Field

This invention relates to a downhole disconnect tool, downhole tool assembly and method.

Background

In the oil and gas industry, wells boreholes are drilled to access subsurface hydrocarbon-bearing rock formations, the well boreholes typically then being lined ("cased") with sections of bore-lining tubing which are cemented or otherwise secured in place.

During the drilling of a borehole, there are occasions where it is necessary or desirable to disconnect a portion of the drill string. For example, when the drill string becomes stuck in the borehole and it is not possible to release it, it may be necessary to disconnect the drill string above the point where it has become stuck in the borehole in order to allow the free portion of the drill string to be retrieved to the surface.

Conventionally, the disconnection of the drill string may be achieved by means of cutting tools or explosives, this being carried out only as a last resort when all other attempts have failed.

Alternatively, specialised mechanical disconnect tools can be used. However, there are a number of drawbacks with conventional tools and equipment.

For example, it is often not practical to run a conventional specialised mechanical disconnect tool in the drill string because it is not possible to predict at which point a drill string may get stuck in the borehole.

The use of conventional specialised disconnect tools is also limited due to operational or size limitations.

Moreover, conventional specialised tools suffer from poor reliability and are not sufficiently robust for operation in the drilling environment. For example, conventional specialised disconnect tools require left hand rotation from surface and/or utilise complex movable latch mechanisms which, although adequately strong for running in and releasing from a drill string, are not suitable when subjected to the cyclic bending, torsional and/or longitudinal vibration experienced over long periods in the drilling process. Summary

According to a first aspect of the present invention, there is provided a downhole disconnect tool configured for coupling to, or forming part of, a downhole tool string, the downhole disconnect tool comprising:

a first member configured for coupling to, or forming part of, a first portion of the downhole tool string;

a second member configured for coupling to, or forming part of, a second portion of the downhole tool string;

a coupling arrangement for releasably coupling the first member to the second member; and

a disconnect arrangement configured to convert an axial input force applied to the disconnect tool into a rotary output force on the first member to disconnect the first member and the second member and permit disconnection of the first portion of the downhole tool string from the second portion of the downhole tool string.

The disconnect tool may be configured for location between the first, e.g. uphole, portion of the downhole tool string and the second, e.g. downhole, portion of the downhole tool string.

In use, the disconnect tool may be run into a borehole as part of a tool string, e.g. a downhole drill string, the disconnect tool being operable to permit part of the tool string below the disconnect tool to be disconnected, for example in the event the tool string has become stuck in the borehole.

Beneficially, embodiments of the present invention permit disconnection of a portion of a tool string in the borehole, and without the requirement to apply rotation from surface. Embodiments of the present invention are capable of withstanding the tensile, compressive and torsional loads, fluid flows, pressures and temperatures of the other drill string components in which the disconnect tool is run. Moreover, embodiments of the present invention can withstand long periods of downhole rotation within the drilling process where it could be subjected to significant cyclic bending, torsional and longitudinal vibrations without failure and maintaining reliable operation.

Embodiments of the present invention may be particularly suited for downhole operations which require a robust and reliable connection during drill string operable while also permitting a portion of the tool string to be disconnected; after long periods of rotation in the borehole. Such operations may, for example, include deep water drilling for well testing, or hanging off the drill string at the subsea blow out preventer (BOP) in bad weather or disconnecting the string from a downhole BOP system in the event of severe gas influx.

As described above, the disconnect tool comprises a first member configured for coupling to, or forming part of, a first portion of the downhole tool string.

The first member may take the form of a first, lower, sub of the disconnect tool.

The first member may be tubular.

The first member may comprise a throughbore.

The first member may comprise a body.

The first member may comprise a connector for connecting the first member to the second member of the disconnect tool. This connector may form part of the coupling arrangement of the disconnect tool.

The connector for connecting the first member to the second member of the disconnect tool may be formed or otherwise provided in the body.

The connector for connecting the first member to the second member of the disconnect tool may comprise a threaded connector.

In particular embodiments, the connector for connecting the first member to the second member of the disconnect tool may comprise a threaded box connector.

In other embodiments, the connector for connecting the first member to the second member of the disconnect tool may comprise a threaded pin connector.

In particular embodiments, the connector for connecting the first member to the second member of the disconnect tool may comprise a coarse pitch thread.

Beneficially, the flank contact between the thread connections of the first member and the second member provides torsional, tensile, compressive and bending strength in excess of the drill string connections. The thread connections which define sections without thread profile enable a pin to be inserted into a box without requiring full rotation of the body. A partial rotation of one of the first or second bodies relative to the other causes the thread course pitch of the pin to engage the thread course pitch of the box, thus securing the connection of the first and second tubular bodies.

In particular embodiments, the connector for connecting the first member to the second member of the disconnect tool may be interupted, that is having clear regions machined or otherwise formed thereon at regular angular intervals.

Beneficially, the coarse pitch and/or interupted thread permits the first member and second member to be coupled and decoupled without the need for rotation of the tool string, requiring only a partial turn to fully make up the connection. In particular embodiments, the connector for connecting the first member to the second member of the disconnect tool may comprise a single start thread.

In other embodiments, the connector for connecting the first member to the second member of the disconnect tool may comprise a multiple start thread.

The first member may comprise a connector for connecting the first member to the first portion of the tool string.

The connector for connecting the first member to the first portion of the tool string may comprise a threaded connector.

In particular embodiments, the connector for connecting the first member to the first portion of the tool string comprises a threaded pin connector.

The first member may comprise a splined profile portion.

The splined profile portion may be formed or otherwise provided on the body of the first member.

The splined profile portion may be formed or otherwise provided on the interior surface of the body of the first member.

