GB2268770A

GB2268770A - A valve having releasable latch mechanism

Info

Publication number: GB2268770A
Application number: GB9314767A
Authority: GB
Inventors: Paul Bernard Lee
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-07-17
Filing date: 1993-07-16
Publication date: 1994-01-19
Anticipated expiration: 2013-07-16
Also published as: GB2268770B; CA2100389A1; GB9314767D0; GB9215218D0

Abstract

A valve having a releasable latch mechanism and serving to control the flow of liquid between a drill string and the borehole annulus comprises: a tubular body connected as part of the drill string, a first port formed in the wall of the tubular body for communicating annulus pressure into the tubular body; a piston movable axially within the tubular body between a closed position and an open position, the piston comprising a second port 18 allowing passage of fluid from within the piston and further comprising a passage extending through the piston; latching means 14 for holding the piston in the closed position; and biasing means 22 for biasing the piston to the closed position, and a third port 17 formed in the wall of the tubular body; whereby when the piston is in the open position the second and third ports 17, 18 are aligned, allowing passage of fluid from within the piston to the annulus, thereby by-passing the tubular body. The piston may be shifted by dropping a plastic ball into the drill string, the plastic ball seating in the piston to block the through passage in the piston. <IMAGE>

Description

A VALVE HAVING RELEASABLE LATCH MECHANISM This invention relates to a valve having a releasable latch mechanism and of the type used to control the flow of fluid through a device. The invention is particularly, though not exclusively, suitable for incorporation into a drilling string positioned within a bore for the control of the flow of fluids through the drill string during drilling operations.

When drilling or extracting materials a number of operational problems can occur. For example, there may be a loss of or reduction in the pressure of circulating fluids which are necessary during drilling. Circulating fluids are pumped down the drill string to remove debris and particles of rock which have been cut by the drill bit. Loss of circulating fluids may arise due to underground rock formations. In these circumstances it is necessary to plug the formation, often known as the "Thief Zone" or "Lost Circulation Zone", to prevent further loss of circulating fluid and possible drill failure. Plugging the "Lost Circulation Zone" is usually achieved by pumping thicker more concentrated fluids down the drill string and out into the formation.However, this procedure tends to be hazardous because the thicker fluids also have a tendency to plug the drill bit or drill string bore.

One known system for preventing the thick fluids blocking the drill string provides a tool which operates on a shear pin mechanism. The tool redirects the flow of thick fluids to prevent the drill bit from being plugged and is activated by pulling on the drill string. However, the shear pin mechanism is not resettable and considerable disruption and loss of production in the drilling operation is incurred during the resetting of the mechanism.

According to the invention there is provided a valve having a releasable latch mechanism and for controlling the flow of liquid within an outer conduit, the valve comprising: an inner conduit positionable substantially co-axially within the outer conduit and defining an annulus between the outer conduit and the inner conduit; a first port formed in the wall of the inner conduit for communicating annulus pressure into the inner conduit; a piston moveable axially within the inner conduit between a closed position and an open position, the piston comprising a second port allowing passage of fluid from within the piston into the inner conduit, and further comprising a passage extending through the piston; latching means for holding the piston in the closed position; and biassing means for biassing the piston to the closed position, and a third port formed in the wall of the inner conduit; wherein when the piston is in the open position the second and third ports are aligned, allowing passage of fluid from within the piston to the outer conduit, thus by-passing the inner conduit.

The valve latch mechanism according to the present invention is particularly appropriate for use in drilling applications, when it may be incorporated into a drilling string. The drilling string will be positioned within a bore.

When pressure builds up within the drilling string caused by thicker more concentrated fluids plugging the drill string, the piston will move to the open position thus allowing the thicker fluids to escape from the drill string into the bore. This reduces problems caused by the thicker fluids plugging the drill string.

Preferably, the valve further comprises abutment means which abut with the piston in the closed position, thus defining the closed position.

