Subsurface Safety Valve Apparatus

Abstract

A surface controlled, subsurface safety valve includes a tubular housing carrying a hinged flapper valve element that is moved to open position by a valve actuator sleeve. The sleeve is moved under the thrust of a coil spring that is compressed in response to downward movement of a hydraulically operated piston assembly, with hydraulic pressure being applied from the surface via a control line. The relative movement between the piston assembly and the actuator sleeve during compression of the spring is utilized to open a fluid bypass across the valve element so that the valve is opened under conditions of substantially equalized pressures.

Description

This invention relates generally to subsurface safety valves, and particularly to a new and improved remote controlled safety valve having a uniquely arranged pressure equalizing system that enables reopening the valve after closure without substantial risk of damage to the valve element and associated parts.

Remote controlled safety valves are commonly employed in producing wells as a means of providing downhole protection against disastrous surface fires and blowouts due to failure, leakage or loss of surface equipment such as valves and flow lines. A remote controlled valve of typical construction includes a valve actuator and closure element that are biased toward closed position by a coil spring, however the closure element is held open during normal production operation in response to the pressure of fluids in a control line that extends externally of the tubing to a source of pressure at the surface. The pressure acts upon a piston assembly that is mechanically coupled to the valve element in a manner to actuate it to the open position. So long as the control line remains pressurized, the valve is open to the flow of production fluids; a loss of control line pressure due to the sensing of heat, collision or the like at the surface enables the coil spring to force the actuator in a direction to cause automatic closure of the valve element to shut off the production fluid flow.

In order to reopen the safety valve so that the well can be put back into production subsequent to performing the necessary repair of surface damage, or where the valve is purposely closed in order to test the operability of the system, it is generally necessary to pressurize the control line to force the actuator and valve element against the bias of the spring to the open position. However it is quite likely that valve element will be rather forcefully held in the closed position because it is being subjected to the difference in pressures between production pressure and hydrostatic head in the tubing. In fact, it may not be possible to apply enough pressure to the control line to overcome the closing force without endangering the integrity of the control line itself. Moreover, where the closure element is a hinged disc mounted on a pivot pin, there is a substantial risk of shearing off the pivot pin or otherwise damaging the valve element to the extent that the safety valve becomes inoperable.

Accordingly, some prior art safety valve have included means to equalize pressures across the valve element in order to aid the re-opening process. However, such devices are either extremely complicated, or have been constructed in such a manner as to necessitate pressurizing the production string, or both, and therefore are unsatisfactory, since pressurization of the tubing requires pumps and auxiliary pressure equipment and services which are costly and inconvenient. Yet other equalizing arrangements are operated by wireline techniques which also can be cumbersome and time consuming. In sum, all such systems are not considered to have the reliability that is necessary to insure against damage during reopening, or to enable reopening with a minimum of inconvenience to the well operator.

Accordingly, it is an object of the present invention to provide a new and improved surface controlled, subsurface safety valve that can be readily reopened with minimal risk of damage to the valve element and associated parts.

Another object of the present invention is to provide a surface controlled, subsurface safety valve having a new and improved pressure equalizing arrangement that enables the valve to be safely and reliably reopened subsequent to closure without the necessity for pressurizing the production tubing.

Yet another object of the present invention is to provide a new and improved surface controlled, subsurface safety valve having a means to equalize pressures across the closure element in response to pressurization of the control line leading to the valve so that the closure can be moved to open position under low opening force to prevent damage.

These and other objects are attained in accordance with the concepts of the present invention through the provision of a safety valve apparatus including a housing adapted for positioning downhole in the production tubing of an oil well. The housing provides a valve seat that surrounds the flow passage for the production fluids, and carries a valve element, preferably of the pivoted or hinged disc type, that is movable between open and closed positions with respect to the valve seat. A tubular valve actuator is mounted for linear movement within the housing and has an end portion that can be protruded through the seat to open the valve element and then hold it in the open position, and which is withdrawn from the valve seat in order to enable the valve element to close against the seat. The housing further contains an operator piston assembly that is responsive to the pressure of fluids in a control line extending externally of the tubing to the surface and is movable longitudinally relative to the valve actuator. A yieldable means such as a coil spring is interposed to react between the piston assembly and the valve actuator and is energized by movement of the piston assembly in such a manner as to cause the actuator to force the valve element open. The relative movement that causes the coil spring to be energized also opens a normally closed pressure equalizing passage extending between locations in communication with upstream and downstream pressures. Thus when the control line is repressured after the valve has closed, the coil spring will apply a selected opening force to the valve actuator that is well within the strength limitations of the valve element and associated parts, however the valve will not be forced open until the pressures have equalized sufficiently to enable this force to cause the valve to open. In this manner the valve element is always opened under conditions of substantially equal pressures and a pre-selected opening force to prohibit damage thereto during such opening movement. Moreover, there is no need to pressurize the tubing to accomplish opening or reopening.