As described above, the disconnect tool comprises a second member configured for coupling to, or forming part of, a second portion of the downhole tool string.

In particular embodiments, the second portion of the downhole tool string may comprise an actuator tool with which the disconnect tool is coupled or operatively associated.

The second member may take the form of a second, upper, sub of the disconnect tool.

The second member may be tubular.

The second member may comprise a throughbore.

The second member may comprise a body.

The second member may comprise a connector for connecting the second member to the first member of the disconnect tool. This connector may form part of the coupling arrangement of the disconnect tool.

The connector for connecting the second member to the first member of the disconnect tool may be formed or otherwise provided in the body.

The connector for connecting the second member to the first member of the disconnect tool may comprise a threaded connector.

In particular embodiments, the connector for connecting the second member to the first member of the disconnect tool may comprise a threaded pin connector. In other embodiments, the connector for connecting the second member to the first member of the disconnect tool may comprise a threaded box connector.

In particular embodiments, the connector for connecting the second member to the first member of the disconnect tool may comprise a coarse pitch thread. The coarse pitch thread may be configured to match the pitch of the first member.

Beneficially, the flank contact between the thread connections of the first member and the second member provides torsional, tensile, compressive and bending strength in excess of the drill string connections. The thread connections which define sections without thread profile enable a pin to be inserted into a box without requiring full rotation of the body. A partial rotation of one of the first or second bodies relative to the other causes the thread course pitch of the pin to engage the thread course pitch of the box, thus securing the connection of the first and second tubular bodies.

In particular embodiments, the connector for connecting the second member to the first member of the disconnect tool may be interupted, that is having clear regions machined or otherwise formed thereon at regular angular intervals.

Beneficially, the coarse pitch and/or interupted thread permits the first member and second member to be coupled and decoupled without the need for rotation of the tool string, requiring only a partial turn to fully make up the connection.

In particular embodiments, the connector for connecting the second member to the first member of the disconnect tool may comprise a single start thread.

In other embodiments, the connector for connecting the second member to the first member of the disconnect tool may comprise a multiple start thread.

The second member may comprise a connector for connecting the second member to the second portion of the tool string.

The connector for connecting the second member to the second portion of the tool string may comprise a threaded connector.

In particular embodiments, the connector for connecting the second member to the second portion of the tool string comprises a threaded box connector.

In other embodiments, the connector for connecting the second member to the second portion of the tool string comprises a threaded pin connector.

As described above, the disconnect tool comprises a disconnect arrangement configured to convert an axial input force applied to the disconnect tool into a rotary output force on the first member to disconnect the first member and the second member and permit disconnection of the first portion of the downhole tool string from the second portion of the downhole tool string. The disconnect arrangement may be configured to convert the axial input force applied to the disconnect tool into the rotary output force and an axial output force on the first member.

The disconnect tool may comprise a torque member.

The torque member may form part of the disconnect arrangement of the disconnect tool.

The torque member may be disposed between the first member and the second member.

The torque member may be tubular.

The torque member may comprise a throughbore.

The torque member may comprise a body.

The torque member may comprise a splined profile portion.

The splined profile portion may be formed or otherwise provided on the body of the torque member.

The splined profile portion may be formed or otherwise provided on the exterior surface of the body of the torque member.

The torque member may be coupled to the first member, rotation of the torque member configured into axial and/or rotational movement of the first member;

facilitating disconnection of the first member and the second member.

The disconnect tool may comprise a piston and cylinder arrangement.

The piston and cylinder arrangement may form part of the disconnect arrangement of the disconnect arrangement.

The piston and cylinder arrangement comprises a piston member.

The piston and cylinder arrangement comprises a cylinder.

The piston member is disposed within the cylinder.

In particular embodiments, the piston member is coupled to, or formed with, the torque member. In use, axial movement of the piston member moves the torque member.

The disconnect tool may comprise a cam arrangement.

The cam arrangement may form part of the disconnect arrangement of the disconnect tool.

The cam arrangement may comprise a rotating cam arrangement.

The cam arrangement may comprise a torque sleeve.

The torque sleeve may be configured (not to rotate) to be static with respect to at least one of the first or second members. The torque sleeve may define one or more cam slots. The cam slot or slots may define a bent path. The cam slot or slots may define a spiral path.

The cam arrangement may comprise a torque sub.

The torque sub may be integral with the torque member.

The torque sub may be configured to engage with the torque sleeve.

The torque sub may comprise cam followers.

The cam followers may be configured to engage with the cam slot or slots of the torque sleeve.

The cam followers may be configured to freely move in the cam slot or slots slots of the torque sleeve.

The disconnect tool may comprise a biasing member.

The biasing member may form part of the disconnect arrangement of the disconnect tool.

The biasing member may take the form of a spring.

The biasing member may comprise a compression spring.

The resilient element may bias the tool towards the first extended configuration.

In use, movement of the piston member will cause the piston member to move down against the biasing member.

The disconnect tool may comprise a seal arrangement.

In particular embodiments, the seal arrangement may comprise one or more seal elmeent, such as an o-ring seal element. The seal arrangement may prevent or at least mitigate fluid leakage between the coupling arrangement between the first member and the second member.

A connected throughbore may be provided through the disconnect tool, permitting fluid and/or tool passage through the disconnect tool.

The downhole disconnect tool may be configured to be activated by means of an axial force.

The axial force may be mechanical or hydraulic force.

The axial force may cause the torque member to move with respect to the second tubular body.

The torque tube may be configured to move in a clockwise fashion with respect to the second tubular body.

