Downhole safety ball valve

Abstract

A downhole ball type safety valve for installation in a well at a subsurface location to control, in a failsafe manner, the fluid flow from the well. The valve is equipped with spring means to close it automatically should the hydraulic pressure employed to hold it open drop below a predetermined level, and a means to open and releasably lock open the valve in the event it cannot be opened by the main hydraulic system.

Description

BACKGROUND OF THE INVENTION

The present invention relates to downhole safety valves for installation in fluid producing wells, and more particularly to ball-type, fail-safe flow control valves designed for use in oil or gas well production tubing.

In order to satisfy governmental safety requirements imposed to protect the ocean and marine life from the adverse effects of petroleum and other fluids leaking or flowing wildly from offshore wells that have been damaged by fire, storm, collisions, etc., it has been conventional practice to use storm-chokes, ball-type safety valves and other devices in the well tubing to automatically close the tubing to fluid flow when the well pressure reaches a predetermined figure. However satisfactory this equipment might be on the drawing board, in actual practice malfunctions are not infrequent, for sand and other abrasives carried by the oil can plug up critical passages and abrade elements designed for close tolerances. This is especially true of such safety devices that have been in the well for a prolonged period of time, as frequently is the case since it is quite expensive to shut the well down, pull the device, service or replace it, and put the well back into production.

Many of the later safety valves are hydraulically operated, that is to say they rely on hydraulic pressure from the surface to maintain them in open position. Should that pressure fail, as if the hydraulic line becomes fouled or is ruptured, the valve automatically closes and often cannot be readily reopened.

Other problems arise when hydraulic pressure is not available to open the valve and hold it open, as where it is desirable to pump down through the tubing in which the valve is located, to kill the well, or to perform other desirable tubing operations. Also it usually is best to run the valve in locked open position into the well, and then place it on the fail-safe mode, but many valves for this purpose have not been entirely successful.

SUMMARY OF THE INVENTION

Broadly considered, the present invention comprises a fail-safe, ball-type safety valve that normally is opened, and held open by hydraulic pressure conducted from the surface, and that can be opened in an emergency and releasably locked open by fluid pressure exerted from the surface down through the tubing string in which the valve is positioned. The valve has a ball closure element that rotates between open and closed positions without moving longitudinally in the valve's housing, and this ball is actuated by annular control pistons that are spring-biased towards the valve's "closed" position, and that can be moved to open the valve either by hydraulic line pressure or tubing string fluid. The invention further includes a floating piston and snap ring that cooperate to open and releasably lock the valve in its open position, and a novel manner of unlocking is provided to restore the valve to its original normal functioning.

Accordingly, one object of the present invention is to provide a new and superior downhole ball-type safety valve especially for use in offshore wells.

Another object of the present invention is to provide an improved means for opening an hydraulically-operated downhole safety valve in the event of an emergency wherein the hydraulic supply is non-functional.

Another object of the present invention is to provide an improved system for locking a downhole safety valve in its open position.

Yet another object of the present invention is to provide an improved means for releasing the locked-open valve and restore it to its normal functioning mode.

The foregoing and other objects and advantages of the present invention will become apparent from the following description of a preferred embodiment thereof, as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in elevation and in section of a downhole safety ball valve embodying the principles of the present invention, showing the valve incorporated in a tubing string and in its closed position.

FIG. 2 is an enlarged isometric view of the ball closure element's lower control piston.

FIG. 3 is an enlarged isometric view of the valve's ball closure element.

FIG. 4 is a fragmentary elevation view of the valve in closed position with its lower control piston in phantom.

FIG. 5 is a view like FIG. 4, but with the valve in its open position.

FIG. 6 is a view like FIG. 1, showing the valve in its open, but unlocked position.

FIG. 7 is a view like FIG. 1, but also including an override wireline plug in position for opening the valve by fluid pressure exerted through the tubing string.

FIG. 8 is a view like FIG. 7, showing the valve after fluid pressure has been applied through the tubing string.

FIG. 9 is a view like FIG. 8, showing the valve locked open and the wireline plug removed.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference first to FIGS. 1-5 of the drawings, a downhole safety ball valve 10 embodying the features of the present invention generally comprises a tubular housing 12, a tubular landing nipple 14 threaded at 16 into the upper end of the housing 12 and providing a means for connecting the top of the valve to a tubing string 18, and a tubular bottom sub 20 threaded at 22 into the lower end of the housing 12 and suitably equipped to connect the tubing string's lower portion 18a to the bottom of the valve. Upper and lower annular seals 26, 28 in grooves around the outer surfaces of the landing nipple 14 and the bottom sub 20, respectively, function to provide a fluid-tight barrier between these elements and the housing 12.

Within the housing 12 is a ball closure element 30 mounted for pivotal movement about an axis A that is transverse to the centerline B through the valve's flow passage 32. When the ball 30 is in its "closed" position as shown in FIG. 1, it prevents flow of well fluid through the valve and thus through the tubing string 18. The ball has a bore 34 of the same diameter as that of the valve's flow passage 32, so that when the ball has been rotated 90.degree. about its axis A into its "open" position the flow of well fluid through the valve is unobstructed.