The present invention has other objects and advantages which will become more fully apparent in connection with the following detailed description of a preferred embodiment, taken in conjunction with the appended drawings, in which:

FIG. 1 is an overall view of a subsurface safety valve installation in an oil well;

FIGS. 2A and 2B are longitudinal sectional views, with portions in side elevation, of a safety valve apparatus in accordance with the present invention; FIG. 2B forming a lower continuation of FIG. 2A;

FIG. 3 is a sectional view the parts showing the equalizing valve in the open position;

FIG. 4 is a sectional view of the lower end portion of the safety valve with the closure element in the open condition; and

FIG. 5 is an enlarged fragmentary view of the pressure equalizing feature of the safety valve.

Referring initially to FIG. 1, the subsurface safety valve indicated generally at 10 may be fixed to a landing nipple 11 that is connected in the production string 12 of tubing or the like. The landing nipple 11 has spaced-apart internal seal surfaces and a fluid communication port 13 leading to the outside. A control line 14 is arranged to extend to the surface externally of the tubing 12 and is suitably attached to a port block 15 so that fluid pressure from the surface or other remote location can be utilized to control the operating position of the valve 10, as will be described in greater detail below. The tubing 12 will normally be concentrically disposed within the well casing 16, with the lower end of tubing attached to a packer 17 that seals off the upper end of the producing zone. Production fluids enter the casing 16 through perforations below the packer 17 and pass upwardly through the tubing 12 until the fluids reach the safety valve 10, where the total of the flow is constrained to pass therethrough. The safety valve 10 is located and locked with respect to landing nipple 11 by a locking assembly 18 of typical and well known construction, which enables the valve to be positioned and removed by wireline techniques as will be apparent to those skilled in the art.

As shown in greater detail in FIGS. 2A and 2B, the valve 10 includes a tubular outer housing 22 having threaded upper sections 23 and 24, each of which carries a seal packing unit 25, 26 suitably arranged to engage seal surfaces 27 and 28 within the landing nipple 11. Each packing unit can comprise a plurality of chevron elements 29 located between back-up rings 30 and 31. The lower end of the housing 22 is open to the flow of production fluids, and a side window 32 is provided for receiving a valve element that preferably is constituted by a hinged disc or "flapper" element 33. The disc 33 has an ear 34 to one side with an opening that receives a hinge or pivot pin 35 with its opposite ends received in aligned apertures (not shown) in the wall of the housing 22. A hinge spring 36 is shaped to coil around the pin 35 and has a tang 37 that engages within a notch 38 in the housing 22, and a finger 39 that lays within a groove 40 on the lower face of the disc 33. The spring 36 continuously urges the disc 33 to pivot inwardly and upwardly from an open position, where it extends downwardly within the window 32, to a transverse or closed position where the upper outer surface thereof engages a face seal 41 bonded within a groove on an annular valve seat 42 provided by an inwardly directed shoulder 43 on the housing 22.

The disc 33 is moved from closed to open position by a valve actuator sleeve 48 that is movable longitudinally in both directions within the housing 22. The sleeve 48 has an open bore 49 and may be comprised of threadedly attached upper and lower sections 50 and 51 with the lower section of a diameter sized to pass through the opening of the valve seat shoulder 43. As the actuator sleeve 48 is advanced downwardly from the position shown in FIG. 2B, it engages and pushes the disc 33 to the open position and then extends therepast to retain it in such position as shown in FIG. 4. When the actuator sleeve 48 shifts upwardly to a position where its lower end surface 52 is above the lower face 42 of the seat shoulder 43, of course the spring 36 will apply closing torque to cause the disc 33 to pivot to the closed position.

A pressure responsive operator assembly 60 is constructed in the form of an elongated sleeve piston and may include, for convenience of manufacture, several separate sections that are threaded together. The upper section 61 is provided with a stepped outer diameter, and the adjacent portion 62 of the housing 22 is complementarily shaped and arranged to carry seal rings 63 and 64 that slidably engage the outer wall surfaces 65 and 66 of the section 61. The pressure port 13' is located between the seal rings 63 and 64, so that fluid pressure applied to the space 67 will develop a magnitude of downward force on the operator piston 60 that is a function of the applied pressure and the transverse cross-sectional area bounded by the seal rings. Such force will tend to move the operator assembly 60 downwardly or toward the valve seat 42.

