Abstract:
A lock open device for a flapper is disclosed. The tool engages in the sub-surface safety valve (SSSV) body and rotates the flapper to the open position, without shifting the flow tube. The flapper base is preferably held by a shearable thread and has a groove for engagement by the tool. The tool jars down on the flapper base to shear the thread and force the held open flapper into a retaining groove. Optionally, a penetrating tool can be connected so that, in a single trip, the flapper can be locked open and the pressurized control system can be accessed. Shearing the thread allows the flow tube spring to bias the held open flapper into its retaining groove.

Description:
FIELD OF THE INVENTION 
   The field of this invention is lock open devices for sub-surface safety valves (SSSV) and related techniques for gaining access to the pressurized control system for subsequent operation of an inserted replacement. 
   BACKGROUND OF THE INVENTION 
   SSSVs are normally closed valves that prevent blowouts if the surface safety equipment fails. Conditions can arise where the SSSV fails to function for a variety of reasons. One solution to this situation has been to lock open the SSSV and to gain access into the pressurized control system that is used to move the flow tube to push the flapper into an open position against the force of a closure spring that urges the valve into a closed position. Thereafter, a replacement valve is delivered, normally on wireline, and latched into place such that the newly formed access to the control system of the original valve is now straddled by the replacement valve. This allows the original control system to be used to operate the replacement valve. 
   There have been several variations of lock open devices in the past. U.S. Pat. No. 4,577,694 assigned to Baker Hughes teaches the use of a flapper lock open tool (FLO) which delivers a band of spring steel to expand when retaining sleeves on the FLO tool are retracted. The tool latches inside the SSSV and with the flow tube in the flapper-closed position the band is released. This design offered the advantages of the lockout device not being integral to the SSSV. Instead it was only introduced when needed through a wireline. Another advantage was that the release of the band did no damage to the SSSV or the FLO tool. The band expanded into a recessed area so as to allow full-bore through-tubing access. The flow tube did not have to be shifted so that no spring forces acting on the flow tube had to be overcome to actuate the FLO tool. Subsequently, when the SSSV was retrieved to the surface, the band was easily removed by hand without special tools. The FLO tool had safety features to prevent premature release or incorrect placement. The FLO tool did not require fluid communication with the control system, as its purpose was solely flapper lock out. 
   The FLO tool did have some disadvantages. One was that the band could become dislodged under high gas flow rates. The tool was complicated and expensive to manufacture. The expanding ring presented design challenges and required stocking a large variety to accommodate different conditions. The running method required two wireline trips with jar-down/jar-up activation. 
   U.S. Pat. No. 4,574,889 assigned to Camco, now Schlumberger, required latching in the SSSV and stroking the flow tube down to the valve open position. The flow tube would then be outwardly indented in the valve open position so that the indentations would engage a downwardly oriented shoulder to prevent the flow tube from moving back to the valve closed position. This design had some of the advantages of the Baker Hughes FLO design and could accomplish the locking open with a single wireline trip. The disadvantages were that the flow tube was permanently damaged and that the flow tube had to be forced against a closure spring force before being dimpled to hold that position. This made disassembly of the SSSV with the flow tube under spring pressure a potentially dangerous proposition when the valve was later brought to the surface. 
   U.S. Pat. No. 5,564,675 assigned to Camco, now Schlumberger, also involved forcibly pushing the flow tube against the spring to get the flapper into the open position. In fact, the flow tube was over-stroked to push the actuator piston out of its bore in the pressurized control system, at which point the piston would have a portion splay out preventing its re-entry into the bore, thereby holding the flow tube in the flapper open position. This design had the safety issues of disassembly at the surface where the flow tube was under a considerable spring force. Additionally, fluid communication into the control system was not an option when locking open using this tool. 
   U.S. Pat. No. 6,059,041 assigned to Halliburton uses a tool that forces the flow tube down to get the flapper in the open position. It then releases a band above the flow tube that lodges on a downwardly oriented shoulder to hold the flapper open. This system has the risk of a flow tube under a spring force causing injury when later disassembled at the surface. This tool is fluid activated and must overcome the spring force to get the flow tube to the flapper open position. Finally, the tool is fluid pressure actuated, which will require a long fluid column to eventually communicate with the formation, a particular disadvantage in gas wells. 
   Also of interest in the area of lock open devices for SSSVs are U.S. Pat. Nos. 4,624,315; 4,967,845 and 6,125,930 (featuring collet fingers on the end of the flow tube that engage a groove in the SSSV body). 
