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CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. Non-Provisional application Ser. No. 11/249,809, filed Oct. 13, 2005, which claims the benefit of an earlier filing date from U.S. Provisional Application Ser. No. 60/618,826 filed Oct. 14, 2004, the entire disclosure of each of which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    Downhole tools having movable components, such as but not limited to surface controlled subsurface safety valves (SCSSV) are ubiquitously utilized and sometimes mandated in the hydrocarbon exploration and recovery art. Both safety systems and simply exploration or production devices could be improved by enhancements in means to monitor the positions thereof. 
         [0003]    Using SCSSV&#39;s as a particular example, it is important for an operator to have knowledge of the position and/or condition of SCSSV&#39;s for various reasons. Traditionally, such knowledge has been gained by monitoring flow volume from the well and control line pressure at the surface. These methods work well in instances where the well is operating correctly and where the SCSSV is not an excessive distance from the source of the control signal. Where operating parameters of the well are not ideal however, and/or the SCSSV is a substantial distance from the source, such as in sub-sea applications, traditional methods for adjudging the position of the valve are suspect and cannot be relied upon. Doubt in this regard for any downhole tool is generally the initiator of lost time and potentially unnecessary expense. Uncertainty is never beneficial to the hydrocarbon industry; better means of determining things such as SCSSV position/condition will be welcomed by the art. 
       SUMMARY 
       [0004]    Disclosed herein is a downhole tool that includes a moveable component and a stationary component. A sensor element is also included to sense position of the moveable component relative to the stationary component. 
         [0005]    Further disclosed herein is a method for sensing position of an object which includes placing a component comprising magnetostrictive material in a location calculated to be contacted by a separate component and causing a stress on the material with the separate component. The method further includes measuring a change in magnetic permeability of the material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0006]    Referring now to the drawings wherein like elements are numbered alike in the several figures: 
           [0007]      FIGS. 1A and 1B  are schematic views of a closure member and a stationary element in open and closed positions of a valve; 
           [0008]      FIG. 2  is a schematic view of a closure member with a torsion spring and sensor; 
           [0009]      FIG. 3  is a schematic view of a closure member with an alternate sensing arrangement; 
           [0010]      FIG. 4  is a schematic view of a flow tube in a housing with a sensor arrangement between the power spring and the spring stop; 
           [0011]      FIG. 5  is a schematic view of a flow tube in a housing with a sensor arrangement at both ends of travel; 
           [0012]      FIG. 6  is a schematic view of a piston of a valve and a sensor arrangement to indicate position throughout travel; and 
           [0013]      FIG. 7  is a schematic view of an alternate embodiment of the concept of  FIG. 6 ; 
           [0014]      FIG. 8  is a schematic view of another alternate embodiment of the concept of  FIG. 7 ; 
           [0015]      FIG. 9  is a schematic view of a closure member with a single-position sensing arrangement; it is an alternate embodiment of the concept of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION  
       [0016]    Obtaining more knowledge about downhole tools can be occasioned, even in real time, by careful and creative positioning of sensory devices. In some embodiments hereof, the sensing device(s) comprise a magnetostrictive material such as Terfenol-D commercially available from Etrema Products, Inc. The magnetostrictive material exhibits different magnetic permeability when placed under stress, and particularly compression, than it does when not under stress. Magnetic permeability is measured by supplying a current to a coil around the magnetostrictive material. This property is reliable and repeatable and the material itself is highly robust making Terfenol-D a useful sensing material for downhole tools. It is to be appreciated that Terfenol-D is but a single example of a magnetostrictive material and that others with similar properties could be substituted. In the exemplary embodiment of Terfenol-D, reference is made to U.S. Pat. No. 6,273,966 which is fully incorporated herein by reference, wherein Terfenol-D is described in more detail. In the event a check is desired, a second magnetostrictive device is deployed in proximity to the first but which is not exposed to the stress creator intended to be measured. Any permeability change due to conditions not related to the stress creator being measured will register on both devices, making resolution of the target stress creator clear and reliable. In other embodiments hereof permanent magnets, hall effect sensors and mechanical, electrical or optical limit switches or optical readers may be employed. In each embodiment the goal is to obtain more direct and rapid indication of a particular condition or position of a device downhole, such as for example one or more of the components of a SCSSV. It is also to be understood that one or more of the types of sensors may be employed in the same device and one or more of the same type of sensor may be employed in the same devices. 