Rotation of the ball 30 between its open and closed positions is accomplished by longitudinal movement of an annular lower control piston 36 (seen best in FIG. 2) that has a pair of diametrically opposed, downwardly extending legs 36a, 36b between which the ball 30 is positioned. As seen in FIG. 1, the ball has a pair of flat, oppositely facing exterior surfaces 30a, 30b that define planes which are parallel to each other and to the axis C through the valve's bore 34. Cylindrical pins 38,40 protrude outwardly from the surfaces 30a, 30b on a common axis D (FIG. 1) that is offset but parallel to the axis A, and extend through bearing elements 42,44 that are suitably shaped to slidably fit within relieved areas 46,48 on the inside surfaces of the lower control piston's legs 36a, 36b. In the assembled valve the ball is precluded from longitudinal movement by the upper end surface 20a of the bottom sub 20, and the lower end surface 14a of a sleeve 14b that extends downwardly from the landing nipple's upper section 14c. Accordingly, when the lower control piston 36 moves downwardly from its uppermost position illustrated in FIG. 1, it exerts a camming-type force on the pins 38,40 and causes them to move downwardly along an arc F (FIGS. 4 and 5) from their position wherein the valve is fully closed (FIG. 4) towards their position wherein the valve is fully open (FIG. 5). Upward movement of the lower control piston 36 towards the position illustrated in FIG. 1 causes the pins 38,40 to follow upwardly in the same arc F, thereby rotating the ball 30 towards its closed position.

The lower control piston 36 is caused to move from its uppermost position wherein the valve is fully closed (FIG. 1) to its lowermost position wherein the valve is fully open (FIG. 6) by hydraulic fluid conducted to the valve 10 from a surface control means (not shown) through a line 50 (FIG. 1). Just below the level at which the hydraulic line 50 is connected to the valve's housing 12 by a fitting 52, an annular upper control piston 54 is slidably positioned between the housing 12 and the landing nipple's sleeve section 14b, with annular seals 56 providing fluid-tight barriers between these elements. The upper control piston 54 has a lower sleeve 54a that is threaded at 58 into the lower control piston 36, so that as hydraulic fluid is pressured against the top of the upper control piston 54 this element and the lower control piston 36 move downwardly in a ball-opening direction.

The downward movement of the pistons 54,36 is resisted by a system of annular wave springs 60 that surround the upper control piston's sleeve 54a and extend between this piston's downwardly facing shoulder 54b and an inwardly extending annular flange 12a of the valve's housing 12. This spring system exerts an upward bias against the control pistons 36,54, and thus when the hydraulic pressure is insufficient in the line 50, such as if the line is fouled or ruptured, the valve will automatically close, a "fail-safe" feature of high importance particularly when the valve is employed in offshore wells. The valve-closing force exerted by the spring system 60 can be varied to suit the particular conditions under which the valve will be operating.

When the valve 10 is in operational position in a producing well, the production fluid in the tubing string 18a exerts its pressure against the lower control piston 36 through ports 20b in the bottom sub 20. Inner and outer annular seals 62 between the lower control piston 36, the sleeve 14b, and the housing 12 prevent upward migration of the production fluid. In order to open the valve, the tubing string 18 above the ball 30 is pressured to approximately the same pressure as the production pressure in the string's lower section 18a, and hydraulic fluid is exerted through the line 50 against the upper control piston 54. When this hydraulic pressure exceeds the production pressure plus whatever predetermined additional pressure has been designated, such as 50 psi, the pistons 54,36 move downwardly and rotate the ball 30 to its open position. This 50 psi pressure is arbitrary, and can be changed to another figure if desired.

Two of the more important features of the present invention are the provision of an annular floating piston 70 to open the valve 10 in the event of an emergency, such as if the hydraulic line 50 is broken or plugged so that hydraulic pressure cannot be applied to the upper control piston 36, and the provision of a normally contracted expansible snap ring 72 that cooperates with the piston 70 to releasably lock the valve in its open position. As seen in FIG. 1, the floating piston 70 normally resides in the annulus between the valve's housing 12 and the landing nipple's sleeve section 14b, generally above the point where the hydraulic fitting 52 communicates with this annulus. The piston 70 has inner and outer annular fluid seals 74 that establish a fluid-tight barrier between the piston and the adjacent surfaces of the housing 12 and sleeve 14b, yet facilitate longitudinal movement of the piston between its uppermost position (FIG. 1) and its lowermost position as seen in FIGS. 8 and 9. Thus a fluid-tight chamber 76 is formed between the floating piston 70, the valve housing 12, the upper control piston 54, and the sleeve 14b, which chamber of course expands and contracts during movemment of the pistons 54,70.

