [0036]     Referring to  FIG. 4 , in some embodiments of the invention, a valve assembly  100  may be used. It is noted that only one half of the valve assembly  100  is depicted and it is understood that the other half of the valve assembly  100  appears on the other side of a longitudinal axis  80  of the valve assembly  100 . The valve assembly  100  includes an internal tubular member  130  that is concentric with the longitudinal axis  80  and is concentric with the portions of the tubular string immediately above and below the valve assembly  100 . The inner tubular member  130  includes radial ports  150  that are selectively opened and closed by a sliding outer sleeve  120 .  
         [0037]     As depicted in  FIG. 4 , in some embodiments of the invention, the valve assembly  100  includes an impulse/vibration generator  104  that is coupled to the inner tubular member  130  and receives an upper end  124  of the outer sliding sleeve  120 . Thus, in these embodiments of the invention, the generator  104  may directly apply a vibration stimulus or impulse stimuli to the sliding sleeve  120 . As also depicted in  FIG. 4 , a linear actuator  110  may be coupled to the inner tubular member  130 , via the generator  104 , or may be directly coupled to the inner tubular member  130 , depending on the particular embodiment of the invention.  
         [0038]     The linear actuator  110  includes a shaft  112  that moves upwardly and downwardly in response to the desired position of the sliding sleeve  120 . As shown in  FIG. 4 , in some embodiments of the invention, the shaft  112  may be connected via a coupler  114  to the outer sleeve  120 . Thus, due to the arrangement shown in  FIG. 4 , when restriction of flow through the valve assembly  100  is desired, the linear actuator  110  is controlled to extend the shaft  112  and move the sleeve  120  in a downward direction. Conversely, when it is desired to increase the cross-sectional view path through the valve assembly  100 , the linear actuator  110  is operated to retract the shaft  112  to move the sleeve  120  in an upwardly direction. In the state that is depicted in  FIG. 4 , the valve assembly  100  is in its fully open position.  
         [0039]     The impulse/vibration generator may take on various forms, depending on the particular embodiment of the invention. For example, referring to  FIG. 5 , in some embodiments of the invention, an impulse/vibration generator  200  may include a ratchet wheel  220  that includes ratchet teeth  221 . When vibrational force is to be applied to the valve assembly, the ratchet wheel  220  moves. As shown in  FIG. 5 , a flexible member  214  (a spring, for example) is positioned to be deflected by the ratchet teeth  221 , as the ratchet wheel  220  rotates (rotates in a clockwise direction, for example).  
         [0040]     The end of the member  214  that is near the ratchet teeth  221  is fixed to a coupling member  210  that couples the member  214  to the sleeve  120  (see  FIG. 3 ). Thus, as the ratchet wheel  220  turns, each ratchet tooth  221  deflects the member  214  to transfer energy to the sleeve  120 .  
         [0041]     As a more specific example, continuous rotation (for some duration) of the ratchet wheel  220  causes the ratchet teeth  221  to strike the flexible member  214  at some frequency (constant or sweep) to generate a vibration impulse. In some embodiments of the invention, an impulse stimulus may be generating by turning the ratchet wheel  220  to cause a single ratchet tool  221  to strike the flexible member.  
         [0042]     When it is no longer desired to apply vibration and/or impulse stimuli to the sleeve  120 , rotation of the ratchet wheel  220  is halted. Thus, in some embodiments of the invention, the generator  200  may include a motor (not shown in  FIG. 5 ) to turn the ratchet wheel  220  as described above to selectively generate the impulse/vibrational energy. As a few examples, operation of this motor may be performed automatically by downhole electronics (in response to sense a force exerted by the sleeve&#39;s actuator or always when movement of the sleeve is desired, as examples) or may be remotely operated from the surface of the well, depending on the particular embodiment of the invention.  
         [0043]     In another embodiment of the invention, a vibration generator  250  may have the form that is depicted in  FIG. 6 . In this embodiment of the invention, the generator  250  includes an ultrasonic transducer  252  that is coupled to the sleeve  120 . The transducer  252 , in turn, communicates (via one or more communication lines  261 ) to an oscillator  260 . When activation of the generator  250  is desired, the oscillator  260  is enabled to allow an oscillating electrical signal to be communicated (via the communication line(s)  261 ) to the transducer  252 . In response to the oscillating signal, the transducer  252  produces ultrasonic waves that propagate through the sliding sleeve  120 . The oscillator  260  is disabled, in some embodiments of the invention, when it is desired that the impulse generator  250  no longer applies vibrational energy to the valve assembly.  
         [0044]     In another embodiment of the invention, an impulse generating circuit may be coupled to the transducer  252  (in replacement or as a supplement to the oscillator  260 ) to provide (when actuated) an electrical impulse signal to the transducer  252  to cause the transducer  252  to produce an ultrasonic impulse stimulus that travels to the sleeve.  
         [0045]     As yet another example of embodiment of the invention, in some embodiments of the invention, an impulse/vibration generator  300  that is depicted in  FIG. 7  may be used. The generator  300  includes a solenoid  320  that includes a main body  321 . The main body  321  includes a coil (not shown in  FIG. 7 ) that defines a central passageway through which a solenoid shaft  322  extends. The solenoid  320  may be electrically activated to control movement of the shaft  322 . As depicted in  FIG. 6 , the shaft  322  may be extended by the solenoid  320  to strike an upper surface  328  of the sleeve  120 .  