         [0017]    Referring to  FIGS. 1A and 1B  a schematic representation of a closure member (such as a flapper valve) portion of a SCSSV is used to illustrate the inventive concept, which as stated above applies to other tools as well. The closure member portion of the SCSSV is illustrated generally at  10 . The closure member is disposed in a housing  12  which includes a sensor element  14 . The element  14  is configured to sense pressure exerted thereon by a cam surface  16  of closure member  18  (flapper). The closure member pivots around pin  20  and based upon position will exert pressure on element  14  or will not exert pressure on element  14 .  FIG. 1A  illustrates the device  10  in a valve closed position and  FIG. 1B  illustrates the device  10  in the valve open position. In the open position of  FIG. 1B , it is apparent that cam surface  16  has come into contact with sensor element  14 . In the event sensor element  14  is a magnetostrictive material, a change in magnetic permeability of sensor element  14  will be measurable to provide an indication that the flapper  18  is indeed open. Other sensor elements can be substituted such as magnetic sensors, hall effect sensors, switch type elements, etc. ( FIG. 9 ) which all would be positioned as is the illustrated magnetostrictive sensor element  14 . Information obtained by sensor element  14  is communicated to a remote location such as a surface location by a communication means (not shown) such as a hydraulic conduit, electrical conductor, optic conductor or wireless method. 
         [0018]    Referring now to  FIG. 2 , shown is an illustration of a flapper valve  18  which is actuated to close by at least one torsion spring  22 . As the arrangement is illustrated, two torsion springs  22  are apparent although it is to be understood that a single torsion spring is also contemplated. Each of the illustrated springs  22  include a leg  24 . In one embodiment, at least one of the two illustrated legs  24  rests upon a magnetostrictive material  26  such that upon opening the flapper  18 , the magnetostrictive material  26  is placed under a greater compressive load occasioned by the tightening of torsion spring  22 . It is to be understood that both illustrated legs  24  could be placed on one portion of material  26  or individual portions of material  26 . Compressive stress at material  26  causes altered magnetic permeability thereof, which property is remotely readable by current charge. In another embodiment, similar to the foregoing embodiment, magnetostrictive material  26  may be substituted for by a switch member where the benefits of the magnetostrictive material are not needed. 
         [0019]    Referring now to  FIG. 3 , another alternate embodiment is schematically illustrated. Flapper  18  is pivotally connected at hinge pin  20  to flapper housing  12 . As illustrated SCSSV  10  includes sensors to verify both the open and closed positions of the flapper  18 . To this end, flapper  18  is endowed with a high temperature magnet  28  while housing  12  includes a “closed” sensor  30  and an “open” sensor  32 . Sensors  30  and  32  are sensitive to a magnet in proximity thereto and thus can verify a closed or open position of flapper  18  due to magnet  28  coming into proximity to sensors  30  and  32 , respectively. In one embodiment, the magnet  28  is of permanent type and the sensors  30  and  32  are Hall-effect. 
         [0020]    Sensors  30  and  32  are informationally connected to sensor electronics  34  which are programmed to interpret what has been sensed and emit a signal to be propagated to a remote location along schematic cable  36 , which may be hydraulic, electric, optic or wireless in configuration. 
         [0021]    Referring now to  FIG. 4 , one of ordinary skill in the art will appreciate a schematically represented flow tube  41  within a housing  42 . The flow tube  41  is moveably positioned by a piston  66  and this movement is resisted by a power spring  43 , the stationary end of which is fitted with a sensor substantially similar to that described in conjunction with  FIG. 2 . In one embodiment, the end of the power spring  43  rests upon a magnetostrictive material  26  such that upon opening the SCSSV, the magnetostrictive material  26  is placed under a greater compressive load occasioned by the compression of power spring  43 . Compressive stress at material  26  causes altered magnetic permeability thereof, which property is remotely readable by current charge. In another embodiment, similar to the foregoing embodiment, magnetostrictive material  26  may be substituted for by a switch member where the benefits of the magnetostrictive material are not needed. 