The valve may further comprise alignment means for circumferentially aligning the piston relative to the inner conduit. This ensures that the second and third parts align when the valve is in the open position.

Advantageously, the alignment means comprises a keyway formed in the inner conduit.

Preferably, the latching mechanism comprises a finger sleeve comprising a plurality of fingers, which fingers are engageable with an upper sleeve, which upper sleeve is in turn engageable with a spline on a spline sleeve, the finger sleeve being attachable to the piston.

When the valve is in the closed position, the piston is attached to the finger sleeve, which in turn is engaged with an upper sleeve. The fingers are biassed to grasp the upper sleeve and thus hold the piston in the closed position.

When pressure drops in the annulus relative to that within the inner conduit, the first port communicates that pressure to a lower portion of the piston. This differential pressure causes the piston to move downwards away from the upper sleeve. Movement of the piston in this direction causes the fingers of the finger sleeve to release from the upper sleeve, allowing the piston to continue its downward movement.

When the differential pressure reduces or disappears, the piston-will move towards the closed position, and the fingers will again grasp the upper sleeve locking the piston back into the closed position.

Preferably, the latching means is adjustable to release at any desirable differential pressure. The differential pressure at which the latching means releases is determined by the relative position of the spline sleeve within the inner conduit.

Advantageously the biassing means comprises a spring, positioned around a mandrel and below the piston. The piston is slideably moveable along the mandrel which is substantially co-axial with the piston. As the piston moves downward towards the open position, the movement of the piston compresses the spring. When the pressure differential reduces or disappears the compressed spring will urge the piston back to the closed position.

Preferably, the valve further comprises a deformable object, which is positionable within the piston to completely or partially block the internal passage of the piston. The presence of the deformable object results in fluid pressure above the piston building up, and a lower pressure within the inner conduit is required in order to cause the piston to move from the closed position to the open position.

Conveniently, the deformable object is a ball made from a plastics material, and the piston further comprises a ball seat for positioning the ball appropriately.

Advantageously, the valve further comprises a nondeformable object positionable on the deformable object, when it is required to re-set the valve. The non-deformable object is smaller than the deformable object and is positioned to partially or totally block the second port. This prevents passage of fluid from within the piston to the bore. This causes pressure to build up considerably to a point where the deformable object deforms sufficiently to be forced through the piston channel. Because the non-deformable object is smaller than the deformable object and the channel, it too will pass down the passage within the piston.

Preferably the non-deformable object is a steel ball.

Advantageously, the valve further comprises a ball catcher system, positioned towards the bottom end of the valve for retaining the plastic and steel balls.

Once the balls have been pulled down in the ball catcher, the differential pressure will be reduced and the biassing means will return the piston to the closed position.

The valve latch mechanism of the present invention has the advantage that it is easily reset and may be used in conjunction with "downhole BOPS", "adjustable stabilizers", "pressure activated circulating tools, "casing circulators" and "drilling jars". The tool may be suitable for use in other industrial applications for controlling fluid flow.

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a cross-sectional view of an inactivated drilling tool incorporating a valve latch mechanism according to the present invention allowing flow of fluids through the drill string; Figure 2 shows a cross-sectional view of a drilling tool incorporating to the valve latch mechanism of the present invention being set by use of a plastics ball; Figure 3 shows a cross-sectional view of an activated and set drilling tool being reset with the use of a steel ball; and Figures 4 and 5 illustrate a drilling tool incorporating a valve latch mechanism according to the present invention and comprising a ball valve.

Referring to the drawings in detail, Figure 1 shows a drilling tool, generally indicated by reference numeral 1, which is used to control the Passage of circulating fluids through a drill string 2. The drilling tool comprises three sections: an upper tool section 3 which houses adjusting means for controlling the setting and resetting of the tool; a middle tool section 4 which houses an activation mechanism which controls the passage of fluids through the tool and; a lower tool section 5 which captures a plastic ball and a steel ball which may be used to set and reset the system. Each of the tool sections is connected by known standard male and female threaded portions 6 and 7. The drilling tool is fitted between drill string sections by similar and standard threaded portions.