   The present invention addresses these shortcomings by providing a technique to use a tool to get the flapper open without shifting the flow tube. In the preferred embodiment the flapper base is shifted with the flapper in the open position to trap the flapper in the open position. The closure spring that normally biases the flow tube into the flapper closed position is employed after the flapper base is liberated to bias the held-open flapper into its retaining grove. The lock open feature can be combined with stroking an oriented penetrating tool into the control system conduit for access to operate a subsequently installed valve to replace the locked open SSSV. The penetration step is not required to obtain the lock open state. Optionally the flapper base can be retained in its normal operating position by a shearable thread to allow taking advantage of a metal-to-metal sealing feature of the thread. These and other advantages of the present invention will become more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the claims appended below. 
   SUMMARY OF THE INVENTION 
   A lock open device for a flapper is disclosed. The tool engages in the sub-surface safety valve (SSSV) body and rotates the flapper to the open position, without shifting the flow tube. The flapper base is preferably held by a shearable thread and has a groove for engagement by the tool. The tool jars down on the flapper base to shear the thread and force the held open flapper into a retaining groove. Optionally, a penetrating tool can be connected so that, in a single trip, the flapper can be locked open and the pressurized control system can be accessed. Shearing the thread allows the flow tube spring to bias the held open flapper into its retaining groove. 

   
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIGS. 1   a - 1   e  are a section view of the SSSV in the closed position; 
       FIGS. 2   a - 2   e  are a section view of the SSSV with the lock open tool latched; 
       FIGS. 3   a - 3   e  show the collets freed at the base of the tool to push the flapper into the fully open position; 
       FIGS. 4   a - 4   e  are a section view showing the flapper base engaged by the tool just before the threads shear; 
       FIGS. 5   a - 5   e  are a section view with the flapper base sheared and the flow tube spring acting on the flapper base to retain the flapper in the lock open recess; 
       FIGS. 6   a - 6   e  show the SSSV in section with the lock open tool removed; 
       FIGS. 7   a - 7   c  shows the addition of the penetrating tool above the lock open tool; 
       FIG. 8  is the penetrating tool after rotation; 
       FIG. 9  is the penetrating tool after penetration; 
       FIG. 10  shows the flapper in the normal operating closed position with an enlarged hinge diameter; and 
       FIG. 11  is the view of  FIG. 10  with the enlarged hinge diameter forced down into interference with an adjacent reduced bore diameter. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The sub-surface safety valve is illustrated in the closed position for the flapper  12 , in FIG.  1 . Spring  16  bearing on shoulder  18  biases the flow tube  14  upwardly. Flapper  12  is secured to flapper base  20  at pivot  22 . Spring  24  biases flapper  12  to the closed position shown in  FIG. 1   d . Flapper base  20  is secured by sleeve  26  to body  28 . That connection is preferably by a thread  30 . Thread  30  is designed to release under a predetermined force applied to flapper base  20 . Other retainers that selectively release such as shear pins or collets can be used instead of thread  30  as contemplated in alternative forms of the present invention. A piston  32  sees pressure from a control line extending from the surface (not shown) and connected to port  34 . Piston  32  engages groove  36  to push the flow tube  14  down against the force of spring  16 . Grooves  38  and  40  are for locating the lock open tool T as shown in  FIG. 2   b .  FIG. 1   d  shows an enlargement of the area around thread  30 . 
     FIGS. 2   a - 2   e  illustrate the initial insertion of the tool T. Tool T has a mandrel  42  made up of a top sub  44  connected to segment  46  at thread  48 . Segment  50  is connected to segment  46  at thread  52  with the connection held locked by screws  54 . Segment  56  is held to segment  50  at thread  58  with the connection locked by screws  60 . Segment  56  further comprises a tapered shoulder  62 . Collet retainer  64  is secured by thread  66  to segment  56  by screws  67 . Collet retainer  64  comprises an extension segment  68  that defines an annular groove  70  in which the lower ends  71  of the collets  82  are disposed. The outer assembly  72  fits over the mandrel  42  and comprises a top sub  74  retained to segment  46  of mandrel  42  by a shear pin or pins  76 . Segment  75  is retained to top sub  74  at thread  77 . Projections  79  and  81  latch respectively into grooves  38  and  40  of body  28  due to the flexible nature of segment  75 . Segment  78  is retained to segment  75  by a shear pin or pins  80 . Collets  82  are secured to segment  78  by shear pin or pins  84 . Collets  82  have an internal shoulder  86  for jarring down and an external shoulder  88  to engage groove  90  on flapper seat  20 . Flapper seat  20  can be made of several interconnected parts. Spring  16  bears on flapper seat  20  for reasons to be explained below. Insertion of tool T results in a partial rotation of the flapper  12  toward the fully open position. The flapper is in the fully open position when in alignment with groove  92  in body  28   as  shown in  FIGS. 3   d - 3   e.    