An intermediate section 70 of the operator piston 60 is constituted by a sleeve 71 that is surrounded by a helical coil spring 72. The upper end of the spring 72 presses upwardly against a ring 73 that engages below an outwardly directed shoulder 74, and the lower end of the spring presses against a retainer 75 which is itself seated against an oppositely facing shoulder 76 on the housing 22. Thus the coil spring 72 is disposed between the operator assembly 60 and the housing 22 and arranged to react, when compressed, to urge the operator assembly upwardly or away from the valve seat 42. The lower section 80 of the operator piston 60 is sized and arranged to extend into the bore 49 of the upper section 50 of the actuator sleeve 48, is also surrounded by a coil spring 81 whose upper end pushes against a shoulder 82 formed at the threaded interconnection of the sections 70 and 80, and whose lower end pushes downwardly on the upper end face 83 of the actuator sleeve 48. The spring 81 reacts to urge the operator assembly 60 and the actuator sleeve 48 in opposite longitudinal directions, and when compressed will urge the actuator sleeve 48 in a downward direction to tend to cause it to open the valve element 33.

It will be recognized that the operator assembly 60 and the actuator sleeve 48 have the capability for limited longitudinal movement relative to one another, and such relative movement is utilized to open and close an equalizing passage extending between points up-and-downstream of the valve element 33. In the mutually extended position of these members shown in FIG. 5, an enlarged, annular valve head 86 with a longitudinally grooved exterior is formed at the upper end portion of the actuator sleeve 48 and normally engages a stop shoulder 87 on the piston section 80. A seal ring 88 carried by the head engages an external annular seal surface 89 to prevent fluid leakage. Of course it will be recognized that the actuator sleeve 48 can move relatively upwardly along the lower section 80 to a position where the seal 88 and the surface 89 are disengaged. When this occurs a flow passage from the respective bores 49 and 49' of the operator assembly 60 and the actuator sleeve 48 to the annular space 90 between these members and the inner wall surface of the housing 22 is provided. This space is communicated to the exterior of the housing 22 by a plurality of ports 91 (FIG. 2B) through the wall thereof located preferably just above a seal 92 that prevents leakage between the housing and the valve actuator sleeve 48. The uppermost portion 93 of the actuator sleeve 48 is provided with flow openings 94, and the lowermost portion of the section 51 is grooved at 95, to provide ample fluid flow space. When the valve head 86 is off of the seal surface 89, the passages and openings provide fluid communications between locations upstream and downstream of the valve element 33 in order to equalize pressures and thus relieve the element of upward closing force due to a greater pressure therebelow. Normally however, the valve head 86 is in the closed position shown in FIGS. 2B, 4 and 5, where the seal 88 together with metal-to-metal contact between the head 80 and the stop shoulder 87 provide a dual valve construction.

In operation, the safety valve 10 is positioned within the production pipe 12 and locked by the assembly 18 with respect to the landing nipple 11 using typical wireline setting procedures. When in position, the packing elements 25 and 26 prevent fluid leakage past the housing 22 so that the total flow well fluids must pass through the safety valve. Fluid pressure applied to the control line 14 from a source of pressure at the surface will enter the space 67 and force the operator piston 60 downwardly so that normally the valve parts occupy the position shown in FIG. 4 where the valve disc 33 is open to enable production fluids to flow upward to the surface. In the event of a loss of applied control line pressure due, for example, to the action of various known surface sensors which cause the pressure to be vented, the main spring 72 forces the operator piston assembly 60 upwardly. The actuator sleeve 48 also moves upwardly also due to engagement of the valve head 86 by the stop shoulder 87. The lower portion 51 of the actuator sleeve 48 retreats from its position through the valve seat 43, enabling the hinge spring 36 to pivot the disc 33 to closed position. Any excess of production pressure over hydrostatic head within the tubing string 12 at the level of the valve 10 will apply upward force to the disc 33 in the closed position. Thus the valve 10 shuts-in the well to prevent any further flow of production fluids. It should be noted at this point that the configuration of the lower surface of the shoulder 43 as a flat surface enables the disc 33 to seat against the seal ring 41 even though there may be some slight misalignment.

