Abstract:
A flow tube exercising tool and method for use are described for actuating the flow tube of a downhole safety valve in order to remove build ups of scale and debris from the safety valve and ensure proper operation. The exercising tool provides a lower engagement portion that underlies the lower end of the safety valve flow tube so that upward movement of portions of the exercising tool will move the flow tube upwardly. An upper engagement portion overlies the upper end of the flow tube so that downward movement of portions of the exercising tool will move the flow tube downwardly. Only a single trip of the flow tube exercising tool is necessary to accomplish multiple upward and downward movements of the flow tube.

Description:
This application is a continuation-in-part to U.S. patent application Ser. No. 11/131,726 filed May 18, 2005. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates generally to methods and devices for cleaning and remediating a subsurface safety valve or other downhole tool having a sliding flow tube member. 
   2. Description of the Related Art 
   Flapper-type valves are often used as safety valves within wells to selectively close off production. The usual flapper valve uses a torsion spring to bias the valve member toward a closed position. During normal operation, however, the flapper member is retained in an open position by an axially moveable flow tube. When the flow tube is moved upwardly within the production tubing, the flapper member is permitted to close under influence of the spring. To reopen the valve, the flow tube is moved downwardly within the production tubing to urge the valve back towards its open position. 
   One problem that has traditionally been faced by valves of this type is that scale, dirt, and other debris will often build up within the production tubing during typical production operations. This build up can render the safety valve partially or completely inoperable. The most deleterious build up will be that which occurs on and around the flow tube that is used to open the valve, making the flow tube difficult to physically move upwardly and downwardly. Additionally, the flapper mechanism may be encrusted with scale and other debris making it less likely to fully close when necessary. This means that the valve will be unable to function well in the event of an emergency requiring production flow to be closed off. 
   U.S. Pat. No. 6,273,187, entitled “Method and Apparatus for Downhole Safety Valve Remediation,” describes a technique for removing scale and debris build up using explosive charges. The use of explosives, however, carries with it risks of damage to wellbore valve components as well as the potential for a breach of the production tubing string. 
   The harmful effects of scale and debris build up can be prevented and reduced by exercising the safety valve, through operation of its components, before the build up has reached a point where the safety valve is no longer fully operational. In the past, this has been accomplished using a gripping tool having mechanical slips that are set against the inside of the flow tube. Once the slips are set, the gripping tool can be pulled upwardly to move the flow tube upwardly or jarred downwardly to move the flow tube downwardly. Unfortunately, tools of this type tend to physically damage the flow tube and other wellbore components, due to the use of the slips. 
   The parent application to this one describes a flow tube exercising tool that is used in conjunction with the hydraulic controller of a safety valve to move the flow tube axially upwardly and downwardly in order to remove build ups of scale and debris from the safety valve and ensure proper operation. This exercising tool provides an engagement portion that underlies the lower end of the safety valve flow tube so that upward movement of the exercising tool will move the flow tube upwardly. Hydraulic fluid is provided to the hydraulic controller to move the flow tube downwardly. This exercising tool represents a significant improvement over the prior art. However, there may be instances wherein this type of flow tube exerciser is not practical. One example would be an instance where the flow tube of the safety valve is not controllable hydraulically. 
   The present invention addresses the problems of the prior art. 
   SUMMARY OF THE INVENTION 
   The invention provides an improved flow tube exercising tool and method of use. An exemplary flow tube exercising tool is described that features a mandrel having upper and lower engagement portions that will overlie and underlie the upper and lower ends of the flow tube, respectively. The flow tube exercising tool is run into a production tubing string using a running tool. The tool is landed onto a safety valve within the tubing string. Further downward force upon the exercising tool will cause the upper and lower engagement portions to engage the upper and lower ends, respectively, of the flow tube of the safety valve. 