The lower segment 70a of the floating piston 70 has an outside diameter slightly less than the inside diameter of the upward-extending axial flange 54c at the top of the upper control piston 54, so that this lower segment 70a will fit in between this flange 54c and the sleeve 14b. The snap ring 72, however, has a radial thickness significantly exceeding that of the flange 54c, so that the floating piston's lower segment 70a cannot pass by the ring and move inside the flange 54c so long as the ring is in its contracted condition as seen in FIG. 1. Below the hydraulic fitting 52 the housing has an inner annular groove 78 with a depth sufficient to accommodate enough of the snap ring 72 so that when the ring is opposite this groove the cam surface 70b of the floating piston's lower segment 70a can cam it outwardly, i.e., expand it, into the groove and then pass on through it into the inside of the upper control piston's flange 54c until it reaches the position illustrated in FIGS. 8 and 9. Accordingly, as the floating piston 70 moves downwardly from its uppermost position (FIG. 1), it first presses the snap ring 72 against the upper end of the flange 54c and causes the upper and lower control pistons 54,36 to move downwardly also, thereby rotating the valve's ball 30 to its open position. When the snap ring 72 reaches the groove 78 it is expanded into the groove as described above, thereby preventing upward movement of the control pistons 54,36. At this point the valve ball 30 is fully open, and further downward movement of the floating piston 70 places its lower segment 70a inside the ring 72, retaining it expanded in the groove 78 and thus locking the valve in open position, as shown in FIG. 9.

In order to move the floating piston 70 downwardly to open the ball 30 and lock it in open position, a wireline override plug 80, such as that diagrammatically shown in FIGS. 7 and 8, is run into the valve 10 by conventional wireline techniques and releasably locked into the valve's landing nipple 14 in the conventional manner, such as by means of locking dogs 82 that are caused to expand into matching internal grooves 84,86 in the nipple's upper portion 14c. The plug 80 includes a packer section 88 that is actuated to establish a fluid-tight seal with the sleeve 14b, and a flow passage 90 that is in flow communication at or near its upper end (not shown) with the tubing string 18. The flow passage 90 exits from the side of the plug 80 at a level adjacent the upper end of the sleeve 14b, and communicates with one or more lateral ports 92 extending through this sleeve into the upper end of the annulus between it and the valve's housing 12. Accordingly, when the override plug 80 is properly landed and locked in the landing nipple 14 and the packer 88 set as shown in FIG. 7, fluid pressure admitted into the tubing string 18 will extend into and through the plug's passage 90 and the valve's ports 92 in the direction of the arrows in FIG. 8 to exert a downward force on the floating piston 70, thereby causing this piston to move toward its lowermost position as illustrated in FIG. 8. The plug 80 can then be removed, leaving the valve in its locked open position as shown in FIG. 9.

In order to release the locked valve (FIG. 9) and restore it to its original operating mode, hydraulic pressure is admitted through the line 50 into the chamber 76. This causes the floating piston 70 to move upwardly to its uppermost position, thereby permitting the snap ring 72 to contract out of the groove 78. If the hydraulic pressure is sufficiently great to prevent the released control piston 54 from moving upwardly in response to the springs 60 the valve ball 30 will remain open, otherwise it will close and the valve 10 will be restored fully into the condition illustrated in FIG. 1.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.

Claims

What is claimed is:

1. A downhole safety valve assembly for controlling the flow of well fluids, said assembly comprising

1. a tubular housing element,

2. an inner concentric fluid-conducting sleeve element secured to and spaced from the housing element, said sleeve element forming a well fluid flow passage through said valve assembly,

3. a ball valve for controlling flow through said flow passage,

4. a control piston slidable in the annular space between said housing and sleeve elements and having ball valve operating means at its lower end portion,

5. spring means in said space and extending between said housing element and said control piston for urging said control piston to its valve closed position,

6. a floating piston in said space and above said control piston,

7. control piston retainer means slidably mounted between said pistons,

8. means cooperable with said retainer means for facilitating releasable retention of said control piston in its valve opening position by said retainer means,

9. a port in said housing for supplying fluid under pressure directly to the upper end of said control piston for opening said ball valve,

10. a port in said sleeve element for supplying fluid under pressure directly from the flow passage to the upper end of said floating piston for moving said control piston to its valve opening position via said retainer means, said retainer means thereupon releasably retaining said control piston in its valve opening position, and

11. means on said floating piston for holding said retainer means in its control piston retaining condition.

2. The valve assembly of claim 1 wherein the floating piston is moved into its locked position solely by application of fluid pressure through the flow passage and the port in the sleeve element to the upper end of said floating piston.

3. The valve assembly of claim 1 wherein the ball valve is mounted in the lower end portion of the control piston for rotation with respect thereto, and wherein said ball valve is restrained by the sleeve element against upward movement in the housing element.

4. The valve assembly of claim 1 wherein the lower end of the sleeve element includes an annular valve seat with which the ball valve cooperates to establish a fluid-tight barrier preventing flow of well fluid through the valve assembly when said ball valve is in its closed position.

5. The valve assembly of claim 1 wherein the retainer means comprises a normally contracted, expansible snap ring.

6. The valve assembly of claim 5 wherein the snap ring is circular in cross-section configuration.

7. The valve assembly of claim 1 wherein the retainer means comprises a split ring and a ring-receiving groove formed in one of said elements, said ring being inherently biased out of said groove, and wherein the floating piston has means for camming said ring into said groove.