WO2015189644A2

WO2015189644A2 - Downhole tool and method

Info

Publication number: WO2015189644A2
Application number: PCT/GB2015/051747
Authority: WO
Inventors: Lance Stephen Davis; Edward Docherty Scott; Magnus John WARDLE
Original assignee: Deep Casing Tools Limited
Priority date: 2014-06-13
Filing date: 2015-06-12
Publication date: 2015-12-17
Also published as: WO2015189644A3; EA201790015A1; EP3155211A2; GB201410630D0; US20170145783A1; CA2952164A1; AU2015273240A1

Abstract

A downhole tool (10) configured to condition a borehole (B) and deliver a settable material, such as cement slurry, into a borehole annulus (A)for securing and supporting a casing string (C)in the borehole (B)comprises a body in the form of tubular housing (12), a shaft (14) rotatably mounted within the housing(12), a head portion (22) and a drive arrangement (20). In use, borehole cleaning and cementing operations may be carried out by directing a drive fluid, such as drilling mud,through the drive arrangement (20)to drive rotation of the head portion (22) to clean or condition the borehole (b). A cement slurry or the like,may then be directed through the casing string (C) or via a cementing string (S) into the shaft(14), and through the drive arrangement (20),the fluid then being ejected from the head portion (22).

Description

DOWNHOLE TOOL AND METHOD

FIELD OF THE INVENTION

This invention relates to a downhole tool and method. More particularly, but not exclusively, embodiments of the invention relate to a downhole tool and method for use in the delivery of cement in a well borehole.

BACKGROUND TO THE INVENTION

In the oil and gas production and extraction industry, in order to access a hydrocarbon-bearing formation a well borehole may be drilled from surface, this typically then being lined with sections of metal tubing known as casing. In many instances, a number of casing sections or stands are coupled together to form a casing string for running into the borehole.

In order to secure and support the casing or casing string in the borehole, the casing is typically cemented in place, a common cementing operation involving directing a cement slurry or the like through the casing from surface, this then exiting the casing at or towards its distal end to fill the annulus defined between the casing and the borehole.

The task of running casing to total depth with the intention of cementing the casing in place is technically challenging, and there are a number of obstacles to the successful deployment of casing and to the subsequent cementing of the casing in place.

One such challenge is the efficient cleaning of the borehole wall, particularly in key areas such as the shoetrack, the lowermost section of the casing.

Another challenge is to avoid problems that can occur during the cementation process, which may result from one or more of several phenomena. For example, cementing operations may fail due to Flash Setting, which is the result of incorrect chemistry mix in the cement; False Setting, where the aqueous phase of the slurry quickly becomes supersaturated with gypsum; and/or Excessive Shear, where the cement slurry is subject to shear for excessively long periods, with the result that the thickening time is reduced to less than the total job pumping time. For cementing operations, another challenge is the tendency for the cement slurry to take the path of least resistance and flow along the high side of the casing string, providing a nonuniform cementing operation. Another challenge is to support the casing, particularly in the area of the shoetrack and other key zones, to allow the cement slurry to pass on the low side of the casing, and to allow the centralisers to pass down the borehole unimpeded.

Another challenge is to ensure that the pumped cement does not return up the casing.

Another challenge is that any and all devices within the shoetrack area be easily drilled through by the next drill bit.

SUMMARY OF THE INVENTION

According to a first aspect, there is provided a downhole tool for cleaning or conditioning a well borehole, the downhole tool comprising:

a body;

a head portion;

a drive arrangement for rotating the head portion; and

at least one bore-engaging member disposed on the head portion, the at least one bore-engaging member engaging the borehole to clean or condition the borehole on rotation of the head portion.

Beneficially, a downhole tool according to embodiments of the present invention may be run into a borehole on a conveyance, such as a casing string, tubing string or the like, and in particular embodiments without rotation or substantially without rotation of the conveyance, the downhole tool being operable to clean or condition the borehole and facilitate other borehole operations to be carried out, such as a downhole cementing operations or the like. The ability to clean or condition the borehole, and in particular but not exclusively the shoetrack or lowermost portion of the borehole, facilitates efficient and effective cementing operations to be carried out to total depth.

Amongst other things, this permits the casing to be fully supported off the borehole wall by centralisers, the use of which may otherwise be restricted or prevented by borehole restrictions. This enhanced ability to support the casing, particularly in the area of the shoetrack and other key zones, in the case of a cementing operation allows the cement slurry to pass on the low side of the casing, improving the cementing operation and avoiding shear effects.