   In a currently preferred embodiment, the flow tube exercising tool includes an inner mandrel and an outer mandrel that are axially moveable with respect to one another, and initially releasably affixed to one another via a shear member. The outer mandrel carries a stop shoulder that is shaped and sized to abut a landing shoulder within the tubing string that is associated with the safety valve. After the tool is landed in this manner, fluid pressure is increased above the tool within the tubing string to shear the shear member. Further increase in fluid pressure will urge the inner mandrel axially downwardly with respect to the outer mandrel. Downward movement of the inner mandrel will cause the lower engagement portion of the exercising tool to become aligned with the lower end of the flow tube and the upper engagement portion to become aligned with the upper end of the flow tube. The upper and lower engagement portions are shaped and sized to overlie and underlie, respectively, the upper and lower ends of the flow tube. In a currently preferred embodiment, the upper and lower engagement portions are provided by collets. 
   The flow tube of the safety valve is exercised by moving it axially upwardly and downwardly with respect to the safety valve housing. The flow tube can be moved upwardly by pulling upwardly on the running arrangement for the exercising tool. The flow tube can also be moved downwardly by increasing fluid pressure within the tubing string. An increase of fluid pressure within the production tubing string will exert fluid pressure upon a fluid pressure receiving area of the tool to urge the flow tube axially downwardly. The flow tube may be repeatedly moved up and down to clean scales and other debris from it. 
   The flow tube exercising tool of the present invention provides a number of advantages over conventional systems. The flow tube of the safety valve may be exercised (i.e., moved axially with respect to the safety valve housing) without the risk of damage from the setting of slips. Only a single trip of the flow tube exercising tool is necessary to accomplish multiple upward and downward movements of the flow tube. Additionally, the flow tube is exercised without the need to operate the hydraulic actuator of the safety valve. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawing. 
       FIGS. 1A ,  1 B and  1 C present a side, cross sectional view of an exemplary flow tube exercising tool constructed in accordance with the present invention in a position for being run into production tubing. 
       FIGS. 2A ,  2 B and  2 C are a side, cross-sectional view of the exercising tool shown in  FIGS. 1A-1C , now with the lower engagement portion of the exercising tool engaging the lower end of the safety valve flow tube and the upper engagement portion of the exercising tool engaging the upper end of the flow tube. 
       FIGS. 3A ,  3 B and  3 C are a side, cross-sectional view of the exercising tool shown in  FIGS. 1A-1C , now with the safety valve flow tube having been raised to an upper position. 
       FIG. 4  is a side, cross-sectional view of the upper portion of the exercising tool now with the emergency release feature activated. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1A ,  1 B and  1 C illustrate a section of portion of a string of production tubing  10 , of a type known in the art that defines a production flowbore  12  along its length. A safety valve, generally indicated at  14  is integrated into the production tubing string  10 . The safety valve  14  is a flapper valve, of a type that is well known in the art and described in, for example, U.S. Pat. No. 4,415,036 issued to Carmody. U.S. Pat. No. 4,415,036 is owned by the assignee of the present invention and is incorporated herein by reference. In the safety valve  14 , a flapper valve member  16  rotates in a pivoting manner about a hinge  18  and is biased toward a closed position by a spring (not shown), in a manner well known in the art. The flapper member  16  is opened and retained in an open position (as illustrated in  FIG. 1C ) by an axially moveable flow tube  20  which, in turn, is actuated by a hydraulic piston-type controller (not shown) of a type known in the art. 
   At its upper end, the safety valve  14  includes a nipple adapter  22  that is secured by threaded connection  24  to the production tubing string  10 . The nipple adapter  22  defines an interior axial flowbore  26  along its length, and an annular dog recess  28  is located within the flowbore  26 . An upwardly directed stop shoulder  30  is also located within the flowbore  26 . 