   The significant components now having been described, the operation of the tool will be reviewed in detail. The tool T is lowered into the valve  10  until projections  79  and  81  spring into grooves  38  and  40  for latching contact. This position is shown in  FIGS. 2   a - 2   b . The collets  82  still have their lower ends  71  held by collet retainer  64 , but the insertion itself has resulted in partial rotation of flapper  12  towards its fully open position. Actuating the mandrel  42  downwardly with a wireline operated jarring tool (not shown) connected to top sub  44  forces down the mandrel  42 . Initially, shear pin or pins  76  break as the mandrel moves with respect to the outer assembly  72 , which is supported to body  28  at grooves  38  and  40 . Downward movement of the mandrel  42  moves collet retainer  64  away from lower ends  71  of collets  82 , allowing them to spring radially outwardly so that shoulder  88  engages groove  90  in flapper seat  20 . This is shown in  FIG. 3   d . The mandrel  42  continues moving down until shoulder  51  on segment  50  engages shoulder  53  on segment  78  of the outer assembly  72 . At this time shear pin or pins  80  will break after the application of a predetermined force. When shear pin or pins  80  break, segment  78  of the outer assembly  72  is driven down until lower end  83  engages shoulder  86  on collets  82 . By this time the collets  82  have pushed the flapper  12  into the fully open position so that it is in alignment with groove  92  in body  28 . Movement of the lower end  83  of segment  78  breaks shear pin or pins  84 , as shown in  FIG. 4   d . When a predetermined force is applied to shoulder  86  from lower end  83  the thread  30  holding flapper base  20  to sleeve  26  shears or otherwise fails and the flapper base  20  is driven down, now also with the help of spring  16  until the flapper  12  has entered groove  92 . Spring  16  retains flapper  12  in groove  92 . Collets  82  insure the alignment of flapper  12  with groove  92  as the flapper is driven down from the force of the jarring tool on the wireline (not shown) acting on mandrel  42  and from spring  16 . The tool T can now be removed by an upward force on the wireline (not shown) and the flapped remains locked in groove  92  under the force of spring  16 , as shown in  FIGS. 6   a - 6   e . The downward movement of flapper base  20  can be purely translation, as described for the preferred embodiment, or rotation or a combination of both movements to get the flapper  12  into groove  92 . 
   Referring to  FIGS. 7   a - 7   c , the penetration tool P can be added above the lock open tool T. The lock open tool terminates near shoulder  51  at thread  95 . The assembly of the tool T and the tool P are initially suspended in grooves  38  and  40  as collet  94  springs outwardly. Collet  94  comprises an internal shoulder  96  and a lower end  98 , which covers window  100 . Mandrel  102  is connected to the jarring tool (not shown). Shear pin  104  secures sleeve  106  to mandrel  102  so that the entire assembly is initially supported by collet  94 . Outer housing  108  has an exterior shoulder  110  near its upper end  112 . Window  100  is in outer housing  108 . At its lower end  114 , outer housing is attached by shear pin  80  to segment  78 , as previously described. Guide pin  114  is biased by spring  116  but lower end  98  of collet  94  holds in pin  114  until shear pin  104  is broken. When mandrel  102  is advanced after shear pin  104  is broken, pin  114  is pushed out by spring  116  to contact spiral ramp  118  that is part of the SSSV. Such contact coupled with advancement of the mandrel  102  creates rotation as pin  114  advances along spiral ramp  118  and toward longitudinal groove  120 . Eventually, all rotational movement is complete as pin  114  in groove  120  and shoulder  110  hits shoulder  96 . This is the position in FIG.  8 . Now shear pin  122  can break as mandrel  102  and wedge surface  124  push penetrator assembly  126  through window  100  and into control system  128  above piston  32  (see FIG.  9 ). 
   While the rotation to get alignment for penetration is going on, the tool T is opening the flapper  12  and latching into groove  90  as shown in  FIGS. 2   e - 4   e . When the penetration occurs the shear out of thread  30  occurs and the flapper  12  is displaced into groove  92 . Thus both steps can occur in a single trip or either step can be done individually without the other. 
     FIGS. 10 and 11  show a variation of holding the flapper  12 in the open position. It can be held open with a combination of groove  92 , as previously described as well as an enlarged diameter hinge  130  that is forced down into a reduced diameter segment  132  for an interference fit.  FIG. 11  shows that groove  92  can be eliminated and the interference fit between hinge  130  and reduced diameter segment  132  can be the sole mechanism to insure the flapper  12  stays open after the thread  30  is sheared out. 
   The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.