         [0046]     Thus, when vibrational energy is to be applied to the sleeve  120 , the solenoid  320  may be actuated to move the shaft  322  to strike the surface  328  to introduce vibration and/or impulse stimuli to the sleeve  120 . In some embodiments of the invention, the solenoid  320  may be connected to, for example, an oscillator that is enabled to cause the solenoid  320  to transfer vibrational energy is to be applied to the valve assembly. More specifically, when vibrational energy is to be applied, the oscillator is enabled to cause the linear movement of the shaft  322  to oscillate between upward and downward positions, thereby continually striking the surface  328  to communicate a vibration stimulus to the sleeve  120 . When vibrational energy is no longer to be applied to the sleeve  120 , the oscillator may then be disabled. The solenoid  320  may also be operated in a non-periodic manner to apply impulse stimuli to the sleeve  120 .  
         [0047]     In some embodiments of the invention, the valve assembly may include multiple linear actuators to move the sleeve. This arrangement balances the forces that are applied to the sliding sleeve and provides the valve with mechanical redundancy. For these embodiments of the invention, impulse/vibration generators may be distributed around the outer periphery of the valve assembly equally spaced from the longitudinal axis of the valve assembly. As a more specific example,  FIG. 8  depicts a cross-sectional view of a valve assembly  400  in accordance with an embodiment of the invention. The cross-section depicted in  FIG. 8  is taken along the cross-section that extends through the tubing string (such as the tubing string  14  ( FIG. 1 )) so that, as depicted in  FIG. 8 , an inner tubular member  130  that is concentric with the tubing string is surrounded by an outer sliding sleeve  440 . Instead of only having one linear actuator and impulse/vibration generator pair, the valve assembly  400  includes multiple pairs of linear actuators and impulse/vibration generators.  
         [0048]     For example, as depicted in  FIG. 8 , in some embodiments of the invention, the valve assembly  400  may include four pairs of linear actuators  404  and impulse/vibration generators  405 . These pairs may extend around the periphery of the sliding sleeve  440  to distribute the forces provided to the sleeve  440  as well as provide mechanical redundancy should one of the generators  405  or linear actuators  404  fail.  
         [0049]     In some embodiments of the invention, the impulse/vibration generator is continuously active whenever the linear actuator (i.e., the sliding sleeve&#39;s actuator) is turned on. However, in some embodiments of the invention, the impulse/vibration generator may be triggered on, or actuated, when a certain threshold of a force and/or torque is reached. More specifically, referring to  FIG. 9 , in some embodiments of the invention, a technique  500  may be used to operate the valve assembly for purposes of transitioning the sliding sleeve from one position to another position.  
         [0050]     Pursuant to the technique  500 , the actuation of the valve assembly begins, as depicted in block  502 . Next, a determination is made (diamond  504 ) whether a force/torque threshold is exceeded. In this regard, in some embodiments of the invention, the valve assembly may include a torque or force sensor, such as the sensor  65  that is depicted in  FIG. 3 , for example. The sensor measures the amount of force/torque that the linear actuator applies to the sliding sleeve. If, pursuant to the technique  500 , a determination (diamond  504 ) is made that the force/torque threshold is exceeded, then vibrational/impulse energy is applied to the valve assembly, as depicted in block  506 .  
         [0051]     If a determination (diamond  504 ) is made that the force/torque threshold has not been exceeded, then a determination (diamond  508 ) is made whether the valve has reached its final position. If not, actuation of the valve assembly is continued (block  510 ) and control returns to diamond  504 . If the valve has reached its final position (diamond  508 ) then the technique  500  ends. It is noted that after the energy is applied to the valve assembly in block  506 , control transitions to diamond  508 .  
         [0052]     Other embodiments are within the scope of the appended claims. For example, in some embodiments of the invention, the impulse/vibration generator(s) may be independently controlled from the surface of the well. Thus, in these embodiments of the invention, an operator at the surface of the well may communicate command-encoded stimuli downhole for purposes of controlling the valve assembly. Depending on a variety of potential factors (a downhole sensor indicates the linear actuator is exerting a large amount of force on the sleeve, the time that the valve has been installed downhole (and thus, more susceptible to heavier deposits), indications (from downhole sensors, etc.) that the valve assembly is not behaving properly, etc.), the operator at the surface may then communicate other command-encoded stimuli downhole for purposes of independently controlling the impulse/vibration generator(s) to superimpose additional energy to operate the valve assembly.  
         [0053]     Electronics  600  of the valve assembly may have a general form that is depicted in  FIG. 10 , in some embodiments of the invention. The electronics  600  includes a processor  602  (representative of one or more microprocessors or microcontrollers, for example) that is coupled to a system bus  604 . The electronics  600  also includes a memory  610  that is coupled to the system bus  604  and is accessible by the processor  602 . The memory  610  stores, for example, data  612  collected from sensors as well as possibly commands decoded by the electronics  600  for operation of the valve assembly. The memory  610  may also store, for example, instructions  614  to cause the valve assembly to perform one or more of the techniques that are disclosed herein. For example, in some embodiments of the invention, the instructions  614  may cause the processor  602  to control the valve assembly pursuant to the technique  500  ( FIG. 9 ). The electronics  600  may also include an impulse/vibration generator interface  652  for purposes of controlling the impulse/vibration generator.  
         [0054]     Among its other features, the electronics  600  may also include, for example, a force/torque sensor  650  (to serve the torque and/or other force that the actuator applies to the sliding sleeve), a valve actuator interface  670  (controlling the linear actuator) and a fluid pressure sensor  656  (for purposes of decoded command-encoded fluid pulses that propagate through the annulus, for example), all of which are coupled to the processor  602  via the system bus  604 .  
         [0055]     The electronics  600  depicted in  FIG. 10  is merely an example of one of many possible embodiments for the electronics of the valve assembly. Thus, other embodiments are possible and are within the scope of the appended claims.  
         [0056]     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, may 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 this present invention.