Activation of the tool causes the torque tube to overcome the bias and move from the first extended configuration to the second, retracted configuration. Activation of the tool causes the torque tube to move inside the second tubular body following the path of the cam slots in the cam sleeve. When passing from the first extended configuration to the second, retracted configuration the torque tube compresses the resilient element overcoming the bias.

In particular embodiments, the disconnect tool may be configured for activation by a downhole actuator tool.

Beneficially, embodiments of the present invention permit activation of the disconnect tool in real time from surface without the need for drill string rotation.

In other embodiments, the disconnect tool may be configured for activation by wireline jar, fluid pressure or other mechanical means.

Alternatively or additionally, the disconnect tool may be configured to receive an actuation member, such as a ball. The disconnect tool may be configurable to operate in response to landing the actuation member on the disconnect tool. Beneficially, embodiments of the invention permit the disconnect tool to be operated in the event an associated actuator tool fails to operate, and/or where the operator desires such an actuation method to be provided.

The downhole disconnect tool may comprise a lock.

The coupling arrangement may form, or may form part of, the lock.

Additionally or alternatively, the disconnect arrangement when not activated to disconnect the first member and the second member may be configured to lock the first member and the second member.

The lock may be configured to prevent rotation of the first and second members relative to the torque member, or vice versa.

The lock may be formed by the interaction between the splined section of the torque member and the splined section of the first member.

The lock may be configured to be released by axial movement of the piston assembly.

The disconnect tool may be coupled to, or formed part of, a downhole tool assembly.

The disconnect tool may comprise a clutch arrangement.

The clutch arrangement comprises a dog clutch.

In use, the parallel section of the spiralled groove form of the cam groove may be used to push the clutch arrangement out of engagement before the spiralled section of the cam groove disconnects the first member and the second member.

Beneficially, the provision of the clutch arrangement supplements the back out resistance of the connection between the first member and the second member. According to a second aspect of the present invention, there is provided a downhole tool assembly comprising:

the downhole disconnect tool of the first aspect; and

a downhole actuator tool.

The downhole actuator tool may comprise:

a body;

an actuation member moveable relative to the body;

an actuation arrangement configured to move the actuation member relative to the body; and

a lock configured in a first configuration to permit movement of the actuation member by the actuation arrangement and configured in a second configuration to provide a fluid lock across the actuation member which prevents movement of the actuation member by the actuation arrangement.

The downhole actuator tool may be integrally formed one or more downhole tool or device to be controlled or may be configured to engage and control actuation of said one or more associated downhole tool or device to be controlled. For example, the downhole actuator tool may define a lock module or lock sub coupled to the downhole tool or device to be controlled. Any suitable means for engaging the associated downhole tool or device to be controlled may be utilised. The actuation member of the downhole actuator tool may be configured for direct attachment to, or otherwise configured to directly engage, the actuation mechanism or systems of the tool or device to be controlled. By way of example, the actuation member of the downhole actuator tool may be utilised with a biasing piston or the like to move a sliding sleeve or other type of valve system to allow drill string pressure to act on the actuation piston or operating components of the tool or device to be controlled. Alternatively, or additionally, the actuation member of the downhole actuator tool may be used with a biasing piston or the like to release and or re- apply a mechanical sear or trigger mechanism to pull a supporting sleeve from a finger collet type locking system or the like.

Beneficially, embodiments of the present invention may provide a downhole actuator tool for selectively actuating or operating an associated downhole tool or device and which is simple, reliable, is capable of real time activation, is selectively isolated from normal pumping flow and pressure requirements, and which permits the passage of further downhole tools, devices or equipment through the tool and does not require additional elements such as balls, darts or RFID tags to be pumped from surface to operate.

Providing a selective fluid lock across the actuation member may permit the actuation member to be locked or held in place at any required position or stage of operation and for any required time interval. Since the actuation member is incapable of movement while the fluid lock is in place, the actuator tool can be isolated from pressures, such as normal pumping flow and other pressure events, or other forces in the bore which may otherwise act on the actuation member.

The downhole actuator tool may be operable between a retracted configuration and an extended configuration. The downhole actuator tool may be configured so that movement of the actuation member from the retracted configuration to the extended configuration performs, or permits performance of, a downhole operation. For example, movement of the actuation member from the retracted configuration to the extended configuration may apply a push force to an associated tool or device. Alternatively, or additionally, the downhole actuator tool may be configured so that movement of the actuation member from the extended configuration to the retracted configuration performs, or permits performance of, a downhole operation. For example, movement of the actuation member from the extended configuration to the retracted configuration may apply a pull force to an associated tool or device.

The lock may be of any suitable form and construction.

The lock may be configured to retain the actuation member in the retracted configuration. The lock may be configured to retain the actuation member in the extended configuration. The lock may be configured to retain the actuation member in one or more intermediate position between the retracted configuration and the extended configuration.

The lock may be separate from and/or isolated from the actuation arrangement.

The lock may comprise a closed fluid system.

The tool may comprise a first fluid chamber. The first fluid chamber may comprise an annular chamber. The tool may comprise a second fluid chamber. The second fluid chamber may comprise an annular chamber.

The lock may be configured in the first configuration to permit fluid communication between the first fluid chamber and the second fluid chamber (that is, from the first fluid chamber to the second fluid chamber or vice-versa) and configured in the second configuration to prevent fluid communication between the first fluid chamber and the second fluid chamber. By preventing fluid communication between the first fluid chamber and the second fluid chamber, the fluid lock may be created across the actuation member to lock the actuation member and prevent movement of the actuation member by the actuation arrangement.

The first fluid chamber and the second fluid chamber may be configured to receive a fluid. The fluid may comprise a hydraulic fluid, such as hydraulic oil or other suitable fluid. Providing a substantially incompressible fluid in a closed fluid system permits the fluid lock to be created across the actuation member in use.