The upper tool section 3 houses adjusting means for controlling the setting and resetting of the tool (via a releasable latching mechanism), and which comprises a preloading spring 8, upper sleeve 9, spline sleeve 10 and finger sleeve 14 having fingers releasably engageable with upper sleeve 9. A spline 11 on the spline sleeve 10 engages the upper sleeve 9 and this positions the spline sleeve 10 in the upper tool section 3. The vertical position of the spline sleeve 10 within the upper tool section 3 determines when the tool is set or reset. Once a desired position is achieved the spline sleeve 10 may be locked in position by screw 12 which is threaded in the upper tool section 3 and which may be tightened externally. The upper face 13 of the upper sleeve 9 is machined to allow a wrench or other tool to engage it through the aperture of the upper tool section.Therefore, the tool may be set up, locked and then reset to a different activation force by using a wrench to turn the upper sleeve 9 which in turn moves the spline sleeve 10 changing the release setting of the finger sleeve 14 by being threaded in or out of the upper tool section 3.

The middle tool section 4 houses an activation mechanism which controls the passage of fluids through the tool, and which comprises the finger sleeve 14 having a plurality of fingers which engage the upper sleeve 9 (as shown in Figure 1).

A piston 16 is connected to the finger sleeve 14 and is slidable within the middle toQlsec-uQn4- The mid1e too section has a port 17 through which fluids within the tool may flow when the port 17 is aligned with port 18 in the piston 16, thereby providing a path for fluids out into the annulus or space between the drill string and the bore. When the pressure within the tool increases relative to the pressure in the annulus the pressure differential acts on the piston and causes it to move down. The bottom surface of the piston 16 is exposed to the annulus pressure and the top surface of the piston 16 is exposed to the pressure within the drill string.

The downward displacement of the piston 16 is controlled and balanced by springs 19. As the piston 16 moves it pulls on the fingers of the finger sleeve 14 which in turn causes the springs 19 to compress. When the internal diameter of the fingers is greater than the dimension of the upper sleeve 9 the fingers are released from the upper sleeve 9 and slide downwards until the piston is stopped by shoulder 20 on the internal surface of the middle tool section 4. In this position the port 18 in the piston 16 and the port 17 in the middle tool section 4 are aligned and fluid is allowed to flow from the drill string into the annulus and by-pass the drill bit. Circumferential misalignment of the ports is prevented by the keyway 21 in the internal surface of the middle tool section 4 and along which the piston 16 slides.The pump pressure must be maintained to keep the ports 17 and 18 aligned. As the pressure is reduced the main spring 22 acts on the piston and causes upward sliding motion within the middle tool section 4. The ports 17 and 18 are no longer aligned and fluid flow into the annulus stops. The main spring 22 continues to act on the piston forcing the fingers of sleeve 14 into engagement with the upper sleeve 9 thereby resetting the tool. Therefore, the tool is set by a sufficient increase in internal pressure and is reset by a reduction in internal pressure.

Referring to figures 2 and 3 the tool may be set by dropping a plastic ball 30 down the drill string. The plastic ball 30 is pushed through the drill string and becomes seated on a--bal7--seat 31 in the upper surface of the-plston 14--. This immediately seals the internal passage through the tool causing an increase in pressure above the ball which depresses the piston 16 in a similar manner to that described above. Once the ports 17 and 18 are aligned fluids may flow from within the tool to the annulus. Use of the plastic ball has the advantage that lower pressures may be used to set the tool. To reset the tool the plastic ball 30 must be unseated and this is achieved by increasing the internal pressure to force the plastic ball 30 through the piston flow passage in the piston 16. The plastic ball 30 is deformed during this process.However, as the port 17 is relatively large (about 4 cms) it is difficult to achieve an internal pressure which is capable of forcing the plastic ball 30 through the piston 16. Therefore, a steel ball 31 is dropped into the drill string and this rests on top of the plastic ball 30 and blocks the port 18. An increase in internal pressure immediately results and the plastic ball is forced through the piston flow passage. Once the plastic ball 30 has passed through the piston the pressure falls and the steel ball 31 drops and also passes through the piston flow passage. The steel ball 31 has a diameter smaller than the flow passage in the piston 16 and does not disrupt flow nor does it need to deform. With both balls released the tool resets by the action of main spring 22.