   The body of the safety valve  14  defines a piston chamber  32  that houses actuation piston  34 . The actuation piston  34  is secured to the flow tube  20  and presents an upper pressure receiving end  36  with fluid seals  38  to form a fluid tight seal within the piston chamber  32 . A hydraulic controller (not shown) of a type known in the art is interconnected with the nipple adapter  22 , as is know, to provide fluid pressure to the interior of the chamber  32  in order to actuate the flapper valve  14  to an open position by axial movement of the flow tube  20 . The upper pressure receiving end  36  of the piston  34  is adapted to receive increased fluid pressure. The lower end of the nipple adapter  22  is secured to a flapper valve housing  40  that encloses the flapper valve member  16  and compression spring  42 . 
   Also shown in  FIGS. 1A ,  1 B and  1 C is a flow tube exercising tool  50  that is run into the flowbore  12  of the production tubing string  10  at the lower end of a wireline “GS” type running tool (not shown) or other suitable running arrangement of a type known in the art. Beginning at its upper end, the flow tube exercising tool  50  includes a fishing neck sub  52  having a fishing neck  54  at its upper end. The lower end of the fishing neck sub  52  is secured by threading to a fishing neck extension  56 . An abutment shoulder  58  is also formed at the lower end of the fishing neck sub  52 . The fishing neck extension  56  has a radially reduced body portion  60  and an enlarged body portion  62 . A fluid seal  64  surrounds the enlarged body portion  62 . 
   Radially surrounding the fishing neck extension  56  is a tubular sealing mandrel  66 . The sealing mandrel  66  includes a body  68  that defines an axial passage  70  along its length. The axial passage  70  contains a reduced-diameter flow portion  71  and an enlarged diameter portion  72 . The upper end of the body  68  presents a landing shoulder  74  within the passage  70  while the lower end of the body  68  presents an exterior landing shoulder  76 . 
   The sealing mandrel  66  is releasably affixed by shear members  78  to an inner mandrel  80 . The inner mandrel  80  features an enlarged head portion  82  and an exterior dog recess  83 . The inner mandrel  80  is affixed at its lower end to an inner sleeve  84 . The inner sleeve  84  features a set of collet windows  86  in its body. 
   The lower end of the inner sleeve  84  is secured to a lower collet sub  88 . The lower collet sub  88  presents a number of axially extending collets  90  having latch end portions  92  that are shaped and sized to underlie the lower end  94  of the flow tube  20 . The lower collet sub  88  also includes a plurality of slots  96 ,  98  above the collets  90 . In a currently preferred embodiment, there are four slots  96 ,  98 , which are spaced about the circumference of the lower collet sub  88  at approximate 90 degree angles from each other. Pins  100  extend through each slot  96 ,  98  and are secured to a ring  102  retained within the lower collet sub  88  and a lower outer sleeve  104  that radially surrounds the lower collet sub  88 . 
   The lower outer sleeve  104  is releasably affixed by shear screws  106  to an upper outer sleeve  108 . The upper outer sleeve  108  includes a set of outer collet windows  110  and a set of locking dog windows  112 . The upper outer sleeve  108  terminates in an upper end  114 . The upper outer sleeve  108  is releasably secured by shearable pin members  116  to the inner mandrel  80 . Additionally, the upper outer sleeve  108  presents an outward and downwardly directed landing shoulder  117  that is shaped and sized to land within and contact the shoulder  30  in the nipple adapter  22 . During run in, the locking dogs  118  initially reside within the locking dog slots  112  and partially within the dog recess  83  of the inner mandrel  80 , as depicted in  FIG. 1B . 
   A set of upper collets  118  are disposed generally within the radial space  120  between the inner sleeve  84  and the upper outer sleeve  108 . Each of the upper collets  118  has a prong-type end portion  122  that is shaped and sized to overlie and engage the upper end  124  of the flow tube  20 . The upper and lower collets  118 ,  90  collectively provide a mandrel body that is shaped and sized to reside within the flow tube  20  of the safety valve  14  and, as will be described, are capable of moving the flow tube  20  axially upwardly and downwardly with respect to the safety valve  14 . 