A fluid communication arrangement may communicate the fluid between the first fluid chamber and the second fluid chamber. The fluid communication arrangement may be of any suitable form and construction. The fluid communication arrangement may comprise at least one fluid passage or gallery. At least part of the fluid communication arrangement may be formed or otherwise provided in the body of the actuator tool. Alternatively, or additionally, at least part of the fluid communication arrangement may comprise a fluid conduit, such as a hydraulic line or the like.

The lock may comprise a valve. In use, the valve may be movable between an open condition and a closed condition to selectively permit fluid communication between the first fluid chamber and the second fluid chamber.

The valve may be of any suitable form and construction.

The valve may comprise a control valve.

The valve may be logic controlled.

In some embodiments, the valve may comprise an electro-mechanical valve. The valve may comprise a pilot valve. The valve may comprise a solenoid valve. In particular embodiments, the valve may comprise single coil piloting solenoid valve or the like.

In other embodiments, the valve may comprise a hydraulic valve, or valve arrangement or the like.

The hydraulic valve arrangement may be of any suitable form and construction. The hydraulic valve arrangement may comprise an actuating arrangement. The hydraulic valve actuating arrangement may comprise a piston. The hydraulic valve actuating arrangement may comprise a first fluid chamber and a second fluid chamber. The first chamber may communicate with annulus pressure. The second chamber may communicate with throughbore or string pressure within the downhole actuator tool. The hydraulic valve actuating arrangement may comprise a biasing member, such as a spring. In use, changes in the differential pressure between throughbore pressure and annulus pressure may act on the piston to translate the piston. In particular embodiments, the hydraulic valve actuating arrangement may be operable at a significantly lower pressure than that used to operate the system that it controls.

The hydraulic valve arrangement may comprise a linear return and delay arrangement. The linear return and delay arrangement may comprise a piston and cylinder arrangement. The piston and cylinder arrangement may comprise a piston disposed within an oil-filled cylinder. The linear return and delay arrangement may be configured so that the piston has a slow stroke and fast stroke. In particular

embodiments, the linear return and delay arrangement may be configured so that the piston has a slow outward stroke and fast return stroke. The linear return and delay arrangement comprise a choke or fluid restriction device. In use, the choke or fluid restriction device may control or provide the slow outward stroke. The linear return and delay arrangement comprise a non-return valve. In use, the non-return valve may control or provide the fast return stroke.

The hydraulic valve arrangement may comprise a cam arrangement. The cam arrangement may comprise a rotating cam arrangement. In particular embodiments, the cam arrangement may comprise a rotating j slot cam. The cam arrangement may comprise or define a plurality of paths. The cam arrangement may comprise or define a short stroke and a long stroke.

The hydraulic valve arrangement may comprise pilot valve. The pilot valve may be of any suitable form and construction. In particular embodiments, the pilot valve may comprise a spool type pilot valve. The pilot valve may permit selective

communication between the first fluid chamber of the downhole tool and the second fluid chamber of the downhole actuator tool.

The hydraulic valve arrangement may be configured to provide for a short cycle in a closed position and a long stroke in an open position.

The body of the actuator tool may be of any suitable form and construction.

The body may have a throughbore. The actuation member may be disposed in the body throughbore.

The body may comprise a unitary component. In particular embodiments, the body may comprise a modular body.

The actuator tool may form part of a downhole tool string. A connection arrangement may be provided for coupling the downhole tool to other components of the tool string. The connection arrangement may comprise threaded connectors, such as a threaded box and pin connectors. The actuation member may be of any suitable form and construction. The actuation member may comprise a mandrel. The actuation member may comprise a piston. The actuation member may comprise a double acting piston. The actuation member may comprise an axial passage or throughbore. The actuator tool may be configured so that the throughbore permits the passage of an object, for example but not exclusively a downhole tool, therethrough.

The actuator tool may be configured to activate the fluid lock in response to a selected activation event. The activation event may be of any suitable form.

The activation event may comprise an activation signal. The activation signal may be transmitted from surface.

The activation event may, for example, comprise a sequence of pressure changes in a particular time interval. The downhole actuator tool may comprise one or more pressure sensor or transducer. By way of example, the activation event may comprise a sequence of turning fluid pumps at surface on and off in a predetermined sequence over a predetermined time interval. Any sequence or time interval may be used, as appropriate.

Alternatively or additionally, the activation event may comprise or involve a movement, for example but not exclusively a movement of the tool string. The downhole tool may comprise one or more movement sensor, accelerometer or the like. In particular embodiments, the accelerometer may comprise a tri-axial accelerometer. In use, the downhole tool may be configured to interpret a sequence of movement as opposed in order to actuate.

Alternatively or additionally, the activation event may comprise a mud pulse or the like.

The activation event may correspond to a selected activation command for the downhole actuator tool and the downhole actuator tool may be configured to carry out the activation command in response to the activation event. By way of example, but not exclusively, the downhole actuator tool may be configured to unlock for a period of one minute, three minutes, five minutes or ten minutes on receipt of a particular activation signal.

The downhole actuator tool may comprise a control system for interpreting the or each activation signal.

The downhole actuator tool may comprise a communication arrangement for communicating with surface. The communication arrangement may be configured to receive the activation event. The communication arrangement may additionally be configured to transmit information to surface.

The downhole actuator tool may comprise an onboard power supply. The onboard power supply may comprise a battery or battery pack. In particular embodiments, the tool may be configured so that the onboard power supply need only supply power to the lock. Beneficially, it will be recognised that the lock may require a comparatively little amount of power to operate since the lock may not itself actuate the actuation member, this being operated by the actuation arrangement of the downhole tool. The downhole actuator tool may alternatively or additionally receive at least some power from surface.

The actuation arrangement may be of any suitable form and construction.

The actuation arrangement may comprise a piston. The actuation arrangement may be moveable relative to the body in response to a fluid pressure in the throughbore. Alternatively or additionally, the actuation arrangement may be moveable relative to the body in response to a fluid pressure in a bore annulus.

The actuation arrangement may be directly coupled to the actuation member. Alternatively, the actuation member may be operatively coupled to the actuation member.

The actuator tool may comprise a biasing member, such as a spring. The biasing member may be operatively associated or form part of the actuation arrangement. In use, the biasing member may be configured to bias the actuation member to a retracted position.

According to a third aspect of the present invention, there is provided a method of disconnecting a first portion of a tool string from a second portion of a tool string, comprising:

applying an axial force to a downhole disconnect tool according to the first aspect, the disconnect tool converting the applied axial force into a rotary output force for disconnecting the first member of the disconnect tool and the second member of the disconnect tool and permit disconnection of the first portion of the downhole tool string from the second portion of the downhole tool string.

It should be understood that the features defined above in accordance with any aspect of the present invention or below in relation to any specific embodiment of the invention may be utilised, either alone or in combination, with any other defined feature, in any other aspect of the invention. Brief Description of the Drawings

These and other aspects will now be described by way of example with reference to the drawings, of which:

Figure 1 shows an isometric view of a downhole disconnect tool according to an embodiment of the invention;

Figure 2 shows a ghosted isometric view of the downhole disconnect tool shown in Figure 1 ;

Figure 3 shows an exploded isometric view of the downhole disconnect tool shown in Figure 1 ;

Figure 4 shows an enlarged view of a lower sub of the downhole disconnect tool shown in Figure 3;

Figure 5 shows an enlarged view of an upper sub of the downhole disconnect tool shown in Figure 3;

Figure 6 shows an exploded perspective view of part of the downhole disconnect tool shown in Figure 1 ;

Figures 7 to 12 show a cam arrangement of the downhole disconnect tool shown in Figure 1 ;

Figure 13 shows a perspective view of a downhole tool assembly comprising the downhole disconnect tool shown in Figure 1 ;

Figure 14 shows an exploded view of the downhole tool assembly shown in

Figure 13;

Figure 15 shows a longitudinal section view of a downhole actuator tool according to a first embodiment of the present invention, the actuator tool shown in a retracted configuration;

Figure 16 shows a longitudinal section view of the downhole actuator tool shown in Figure 15, shown in an extended configuration;

Figure 17 shows a schematic view of a control system for use in embodiments of the actuator tool;

Figure 18 shows a valve tool in the form of a float shoe with which the downhole disconnect tool shown in Figure 1 is operatively associated; and

Figures 19 to 22 show a downhole disconnect tool according to another embodiment of the invention. Detailed Description of the Drawings

Referring first to Figures 1 to 1 1 of the accompanying drawings, there is shown a downhole disconnect tool 10 according to an embodiment of the present invention.

In use, the disconnect tool 10 is configured to form part of a downhole tool assembly 100 which is run into a borehole B as part of a tool string 1000, such as a drill string (see Figures 12 and 13), the disconnect tool 10 being operable to permit part of the tool string 1000 below the disconnect tool 10 to be disconnected, for example in the event the tool string 1000 has become stuck in the borehole B.

As shown, the disconnect tool 10 comprises a first, lower, sub 12 and a second, upper, sub 14.

The first, lower, sub 12 has a generally tubular body 16 defining a throughbore

18.

A connector 20 for connecting the first, lower sub 12 to the second, upper, sub 14 is provided at a first end (right end as shown in Figures 3, 4 and 5) of the first, lower, sub 12. The connector 20 takes the form of a threaded female or box connector having an internal thread 22 machined or otherwise formed thereon. The thread 22 has a coarse pitch. In the illustrated embodiment, the thread 22 is a single start thread. However, in other embodiments the thread 22 may be a multiple start thread. The thread 22 is interrupted, having clear regions 24 machined or otherwise formed thereon at regular angular intervals.

A connector 26 for connecting the first, lower, sub 12 to an adjacent (downhole) component of the string 1000 is provided at a second end (left end as shown in Figures 3, 4 and 5) of the first, lower, sub 12. In the illustrated embodiment, the connector 26 comprises a threaded male or pin connector having an external thread 28. However, it will be understood that the connector 26 may alternatively comprise a threaded female or box connector.

The second, upper, sub 14 has a generally tubular body 30 defining a throughbore 32.

A connector 34 for connecting the second, upper, sub 14 to the first, upper, sub 12 is provided at a first end (left end as shown in Figure 3, 4 and 5) of the second, upper, sub 14. The connector 34 takes the form of a threaded male or pin connector having an external thread 36 machined or otherwise formed thereon. The thread 36 has a coarse pitch configured to match the thread 22 on the first, lower, sub 12. In the illustrated embodiment, the thread 36 is a single start thread. However, in other embodiments the thread 36 may be a multiple start thread. As with the thread 22, the thread 36 is interrupted, having clear regions 38 machined or otherwise formed thereon at regular angular intervals.

A connector 40 for connecting the second, upper, sub 14 to an adjacent

(uphole) component of the string 1000 is provided at a second end of the second, upper, sub 14 (right end as shown in Figures 3, 4 and 5). In the illustrated embodiment, the connector 40 comprises a threaded female or box connector having an internal thread 42. However, it will be understood that the connector 40 may alternatively comprise a threaded male or pin connector.

In use, the connector 34 of the second, upper, sub 14 engages the connector 20 of the first, lower, sub 12, with a shoulder 44 on the second, upper, sub 14 engaging a shoulder 46 on the first, upper, sub 12. Beneficially, the interupted thread profiles permit the pin of the upper sub 14 to be inserted into the box of the lower sub 12 without the need for rotation, requiring only a partial turn to fully make up the connection between the lower sub 12 and upper sub 14.

A seal arrangement, which in the illustrated embodiment comprises one or more o-ring seal element 48 disposed within a groove 50 in second, upper, sub 14 prevents fluid leakage between the connector 34 and the connector 20.

A piston and cylinder arrangement 52 is provided in the tool 10, the body 30 of the second, upper, sub 14 defining a cylinder 54 configured to receive a piston member 56. The piston member 56 is slidably disposed in the cylinder 54. A seal arrangement, which in the illustrated embodiment comprises one or more o-ring seal element 58 in the piston member 56, prevents fluid leakage between the piston member 56 and the cylinder 54.

A torque tube 60 extends from the piston member 56 and, in use, forms a piston rod of the piston and cylinder arrangement 52, the torque tube 60 moving axially with axial movement of the piston member 56 within the cylinder 54. As shown, the torque tube 60 extends through the connector 34 of the second, uphole, sub 14 and into and through the first, lower, sub 12.

As shown in Figure 3, 4 and 5, the torque tube 60 has a spline profile 62. The spline profile 62 is formed or otherwise provided on an external surface portion of the torque tube 60. The torque tube 60 is configured so that the spline profile 62 engages a corresponding internal spline portion 64 formed or otherwise provided on an internal surface portion of the first, lower, sub 12. When in the made up condition, i.e. with the connector 34 of the second, upper, sub 14 engaging the connector 20 of the first, lower, sub 12, the spline profile 62 of the torque tube 60 mates with the spline profile 64 of the first, lower, sub 12.

The disconnect tool 10 further comprises a torque sub 66. In the illustrated embodiment, the torque sub 66 is integrally formed with the piston 56. The torque sub 66 extends in an opposite direction to that of the torque tube 60 (to the right as shown in the drawings), the torque sub 66 located at an uphole location relative to the piston 56.

The disconnnect tool 10 further comprises a torque sleeve 68. The torque sleeve 68 is generally tubular in construction having a thoughbore 70. The torque sleeve 68 is provided in a fixed non-rotatable position within a larger diameter portion of the cylinder 54 of the upper sub 14. The torque sleeve 68 is configured for location on the torque sub 66.

A cam arrangement is provided by/between the torque sleeve 68 and the torque sub 66, the torque sleeve 68 comprising one or more cam slot 72 configured to engage cam followers 74 provided on the torque sub 66.

The cam followers 74 move within the cam slots 72 in the torque sleeve 68. The disconnect tool 10 is configured so that axial force applied to the torque sleeve 68 is translated into rotational movement of the torque sub 66, piston member 56 and torque tube 60.

A biasing member, which in the illustrated embodiment comprises a compression spring 76 forms a return spring of the disconnect tool 10. The compression spring 76 is provided between the second, upper, sub 14 and the piston member 56. The compression spring 76 is configured for location within the larger diameter portion of the cylinder 54. The compression spring 76 is configured to urge the piston member 56 in an uphole direction (to the right as shown in Figures 3 to 5). The compression spring 76 is restrained from downward movement by the shoulder 44 of the second, upper, sub 14.

In use, movement of the piston member 56 will cause the piston member 56 to move down against the compression spring 76, as described further below.

It will be recognised that a connected throughbore 78 is provided through the disconnect tool 10 via the connected throughbores of the torque tube 60, piston member 56 and torque sub 66, permitting fluid and/or tool passage through the disconnect tool 10.

Referring now also to Figures 7 to 12 of the accompanying drawings, the disconnect tool 10 is assembled with the upper sub 14 stabbed into the lower sub 12 such that the tapered pin connection thread 36 is fully inserted into the tapered box connection thread 22. In use, a downward force applied to the piston member 56, e.g. provided by mechanical or hydraulic means, will cause the piston member 56 and torque sub 60 to move down against the action of the compression spring 76.

As the torque sub 60 is constrained within the torque sleeve 68 by the cam followers 74, it will follow the path of the cam slots 72, thereby rotating the torque tube 60 in a clockwise or right-hand direction with respect to the upper sub 14 (and/or turning the upper sub body in an anti-clockwise or left-hand direction with respect to the torque tube 60).

With the piston member 56 fully down against the compression spring 76 and the cam followers 74 at the bottom of the cam slots 72, the torque tube 60 will be fully rotated clockwise when the spline profile 62 engages in its mating spline profile 64 in the lower sub 12.

Release of the downward force applied the piston member 56, e.g. provided by mechanical or hydraulic means, will allow the piston member 56 together with the torque sub 66 (again constrained by the cam followers 74 within the cam slots 72) to move back under the force of the compression spring 76, thereby applying left-hand torque to the torque tube. As the torque tube 60 is rotationally constrained in the lower sub body 16 by means of the spline profiles 62, 64, this effects rotation of the upper sub body clockwise with respect to the lower sub body 16, fully engaging the interrupted pin thread form 36 of the upper sub 14 with the interrupted box thread form 22 of the lower sub 12, shouldering out on the shoulders 44, 46. In this made up condition, the combination of abutment of the shoulders 44, 46 and the flank contact between the interrupted thread forms 22, 36 provides torsional, tensile, compressive and bending strength in excess of the drill string connections. Fluid sealing of this connection is provided by the seal element 48.

Additionally, the engagement between the torque tube 60 and the lower sub 12, and between the piston member 56 and the torque sleeve 68 provides a locking arrangement for the connection which can only be unlocked by forcible downward movement of the piston member 56 against the compression spring 76 above a selected threshold force.

In the configuration described, the disconnect tool 10 is operable in a passive condition, handling all the drilling forces, fluid flows and pressures until such time that is operated or activated e.g. on instructions from surface by a downhole actuator tool (such as the actuator tool 1 10 described below) configured to apply mechanical or hydraulic force to the disconnect tool 10. Urging the torque tube 60 to move down and apply back out to the pin and box connections by means of the profiles causes the pin and box connection to partially rotate to the release position allowing them to be pulled apart, thereby disconnecting the lower section of string connected to the lower sub body from the upper section of the string connected to the upper sub body.

It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention.

For example, in the unlikely event that the downhole actuation device 1 10 fails to operate, then an alternative or fail safe secondary means of operation could be employed. For example, by dropping a ball or dart from surface and circulated to the top of the piston member 56, the flow through the bore of the piston member 56 could be restricted or temporarily blocked to create a hydraulic force on top of the piston member 56 to create a downward move of the torque tube 60, effecting a disconnect of the upper and lower subs 12, 14.

Referring now also to Figures 13 and 14 of the accompanying drawings, and as described above, the disconnect tool 10 is configured to form part of a downhole tool assembly 100 which is run into a borehole B as part of tool string 1000, such as a drill string, the disconnect tool 10 being operable to permit part of the string 1000 below the disconnect tool 10 to be disconnected, for example in the event the string 1000 has become stuck in the borehole B.

As shown, the tool assembly 100 comprises the disconnect tool 10 and a downhole actuator tool 110, the actuator tool 110 operable to apply the forces required to operate the disconnect tool 10.

An exemplary actuator tool is shown and described in WO 2014/009756 the contents of which are incorporated in its entirety, and is shown in Figures 15 to 17 of the accompanying drawings.

As shown in Figures 15 and 16, the tool 1 10 comprises an annular body 1 14 having a throughbore 1 16. In the illustrated embodiment, the body 1 14 is modular in construction and comprises loading bearing upper and lower subs 118, 120. However, it will be understood that the body 114 may alternatively comprise a unitary component. A threaded pin connector 122 is provided at a downhole end (to the right as shown in the figures) of the lower sub 120 for coupling the tool 110 to an associated tool or component. A threaded pin connector 124 is provided at an uphole end (to the left as shown in the figures) of the lower sub 120 for coupling to a threaded box connector 126 provided at the downhole end of the upper sub 118. A threaded box connector 128 is provided at an uphole end of the upper sub 118 for coupling the tool 1 10 to an uphole tool or component. As described above, the tool 1 10 may form part of a downhole tool string 1000, the tool 110 run into the bore B with the string 1000 and operable to actuate the disconnect tool 10.

A central mandrel 130 is slidably disposed in the body 1 14 and forms an actuation member of the tool 1 10. The mandrel 130 is tubular in construction having an axial throughbore 132 which allows for the free circulation of fluid and the passage of smaller tools and equipment (not shown) through the tool 110.

A central portion of the mandrel 130 defines a stepped and radially extending lock piston 134 disposed in a recess 136 in the body 1 14. In the illustrated embodiment, a downhole end of the recess 136 is defined by a portion of the lower sub 120 and an uphole end of the recess 136 is defined by a cap ring 138 secured within the upper sub 1 18. The cap ring 138 facilitates assembly of the tool 1 10 by permitting the mandrel 130 to be located in the recess 136.

The piston 134 sealingly engages the body 1 14 such that first and second fluid chambers 140, 142 are defined between the mandrel 130 and the body 114. A spring 144 is disposed in the first fluid chamber 140 and acts upon the piston 134, the spring 144 biasing the piston 134 and the mandrel 130 towards the retracted configuration as shown in Figure 8.

The tool 110 further comprises an actuating piston 146 and, in use, the actuating piston 146 forms an actuation arrangement of the tool 110. In the illustrated embodiment, the actuating piston 146 comprises a separate component coupled around an upper end of the mandrel 130, although the actuating piston 146 could alternatively be formed by the mandrel 130. As shown in Figures 15 and 16, the actuating piston 146 sealingly engages the body 1 14 and has an upper end face 148 which is exposed to flow and pressure in the throughbore 116 and a lower end face 150 which is exposed to annulus flow and pressure via a port 152 in the body 114. In use, differential pressure acting across the larger area of the upper end face 48 of the actuating piston 146 urges the actuating piston 146 and the mandrel 130 towards the extended configuration as shown in Figure 16.

Thus, where there is a positive pressure difference between the throughbore 1 16 and the annulus which exceeds the spring force, for example when fluid is circulating in the well during drilling, the actuating piston 146 urges the mandrel 130 towards the extended configuration. Where the pressure differential is insufficient to overcome the spring force, for example where there is no circulation, the spring 144 urges the mandrel 130 towards the retracted configuration.

As shown in Figures 15 and 16, the first and second fluid chambers 140, 142 are filled with a substantially incompressible fluid, such as hydraulic fluid or oil 154, via fill ports 156 and a fluid communication arrangement is provided to permit fluid communication between the chambers 140, 142. In the embodiment shown in Figures 15 and 16, the fluid communication arrangement comprises galleries 158 formed in the body 1 14, although any suitable communication arrangement may be used where appropriate.

A control valve 160 is disposed in the galleries 158, the control valve 160 configurable between an open configuration and a closed configuration and it will be recognised that the chambers 140, 142, galleries 158 and control valve 160 define a closed fluid system, such that when the control valve 160 is in the closed configuration a fluid lock is formed which prevents movement of the mandrel 130.

Thus, in use, opening the control valve 160 releases the fluid lock and allows the activating piston 146 to move against the return spring 144 when flow and pressure are applied, in turn activating the associated tool or equipment being controlled by the actuator tool 110 while closing the control valve 160 reapplies the fluid lock locking the actuator tool 1 10 and the tool or device that it is controlling in its activated or deactivated state. Beneficially, the ability to selectively provide a fluid lock permits the tool 1 10 and any pressure operable tools or equipment operatively associated with the tool 1 10 to be isolated from variations in flow and pressure which occur in the bore.

In the illustrated embodiment, the control valve 160 comprises an electromechanical control valve in the form of a single coil piloting solenoid valve.

The tool 1 10 further comprises a control system 162 for controlling the condition of the valve 160 and thus fluid flow between the first and second chambers 140, 142 and an exemplary control system 162 is shown schematically in Figure 17.

As shown in Figure 17, the control system 162 comprises a first pressure transducer 164 communicating with pressure in the throughbore and a second pressure transducer 166 communicating with pressure in the annulus. A transducer module 168 communicates with the first and second pressure transducers 164, 166 and a solenoid controller 170. The solenoid controller 170 controls the valve 160. A battery pack 172 is also provided to supply power to the transducer module 168 and the solenoid controller 170. In use, the transducer module 168 senses pressure changes taking place in the fluid being pumped through the tool 1 10, activating the valve 160 only when it sees a predetermined sequence of pressure changes occurring over a specific period. It is envisaged that the valve 160 will be opened, and the fluid lock released, for a predetermined time period sufficient to actuate the tool 1 10 to enable the tool 110 in turn to activate the associated downhole equipment. After this time period, the fluid lock is reapplied and the tool 1 10 locked.

Whereas conventional actuation mechanisms may be detrimentally affected by changes in pressure and flow, in embodiments of the present invention the control system 162 of the downhole tool 1 10 can interpret the changes in pressure and determine whether these represent a normal event which requires no action. On detecting a specified actuation event, however, such as a specific series of pressure changes in a unit period of time, the control system 162 is configured so transmit a control current to the valve 160 to release the fluid lock for a specified period and thus provide an operational window for actuation of the tool 1 10 and associated equipment, after which the fluid lock is re-applied. By way of example, an operator may start and stop the pumps three times within a period of one minute, the control system 162 of the tool 1 10 recognising this as a particular actuation event corresponding to an instruction to activate the tool 1 10 to release the fluid lock for period of three minutes. Starting the pumps would not trigger the control system 162.

The string 1000 may comprise a number of different downhole tools and the disconnect tool 10 may also be operatively associated with one or more such tools.

For example, Figure 18 shows an exploded view of a valve tool in the form of a float sub 200 with which the disconnect tool 10 may be operatively associated. In the illustrated embodiment, the float sub 200 forms a separate tool to the disconnect tool 10. However, it will be recognised that the float sub 200 and disconnect tool 10 may alternatively be integrally formed.

In use, the downhole disconnect tool 10 may be coupled or otherwise operatively associated with the flapper sub 200, the disconnect tool 10 configured to release the flapper to move to a closed configuration.

As shown in Figure 18 the float sub 200 comprises a body 202. The body 202 is generally tubular in construction, having a throughbore 204.

A connector 206 for connecting the float sub 200 to an adjacent component of the string 1000 is provided at a first end (left end as shown in the figure) of the body 202. The connector 206 takes the form of a threaded male or pin connector having an external thread 208 machined or otherwise formed thereon. A connector 210 for connecting the float sub 200 to the downhole disconnect tool 10 is provided at a second end (right end as shown in the figure) of the body 202. The connector 210 takes the form of a threaded female or box connector having an internal thread 212 machined or otherwise formed thereon.

A flapper valve arrangement having a flapper 214 is provided in the body 202, the flapper arrangement configurable between an open configuration and aclosed configuration.

The throughbore 204 is configured to receive a stem 216. The stem 216 is generally tubular in construction. The stem 216 is configured to be coupled to, and move with, the torque tube 60 of the disconnect tool 10.

In the illustrated embodiment, the stem 216 forms a separate component to the torque tube 60. However, it will be recognised that the stem 216 and torque tube 60 may be integrally formed.

In use, location of the stem 216 within the throughbore 204 adjacent to the flapper 214 maintains the flapper 214 in the open position. Withdrawal of the stem 216 due to movement of the torque tube 60 permits the flapper 214 to close.

As described above, the embodiments described herein are merely exemplary and various modifications may be made thereto without departing from the scope of the invention.

For example, Figures 19 to 22 show a disconnect tool 10' according to another embodiment of the present invention. The disconnect tool 10' is similar to the disconnect tool 10 and like components of the disconnect tool 10 and 10' are represented by like numerals. As in the tool 10, the tool 10' comprises a first, lower, sub 12' and a second, upper, sub 14'. As shown, however, in this embodiment the disconnect tool 10' comprises a clutch arrangement, which in the illustrated embodiment takes the form of a dog clutch 80. The dog clutch 80 is disposed between the pin and the box. In use, movement of the cam follower along the parallel section of the groove of the cam arrangement is used to push and/or guide the dog clutch 80 out of engagement before the spiralled section of the cam groove operates to rotate and disconnect the first member 12' and the second member 14'. Once the dog clutch 80 is disengaged, the dog clutch 80 is retained in place, such as by a spring detent arrangement or other suitable mechanism. Beneficially, the provision of the clutch arrangement supplements the back out resistance of the connection between the first member and the second member.