The drive arrangement may be selectively operable. The drive arrangement may be selectively operable in response to a fluid flow rate, such as a fluid flow rate through the drive arrangement. For example, the drive arrangement may be operable in response to a fluid flow rate exceeding a preset flow rate. Beneficially, the drive arrangement may be selectively operable to permit the operator to clean, cut or otherwise condition the bore at selected locations by controlling the fluid flow rate. The ability to selectively operate the drive arrangement may, for example, facilitate removal of mud cake at selected intervals or in selected zones. Thus, mud cake may be removed in a rigorous fashion in particular zones where required to obtain an effective cement job but may be maintained in other zones where it is desirable to maintain mud cake, for example where the formation porosity, permeability and pressures are such that drilling fluids may be lost through that zone, or where the formation is weak, and it is not desirable to have pump circulation at that point, increasing the effective circulation density.

The downhole tool may be configured to deliver a settable material, such as cement, into the borehole. In particular embodiments the head portion may be configured to deliver the settable material. Beneficially, rotation of the head portion may improve radial distribution of the settable material.

The drive arrangement may condition the settable material in the borehole.

Beneficially, embodiments of the present invention facilitate the delivery of a settable material, such as cement or the like, into an annulus between a downhole tubing or tubing string and a borehole by conditioning the settable material at a downhole location. This may prevent or at least mitigate the risk of problems occuring during the cementation process, such as false setting or excessive shear, and may improve the ability of an operator to carry out a complete and effective cementing job to target depth. For example, by conditioning the settable material in the downhole environment, embodiments of the present invention may add to the mixing energy of the material, reenergizing it and relieving false setting. Moreover, embodiments of the invention may ensure a flow area to be maintained which is outside the shearing critical zone. For example, embodiments of the invention may maintain a flow area of at least 0.5 in² (0.00032258m²) above which area shear does not occur.

In particular embodiments, the tool may be configured to direct the settable material into and/or through the drive arrangement of the downhole tool.

The tool may define, or provide mounting for, a fluid conduit.

The fluid conduit may be configured or arranged to direct a drive fluid through the drive arrangement to drive the drive arrangement. The drive fluid may comprise drilling fluid, drilling mud or the like. In use, the drive arrangement may be driven by the drive fluid, for example as the tool is deployed downhole or on reaching target depth in the borehole, in order to carry out a reaming and/or borehole cleaning operation. In particular embodiments, the tool may be configured to direct the settable material into and/or through the drive arrangement via the fluid conduit.

The tool may be configured such that the drive arrangement is driven by the settable material.

The drive arrangement may be driven by the settable material while at the same time the resulting movement of the drive arrangement maintains, contributes to maintaining, or alters the condition of the settable material for delivery.

The downhole tool may be of any suitable form and construction. For example, the downhole tool may comprise, may be operatively associated with, or coupled to, at least one of: a cementing tool, a cement circulation tool, a reaming tool, a drilling tool, a bore-cleaning tool, or the like.

In particular embodiments, the tool may be configured to permit a reaming operation and/or a borehole cleaning operation to be carried out prior to carrying out a cementing operation.

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

The drive arrangement may comprise a rotary drive arrangement.

The drive arrangement may comprise a stator.

The drive arrangement may comprise a rotor.

In particular embodiments, the drive arrangement may comprise a fluid turbine. The turbine may comprise an axial flow reaction turbine. The turbine may comprise an impulse turbine. When activated, the drive arrangement generates rotation by the fluid acting on the drive arrangement.

The provision of a turbine drive arrangement permits relatively high speed rotation of the head portion relative to a tubular component, such as a casing string, to which the tool may be coupled.

Alternatively, the drive arrangement may comprise a positive displacement motor (PDM), vane motor, pelton wheel or other suitable drive arrangement.

The tool may comprise an intake port for directing the settable material - or the drive fluid - into the drive arrangement. The intake port may be provided in the shaft.

The tool may comprise an exhaust port for directing the settable material - or the drive fluid - out from the drive arrangement. The exhaust port may be provided in the shaft.

In particular embodiments, the body may comprise or provide mounting for the stator and the shaft may define or provide mounting for the rotor. In such embodiments, the shaft/rotor may be disposed at least partially within the body/stator. In other embodiments, the body may comprise or provide mounting for the rotor and the shaft may comprise or provide mounting for the stator. In such embodiments, the body/rotor may be disposed outside the shaft/stator.

The head portion may be of any suitable form and construction.

The shaft may be coupled to the head portion. Alternatively, the shaft and the head portion may be integrally formed.

The head portion may be coupled to the rotor, whichever of the body and the shaft comprises the rotor.

In particular embodiments, the head portion may be configured for rotation relative to the body, for example the head portion may be rotatably coupled to the body.

The head portion may be configured for rotation relative to the shaft, for example the head portion may be rotatably coupled to the shaft.

The drive arrangement may drive rotation of the head portion relative to the body. The rotary drive arrangement may be configured to drive the head portion at a relatively high rotational velocity. For example, the rotary drive arrangement may be configured to drive the head portion at up to, or some embodiments exceeding, 500 rpm.

The tool may be configured to rotate the head portion in a given direction. In particular embodiments, the apparatus may be configured to rotate the head portion in a clockwise direction (that is clockwise looking from above). This may add to the kinetic energy of the fluid stream directed to the wellbore or casing wall providing a superior wellbore wall cleaning and cementing process.