   Both sets of collets  90  and  118  are biased radially outwardly due to shape memory, and, in the initial run-in configuration depicted by  FIGS. 1A ,  1 B and  1 C, are restrained radially inwardly by a surrounding member. In the case of the upper collets  118 , the upper prong portion  122  is contacted by sloped side surfaces  126  on the upper outer sleeve  108 , which cam the collets  118  radially inwardly. The lower collets  90  are retained radially inwardly by the surrounding lower end of the lower outer sleeve  104 . 
   In operation, the flow tube exercising tool  50  is run down into the flowbore  12  of the production string  10 , in the initial condition shown in  FIGS. 1A ,  1 B, and  1 C.  FIGS. 2A ,  2 B and  2 C illustrate the exercising tool  50  now having been landed within the nipple adapter  22  of the safety valve  14 . The landing shoulder  117  of the upper outer sleeve  108  has been landed into the shoulder  30  of the nipple adapter  22 . Further downward force is then applied to the upper fishing neck sub portion of the tool  50  via fluid pressure, a jarring tool, weight, or otherwise to cause the shear members  78  to shear. This will release the inner mandrel  80  from the surrounding upper outer sleeve  108 . Downward movement of the inner mandrel  80  with respect to the upper outer sleeve  108  will cause the locking dogs  118  to be cammed out of the dog recess  83  of the inner mandrel and into the dog recess  28  of the nipple adapter  22 , thereby securely locking the exercising tool  50  to the nipple adapter  22 . The inner mandrel  80  continues to move downwardly with respect to the upper outer sleeve  108  until the enlarged head portion  82  of the inner mandrel  80  shoulders out against the upper end  114  of the upper outer sleeve  108 , as depicted in  FIG. 2B . In this position, the lower collets  90  will be moved to a position wherein they are not restrained by the lower outer sleeve  104 . The prong ends  92  of each lower collet  90  will then underlie the lower end  94  of the flow tube  20 . 
   Downward movement of the inner mandrel  80  with respect to the upper outer sleeve  108  will also cause the upper collets  118  to slide downwardly within outer collet windows  110 . The prong portions  122  of each upper collet  118  will enter the recessed area  130  above the upper end  124  of the flow tube  20 . Thus, the prong ends  122  will overlie the upper end  124 . 
   It is further noted that, as the inner mandrel  80  is moved downwardly, the enlarged body portion  62  of the fishing neck extension  56  is moved out of the enlarged diameter portion  72  of the axial passage  70  of the sealing mandrel  66  so that the fluid seal  64  surrounding the enlarged body portion  62  will create a fluid seal against the side of the axial passage  70  (see  FIG. 2B ). Downward movement of the fishing neck extension  56  within the sealing mandrel  66  is limited by the landing of shoulder  58  against shoulder  74 , as shown in  FIG. 2B . 
   Once the exercising tool  50  has been landed into the nipple adapter  22  and safety valve  14  in the manner described above, the flow tube  20  may then be exercised by the tool  50  to move the flow tube  20  axially upwardly and downwardly with respect to the safety valve  14 , thereby removing scales, paraffins, debris and other build up that might tend to preclude proper operation of the safety valve  14 . To raise the flow tube  20  with respect to the safety valve  14 , an operator at the surface of the well (not shown) will pull up on the running arrangement (not shown) for the exercising tool  50  which, in turn, will cause the fishing neck sub  52  and affixed fishing neck extension  56  to be raised. The enlarged body potion  62  will shoulder against the upper reduced diameter flow portion  71  of the axial passage  70  of the surrounding sealing mandrel  66  and cause the sealing mandrel  66  to be moved upwardly as well. Because the sealing mandrel  66  is affixed by pins  78  to the inner mandrel  80 , the inner mandrel  80  and affixed inner sleeve  84  and lower collet sub  88  are raised as well.  FIGS. 3A-3C  illustrate the configuration of the exercising tool  50  with the flow tube  20  now having been raised to an upper position with respect to the safety valve  14  by virtue of the underlying relation of the prong portions  92  of lower collets  90  beneath the lower end  94  of the flow tube  20 . 