The lower tool section 5 houses a ball retaining sleeve 40 which prevents either of the released balls 30 or 31 from blocking the drill bit but allows free flow of fluids through the tool and through the drill bit. The number of times that the tool may be set and reset using this method is limited to the ball capacity of the ball retaining sleeve 40 ie. to the number of steel and plastic balls that may be retained in the ball retaining sleeve 40.

Referring to Figures 4 and 5, an alternative embodiment has a ball valve 50 which may be used in place of the two balls 30, 31 to set and re-set the latch mechanism. This does not require the use of steel or plastic balls to block the appropriate flow ports in the tool. At a sufficiently high internal pressure a-2istoo-52--of-the valve 50 (replacing piston 16 of Figures 1 to 3) slides downwards and the fingers of the finger sleeve 14 are released. A pin 51 adjoining the ball valve 50 to the piston 52 acts to roll the ball valve closed.

This stops the flow of fluid below the tool and all fluid moves out of the port 17. When the internal pressure is reduced the tool resets in a similar manner to that described above. With this arrangement there is no need for the ball retaining sleeve.

Claims

1. A valve having a releasable latch mechanism and for controlling the flow of liquid within an outer conduit, the valve comprising: an inner conduit positionable substantially co-axially within the outer conduit ar,ddefining--an annulus between the outer conduit and the inner conduit; a first port formed in the wall of the inner conduit for communicating annulus pressure into the inner conduit; a piston moveable axially within the inner conduit between a closed position and an open position, the piston comprising a second port allowing passage of fluid from within the piston into the inner conduit, and further comprising a passage extending through the piston; latching means for holding the piston in the closed position; and biassing means for biassing the piston to the closed position, and a third port formed in the wall of the inner conduit; wherein when the piston is in the open position the second and third ports are aligned, allowing passage of fluid from within the piston to the outer conduit, thus by-passing the inner conduit.

2. A valve according to Claim 1, including abutment means arranged to abut with the piston in the closed position, thus defining the closed position.

3. A valve according to Claim 1, comprising alignment means for circumferentially aligning the piston relative to the inner conduit.

4. A valve according to Claim 1, in which the latching mechanism comprises a finger sleeve attached to said piston, an upper sleeve, and a plurality of fingers provided on the finger sleeve and engageable with said upper sleeve to hold the piston in the closed position.

5. A valve according to Claim 4, in which the upper sleeve is adjustable whereby the latching means can be set to release at any desired differential pressure.

6. A valve according to Claim 1, in which the biasing means comprises a mandrel arranged below the piston, and a spring surrounding said mandrel.

7. A valve according to Claim 1, including a deformable object which can be introduced into the valve in order to at least partially block the internal passage of the piston in order to initiate release of the piston from the closed position.

8. A valve according to Claim 7, in which the deformable object comprises a ball made from plastics material, and said piston is formed with a seat to receive said ball.

9. A valve according to Claim 7, including a nondeformable object positionable on said deformable object, when it is required to re-set the valve.

10. A valve according to Claim 9, in which the nondeformable object comprises a steel ball.

11. A valve according to Claim 10, including a ball catcher system, positioned towards the bottom end of the valve for retaining the plastic ball and the steel ball.

12. A valve according to Claim 1, in which said piston forms part of a ball valve arrangement having a pin responsive to downward movement of said piston in order to close the ball valve and thereby prevent passage of fluid through the ball valve and which is thereby diverted to the outer conduit.