         [0022]    Referring now to  FIG. 5 , one of ordinary skill in the art will appreciate a schematically represented flow tube  41  within a housing  42  and limited in axial movement by a top sub  44  and a bottom sub  46 . This illustration is limited to a flow tube and housings relevant thereto but should be understood to be some of the components of a SCSSV. The illustration has been done in this way to more readily show the sensor elements  48  and  50 . In this embodiment, verification is available for position of the flow tube  41  in the “open” position or the “closed” position by receiving a signal from sensor element  48  or sensor element  50 . In either position one of the two identified sensors will be fully loaded while the other will be fully unloaded. Where neither is loaded, the tube is in mid-stroke and where both are loaded there is significant indication that one or both sensors are malfunctioning. Based upon exposure to the foregoing embodiments described herein, one will appreciate that the sensor elements  48  and  50  may comprise magnetostrictive material functioning as noted above, or mechanical, electrical or optic switches. 
         [0023]    In yet another embodiment, referring to  FIG. 6 , a magnetic or optical sensing device  60 , such as a hall effect sensor or optical “bar-code” reader, is positionable within a piston housing  62  operably near piston  66  with magnetic or optical indicator  64  running down the side of piston  66  such that the amount of movement of indicator  64  mounted to piston  66  can be measured as it passes device  60 . As the indicator  64  is fixedly mounted at piston  66 , the movement of indicator  64  is the same as the movement of piston  66 . Alternatively, a row or column of individual units of magnetostrictive material can be utilized to register variable positioning of the piston  66  or other moving device in near or real time. This occurs by altering magnetic permeability of the column or row in sequence. Direction of movement and speed of movement are resolvable in this way. 
         [0024]    Referring now to  FIG. 7 , a magnetic sensing device  60 , such as a hall effect sensor, is positionable within a piston housing  62  operably near piston  66  with magnetic indicator  64  mounted at a single position on piston  66  such that the movement of piston  66  can be measured as it passes device  60 . As the magnetic indicator  64  is fixedly mounted at piston  66 , the movement of indicator  64  is the same as the movement of piston  66 . 
         [0025]    Referring now to  FIG. 8 , the same arrangement as described in  FIG. 7  is illustrated with sensing element  60  located in a hole  61  in piston housing  62  (and as illustrated filling the hole such that the hole is not separately visible in the drawing) running parallel to and located in proximity to the primary piston  66 . 
         [0026]    Referring now to  FIG. 9 , a schematic representation of a closure member  18  (such as a flapper valve) portion of a SCSSV is illustrated generally. The closure member includes a magnetic element  70  positioned such that as the closure member  18  pivots around the flapper hinge  20  and moves into the full-open position the element  70  comes into contact with the sensing mechanism  72  mounted on sensing bracket  74 . The sensing mechanism registers the change in magnetic field and transmits this information such that a “full open” signal is sent to the surface. 
         [0027]    It is important to understand that all of the above embodiments are exemplary in nature and that the concept of positioning a sensor element relative to a moveable and stationary component to sense relative position of the two components is applicable to all tools that include a moveable and stationary (or even another moveable) component. These include such as sliding sleeves, cross-over tools moveable service tools, any type of safety valve, open/close sleeves, etc. 
         [0028]    While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.

Summary:
Disclosed herein is a surface controlled subsurface safety valve (SCSSV) that includes a moveable component of the SCSSV and a stationary component of the SCSSV. A sensor element is also included which is configured to sense position of the moveable component relative to the stationary component. Further disclosed herein is a method for sensing position of an object which includes placing a component comprising magnetostrictive material in a location calculated to be contacted by a separate component and causing a stress on the material with the separate component. The method further includes measuring a change in magnetic permeability of the material.