   To return the flow tube  20  to its downward position (as depicted in  FIGS. 2A-2C ), fluid pressure is increased in the flowbore  12  above the exercising tool  50 . The fluid pressure increase will exert force upon the upper axial ends of the fishing neck sub  52 , the sealing mandrel  66 , and the inner mandrel  80 . By virtue of fluid seals  64  and  132  (between the inner mandrel  80  and the sealing mandrel  66 ), a substantially uniform pressure receiving area is created. The inner mandrel  80 , sealing mandrel  66 , and fishing neck sub  52  and extension  56  and upper collets  118  are all moved radially downwardly within the surrounding upper and lower outer sleeves  108 ,  104 . It should be noted that the upper and lower outer sleeves  108 ,  104  collectively form a unitary outer sleeve that surrounds the inner mandrel  80  and associated components. This downward axial movement will cause the upper collets  118 , whose flange portions overlie the upper end  124  of the flow tube  20 , to urge the flow tube  20  axially downwardly. The upper collets  118  are capable of movement within the collet windows  110  for movement of the flow tube  20  while the outer sleeves  104 ,  108  remain securely locked to the nipple adapter  22 . 
   The procedures described above for movement of the flow tube  20  upwardly and downwardly with respect to the safety valve  14  may be repeated as necessary in an alternating manner to remove scale and other debris and ensure proper operation of the safety valve  14 . Movement of the flow tube  20  may be exercised in this manner using only a single trip of the exercising tool  50  into the production tubing  10 . However, the exercising tool  50  may also be run into the production tubing  10  on several separate occasions during the life of the wellbore to ensure continued proper operation of the safety valve  14  throughout. 
   Normally, the exercising tool  50  may be detached from the flow tube  20  by merely pulling upwardly on the running arrangement with sufficient force that the lower collets  90  are deflected radially inwardly and thus released from the lower end  94  of the flow tube  20 . Further upward pulling of the running arrangement will cause the fishing neck sub  52 , fishing neck extension  56 , sealing sub  66 , inner mandrel  80 , inner sleeve  84  and lower collet sub  88  and affixed outer sleeves  104 ,  108  to be moved axially upwardly. The locking dogs  112  will retract back into the dog recess  83  of the inner mandrel  80 , thereby freeing the exercising tool  50  from locking engagement with the safety valve  14 . At this point, the exercising tool  50  is withdrawn from the safety valve  14  and from the tubing string  10 . 
   If, however, the exercising tool  50  cannot be detached in this manner, the tool  50  may be released using a technique for emergency disengagement of portions of the tool  50  from the safety valve  14 . An operator at the surface (not shown) will apply an upward pull on the fishing neck sub  52  that is sufficient to shear the pins  78  that are securing the sealing mandrel  66  to the inner mandrel  80 . Further upward pulling will remove the fishing neck sub  52 , fishing neck extension  54  and sealing mandrel  66  from the exercising tool  50  and then from the production tubing  10  (see  FIG. 4 ). With these components removed, a fishing tool (not shown) of a type known in the art may be inserted into the production tubing  10  and used to engage the enlarged head portion  82  of the inner mandrel  80  and remove it from the valve  14  and tubing string  10  as well. A further release tool (not shown), such as a standard sinker bar or weight, may subsequently be run into the tubing string  10  and used to contact the ring  102  to urge these additional components out of engagement with the surrounding valve  14 . The release tool will be effective to release the lower collets  90  from the lower end  94  of the flow tube  20  because downward urging of the ring  102  will cause shifting members, or pins,  100  to slide downwardly within slots  96 ,  98  in the lower collet sub  88 . The shifting members  100  are affixed to the lower outer sleeve  104  and will cause the lower end  130  of the lower outer sleeve  104  to wedge between the lower collets  90  and the flow tube  20 , thereby forcing disengagement. 
   Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.