To reopen the valve 10, pressure is applied to the control line 14 at the surface. Downward force on the operator assembly 60 due to such pressure will overcome the opposing influence of the main spring 72 and cause the spring to compress and allow downward movement of the operator assembly. Since the disc 33 will normally be held closed by production pressure as described above, there is a need to equalize the pressures so that the disc and the pivot pin 35 will not be damaged during opening movement. Equalization is accomplished by virtue of the fact that the operator assembly 60 can shift downwardly relative to the actuator sleeve 48 to some extent as the lower spring 81 yields and compresses as shown in FIG. 3. Such relative movement disengages the seal surface 89 from the equalizing valve seal 88 so that, as required, formation fluid can flow via the ports 91, the annular space 90 and the passages 94 past the valve head and into the interior of the operator assembly 60. This enables a pressure differential across the disc 33 to be equalized to a point where the lower spring 81, having been compressed or energized by such relative movement, will force the actuator sleeve 48 downwardly to cause the disc 33 to swing open, thus opening the valve to the flow of production fluids. Continued downward relative movement of the actuator sleeve 48 under the thrust of the spring 81 will cause the equalizing valve head 86 to engage the surface 89 to close the equalizing passages. Hereagain the valve 10 will remain open as long as sufficient pressure is applied to the control line 14 to compress the main spring 72.

It will now be recognized that a new and improved subsurface safety valve has been provided that is surface controlled by hydraulic pressure in a control line. Due to the new and improved equalizing arrangement provided therein, there is practically no chance of damage to the disc valve element or its pivot pin during opening procedures since the valve is opened under essentially no pressure differential across the disc. In addition, the disc valve is pushed open only under the thrust of the spring 81 which is energized by downward movement the operator assembly 60. Thus the rate of the spring 81 can be carefully selected to provide a maximum opening force that is well within design limitations that ensure against any structural damage to the disc 33 or the pivot pin 35. It will be recognized that there is no need to pressurize the tubing as a prerequisite to opening the valve, nor is there any need to pressurize the control line to a value in excess of that normally required to compress the springs and overcome seal friction and the like.

Since certain changes or modifications may be made by those skilled in the art without departing from the inventive concepts involved herein, it is the aim of the appended claims to cover all such changes or modifications falling within the true spirit and scope of the present invention.

Claims

I claim:

1. A safety valve apparatus comprising: a housing having a flow passage therethrough and valve means for opening and closing said flow passage; actuator means for moving said valve means from closed to open position; hydraulically operable means within said housing and movable relative to said actuator means and toward said valve means in response to fluid pressure; fluid bypass passage means extending past said valve means and arranged when open to equalize pressures upstream and downstream of said valve means; equalizing valve means including coengageable means on said actuator means and said hydraulically operable means for opening said bypass passage in response to movement of said hydraulically operable means relative to said actuator means; and spring means reacting between said hydraulically operable means and actuator means and being energized by said relative movement to cause said actuator means to move said valve means from closed to open position under conditions of substantially equalized pressures.

2. The apparatus of claim 1 wherein said hydraulically operable means and said actuator means are tubular members having telescopically interfitted end portions, said coengageable means being arranged on said portions.

3. The apparatus of claim 2 wherein said coengageable means comprises a valve head on one of said portions carrying a seal element that is engageable with a seal surface on the other of said portions, said seal element and surface when engaged closing off said bypass passage, a part of which extends between said end portions.

4. The apparatus of claim 3 wherein said end portions have opposed shoulder surfaces that are engageable to limit relative movement in one direction and to provide additional means for closing off said bypass passage.

5. A subsurface safety valve apparatus comprising: a housing defining a flow passage and carrying valve means for opening and closing said flow passage, said housing having a cylinder section; hydraulic means movable longitudinally within said housing in response to the application of fluid pressures within said cylinder section; valve actuator means arranged to move longitudinally within said housing to effect opening of said valve means; spring means reacting between said hydraulic means and said actuator means and adapted when compressed to cause movement of said actuator means; a fluid bypass passage extending from upstream of said valve means to downstream thereof; equalizing valve means for opening and closing said bypass passage; and a lost-motion connection between said hydraulic means and said actuator means, the relative movement afforded by said connection enabling opening of said equalizing valve means and compression of said spring means so that said spring means can force said valve means open under conditions of substantially equalized pressures.

6. The apparatus of claim 5 wherein said hydraulic means and said actuator means comprise tubular members having telescopically interfitted end portions, said bypass passage extending in part between said end portions, said equalizing valve means including a valve head on one of said portions carrying a seal element adapted to engage a seal surface on the other of said portions to close said bypass passage.