At outlined above, the tool may be configured to distribute the settable medium from the head portion.

The tool may be configured to eject the settable material in a given direction. The tool may be configured to eject the settable material in a radial direction. Alternatively, or additionally, the tool may be configured to eject the settable material in an axial direction. The tool may be configured to eject the settable material in an uphole hole direction. The tool may alternatively or additionally be configured to eject the settable material in a downhole direction.

In particular embodiments, the tool may be configured to eject the settable material in the same direction as the direction of rotation of the head portion.

The tool may be configured to eject the settable material at a given velocity or flow rate. The tool may comprise at least one fluid port. The at least one fluid port may permit the settable material to be directed to the exterior of the tool.

The at least one port, or where the apparatus comprises a plurality of ports at least one of the ports, may comprise or define a nozzle. The port or nozzle may be configured to meter or control the exit velocity of the fluid. Beneficially, the number and arrangement of the ports may permit the exit velocity of the fluid to be selected according to the desired cementing and/or fluid distribution application.

Alternatively, or additionally, the provision of a port permits fluid, such as drilling fluid, drilling mud or the like, to be directed through the tool to assist in the removal and/or displacement of obstructions from the borehole, such as mud cake or the like.

In particular embodiments, at least one of the ports may define, or provide mounting for, a nozzle.

The number, size and/or arrangement of the ports may be configured to condition the settable material for delivery or at delivery. For example, the number, size and/or arrangement of the ports may be configured to meter the flow rate of the settable material.

The number, size and/or arrangement of the ports may be configured to assist in even distribution of the settable material.

The number, size and/or arrangement of the ports may be configured to circulate the settable material.

The number, size and/or arrangement of the ports may be configured to control the direction of the settable material. At least one port may be configured to eject the settable material in an uphole direction. At least one port may be configured to eject the settable material in a downhole direction.

The bore-engaging member or members may be configured to condition or clean the borehole.

The bore-engaging member or members may be of any suitable form and construction. In particular embodiments, the bore-engaging members may comprise spring scratchers. The bore-engaging member may comprise a brush. The bore- engaging member may comprise a reaming member. The bore-engaging member may comprise a cutter. The bore engaging member may comprise several of the above.

The shaft and the body may be operatively coupled by at least one bearing. The bearing may comprise a radial bearing. The tool may comprise a plurality of bearings. The shaft may be rotationally supported in the body by the radial bearings. In particular embodiments, the bearings may be provided at respective ends of the rotary drive arrangement. The tool may further comprise a thrust bearing. The thrust bearing may restrain relative axial movement of the body and the shaft.

The tool may further comprise a seal element adapted for location between the shaft and the body. The seal element may be annular. In particular embodiments, a plurality of seal elements may be provided. The seal element, or elements, may be interposed between the body and the shaft. In use, the seal elements may prevent, substantially prevent or prevent fluid leakage between the shaft and the body.

At least part of the tool may be configured to facilitate drilling through the tool. For example, at least one of the body, shaft, head portion, rotary drive arrangement and fluid port may be constructed from a readily drillable material which may be frangible or otherwise adapted to break. In particular embodiments, at least part of the tool may be constructed from an aluminium, ceramic, polymeric or carbon fibre material, though any other suitable material may be used.

Alternatively, or additionally, the downhole tool may comprise or define an access bore. The access bore may be configured to facilitate the drill through of the downhole tool.

In particular embodiments, the downhole tool may be configured for location at a distal leading end of a tubing string, such as a casing.

The tool may comprise attachment arrangement provided at one or both ends for coupling the tool to another element, such as a casing string or the like. The attachment means may, for example, comprise a threaded connection, in particular but not exclusively a threaded box and pin connection. Alternatively, the attachment arrangement may comprise or further comprise an adhesive bond, quick connect attachment or other suitable connector.

The tool may comprise, or may be operatively associated with, a centraliser.

The centraliser may be disposed on and/or adjacent to head portion. The provision of a centraliser on and/or adjacent to head portion may be used for example but not exclusively where the head portion is configured for use in a drilling, reaming or brushing application. The centraliser may be disposed on the body. The provision of a centraliser on the body may be used for example but not exclusively when the tool is configured for use in a brushing or cutting application. A plurality of centralisers may be provided. In such embodiments, the centralisers may be axially spaced. The centraliser may be of any suitable form and construction. The centraliser may comprise a solid body centraliser. The centraliser may comprise a bow spring centraliser. The tool may further comprise, or may be provided in combination with, a valve, such as a float collar. In use, the valve may be configured to prevent back flow of fluid, and in particular but not exclusively, back flow of the settable material into the downhole tool. In particular embodiments, the valve may be disposed above or uphole of the drive arrangement.

According to a second aspect, there is provided an assembly comprising:

a downhole tool according to the first aspect of the invention; and

a section of tubing.

The assembly may further comprise a tubing string. The tubing string may comprise a casing string. The tubing string may comprise a drill string.

According to a third aspect, there is provided a method for conditioning a well borehole, the method comprising:

providing a downhole tool comprising a body; a head portion; a drive

arrangement for rotating the head portion; and at least one bore-engaging member disposed on the head portion; and

operating the drive arrangement to rotate the head portion, whereby the at least one bore-engaging member engages the borehole to clean or condition the borehole.

A fourth aspect of the present invention relates to the use of a downhole drive arrangement in the delivery of a settable material into a well borehole, the drive arrangement configured to condition the settable material in the borehole for delivery.

Beneficially, embodiments of the present invention facilitate the delivery of a settable material, such as cement or the like, into an annulus between a downhole tubing or tubing string and a borehole by conditioning the settable material at a downhole location. This may prevent or at least mitigate the risk of problems occuring during the cementation process, such as false setting or excessive shear, and may improve the ability of an operator to carry out a complete and effective cementing job to target depth. For example, by conditioning the settable material in the downhole environment, embodiments of the present invention may add to the mixing energy of the material, re-energizing it and relieving false setting. Moreover, embodiments of the invention may ensure a flow area to be maintained which is outside the shearing critical zone. For example, embodiments of the invention may maintain a flow area of at least 0.5 in² (0.00032258m²) above which area shear does not occur.

The drive arrangement may condition the settable material by maintaining the settable material in a fluid condition. Alternatively, or additionally, the drive arrangement may be configured to alter the condition of the settable material downhole.

By conditioning the settable material in the borehole - either by maintaining the settable material in a fluid condition and/or by altering the condition of the settable material and/or by maintaining adequate flow areas - embodiments of the present invention may reduce the risk of problems occuring during the cementation process, such as false setting or excessive shear and provide an operator with a greater degree of control over the delivery of the material downhole.

Moreover, the ability to control the delivery of the settable material may facilitate uniform distribution of the settable material, for example in a continuous radial distribution to cover the entire annulus and so obviate or at least mitigate the problem of the settable material only covering the high side of the bore.

In a downhole cementing operation, for example, the ability to control the delivery of cement at a remote downhole location may permit an operator to carry out a complete and effective cementing job to target depth, which may be many kilometres from surface, with greater reliability and confidence.

The settable material may be directed through the drive arrangement.

The drive arrangement may, for example, be configured to condition the settable material by mixing, chopping, or churning the settable material as it passes through the tool.

Alternatively, or additionally, the drive arrangement may be configured to condition the settable material hydraulically, for example by altering the pressure and/or flow rate of the settable material as it passes through the drive arrangement.

Alternatively, or additionally, the drive arrangement may be configured to agitate the settable material. For example, the action of the drive arrangement may agitate the settable material to condition the settable material for delivery or alter the condition of the settable material for delivery.

In embodiments where the settable material is directed through the drive arrangement, the drive arrangement may directly agitate the settable material in contact with the drive arrangement.

Alternatively or additionally, the drive arrangement may be configured to agitate settable material remotely, that is agitate material not in direct contact with the drive arrangement.

In particular embodiments, the settable material may be directed through the drive arrangement to drive the drive arrangement. Thus, the drive arrangement may be driven by the settable material while at the same time the drive arrangement conditions the settable material for delivery.

In particular embodiments, the settable material comprises cement or the like. According to a fifth aspect, there is provided a tool for use in the delivery of a settable material into a well borehole, the tool comprising a drive arrangement configured to condition the settable material in the borehole for delivery.

The drive arrangement may be configured to condition the settable material by maintaining the settable material in a fluid condition.

Alternatively, or additionally, the drive arrangement may be configured to alter the condition of the settable material downhole.

As described above, by conditioning the settable material in the borehole - either by maintaining the settable material in a fluid condition and/or by altering the condition of the settable material - embodiments of the present invention may reduce the risk of unplanned setting and provide an operator with a greater degree of control over the delivery of the material downhole.

In particular embodiments, the tool may be configured to direct the settable material into and/or through the drive arrangement.

The tool may define, or provide mounting for, a fluid conduit.

In particular embodiments, the tool may be configured to direct the settable material into and/or through the drive arrangement via the fluid conduit.

The tool may be configured such that the drive arrangement is driven by the settable material. Thus, the drive arrangement may be driven by the settable material while at the same time the resulting movement of the drive arrangement maintains, contributes to maintaining, or alters the condition of the settable material for delivery.

The fluid conduit may be configured or arranged to direct a drive fluid through the drive arrangement to drive the drive arrangement. The drive fluid may comprise drilling fluid, drilling mud or the like. In use, the drive arrangement may be driven by the drive fluid, for example as the tool is deployed downhole or on reaching target depth in the borehole, in order to carry out a reaming and/or borehole cleaning operation; the drive arrangement then receiving and being driven by the settable material in order to condition the settable material for delivery.

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

The drive arrangement may comprise a rotary drive arrangement.

The drive arrangement may comprise a stator.

The drive arrangement may comprise a rotor.

The tool may comprise a body.

The body may be tubular. For example, the body may comprise a tubular housing.

The tool may comprise a shaft.

The shaft may be tubular or hollow.

The shaft may comprise an internal flange or cap. The flange may be arranged to define distinct chambers within the shaft. In use, the flange may prevent passage of fluid, such that all or substantially all of the fluid directed to the tool may be directed through the drive arrangement. This may facilitate high speed rotation of the drive arrangement.

The tool may comprise an exhaust port for directing the settable material - or the drive fluid - out from the drive arrangement. The exhaust port may be provided in the shaft. In particular embodiments, the body may comprise or provide mounting for the stator and the shaft may define or provide mounting for the rotor. In such embodiments, the shaft/rotor may be disposed at least partially within the body/stator.

In other embodiments, the body may comprise or provide mounting for the rotor and the shaft may comprise or provide mounting for the stator. In such embodiments, the body/rotor may be disposed outside the shaft/stator.

The tool may comprise a head portion.

The head portion may be of any suitable form and construction.

In other embodiments, the head portion may be configured for rotation relative to the shaft, for example the head portion may be rotatably coupled to the shaft.

The tool may be configured to distribute the settable medium from the head portion.

The tool may be configured to eject the settable material in a given direction.

The tool may be configured to eject the settable material in a radial direction. Alternatively, or additionally, the tool may be configured to eject the settable material in an axial direction. The tool may be configured to eject the settable material in an uphole hole direction. The tool may alternatively or additionally be configured to eject the settable material in a downhole direction. In particular embodiments, the tool may be configured to eject the settable material in the same direction as the direction of rotation of the head portion.

The tool may be configured to eject the settable material at a given velocity or flow rate.

The tool may comprise at least one fluid port. The at least one fluid port may permit the settable material to be directed to the exterior of the tool.

The tool may comprise a bore engaging member. The bore-engaging member or members may be configured to condition or clean the borehole.

The bore engaging member may be disposed on the head portion.

The drive arrangement may be selectively operable. The drive arrangement may be selectively operable in response to a fluid flow rate, such as a fluid flow rate through the drive arrangement. For example, the drive arrangement may be operable in response to a fluid flow rate exceeding a preset flow rate. Beneficially, in

embodiments comprising a bore engaging member the drive arrangement may be selectively operable to permit the operator to clean, cut or otherwise condition the bore at selected locations by controlling the fluid flow rate. The ability to selectively operate the drive arrangement may, for example, facilitate removal of mud cake at selected intervals or in selected zones. Thus, mud cake may be removed in a rigorous fashion in particular zones where required to obtain an effective cement job but may be maintained in other zones where it is desirable to maintain mud cake, for example where the formation porosity, permeability and pressures are such that drilling fluids may be lost through that zone, or where the formation is weak, and it is not desirable to have pump circulation at that point, increasing the effective circulation density.

At least part of the tool may be configured to facilitate drilling through the tool. For example, at least one of the body, shaft, head portion, rotary drive arrangement and fluid port may be constructed from a readily drillable material which may be frangible or otherwise adapted to break. In particular embodiments, at least part of the tool may be constructed from an aluminium, ceramic, polymeric or carbon fibre material, though any other suitable material may be used. Alternatively, or additionally, the downhole tool may comprise or define an access bore. The access bore may be configured to facilitate the drill through of the downhole tool.

The tool may comprise, or may be operatively associated with, a centraliser. The centraliser may be disposed on and/or adjacent to head portion. The provision of a centraliser on and/or adjacent to head portion may be used for example but not exclusively where the head portion is configured for use in a drilling, reaming or brushing application. The centraliser may be disposed on the body. The provision of a centraliser on the body may be used for example but not exclusively when the tool is configured for use in a brushing or cutting application. A plurality of centralisers may be provided. In such embodiments, the centralisers may be axially spaced. The centraliser may be of any suitable form and construction. The centraliser may comprise a solid body centraliser. The centraliser may comprise a bow spring centraliser.

According to a sixth aspect, there is provided an assembly comprising:

a downhole tool according to the fifth aspect of the invention; and

a section of tubing.

According to a seventh aspect of the present invention there is provided a method comprising:

operating a drive arrangement of a downhole tool in a borehole to condition a settable material for delivery or maintain the condition of the settable material for said delivery.

The method may comprise directing the settable material through the drive arrangement. Directing the settable material through the drive arrangement of the downhole tool maymaintain the settable material in a fluid condition suitable for delivery into the well borehole. Alternatively, or additionally, directing the settable material through the drive arrangement of the downhole tool may alter the condition of the settable material in a fluid state to improve suitability for delivery into the well borehole.

The method may comprise driving the drive arrangement using the settable material. Thus, the drive arrangement may be driven by the settable material while at the same time the resulting movement of the drive arrangement maintains, contributes to maintaining, or improves the condition of the settable material for delivery.

The method may comprise locating the tool downhole. The downhole tool may be located downhole on a tubing string. In particular embodiments, the downhole tool may be located downhole on a casing string. A housing of the downhole tool may be coupled to, or may form part of, the tubing string.

The method may comprise delivering the settable material. The settable material may be delivered to the annulus between the downhole tool and the borehole.

The method may comprise ejecting the settable material. The settable material may be ejected via one or more fluid port. In particular embodiments, the settable material may be ejected via one or more fluid nozzle. The size, number and/or arrangement of the fluid ports may condition the settable material for delivery. For example, the flow dynamics of the nozzle or nozzles may condition the settable material for delivery.

The method may comprise imparting rotation to the settable material as it is delivered.

The method may comprise rotating a head portion relative a body portion of the downhole tool to impart rotation to the settable material. The head portion may be rotated by the drive arrangement.

Beneficially, by operating a rotary drive arrangement to impart the rotation to the settable material.

The method may comprise permitting the settable material to fill the apparatus. For example, once the settable material has been delivered to the annulus, the settable material may be permitted to fill the apparatus. In particular embodiments, the method may comprise cementing the downhole tool in the wellbore.

The method may comprise drilling through part or all of the downhole tool. At least part of the tool may be configured to facilitate drilling through the tool. For example, at least one of the body, shaft, head portion, rotary drive arrangement and fluid port may be constructed from a readily drillable material which may be frangible or otherwise adapted to break. In particular embodiments, at least part of the tool may be constructed from an aluminium, ceramic, polymeric or carbon fibre material, though any other suitable material may be used. Alternatively, or additionally, the downhole tool may comprise or define an access bore. The access bore may be configured to facilitate the drill through of the downhole tool.

The method may comprise mechanically dressing and/or conditioning the borehole, such as by reaming the borehole, cleaning the borehole or the like. The borehole may be conditioned prior to directing the settable material through the tool. In use,

The method may comprise directing a drive fluid through the drive arrangement. The method may comprise driving the drive arrangement using the drive fluid. The drive fluid may comprise drilling fluid, drilling mud or other suitable fluid.

The drive fluid may be directed through the drive arrangement as the downhole tool is located downhole and/or on reaching target location or depth in the borehole.

The method may comprise conditioning the borehole prior to delivery of the settable material.

The method may comprise drilling or forming the borehole. The method may comprise drilling the borehole prior to directing the settable material through the tool. Alternatively, or additionally, the method may comprise drilling the borehole after delivery of the settable material.

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 or embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 shows a longitudinal section view of a downhole apparatus according to an embodiment of the present invention; and

Figure 2 shows a cross sectional view A-A of the apparatus shown in Figure 1.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring first to Figure 1 of the accompanying drawings, there is shown a longitudinal section view of a downhole tool 10 according to an embodiment of the present invention. In use, the tool 10 is configured for location in a well borehole B on a tubing string, such as a casing string C, and is operable to clean and/or otherwise condition the borehole B and deliver a settable material, such as cement slurry, into borehole annulus A for securing and supporting the casing string C in the borehole B.

The downhole tool 10 is operable to clean or condition the borehole B and facilitate other borehole operations to be carried out, such as a downhole cementing operations or the like. The ability to clean or condition the borehole B, and in particular but not exclusively a shoetrack or lowermost portion of the borehole B, facilitates efficient and effective cementing operations to be carried out to total depth. Amongst other things, this permits the casing to be fully supported off the borehole wall by centralisers, the use of which may otherwise be restricted or prevented by borehole restrictions. This enhanced ability to support the casing, particularly in the area of the shoetrack and other key zones, in the case of a cementing operation allows the cement slurry to pass on the low side of the casing C, improving the cementing operation and avoiding shear effects. Particular embodiments of the present invention facilitate the delivery of a settable material, such as cement slurry or the like, into the annulus A by conditioning the settable material at a downhole location, thereby preventing or at least mitigating the risk of problems occuring during the cementation process, such as false setting or excessive shear, and may improve the ability of an operator to carry out a complete and effective cementing job to target depth.

As shown in Figure 1 , the apparatus 10 comprises a body in the form of tubular housing 12 which, in the illustrated embodiment, forms part of, or is connected to, the cementing string S by suitable connection means, such as a threaded connection.

A shaft 14 is rotatably mounted within the housing 12 on radial bearings 16 and a seals 18 are provided between the shaft 14 and the housing 12 to prevent or substantially prevent fluid leakage therebetween.

The tool 10 comprises a drive arrangement - indicated generally by reference numeral 20 - the housing 12 defining a stator of the drive arrangement 20 and the shaft 14 defining a rotor of the drive arrangement 20. In the illustrated embodiment, the rotary drive arrangement 20 comprises a fluid turbine.

The tool 10 further comprises a head portion 22 and in the illustrated embodiment the head portion 22 is integrally formed with the shaft 14. However, it will be recognised that in other embodiments the head portion 22 may comprise a separate component configured to be coupled to the shaft 14. As shown in Figure 1 , the head portion 22 comprises a hollow main body section 24 and a nose portion 26 defining a distal leading end of the tool 10. In use, the head portion 22 receives fluid exiting from the rotary drive arrangement 20, the head portion 22 directing the fluid to the exterior of the tool 10 via a plurality of ports 28. In the illustrated embodiment, each of the ports 28 forms, or provide mounting for, a nozzle 30. The provision of one or more nozzle 30 permits jetting of the borehole B to assist in the removal of mud cake and the like to assist in the mechanical conditioning of the borehole B. Moreover, the nozzles 30 may be configured to control the exhaust velocity to vary the pressure drop through the tool 10.

The outer surface of the head portion 22 provides mounting for bore engaging members 32 which, in the illustrated embodiment, take the form of spring wire scratchers, brushes or the like. The scratchers 32 facilitate removal of mud cake and other borehole obstructions to mechanically condition the borehole B for subsequent operations.

As shown in Figure 1 , the tool 10 defines a fluid conduit. A first portion 34 of the first conduit is disposed within the shaft 14 towards a first end. A second portion 36 of the fluid conduit is disposed between the outside of the shaft 14 and the inside of the housing 12 and through the drive arrangement 20. A third portion 38 of the fluid conduit is disposed in the head portion 22.

In use, the fluid conduit is arranged to direct fluid through the tool 10 and through the rotary drive arrangement 20 to drive relative rotation therebetween.

As can be seen from Figure 1 , the shaft 14 is formed or provided with a cap 40. Thus, all or substantially all of the fluid directed through the tool 10 is directed along the fluid conduit, that is through the drive arrangement 20, facilitating high speed rotation of the shaft 14 relative to the body 12.

In use, a cementing operation is carried out by directing fluid in the form of cement slurry or the like through the casing string C (or via a cementing string S) into the shaft 14. Inlet port 42 permits the fluid to exit the shaft 14 and directs the fluid into the turbine 20. The seals 16 prevent or substantially prevent leakage of the fluid between the body 12 and the shaft 14. Once the fluid has passed through the turbine 20, it enters the head portion 22 via turbine outlet port 44, the fluid then being ejected from the head portion 22 via the nozzles 28.

Embodiments of the present invention provide a number of advantages. For example, it has been discovered that passing the settable material through a rotary drive arrangment according to embodiments of the invention has the effect of mixing the setting material and so maintains the settable material in a fluid state until delivery into the annulus, thereby preventing or at least mitigating the risk of flash setting of the settable material before the settable material reaches the annulus.

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, some embodiments of the downhole tool comprise a downhole valve, such as a float collar, which, in use, prevents back flow of the settable material.

Claims

1. A downhole tool for cleaning or conditioning a well borehole, the downhole tool comprising:

a body;

a head portion;

a drive arrangement for rotating the head portion; and

2. The downhole tool according to claim 1 , wherein the drive arrangement is selectively operable.

3. The downhole tool according to claim 2, wherein the drive arrangement is selectively operable in response to a fluid flow rate through the drive arrangement.

4. The downhole tool according to claim 1 , 2 or 3, wherein the downhole tool is configured to deliver a settable material, such as cement, into the borehole.

5. The downhole tool according to claim 4, wherein the head portion is configured to deliver the settable material.

6. The downhole tool according to claim 4 or 5, wherein the drive arrangement conditions the settable material in the borehole at least one of: maintaining the settable material in a fluid condition; and/or altering the condition of the settable material downhole.

7. The downhole tool according to claim 4, 5 or 6, comprising directing the settable material into and/or through the drive arrangement.

8. The downhole tool according to claim 7, comprising driving the drive

arrangement using the settable material directed through the drive arrangement.

9. An assembly comprising:

a downhole tool according to any preceding claim; and

a section of tubing.

10. A method for conditioning a well borehole, the method comprising:

providing a downhole tool comprising a body; a head portion; a drive arrangement for rotating the head portion; and at least one bore-engaging member disposed on the head portion; and

1 1. Use of a downhole drive arrangement in the delivery of a settable material into a borehole, wherein the drive arrangement conditions the settable material in the borehole.

12. The use according to claim 11 , wherein the drive arrangement conditions the settable material by at least one of: maintaining the settable material in a fluid condition; and/or altering the condition of the settable material downhole.

13. The use according to claim 11 or 12, wherein the drive arrangement is configured to condition the settable material by mixing, chopping, or churning the settable material as it passes through the tool.

14. The use according to claim 1 1 , 12 or 13, wherein the drive arrangement is configured to condition the settable material by altering the pressure and/or flow rate of the settable material as it passes through the drive arrangement.

15. The use according to any one of claims 11 to 14, comprising directing the settable material into and/or through the drive arrangement.

16. The use according to claim 15, comprising driving the drive arrangement using the settable material directed through the drive arrangement.

17. The use according to claim 15 or 16, wherein the drive arrangement is configured to agitate the settable material in contact with the drive arrangement as the settable material is directed through the drive arrangement.

18. A downhole tool for use in the delivery of a settable material into a well borehole, the tool comprising a drive arrangement configured to condition the settable material in the borehole for delivery.

19. The downhole tool according to 18, wherein the drive arrangement is configured to condition the settable material by at least one of: maintaining the settable material in a fluid condition; and/or altering the condition of the settable material downhole.

20. The downhole tool according to claim 18 or 19, wherein the drive arrangement is configured to condition the settable material by mixing, chopping, or churning the settable material as it passes through the tool.

21. The downhole tool according to 18, 19 or 20, wherein the drive arrangement is configured to condition the settable material by altering the pressure and/or flow rate of the settable material as it passes through the drive arrangement.

22. The downhole tool according to any one of claims 18 to 21 , wherein the tool is configured to direct the settable material into and/or through the drive arrangement.

23. The downhole tool according to claim 22, wherein the tool defines or provides mounting for a fluid conduit for directing the settable material into and/or through the drive arrangement.

24. The downhole tool according to claim 22 or 23, wherein the tool is configured such that the drive arrangement is driven by the settable material directed through the drive arrangement.

25. The downhole tool according to claim 22, 23 or 24, wherein the drive arrangement is configured to agitate the settable material in contact with the drive arrangement as the settable material is directed through the drive arrangement.

26. The downhole tool according to any one of claims 18 to 25, wherein the tool comprises, is operatively associated with, or is coupled to, at least one of: a cementing tool; a cement circulation tool; a reaming tool; a drilling tool; and a bore-cleaning tool.

27. The downhole tool according to any one of claims 18 to 26, wherein the drive arrangement comprises a rotary drive arrangement.

28. The downhole tool according to any one of claims 18 to 27, wherein the drive arrangement is selectively operable in response to a fluid flow rate.

29. The downhole tool according to any one of claims 18 to 28, wherein the drive arrangement comprises one of:

a fluid turbine;

a positive displacement motor (PDM);

a vane motor;

a pelton wheel.

30. The downhole tool according to any one of claims 18 to 29, wherein the tool comprises a body and a shaft.

31. The downhole tool according to claim 30, wherein the body comprises or provides mounting for a stator and the shaft defines or provides mounting for a rotor.

32. The downhole tool according to claim 31 , wherein the body comprises or provides mounting for a rotor and the shaft comprises or provides mounting for a stator.

33. The downhole tool according to any one of claims 18 to 32, wherein the tool comprises a head portion.

34. The downhole tool according to claim 33, wherein at least one of:

the tool is configured to distribute the settable medium from the head portion; the tool is configured to distribute the settable medium from the head portion and to eject the settable material in a given direction;

the tool is configured to distribute the settable medium from the head portion and to eject the settable material in a radial direction; the tool is configured to distribute the settable medium from the head portion and to eject the settable material in an axial direction;

the tool is configured to distribute the settable medium from the head portion and to eject the settable material in at least one of: an uphole direction; and a downhole direction;

the tool is configured to distribute the settable medium from the head portion and to eject the settable material in the same direction as the direction of rotation of the head portion;

the tool is configured to distribute the settable medium from the head portion and to eject the settable material at a given velocity or flow rate.

35. The downhole tool according to any one of claims 18 to 34, wherein the tool comprises at least one fluid port.

36. The downhole tool of claim 35, wherein the tool comprises a plurality of fluid ports and at least one of:

the number, size and/or arrangement of the ports is configured to condition the settable material for delivery or at delivery;

the number, size and/or arrangement of the ports is configured to assist in even distribution of the settable material;

the number, size and/or arrangement of the ports is configured to circulate the settable material;

the number, size and/or arrangement of the ports may be configured to control the direction of the settable material;

at least one port is configured to eject the settable material in an uphole direction;

at least one port may be configured to eject the settable material in a downhole direction.

37. The tool of any one of claims 18 to 36, wherein at least one of:

the tool comprises a bore engaging member;

the tool comprises a bore engaging member or members configured to condition or clean the borehole;

the tool comprises a bore engaging member and a head portion and the bore engaging member is disposed on the head portion; the tool comprises a bore engaging member comprising at least one of: a brush, a reaming member and/or a cutter.

38. The tool of any one of claims 18 to 37, wherein at least part of the tool is configured to facilitate drilling through the tool.

39. The tool of any one of claim 18 to 36, wherein the downhole tool comprises or defines an access bore to facilitate the drill through of the downhole tool.

40. An assembly comprising:

a downhole tool according to any one of claims 18 to 39; and

one of: a section of tubing; a tubing string; a casing string; and a drill string.

41. A method comprising: