Patent Description:
During well construction, a hole is drilled to a pre-determined depth and a casing is run into the well. Cement is pumped down the casing and is displaced up the annulus between the casing and the original wellbore. The purpose of the cement is to secure the casing in position and ensure that the annulus is sealed.

Over time, which may be several decades, the production of hydrocarbons reduces until the production rate of the well is no longer economically viable, at which point the well has reached the end of its productive life. The well is plugged and abandoned.

Typically to abandon the wellbore a cement plug is placed in the wellbore casing to seal the wellbore casing annulus. It is known to use downhole casing cutters lowered into the casing to cut the casing above the cement plug and to remove the severed casing section from the wellbore. This task involves multiple trips downhole.

Other downhole tools must be lowered into the casing to allow a range of downhole tasks to be performed including drills or milling tools to extend the wellbore or dress-off cement plugs and packers to seal the wellbore.

Often a number of downhole tasks must be completed which require multiple trips downhole to perform each task. This can be a time consuming and expensive process requiring the tool string to be returned to surface to change out the downhole tool for each specific task.

<CIT>, <CIT>, <CIT> and <CIT> disclose downhole cutting tools and/or actuating means therefor which are useful for understanding the invention.

It is an object of an aspect of the present invention to obviate or at least mitigate the foregoing disadvantages of prior art downhole tools.

It is another object of an aspect of the present invention to provide a robust, reliable and compact downhole cutting tool suitable for use on a tool string.

It is a further object of an aspect of the present invention to provide a tool string with a downhole cutting tool and at least one other downhole tool capable of performing a range of downhole tasks with improved productivity and efficiency.

Further aims of the invention will become apparent from the following description.

According to a first aspect of the invention there is provided a downhole cutting tool according to claim <NUM>.

By providing a tool capable of controlling the opening of the fluid flow paths in the downhole cutting tool it may allow the controlled actuation of the cutting tool and at least one other tool on the same tool string. This may facilitate multiple downhole operations to be performed on a single trip.

Axial force may be applied by a set down weight and/or a ball drop. This may allow the tool to perform a number of downhole tasks in a single trip without having to return to surface or perform multiple trips.

A further benefit of this system is that different downhole tools with specific hydraulic actuation flow rates may be controlled on the same tool string. Drill tools and milling tools that require a high flow rate may be located beneath the cutter tool on the tool string and may be independently controlled.

The cutting mechanism may comprise a flow restriction assembly. The flow restriction assembly may comprise a nozzle. The nozzle may be configured to introduce a pressure difference in the fluid upstream of the nozzle and the fluid downstream of the nozzle. The nozzle may be dimensioned to provide resistance to fluid flowing into nozzle. The restriction assembly and/or the piston sleeve may be configured to move axially when fluid acts on the nozzle. The restriction assembly and/or the piston sleeve may be configured to move axially when fluid above a predetermined threshold flows through the second pathway and acts on the nozzle.

The downhole cutting tool may comprise a tool string coupled to a downhole tool. The downhole cutting tool may comprise a tool string coupled to a hydraulically actuated downhole tool. The downhole cutting tool may comprise a tool string coupled to a series of hydraulically actuated downhole tools.

The hydraulically actuated downhole tool may be selected from a drill, mill, packer, bridge plug, hydraulic disconnects, whipstock, hydraulic setting tools or perforating gun.

According to a second aspect of the invention there is provided a method of operating a downhole cutting tool and a hydraulically actuated downhole tool on a single downhole trip according to claim <NUM>.

<FIG>, <FIG> and <FIG> are longitudinal sectional views of a downhole tool in accordance with a first embodiment of the invention in different phases of operation.

<FIG> is a longitudinal section through the downhole tool <NUM>. The downhole tool <NUM> has an elongate body <NUM> and a mandrel <NUM>.

A first end 14a of the mandrel <NUM> is configured to be coupled to an upper tool string such as a drill string (not shown). The second end 14b of the mandrel is axially movably mounted in the body <NUM>.

A first end 12a of the body <NUM> surrounds a portion of mandrel <NUM>. The second end 12b of the body is configured to be coupled to a lower tool string such as a drill string (not shown). The lower tool string may be connected to downhole tool located further downhole. The second end 12b of the body is designed for insertion into a downhole tubular first.

The mandrel <NUM> is configured to be axially moveable in the body and is held in a first position by sheer screws <NUM>. The tool body <NUM> comprises a cutting mechanism <NUM> configured to deploy knifes <NUM> to cut the casing.

<FIG> shows an enlarged view of area A-A" of <FIG>. As shown in <FIG> the cutting mechanism <NUM> comprises a plurality of knives <NUM> disposed circumferentially around the tool body <NUM>. (One knife <NUM> is shown in <FIG>). The knives <NUM> are rotatably mounted on pivot <NUM>, best shown in <FIG>, and are configured to move between a storage position where the knives are retracted shown in <FIG> and an operational position where the knives are deployed shown in <FIG>.

The mandrel <NUM> has a central bore <NUM> which is closed at the second end 14b. At the second end 14b of the mandrel are located a first set of ports <NUM> and second set of ports <NUM>. The first and second sets of ports are axially separated from one another. Ports <NUM> are in fluid communication with channels 32a in the mandrel <NUM>.

<FIG> and <FIG> shows a piston <NUM> which is axially movably mounted in the body <NUM>. The piston <NUM> is configured to move axially between a first position shown in <FIG> and second position shown in <FIG>. Although it is shown to move between a first and second position, intermediate positions may be selected. The piston <NUM> comprises a piston sleeve <NUM>. The piston sleeve <NUM> has a first shoulder <NUM>. Side 44a of shoulder <NUM> is configured to engage a pivot arm <NUM> connected to the cutting knives <NUM>, best shown in <FIG>. In the first mandrel position the position of the first shoulder <NUM> hinders the rotation of the pivot arm <NUM> and maintains the knives in a retracted position.

The piston <NUM> has an inlet nozzle <NUM> to a central bore <NUM> which extends through the piston <NUM>. Ports <NUM> extend into the central bore <NUM> of the piston.

The shoulder <NUM> is configured to minimize the maximum cutting OD (sweep) of the knives when cutting. Side 44b of shoulder <NUM> is configured to stop the piston <NUM> at a set cutting OD (Sweep). The side 44b of shoulder <NUM> may be configured to stop the piston <NUM> by engaging with a shoulder <NUM> on the tool body at a set cutting outer diameter sweep. The maximum cutting OD may be adjusted. The maximum cutting OD may be adjusted by changing the position of the sleeve <NUM> on the piston <NUM>. The sleeve is threaded attached to the piston <NUM> and the maximum cutting OD can be adjusted by rotating the sleeve. The sleeve position is secured in position by set screws <NUM>. Alternatively, or additionally a screw may be provided that limits the amount the sleeve can be adjusted (not shown).

The piston <NUM> comprises a shoulder <NUM>. Shoulder <NUM> is configured to engage the pivot arm <NUM> connected to the cutting knives <NUM> and to pivotally move the knives <NUM> between a knife storage position shown in <FIG> and an operational position shown in <FIG> when a fluid pressure is applied to piston <NUM>.

The mandrel <NUM> is held in a first position relative to the body <NUM> by shear screws <NUM>. The mandrel is configured to move from the first position shown in <FIG> to a second position shown in <FIG>.

In the first mandrel position a first fluid flow pathway through the tool is open. The first pathway consists of channels 32a on the mandrel <NUM> in fluid communication with a bypass channel <NUM>. The bypass channel <NUM> is in fluid communication with ports <NUM> on the piston <NUM>.

In a first mandrel position the ports <NUM> align with ports <NUM> and on the tool body. Fluid that flows through ports <NUM> and <NUM> flows into the annular space which may aid in the removal of cutting and/or debris from cutting and/or drill sites.

During normal circulation mode, fluid flows through a first flow pathway in the tool and may actuate and/or control another tool located further downhole on the tool string.

Fluid flowing through the upper tool string first flows through the first flow pathway then through bore <NUM> of the mandrel. Fluid flows through bore <NUM> through channels 32a into the bypass channel <NUM>. The flow continues through ports <NUM> on the piston <NUM> into the bore <NUM>. The fluid flows in the inner bore of the tool string and may be used to actuate at least one downstream hydraulic tool such as a drill, packer or bridge plug (not shown). Some fluid flows through ports <NUM> and <NUM> into the annular space.

In the first mandrel position the ports <NUM> are blocked by port valve <NUM> which prevents flow from acting on the piston sleeve to actuate the cutter mechanism <NUM>.

In the first mandrel position, the tool <NUM> can be rotated on the work string and fluid may be pumped through this first pathway without actuating the cutting mechanism and deploying the knives. This may facilitate the actuation of a downstream tool to enable multiple tasks to be performed in once the tool is deployed downhole without requiring the tool to return to surface.

Flow through the tool may control the actuation of a downstream tool such as a drill or mill and may enable cement dressing off of a cement plug prior to the casing being cut by the cutting mechanism.

By proving a first pathway which bypasses the actuating of the cutting mechanism in the first mandrel position the tool may allow a high fluid flow rate to be pumped through the tool. The tool may also allow the transfer torque to a downstream tool such as a drill bit or mill without actuating the cutting mechanism. <FIG> shows a longitudinal view of the tool in circulation mode.

In order to move the mandrel from a first position to a second position an axial load is applied to the mandrel <NUM>. The axial load may be provided by a set down weight or hydraulic pressure. In this example the axial load is provided by a set-down weight which moves the mandrel from the first axial position shown in <FIG> to a second axial position shown in <FIG>.

The mandrel <NUM> is configured to be moved within the body <NUM> to a second position as shown in <FIG>. The mandrel is held in the second position by spring activated keys <NUM> located in an internal surface of body <NUM> engaging with grooves 19a located on the outer surface of the mandrel.

<FIG> show the mandrel in the second position where the mandrel <NUM> closes the first pathway and opens a second pathway. The mandrel <NUM> is moved axially such that ports <NUM> are not aligned with ports <NUM> on the body preventing fluid flow from the bore <NUM> into the annular space. The channels 32a are blocked by port valve <NUM> and are no longer in fluid communication with the bypass channel <NUM>. The ports <NUM> on the second end 14b of the mandrel are moved through port valve <NUM> into chamber <NUM> in the body <NUM>.

The piston <NUM> is biased in a direction X by spring <NUM> as shown in <FIG>. In this example the spring <NUM> is a compression spring. However, it will be appreciated that any spring, compressible member or resilient member may be used to bias the sleeve in a first position.

The spring force acting on the piston provided by spring <NUM> in direction X maintains shoulder <NUM> in contact with pivot arm <NUM> and prevents pivot arm <NUM> from rotating and deploying the knives <NUM>.

<FIG> show the actuation of the cutting mechanism when the mandrel in is the second position. Fluid is pumped into the tool string and flows through the second pathway to actuate the cutting mechanism.

Fluid passes through the second pathway. Fluid flows through bore <NUM> of the mandrel into the chamber <NUM> via ports <NUM> on the mandrel <NUM>. The chamber <NUM> is in fluid communication with an axially moveable restrictor assembly <NUM>. The flow resistor assembly <NUM> has an inlet nozzle <NUM>, a bore <NUM> and an outlet <NUM>. The inlet nozzle <NUM> is configured to introduce a pressure difference in the fluid upstream of the inlet nozzle <NUM> and the fluid downstream of the inlet nozzle <NUM>.

The fluid flows through the nozzle <NUM> of the flow restrictor assembly <NUM>. The nozzle <NUM> is dimensioned to provide a resistance to flow. When the fluid pressure applied to the nozzle <NUM> it moves the flow resistor assembly <NUM> in direction Y as shown in <FIG>. The outlet <NUM> of flow restrictor assembly <NUM> is aligned and/or seated on inlet nozzle <NUM>. When the fluid pressure applied to the nozzle <NUM> is sufficient to overcome the spring force of spring <NUM> the flow restrictor assembly <NUM> and piston <NUM> are moved towards second end 12b of the downhole tool, shown as direction Y in <FIG>.

The flow resistor assembly <NUM> may be adjusted to stop at selected position after travelling a predetermined distance in direction Y. When the flow resistor assembly <NUM> stops at this selected position the outlet <NUM> of flow restrictor assembly <NUM> will not be aligned and/or seated in inlet nozzle <NUM>. Flow will bypass the smaller nozzle <NUM>, and will flow through the larger sleeve inlet nozzle <NUM>. This may provide a pressure change when the knives are at a certain cutting OD (sweep) and provide an indication that the knives are deployed and/or the cut has been made.

Movement of the piston <NUM> and sleeve <NUM> in direction Y axially moves shoulder <NUM> to engage and move pivot arm <NUM> connected to the cutting knives <NUM>. The knives <NUM> are moved to an operational position to allow the cutting of a casing shown in <FIG>.

The pivot arm <NUM> has a slot <NUM> (best shown in <FIG>) which prevents the pivot arm impacting the sleeve when the knife is rotated to an extended position.

To retract the knives <NUM>, the fluid flow through the second pathway is reduced. The fluid pressure applied to nozzle <NUM> and/or nozzle <NUM> is no longer sufficient to overcome the spring force of spring <NUM> and the flow restrictor assembly <NUM>, piston <NUM> and sleeve <NUM> are moved towards first end 12a of the downhole tool, shown as direction X in <FIG>.

The movement of the piston <NUM> in direction X moves the shoulder <NUM> to disengage with the pivot arm <NUM>. Shoulder <NUM> engages with the pivot arm <NUM> which rotates pivot arm <NUM> and retract the knives <NUM>.

The fluid pumped through the second pathway may be adjusted to control the degree of deployment of the knives <NUM>.

The tool and/or tool string may be rotated with the knives deployed to cut the tubular. The tool can be rotated when the knifes are in an operational or retracted position. The tool has a spline that transfer the torque in both positions.

The tool described above may be provided with a plurality of seals. Seals may be provided along the first and/or second pathway to prevent fluid egress. Seals may be provided between the mandrel and the tool body.

The above example described the switching between a first mandrel position and a second mandrel position by applying an axial force in the form of a set-down weight. However, an alternative method applying an axial force is a ball-drop.

<FIG>, <FIG> show an alternative design for downhole tool <NUM>. The tool comprises a ball seat <NUM> at end 114b of mandrel <NUM>. The ball seat <NUM> has first series of ports <NUM> and a second series of ports <NUM> (shown best in <FIG>). The first series of ports <NUM> are aligned with the first pathway. The first fluid pathway is similar to the first fluid pathway described in relation to <FIG> and will be understood from the description of <FIG> above.

During normal circulation mode, the first fluid flow pathway through the tool is open. The first pathway consists of first series of ports <NUM> on the ball seat <NUM> which are in fluid communication with a bypass channel <NUM>. The bypass channel <NUM> is in fluid communication with ports <NUM> on the piston <NUM>.

Fluid flows through the first flow pathway and may actuate and/or control a hydraulically operated tool located further downhole on the tool string.

Some flow may pass through the second series of ports <NUM> in the ball seat and into the second flow path. The second flow path is similar to the second fluid pathway described in relation to <FIG> and will be understood from the description of <FIG> above. The second fluid pathway consists of series of ports <NUM> on the ball seat <NUM> which are in fluid communication with chamber <NUM>. The chamber <NUM> is in fluid communication with the cutting mechanism <NUM>. However, during normal circulation mode the flow through the second flow path is not sufficient to actuate the cutting mechanism <NUM>.

<FIG> show actuation of the cutting mechanism. To actuate the cutting mechanism <NUM> a ball <NUM> is dropped in the bore of the tool string and is carried by fluid flow through bore <NUM> until it is retained by the ball seat <NUM>. Once the ball <NUM> has engaged the ball seat <NUM> the ball <NUM> blocks ports <NUM> preventing fluid flow in the first pathway. Fluid is directed though ports <NUM> into the chamber <NUM> and through the second pathway. The actuation of the cutting mechanism is as described in relation to <FIG> and will be understood from the description of <FIG>.

In this example the mandrel is not axially moveable between a first and second position. In this case the first series of ports <NUM> are always aligned with the first pathway and the second series of ports <NUM> are always aligned with the second pathway.

Alternatively, and/or additionally, the mandrel and/or ball seat may be axially movable in the tool body. The mandrel and/or ball seat may be axially moveable when sufficient fluid pressure is applied to the ball and ball seat providing an axial force on the mandrel to move it to a second position. The mandrel and/or ball seat when moved to the second position the second series of ports are aligned with the second pathway.

During normal circulation mode, fluid flows through the bore of the mandrel. The flow passes through the first flow pathway via the series of ports and may actuate and/or control a hydraulically operated tool located further downhole on the tool string.

To actuate the cutting mechanism a ball is dropped in the bore of the tool string and is carried by fluid flow where its retained by the ball seat. Once the ball has engaged the ball seat it blocks the first series of ports preventing fluid flow in the first flow pathway. The fluid pressure may act on the ball seat and when sufficient fluid pressure acts on the ball seat the mandrel and/or ball seat be axially movable to a second position in the tool body. The mandrel and/or ball seat in the second position uncovers a second series or ports which are in fluid communication with the second fluid path way. Subsequent fluid flow through the second fluid flow pathway actuates the cutting mechanism disposed in the second fluid flow pathway.

Throughout the specification, unless the context demands otherwise, the terms 'comprise' or 'include', or variations such as 'comprises' or 'comprising', 'includes' or 'including' will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. Furthermore, relative terms such as", "lower","upper, "up" "down" and the like are used herein to indicate directions and locations as they apply to the appended drawings and will not be construed as limiting the invention and features thereof to particular arrangements or orientations. Likewise, the term "inlet" shall be construed as being an opening which, dependent on the direction of the movement of a fluid may also serve as an "outlet", and vice versa.

The invention provides a downhole cutting tool. The tool comprises a tool body,
a first flow pathway and a second flow pathway through the tool body. The tool also comprises a cutting mechanism configured to be in fluid communication with the second fluid flow pathway and a switching mechanism configured operable to control the opening of the first and/or second fluid flow pathway.

The present invention obviates or at least mitigates disadvantages of prior art downhole tools and provides a robust, reliable and compact downhole cutting tool suitable for actuating multiple downhole tool and cutting a casing in a single trip.

The invention enables multiple downhole operations to be performed on the same downhole trip, which normally would require at least two separate trips. The invention allows sufficient fluid flow to be pumped through the tool to actuate tools on the tool strings further downhole without uncontrolled actuation of the cutting tool.

The invention allows the selective actuation of different tools on the same tools string. This may facilitate the controlled actuation of downhole tools such as drills and mills which require high flow rates on the same tool string as a casing cutter tool which requires a lower fluid flow rate.

This may facilitate the actuation of a drill to dress-off a cement plug and the subsequent activation of the cutting tool to cut the casing in a single downhole trip. The invention avoids the simultaneous and/or accidental actuation of the downhole tools on the tool string. The downhole cutting tool has improved productivity and efficiency, and is capable of reliably performing multiple downhole operations once deployed downhole.

Claim 1:
A downhole cutting tool (<NUM>,<NUM>) comprising:
a tool body (<NUM>);
a first flow pathway through the tool body;
a second flow pathway through the tool body;
a cutting mechanism (<NUM>,<NUM>) configured to be in fluid communication with the second fluid flow pathway and
a switching mechanism;
the switching mechanism comprising a mandrel (<NUM>,<NUM>) having a central mandrel bore (<NUM>) with a first end (14a) configured to be coupled to an upper tool string, and a first set of channels (32a) or ports (<NUM>) at a second end (14b), the switching mechanism operable to close the first flow pathway;
the cutting mechanism (<NUM>,<NUM>) having a plurality of knives (<NUM>) to cut casing, the tool body (<NUM>) having a first end (12a) surrounding a portion of the mandrel and a second end (12b) configured to be coupled to a lower tool string;
the downhole cutting tool further comprising a piston (<NUM>,<NUM>) axially moveable in a chamber (<NUM>,<NUM>) of the tool body and comprising a piston sleeve (<NUM>) with a shoulder (<NUM>) configured to engage a pivot arm (<NUM>) of the cutting mechanism, a piston inlet nozzle (<NUM>) to a central piston bore (<NUM>) and second set of ports (<NUM>,<NUM>) extending into the central piston bore (<NUM>); and
a bypass channel (<NUM>,<NUM>) in fluid communication with ports (<NUM>,<NUM>) on the piston (<NUM>,<NUM>);
the downhole cutting tool being switchable by operation of the switching mechanism between a first position and a second position, wherein:
in the first position:
the first flow pathway is open, and fluid flow from the upper tool string enters the central mandrel bore (<NUM>), passes through the first set of channels (32a) or ports (<NUM>) into the bypass channel (<NUM>,<NUM>) to enter the second set of ports (<NUM>,<NUM>) extending into the central piston bore (<NUM>) and to an inner bore of the lower tool string, and the knives (<NUM>) are retracted and held in a storage position; and
in the second position:
the second flow pathway is open, the first flow pathway is closed as the bypass channel (<NUM>,<NUM>) is closed, and fluid flow from the upper tool string enters the central mandrel bore (<NUM>), passes through a third set of ports (<NUM>,<NUM>) into the chamber (<NUM>,<NUM>) to enter the inlet nozzle (<NUM>) to the central piston bore (<NUM>) and moves the piston (<NUM>) to engage a second shoulder (<NUM>) with the pivot arm (<NUM>) to rotate the knives (<NUM>) to an extended operational position to cut casing.