7. The apparatus of claim 6 wherein said valve means comprises a valve seat surrounding said flow passage and a valve element hinged to the side thereof and arranged for pivotal movement between an open and a closed position with respect to said valve seat.

8. The apparatus of claim 7 wherein said valve actuator means additionally has an end portion opposite said interfitted end portion sized and arranged to be protruded through said valve seat to cause pivotal movement of said valve element to open position, said valve means including means to automatically cause pivotal movement of said element to closed position upon withdrawal of said opposite end portion from within said valve seat.

9. A subsurface safety valve apparatus, comprising: a housing adapted to be fixed in the production pipe of a well; valve means within said housing for opening and closing a flow passage therethrough, including a valve seat and a hinged valve element that is pivotally movable with respect to said seat between open and closed positions; an actuator movable within said housing between a first position enabling closure of said valve element and a second position forcing said valve element open; spring means arranged to push said actuator toward said second position; normally closed equalizing valve and passage means arranged when open to communicate fluid pressures upstream and downstream of said valve element; and hydraulically operable means for opening said equalizing means and energizing said spring means to cause opening of said valve element by said actuator under conditions of substantially equalized pressures.

10. The apparatus of claim 9 wherein said valve seat is provided by an annular, inwardly directed shoulder on said housing, said valve element being a disc that is pivoted to one side of said shoulder, and further including biasing means for pivoting said disc against said valve seat.

11. The apparatus of claim 10 wherein said actuator comprises a tubular element having an end portion that is extendible past said shoulder and through said valve seat, said end portion when thus extended engaging said disc and forcing it to pivot away from said valve seat to open position.

12. The apparatus of claim 9 wherein said hydraulically operable means comprises a sleeve piston within said housing that is movable longitudinally relative to said actuator, said equalizing valve means being coengageable means on said sleeve piston and said actuator.

13. The apparatus of claim 12 wherein said coengageable means comprises opposed shoulder surfaces on said sleeve piston and said actuator for limiting relative movement in one longitudinal direction.

14. The apparatus of claim 13 further including second spring means reacting between said housing and said sleeve piston for continuously urging said sleeve piston in said one direction.

15. A subsurface safety valve apparatus comprising: a tubular housing adapted to be fixed in the production string of a well, said housing having a valve seat surrounding a flow passage therethrough; a valve element pivoted to said housing and movable between an open position to the side of said passage and a closed position against said seat; said housing having a cylinder section; valve actuator means within said housing and having an end portion movable through said seat and into engagement with said valve element to apply opening force thereto; hydraulically operable means having a piston section that is sealingly slidable within said cylinder section and arranged to move toward said valve seat in response to fluid pressure; equalizing valve means for communicating the pressures of fluids upstream of said valve element with the pressure of fluids downstream of said valve element, said equalizing valve means being opened in response to movement of said hydraulically operable means toward said valve seat; spring means reacting between said hydraulically operable means and said actuator means, said spring means being compressed by said movement and when compressed urging said actuator means through said valve seat to apply opening force to said valve element, said opening force causing said valve element to move away from said valve seat under conditions of substantially equalized pressures.

16. The apparatus of claim 15 wherein said hydraulically operable means and said actuator means have overlapping end portions interfitted one within the other and arranged for relative longitudinal movement between mutually extended and contracted positions, said equalizing valve means including a seal element on one portion engageable with a seal surface on the other portion in said extended position to prevent fluid leakage, said seal element being disengaged from said seal surface in said contracted position to enable said pressures to equalize.

17. The apparatus of claim 16 further including opposed shoulder surfaces on said portions that are engaged in said extended position to provide a limit to extensive movement and to provide additional means for preventing fluid leakage.

18. The apparatus of claim 15 further including additional spring means reacting between said housing and said hydraulically operable means for shifting said hydraulically operable means away from said valve seat upon a reduction of fluid pressure within said cylinder section; and means for withdrawing said end portion of said valve actuator through said valve seat upon movement of said hydraulically operable means away from said valve seat to enable closing movement of said valve element.

19. Valve apparatus comprising: valve body means defining a flow passage and a valve seat surrounding said flow passage, a normally closed valve element hinged to said body means and pivotally movable between a closed position against said valve seat and an open position to the side of said flow passage, a valve actuator engageable with said valve element and movable through said valve seat for causing pivoting movement of said valve element from closed to open position, compressible spring means operable when compressed to apply longitudinal force to said actuator, and selectively operable hydraulic means for compressing said spring means to cause said actuator to engage said valve element with a predetermined maximum opening force.