Tubular isolation valve resettable lock open mechanism

Abstract

A safety valve features a flow tube operated flapper for the normal open and closed positions that can be obtained with one or two control lines to a principal operating piston. Pressure applied to the piston moves the flow tube to rotate the flapper open behind the flow tube. Release of pressure to the principal piston allows a closure spring to return the flow tube up to let the flapper close. A secondary piston can drive the flow tube with applied pressure through a control line. Cycling the applied pressure in combination with an indexing mechanism allows the flapper to be locked open and then released to normal operation. The pistons act as backup for each other as they both drive the flow tube. The flow tube has a clearance fit to the body in the locked open position to exclude debris from the flapper.

Claims

1. An isolation valve assembly for a tubular string, comprising: a housing having a passage therethrough and a flapper selectively actuated by a flow tube axially movable in said passage by an actuation assembly located outside said flow tube and at least in part in said housing; wherein movement of said actuation assembly is regulated by an indexing assembly located outside and separate from said flow tube and within said housing surrounding said flow tube, said indexing assembly causing rotation of said actuation assembly as said actuation assembly translates in opposed directions such that said flow tube can be selectively anchored to said housing by said indexing assembly with said flapper in an open position, said actuation assembly releasing said flow tube due to rotation, to allow said flapper to thereafter be closed and opened with said actuation assembly.

2. The assembly of claim 1, wherein: said actuation assembly responsive to a first pressure application and reduction cycle applied to said actuation assembly for said selective locking and further responsive to a second pressure application and reduction cycle applied to said actuation assembly for said allowing said flapper to open and close.

3. The assembly of claim 2, wherein: said actuation assembly comprises a piston engaged to said flow tube for tandem movement therewith in a first direction responsive to pressure application in said first pressure application and reduction cycle.

4. The assembly of claim 3, wherein: said flow tube and piston moving in tandem in a second direction opposite said first direction responsive to a return spring acting on said flow tube and a reduction of pressure to said piston to complete said first pressure application and reduction cycle.

5. The assembly of claim 3, wherein: said flow tube is further selectively anchored to said housing by fluid pressure applied from a surface location upon an upper end of said piston to urge said flow tube downwardly within said passage.

6. The assembly of claim 3, wherein: said piston is operably connected to said indexing assembly that further comprises a j-slot pattern interacting with a pin.

7. The assembly of claim 6, wherein: said housing comprising said pin interacting with ends of slots defining said j-slot pattern during said first and second cycles of pressure application.

8. The assembly of claim 6, wherein: said pin is stationary and supported by said housing and said slots of said j-slot pattern are disposed on said piston for translation and rotation relative to said pin.

9. The assembly of claim 6, wherein: said j-slot pattern has alternating short and long slots such that said flow tube is held against said flapper when said pin is in a said short slot and said flow tube can move away from said flapper when said pin is in a said long slot.

10. The assembly of claim 6, further comprising: a primary piston connected to said flow tube for tandem movement responsive to pressure application and reduction cycles to a primary piston connection of said housing.

11. The assembly of claim 10, wherein: said piston communicating to a piston connection in said housing, whereupon application of said first pressure application and reduction cycle to said piston connection moves said flow tube to hold said flapper open and application and reduction of pressure to said primary piston connection moves said flow tube in opposed directions to open and close said flapper.

12. The assembly of claim 11, further comprising: a return spring to move said flow tube in response to reduction of pressure at said piston connection and at said primary piston connection.

13. The assembly of claim 10, wherein: said piston and said primary piston are rod pistons.

14. The assembly of claim 2, wherein: said flapper is held open with said pressure application of said second pressure application and reduction cycle and said flapper closes on said reduction of pressure for any reason in said second pressure application and reduction cycle.

15. An isolation valve assembly for a tubular string, comprising: a housing having a passage therethrough and a flapper selectively actuated by a flow tube axially moveable in said passage by an actuation assembly located outside said flow tube and at least in part in said housing; said actuation assembly including an indexing assembly for releasably anchoring said flow tube with said flapper in said open position with rotation of at least a part of said actuation assembly, said indexing assembly located outside and separate from said flow tube and within said housing surrounding said flow tube.

16. The assembly of claim 15, wherein: the entirety of said actuation assembly rotates while translating.

17. The assembly of claim 15, wherein: at least part of said actuation assembly translates without rotation.

18. The assembly of claim 17, wherein: said actuation assembly comprises an upper piston operably connected to a lower piston for tandem axial movement while enabling said lower piston to relatively rotate with respect to said upper piston.

19. The assembly of claim 18, wherein: said lower piston is engaged to the indexing assembly for rotation of said lower piston as said upper and lower pistons move axially in tandem.

20. The assembly of claim 15, wherein: said flow tube and said housing forming a clearance fit relationship to prevent debris infiltration in the open position.

21. The assembly of claim 15, wherein: said flow tube is releasably anchored by fluid pressure applied from a surface location upon an upper end of said actuation assembly to urge said flow tube downwardly within said passage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a primary and secondary piston layout with an outer cover removed;

(2) FIG. 1a is a section view along line A-A of FIG. 1;

(3) FIG. 1b is an enlarged view of a part of FIG. 1a;

(4) FIG. 2 is a section view of the safety valve in the closed positon;

(5) FIG. 3 is the view of FIG. 2 with the valve energized open using the secondary piston;

(6) FIG. 4 is the view of FIG. 2 with pressure removed from the secondary piston and the lock open position achieved;

(7) FIG. 5 is a rolled flat presentation of the indexing feature that interacts with the secondary piston;

(8) FIGS. 6a-6d show the secondary piston rotating through two pressure cycles to lock open and then release from the lock open position;

(9) FIG. 6e shows the extending boss at the lower end of the secondary piston that engages a housing shoulder as shown in FIGS. 4 and 6c;

(10) FIG. 7a is a section view of a split piston where the lower portion rotates and the upper portion with a bushing does not rotate;

(11) FIG. 7b is an alternative to the embodiment in FIG. 7a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(12) Referring to FIG. 1 a primary piston 2 and a secondary piston 3 are shown preferably spaced 180 degrees apart on housing 30. The names primary and secondary are used to distinguish the two pistons only as will be apparent from the explanation below where the pistons can be redundant allowing either one to operate the flow tube 6. The basic components of the safety valve are a flapper 10 that is rotated 90 degrees by the flow tube 6. Flow tube 6 has a ring or discrete shoulders 32 as shown in FIG. 2. Primary piston 2 has an external ring 34 that engages ring 32 to move the flow tube 6 against the flapper 10. What drives piston 2 is control line pressure to primary piston connection 12 that is retained by piston seals 46 as chamber 36 enlarges in volume as piston 2 is pushed to the right or toward the flapper 10 which is rotated by the linear movement of flow tube 6 caused by ring 34 pushing ring 32. If the pressure in chamber 36 is relieved the closure spring 8 pushes up on ring 7 that is shouldered on abutment 60 on the exterior of the flow tube 6 thus returning the flow tube 6 and the piston 2 to the FIG. 2 positon that allows the flapper 10 to rotate 90 degrees to the seat 38. Bushings 5 are spaced apart to guide the movement of piston 2 within cylinder 14 and housing 30 as aligned axially with one another. Connection 40 is on the opposite side of piston 2 from connection 12 an is connected to another control line that is not shown so that the hydrostatic pressure in the control lines going to connections 12 and 40 is balanced and spring 8 does not need to overcome control line hydrostatic pressure. Such a balance line operating system is shown in U.S. Pat. No. 6,173,785 B1. Alternatively a single control line system can be used and in that case the spring 8 needs to be sized to overcome the hydrostatic pressure in chamber 36.

(13) A secondary piston 3 has an external ring 42 that engages ring 32. Pressure at piston connection 13 against seal 46 enlarges the volume of chamber 44 and removal of such pressure at connection 13 allows piston 3 to be pushed in the opposite direction with spring 8 pushing on flow tube 6. Piston 3 has an exterior j-slot profile 48 that engages a housing pin 50 (also shown as item 1 in FIG. 1b) that collectively comprise the indexing assembly so that axial movement of piston 3 can also create rotational movement of piston 3. FIG. 5 shows the profile 48 laid flat and the pin 50. Long slots 52 straddle short slots 54 in a preferably 360 degree pattern. FIG. 6e schematically shows an offset lug 56 that can selectively engage a surface 58 to prevent the piston 3 and the flow tube 6 from coming up when pressure is relieved at connection 13. This is one optional way a travel stop can be engaged to limit the movement of the flow tube 6. The indexing pattern 48 rotates the piston 3 90 degrees with each application of pressure and another 90 degrees with each removal of pressure with the illustrated pattern 48. Different patterns can be used to require more than two cycles of pressure application and removal for a full 360 degree rotation without departing from the spirit of the invention. The offset lug 56 is designed to engage the surface 58 after a single cycle depicted in FIGS. 3 and 4. In FIG. 3 pressure applied at connection 13 enlarges chamber 44 and uses external ring 42 to push down on ring 32 to rotate the flapper 10 90 degrees. Relieving the pressure at connection 13 allows lug 56 to engage surface 58 as shown in FIGS. 4 and 6c. In this position the flow tube 6 is retained with the flapper 10 open for the selectively locked open position. Another pressure cycle on connection 13 regains the alignment of pin 50, as shown in FIG. 5, with a long slot 52 to allow the flow tube 6 to come back up under the force of spring 8 so that the flapper 10 can close and the FIG. 2 position resumed. Piston 3 is guided by spaced bushings 62.

(14) An alternate embodiment contemplated would consist of splitting piston 3 into two halves (i.e. an upper 3a and lower 3b half), each terminating at external ring 42 and with a bearing 100 operatively installed in-between the two halves 3a and 3b. In this configuration, the bearing 100 separating the two halves of piston 3 would serve to isolate the rotational movement of piston 3b to just the half containing the j-slot pattern (i.e. the lower half 3b). Consequently, the upper half 3a of piston 3 and its corresponding seal 46 would not be subjected to rotational movement which would thereby increase the longevity of seal 46 and the corresponding piston bore within which it is installed. In normal operation of FIG. 7a, upper piston 3a engages ring 32 of flow tube 6 for tandem axial movement. The j-slot interaction with lower piston 3b allows it to rotate as well as translate as it moves in tandem with upper piston 3a in axial translation. Bearing 100 allows lower piston 3b to rotate relatively to upper piston 3a so as to reduce wear on piston seal 46. Snap ring 104 engages surface 106 to pull up the lower piston 3b when control line pressure is reduced on top of upper piston 3a. FIG. 7b works on the same principle except there is a bushing 108 that engages snap ring 104 because bushing 108 is secured to the upper piston 3a. In all other respects the operation of FIGS. 7a and 7b is the same. The result is that the wear on the seal 46 is reduced in that it does not experience rotation while the ability of the lower piston 3b to rotate on its long axis while translating allows the needed releasable selective locking in the flapper open and flow tube down position.

(15) Several observations need to be made. The flow tube 6 can be operated by either piston 2 or 3 but the piston 3 has the capability of locking the flapper 10 in the FIG. 4 open position. Pistons 2 and 3 comprise an actuation assembly for the flow tube. In the FIG. 4 open position the lower end 64 of the flow tube 6 is preferably a clearance fit to surface 66 of body 11 shown in FIG. 2. This helps to keep debris away from flapper 10 when in the open position behind the flow tube 6. The use of an indexing mechanism such as a j-slot with relatively large open spaces also reduces the risk of jamming from debris in wellbore fluids. The slots in pattern 48 can have ends that engage pin 50 as shown in FIG. 5 but the preferred embodiment envisions the slots being longer than shown so that motion is stopped extraneous to the pin and slot interaction to avoid shear stress on the pin. A travel stop (not shown) on the piston 3 can be provided to engage the housing 30 on application and removal of pressure at connection 13. Piston 3 is in hydrostatic pressure balance as its underside is connected to the balance line (not shown) connected to connection 40. Piston 2 is configured to be insensitive to tubing pressure whereas piston 3 is not, recognizing that tubing pressure acts upon one side of seal 46 and control line pressure acts upon the other. The safety valve can be held open with piston 3 for normal operation in the position of the pin 50, shown in FIG. 5, being in a portion of the slot pattern 48 such that any loss of pressure or removal of pressure from connection 13 will result in a fail-safe closure of the flapper 10 against seat 38. Connections 12 and 13 can be supplied with a single control line or discrete control lines. With a single control line pressure may need to be cycled one time to get the valve out of the FIG. 4 selectively locked position if normal continuing operation is contemplated. In applications for marine risers using an additional control line for connection 13 in addition to lines going to connections 12 and 40 does not present a space problem. In borehole applications there would need to be room for three lines if a balance line to connection 40 is used.

(16) Alternatively, just two control lines could be used, removing the third line (described as a balance line) connected to connection 40 and reconfiguring piston 2 to be sensitive to tubing pressure. In said configuration, a larger return spring 8 would also be required to overcome the control line hydrostatic pressure applied to the primary piston 2 and the secondary piston 3 at connections 12 and 13.

(17) The design allows redundancy with pistons 2 and 3 for a longer service life and a more reliable operation to avoid downtime for replacement. Another option is to run only piston 3 to have the option of locking open as well as a normal operation with pressure on connection 13 and pin 50, shown in FIG. 5, in the position of slot 68 where loss or removal of pressure results in the flow tube 6 moving up so that the flapper can close.

(18) The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: