Note: Descriptions are shown in the official language in which they were submitted.
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DOWN HOLE 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 non-
uniform cementing operation.
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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
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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, 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.
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
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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.
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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.
5 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.
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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
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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.
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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.
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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
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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
5 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
10 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 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 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.
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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.
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 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 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.
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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.
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.
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 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.
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.
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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 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 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-
,
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14
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 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.
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.
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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
5 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
10 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
15 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.
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 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
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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
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17
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.
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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.
Th,e 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.
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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
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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
5 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.
