Note: Descriptions are shown in the official language in which they were submitted.
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
1
Underreamer with radial expandable cutting blocks
Field of the Invention
The present invention relates to a cutting tool for widening the diameter of a
borehole
and a method for operating the cutting tool. The cutting tool comprises a
housing in
which a cutting block and an activation element are arranged. Upon activation,
the
activation element is driven in an axial direction which in turn moves the
cutting block
in a radial direction from a retracted position to an expanded position via a
mechanical
coupling.
Background of the Invention
Today, it is well-known within the oil, gas and water industries to widen the
diameter
of a borehole after the initial drilling using an underreamer having
expendable blocks
with a plurality of cutting elements, such as teeth or cutters. The initial
drilling is done
by using a cutting tool or drill bit without any expendable cutting blocks,
also called a
hole opener. The borehole is normally lined with one or more casing elements
before
the underreamer is inserted into the borehole. The underreamer is lowered into
posi-
tion and the cutting blocks are expanded to widen the diameter of the hole.
US 7900717 B2 discloses an underreamer having a housing with three elongated
slots
in which three slidable cutting blades are arranged. The cutting blades are at
one end
connected to a sleeve surrounding a hollow central tube which allows drilling
fluid to
pass through the tool. A compression spring holds the sleeve in place relative
to the
central tube. The tool is activated by dropping a ball into the drilling fluid
which is
caught in the central tube which in turn forces the central tube downwards
relative to
the housing due to the differential pressure. Drilling fluid is then led into
a chamber
below the sleeve via corresponding openings which in turn forces the sleeve
upwards
relative to the housing. An angled sliding surface in each slot then causes
the cutting
blades to pivot out of the housing. Afterwards the pumping of the drilling
fluid is
stopped and the cutting blades are retracted due to the compression force of
the spring.
This solution is sensitive to torsion forces caused by the rotating movement
of the tool
due to the length of the slots.
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
2
US 7594552 B2 discloses an underreamer having a housing in which a central
hollow
tube is arranged for allowing passage of the drilling fluid. Three radially
moveable
blocks are arranged in the housing relative to the central tube. A flow
restricting open-
ing located in the tube is used to activate the tool. Pressure of the drilling
fluid above
this restrictive opening forces the tube downwards relative to the housing.
Drilling
fluid is then led into a chamber between the tube and cutting block which in
turn
pushes the cutting blocks out of the housing. Afterwards the pumping of the
drilling
fluid is stopped and the cutting blocks are forced back into the housing due
to the
compression force of radially extending springs located between the cutting
blocks
and the housing. This solution has a very limited radial movement since range
of
movement is limited to the thickness of the housing and thus the tool has a
shorter
lifespan compared to other underreamer tools. Also, the tool must be removed
from
the downhole in order to reset the tool.
Cantilever shaped cutting arms can be used instead. However, this mechanism re-
quires long elongated slots to expand and contract the arms making it
sensitive to tor-
sion forces. Furthermore, the arms have limited space for the cutting elements
thus
increasing the wear and reducing the lifespan of the tool.
US 7314099 B2 discloses an underreamer having three cutting blades arranged in
elongated slots in an outer housing, wherein the cutting blades are connected
to a Z-
drive unit located at the bottom of the tool. The Z-drive is arranged around a
central
tube allowing drilling fluid to pass through the tool unit and uses a piston
to push the
cutting blades into an expanded position. The cutting blades are moved in a
combined
longitudinal and radial direction by using guiding grooves and tracks provided
on the
blades and edges of the slots. A compression spring located around the central
tube is
used to move the cutting blades back into the housing. This solution is
sensitive to
torsion forces caused by the rotation of the tool due to the long elongated
slots.
US 2010/0108394 Al discloses an underreamer having a housing with openings in
which three cutting blocks are arranged and a central tube for allowing
drilling fluid to
pass through the tool. The tube has three projecting plates each extending
into a corre-
sponding cavity in the cutting blocks where the side surfaces of the plate and
cavity
have engaging inclined grooves and tracks. When activated, a ball is caught by
the
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
3
tube which in turn forces the tube downwards relative to the housing. The
cutting
blocks are then moved out of the housing due to the engaging grooves and
tracks. A
compression spring is used to force the tube upwards when the pressure of the
drilling
fluid is removed which in turn also forces the cutting block back into the
housing. In
this solution the moveable parts are located in the central hole of the
housing, thus a
certain pressure differential is required to activate the tool.
Object of the Invention
An object of the invention is to provide a cutting tool having improved
torsion proper-
ties during operation.
An object of the invention is to provide a cutting tool that allows for an
increased
range of expansion.
An object of the invention is to provide a cutting tool that allows for a
longer lifespan
and an increased number of cutting elements.
An object of the invention is to provide a simple and easy method of operating
a cut-
ting tool.
Description of the Invention
An object of the invention is achieved by a cutting tool for widening the
diameter of a
borehole, comprising:
- a housing having a top end, a bottom end and a first outer surface,
wherein the hous-
ing defines a longitudinal direction and a transverse radial direction,
- at least one moveable cutting block having at least one cutting element,
each cutting
block being arranged in a first opening located in the first outer surface and
configured
to move in the radial direction between a retracted position and an expanded
position
relative to the housing,
- at least one moveable activation element is arranged relative to the at
least one cut-
ting block and configured to move along the longitudinal direction relative to
the
housing for activation of the at least one cutting block, wherein
- the housing comprises a cavity connected to the first opening in which
the at least
one cutting block and the at least one activation element are arranged,
wherein the
cavity is arranged between the first outer surface and an inner surface of the
housing.
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
4
This provides a simple and compact cutting tool in the form of an underreamer
with
improved torsional and twisting properties as the movement or expansion of the
cut-
ting blocks is limited to a radial movement in and out of the housing. Thus,
the overall
length of the cutting tool can be reduced. No moveable sleeves or tubes need
to be
arranged in the central through hole of the housing, thus no additional
horsepower or
pressure differential is needed to activate the cutting tool. This allows the
central hole
of the housing to act as a passageway for the drilling fluid, thus the inner
diameter of
this passageway can be increased.
The tool is adapted to be placed in any type of borehole in which an
underreaming
process is desired. The outer size and shape of the housing substantially
matches the
inner contours of the borehole, preferably allowing for a gap or annular space
to be
formed between the inner wall of the borehole and the outer surface of the
housing.
Drilling fluid and loose materials may be led past the tool and back up to a
ground
level via the gap or annular space. The housing may have a cylindrical shaped
outer
surface or any other desired shape.
The housing may be a solid or hollow housing made of a high strength material,
such
as steel or any other suitable material. The activation element and/or cutting
block
may be made of a high strength material, such as alloy steel, Polycrystalline
Dia-
monds Compacts (PDC), or any other suitable material. The cutting elements may
be
made of any suitable wear resistance material, such as steel, tungsten
carbide, or a
composite material.
The cutting tool is preferably an underreamer, a back-reamer, a near-bit
reamer or any
other type of reamer tool. This allows the configuration and dimensions of the
cutting
tool to be adapted to the desired application.
According to one embodiment, the activation element is further connected to an
acti-
vation unit arranged in the cavity, wherein the activation unit is configured
to drive
the activation element.
The present configuration allows the cutting tool to be activated by suitable
activating
means arranged in the cavity, no Z-drive or ball seats are needed to activate
the cutting
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
tool. The activation unit may further comprise suitable control means for
controlling
the operation of the cutting tool.
The cavity is formed in the outer surface of the housing and in configured to
receive
5 and hold the moveable parts used to operate the cutting tool. The cavity
has one or
more openings. A hatch or removable cover may be provided at these openings
for
closing off the cavity and protecting the components located inside the
cavity. This
allows the various parts to be accessed from exterior of the housing for
installation,
servicing, and replacement. The opening for the cutting block may be located
in one
of the hatches or covers.
According to a special embodiment, the activation unit is arranged in a
chamber inside
the cavity, the chamber being sealed off from the rest of the cavity.
The cavity may be separated into two or more chambers by means of one or more
in-
ternal walls and/or sealing elements. The activation unit may be arranged in a
first
chamber while the cutting block and the activation element may be arranged in
a sec-
ond chamber. The first chamber may be sealed off from the second chamber by
using
suitable sealing elements, such as 0-rings, lip seals, labyrinth seals, rotary
seals, fluid
barriers or other suitable sealing means. Another set of sealing elements may
be ar-
ranged between each hatch or cover and surrounding edges of the cavity, or
between
adjacent hatches or covers. This allows the electrical drive components and
other sen-
sitive components to be protected from the surrounding drilling fluid which
otherwise
may damage these components.
Drilling fluid may enter the second chamber via gaps formed between the
activation
element and the cutting block, and/or via separate inlets and outlets
connected to the
second chamber. Said separate inlets and outlets may be used to circulate the
drilling
fluid inside the second chamber when the activation element and cutting blocks
are
moved relative to each other. The openings in which the cutting blocks are
arranged
may be connected to the second chamber. Alternatively, the second chamber may
also
be sealed off from the drilling fluid by using yet another set of sealing
elements, e.g.
arranged relative to each cutting block and the surrounding edges of the
respective
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
6
opening. This allows the non-sensitive components to be arranged in the second
chamber.
According to another special embodiment, the activation unit comprises a
linear actua-
tor connected to a control unit configured to control the operation of the
activation
unit.
The activation element may be driven by suitable drive means arranged in the
cavity
and relative to the activation element. In a preferred embodiment, the
activation ele-
ment is connected to a linear actuator via a shaft. The linear actuator may be
arranged
in the first chamber and the shaft may extend through the inner wall of the
cavity. The
linear actuator may be driven by a hydraulic, pneumatic, electrical,
mechanical or an-
other suitable power source. The linear actuator may be a ball screw, a roller
screw, a
pneumatic or hydraulic cylinder with a moveable piston, a motor (e.g. an
electrical
motor), a solenoid with a moveable stem or another suitable linear actuator.
The operation of the linear actuator and power source may be controlled by a
control
unit arranged in the cutting tool, e.g. in the first chamber in the cavity.
The control
unit may be electrically connected to the linear actuator and/or power source
via wires
or a wireless connection. The control unit may be a microprocessor or another
electri-
cal circuitry configured to control the operation of the cutting tool. One or
more sen-
sors, such as a flow-rate sensor, a pressure sensor or a position sensor, may
be electri-
cally connected to the control unit for sensing one or more predetermined
parameters,
such as the flow-rate or pressure of the drilling fluid or the respective
position of the
activation element and/or cutting block. This allows the control unit to
monitor the
operating of the cutting tool.
Optionally a communications module may form part of the control unit for
communi-
cation with a remote unit, e.g. located at ground level. The communication
module
may be connected to the remote unit via a wired connection, e.g. data cables,
or a
wireless connection, e.g. a downhole link or mud pulses.
In a preferred configuration, the control unit monitors the pressure and/or
flow-rate of
the drilling fluid to detect a stable level within a predetermined time window
which in
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
7
turn is used to activate, deactivate or change the operating mode of the
cutting tool.
The control method described in DK 178108 B1 is hereby incorporated into the
appli-
cation by reference.
According to one embodiment, the mechanical coupling comprising a first set of
guid-
ing elements, e.g. a pin, configured to engage a second set of guiding
elements, e.g.
through hole, wherein one of the first and second sets of guiding elements is
arranged
on a third surface of the at least one cutting block and the other set of
guiding ele-
ments is arranged on a fourth surface on the at least one activation element
facing the
third surface.
This configuration allows for the openings in the housing to have a shape and
size that
substantially matches the cross-sectional size and shape of the cutting
blocks. This
eliminates the need for including additional space in order to allow axial
movement of
the cutting blocks during expansion compared to conventional cutting blocks.
The activation element and cutting blocks are mechanically connected by means
of
complementary coupling elements. The coupling elements may be arranged between
the inner end of the cutting blocks and the outer surface of the activation
element
and/or between a side surface of the cutting blocks and an opposite facing
side surface
of the activation element. This allows for a simple and direct engagement
between the
activation element and the cutting blocks which eliminates the need for any
axially
moveable sleeves or tubes for expansion of the cutting blocks. This allows for
a more
compact cutting tool and eliminates the need for inclined surfaces or wedge
shaped
elements to expand the cutting blocks.
The coupling elements may be one or more tracks or pins configured to engage
one or
more complementary grooves or through holes. The coupling elements, e.g.
tracks and
grooves, may be arranged on two opposite facing surfaces of the activation
element
and the cutting block. Alternatively, the coupling elements, e.g. pins, may
extend
through the other coupling elements, e.g. holes, and may be connected to two
opposite
sides of the activation element or the cutting block. Alternatively, one or
more guiding
rollers or wheels may be used and which are configured to move along a rail or
groove
located in the opposite surface. The elements may each comprise a projecting
part
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
8
having a contact surface facing a matching contact surface of the other
element. The
contact surface of the activation element may slide along the other contact
surface as it
is being activated. Other types of guiding systems connecting the activation
element
with the cutting blocks may be used.
Said pins may have a predetermined shear threshold that enables the pins to
shear or
break when a predetermined force is applied to the pins. The respective
cutting block
may then fall back into its retracted position. This increases the safety of
the cutting
tool in an extreme load situation. The pins also reduce the risk of the
cutting blocks
getting stuck due to solids or other particles in the drilling fluid.
Two or more cutting blocks may be arranged in the same radial plane and angled
rela-
tive to each other. Alternatively or additionally, two or more cutting blocks
may be
arranged in two or more radial planes and aligned or offset relative to each
other. Two
or more of the cutting blocks may have the same size and shape and/or
different sizes
and shapes. The use of multiple cutting blocks allows the shape and size of
the cutting
elements to be adapted to the formation surrounding the borehole. This allows
for a
greater number of cutting blocks and enables the cutting elements to be
distributed
over a greater number of cutting blocks, thus reducing the wear on each
cutting ele-
ment and increasing the lifespan of tool. This also allows the surface area on
which
the cutting elements are provided to be increased which in turn further
reduces the
wear on each cutting element and increases the lifespan of tool.
The guiding elements may be placed in a predetermined inclined position
relative to
the longitudinal direction, thus allowing for a simple and easy transfer of
movement
between the activation element and the cutting blocks. The first set of
guiding ele-
ments may be placed in angled position, e.g. between 30 to 60 degrees,
optionally 45
degrees, relative to the longitudinal direction of the activation element. The
second set
of guiding elements may be placed in angled position, e.g. between 30 to 60
degrees,
optionally 45 degrees, relative to the longitudinal direction of the cutting
block. Alter-
natively, the first or second set of guiding elements may be placed in a
substantial
perpendicular angle, e.g. 90 degrees, relative to the other set of guiding
elements or
the longitudinal direction of that element. This allows the guiding elements
of the cut-
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
9
ting blocks to slide or roll along the length of the guiding elements of the
activation
element as it moves in an axial direction.
According to one embodiment, the at least one activation element comprises a
cavity
or through hole located on an outer surface, wherein at least a part of the at
least one
cutting block extends into the cavity or through hole.
This configuration allows for a greater expansion of the cutting blocks
compared to
conventional cutting tools, as the range of expansion is not limited to the
thickness of
the housing. An inner end of the cutting block may extend into a cavity (a non-
through
hole) or a through hole in the activation element. Two or more cutting blocks
may
extend into the same cavity or hole. The outer contours of the cutting block
may sub-
stantially match the inner contours of the cavity/hole allowing for a tight
fit. The cavi-
ty/hole is configured to receive and hold the cutting block in at least the
retracted posi-
tion, preferably in both the retracted and expanded position. The cavity/hole
may ex-
tend in the longitudinal direction for allowing the activation element to move
axially
while maintaining the cutting blocks in their axial positions. The cutting
block and/or
the cavity or hole may have a substantial rectangular, squared, or any other
suitable
cross-sectional profile.
In an alternative configuration, the activation element may extend through an
opening
of a through hole or cavity in each of the cutting blocks. In this embodiment,
the cavi-
ty/hole may extend in a radial direction to allow the cutting blocks to move
radially
while maintaining the activation element in its radial position. Instead, each
cutting
block may be connected to individual activation elements via individual
mechanical
couplings.
According to a special embodiment, the ratio between the relative axial
movement of
the activation element and the relative radial movement of the cutting blocks
is be-
tween 1:1 and 1:100.
The term "relative axial movement" is defined as the relative movement between
the
activation element and the housing in the longitudinal direction. The
"relative radial
movement" is defined by the retracted and expanded positions of the cutting
blocks.
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
The ratio may be determined based on the actual axial movement of the
activation
element from its starting point, i.e. in which the cutting blocks are in their
retracted
position, to its stopping point, i.e. in which the cutting blocks are in their
expanded
position. The ratio may instead be determined based on the length of the first
set of
5 guiding element. The first or second set of guiding elements may be
placed in any
angle relative to the respective longitudinal direction capable of providing a
travel-to-
expansion ratio from 1:1 and 1:100. The present invention allows the travel-to-
expansion ratio to be increased compared to conventional cutting tools,
meaning that
it requires less axial space in order to achieve the same radial expansion.
According to one embodiment, the cutting tool comprises a spring element
configured
to apply a spring force to the activation element, the spring element being
arranged
relative to the activation element inside the cavity.
The activation element may be pushed back into its starting position due to
the spring
force which in turn moves the cutting blocks into the housing and back into
their re-
tracted position. One or more spring elements may be used to push the
activation ele-
ment or individual activation elements back to its/their starting position.
Alternatively
or additionally, the hydraulic pressure of the drilling fluid acting on the
activation
and/or cutting blocks may be used to move the activation back towards the
starting
position. Drilling fluid may be led into the second chamber by separate inlets
located
near one end of the second chamber or by an annular space around the cutting
blocks.
This allows the tool to automatically retract the cutting blocks as the
pressure of the
drilling fluid is reduced, thus preventing the tool from getting stuck in the
borehole.
The spring element may be a compression spring or another type of spring
capable of
generating a spring force as it is being deformed due to the movement of the
activa-
tion element. The spring element may be arranged at or near the bottom end
and/or the
top end of the second chamber. The spring element may lie against one end of
the
activation element and a protrusion located inside the chamber or the
top/bottom end.
Alternatively, one or more spring elements may be arranged between the cutting
blocks and the activation element or housing for pushing the cutting blocks
back into
the housing.
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
11
The top and/or bottom end of the housing may comprise coupling elements, e.g.
a
threaded coupling, for coupling to a complementary coupling element of another
downhole tool, e.g. a motor, an agitator, or a drill bit.
According to one embodiment, the cutting tool further comprises at least one
guiding
block or stabiliser blade arranged in at least one second opening located on
the first
outer surface, wherein the at least one stabiliser blade is moveably connected
to the at
least one activation element.
One or more of the cutting blocks may be replaced by guiding blocks or
stabiliser
blades with suitable guiding elements, e.g. a convex outer surface or rollers,
for guid-
ing the cutting tool during the underreaming process. The tool may comprise at
least
one set of cutting blocks and another set of guiding blocks or stabiliser
blades. One or
more guiding blocks or stabiliser blades may be arranged in the same plane as
one or
more of the cutting blocks. The guiding blocks or stabiliser blades may be
expanded
and retracted in the same manner as the cutting blocks. In this configuration,
the stabi-
liser tool may be at one end mounted to another cutting tool or underreamer.
This al-
lows the cutting tool to act as a stabiliser for stabilising the drill string
during the in-
troduced into the expanded borehole.
An object of the invention may also be achieved by a cutting tool for widening
the
diameter of a borehole, comprising:
- a housing having a top end, a bottom end and a first outer surface,
wherein the hous-
ing defines a longitudinal direction and a transverse radial direction,
- at least one moveable cutting block having at least one cutting element,
each cutting
block being arranged in a first opening located in the first outer surface and
configured
to move in the radial direction between a retracted position and an expanded
position
relative to the housing,
- at least one moveable activation element arranged relative to the cutting
blocks and
configured to move along the longitudinal direction relative to the housing
for activa-
tion of the cutting blocks, wherein
- the activation element comprises a second outer surface facing an inner
surface of
the housing and each cutting block extends into a cavity in the second outer
surface,
and wherein each cutting block is moveably connected to the activation element
by a
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
12
mechanical coupling, the mechanical coupling being configured to transfer the
longi-
tudinal movement of the activation element into the radial movement of the
cutting
blocks.
This also provides a simple and compact cutting tool in the form of an
underreamer
with improved torsional and twisting properties as the movement or expansion
of the
cutting blocks is limited to a radial movement that is less than the thickness
of the
housing. The openings in the housing advantageously have a shape and size that
sub-
stantially matches the cross-sectional size and shape of the cutting blocks as
no addi-
tional space is needed to compensate for the axial movement of the cutting
blocks
during the expansion. It also eliminates the need for any inclined surface or
wedge
shaped elements to expand the cutting blocks.
This configuration also allows for a greater expansion of the cutting blocks
compared
to conventional cutting tools, as the range of expansion is not limited to the
thickness
of the housing. This alternative embodiment differs from the embodiment
described
above by having the activation element arranged in the central through hole of
the
housing where the cutting block extends further through openings located on an
inner
surface of the housing. In this alternative embodiment, the cavity/hole of the
activa-
tion element may have the same configuration as described above.
In this alternative embodiment, the central through hole of the housing acts
as the sec-
ond chamber described above. The inner surface may substantially match the
outer
contours of the activation element allowing for a tight fit during movement of
the ac-
tivation element. The inner and/or outer surface may have a circular,
elliptical, rectan-
gular/squared, triangular, or any other multi-sided cross-sectional profile.
The activa-
tion element may alternatively have an outer profile that differs from the
inner profile
of the housing.
The housing may in both embodiments comprise one or more guiding elements,
e.g. a
spline system, an axial bearing, a sleeve or another guiding system arranged
between
the inner surface of the chamber and the outer surface of the activation
element. One
or more spline elements may be arranged on the inner surface of the chamber
and one
or more complementary spline elements may be arranged on the outer surface of
the
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
13
activation element. This allows the movement of the activation element to be
limited
to an axial movement.
In this alternative embodiment, the cutting tool comprises a pressure
regulating unit
connected to one of the ends of the housing, the pressure regulating unit
being config-
ured to regulate the differential pressure over the cutting tool.
The pressure regulating unit acts as the activation unit described above. The
pressure
regulating unit further enables the differential pressure of the drilling
fluid passing
through the tool to be regulated which in turn is used to move the activation
element.
The pressure regulating unit may be located at one end of the housing and may
be in
fluid communication with one or more fluid paths provided in the housing or in
the
activation element. The fluid path may be a central through hole in the
activation ele-
ment aligned with the centre line of the housing. The fluid path may be
connected to
an outlet or opening at the other end for leading the drilling fluid out of
the cutting
tool. The activation level may be determined based on the length of the first
guiding
elements, the travel-to-expansion ratio, or the compression force of the
spring ele-
ment.
The pressure regulating unit may be a flow restrictor with fixed flow
regulating ele-
ments or adjustable flow regulating elements. The flow regulating elements may
be
pre-set prior to deployment or adjusted during operation by using a downhole
link or a
communications link if a suitable receiver is located in the tool.
In this alternative embodiment, one or more sealing elements may be used to
separate
the drilling fluid being led through the central fluid path from the drilling
fluid being
led back through the annular space at the outer surface of the cutting tool.
The sealing
element may be arranged between the activation element and the housing and/or
be-
tween the activation element and the cutting blocks. The sealing elements may
be 0-
rings, lip seals, labyrinth seals, fluid barriers or other suitable sealing
means. This
generates a differential pressure over the cutting tool which is used to
activate the ac-
tivation element.
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
14
An object of the invention is also achieved by a method for operating a
cutting tool as
described above, wherein the method comprises the steps of:
- moving the at least one activation element in the longitudinal direction
relative to the
housing, and further moving the at least one cutting block in the radial
direction out of
the housing towards an expanded position,
- wherein the at least one activation element is arranged in a cavity in
the outer sur-
face, wherein said at least one activation element is driven along the cavity
by an acti-
vation unit further arranged in the cavity.
This provides a simple and direct activation of the cutting tool without using
axially
moveable sleeves or tubes located in the housing in order to expand the
cutting blocks.
The present configuration enables the expansion of the cutting blocks to be
limited to
only a radial movement relative to the housing unlike conventional cutting
tools. This
allows the length of the openings in the outer surface of the housing as well
as the
length of the housing to be reduced which in turn increases the torsional
strength of
the cutting tool.
The moveable part, i.e. the activation element and the cutting block, is
arranged in an
outer cavity of the housing. The movement is driven by an activation unit also
ar-
ranged in this cavity. Thus, no movable parts are arranged in the central
through hole
of the housing, i.e. defined by the inner surface of the housing, which in
turn allows
the inner diameter of the fluid passageway to be increased. Also, no
additional pres-
sure differential or horsepower is required to activate the cutting tool.
The present cutting tool also allows for easy access to the moveable parts by
simple
removing an outer cover or opening an outer hatch. The respective parts may
then be
installed, serviced or replaced, and afterwards the cover or hatch is closed
again.
According to one embodiment, a linear actuator moves the at least one
activation ele-
ment, wherein the operation of the linear actuator is controlled by a control
unit.
The axial movement of the activation element is carried out using a linear
actuator
driven by a suitable drive unit as described above. The control unit controls
the opera-
tion of the linear actuator, e.g. based on one or more measured parameters.
This al-
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
lows for a simple and fast activation of the cutting tool. This eliminates the
need for a
spring element as the movement can be performed solely by the linear actuator.
Alternatively, the control unit may communicate with a remote unit, e.g. at
ground
level, via a communications module as described above. The control unit may
transmit
5 the measured data and/or status information of the cutting tool to the
remote unit and
receive one or more control signals from the remote unit. The control unit may
then
adapt the operation of the cutting tool according to the received control
signals.
According to one embodiment, the longitudinal movement is transferred into the
radi-
10 al movement by using a mechanical coupling located between the at least
one activa-
tion element and the at least one cutting block.
This provides a simple and reliable way of transferring the axial movement of
the ac-
tivation element into a radial movement without also having to move the
cutting
15 blocks in the axial direction. The first and second sets of coupling
elements are prefer-
ably placed in an inclined angle relative to the longitudinal direction so
that one of
said sets of coupling elements is moved, e.g. slid or rolled, along the length
of the oth-
er set of coupling elements. This allows for the travel-to-expansion ratio to
be in-
creased as it reduces the axial space needed to expand the cutting blocks
compared to
conventional cutting tools. This also increased the radial pressure applied by
the cut-
ting block compared to other conventional cutting blocks.
The cutting tool may comprise a built-in safety function as one of the
coupling ele-
ments may be a pin extending through a hole defining the other coupling
element,
wherein said pin may be a shear pin having a predetermined shear threshold. In
the
event of an overload situation, the pin may shear and the cutting block may
fall back
into the retracted position. The cutting tool may then be retrieved and the
pins may be
replaced and the cutting tool may be lowered into the downhole again.
According to one embodiment, the method further comprises the step of:
- monitoring at least one parameter of the drilling fluid passing through the
cutting
tool via the control unit, and further detecting when the at least one
parameter has
reached a predetermined level within a predetermined time window, or
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
16
- communicating with a remote unit via the control unit, wherein the remote
unit and
the control unit control the operation of the cutting tool.
The control unit may monitor the pressure and/or flow-rate of the drilling
fluid pass-
ing through the drilling tool. The control unit may further determine if the
pressure
and/or flow-rate have reached a stable predetermined level within a
predetermined
time window which in turn is used to activate or deactivate the cutting tool
or switch
between operating modes, such as described in DK 178108 Bl.
Additionally or alternatively, the control unit may communicate with the
remote unit
for displaying status information to an operator or later analysis. The
operator may
transmit control signals to the cutting tool via the communication path, e.g.
a wired or
wireless connection as described above. The control unit then controls the
operation of
the cutting tool according to the received control signals. This allows the
operator to
monitor the operation and optionally adjust the operation if needed.
According to one embodiment, one end of the cutting block extends into an
opening
located on the at least one activation element, wherein the one end is at
least moved
further into the activation element when the at least one cutting block is
moved to-
wards the retracted position.
This enables each cutting block to at least partly be arranged in a cavity
formed in the
outer surface of the activation element when placed in the retracted position.
As the
cutting block is expanded, it is moved further out of the cavity and out of
the housing
by means of the mechanical coupling. One end of the cutting block may remain
in the
cavity when the block is placed in its expanded position, this reduces the
risk of the
cutting block turning or falling out of the cavity during operation, thus
causing a fail-
ure of the tool. This allows for a greater expansion since the range of
movement is not
limited to the thickness of the housing compared to the cutting tool of US
7594552
B2.
An object of the invention may also be achieved by a method for operating a
cutting
tool as described above for widening the diameter of the borehole, wherein the
method
comprises the steps of:
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
17
- moving the activation element in a longitudinal direction relative to the
housing us-
ing a differential pressure of a drilling fluid being circulated in the
borehole,
- moving the cutting block in the radial direction out of the housing
towards an ex-
panded position,
- wherein the longitudinal movement of the activation element is transferred
into the
radial movement of the cutting blocks by using a mechanical coupling located
be-
tween the activation element and the cutting block, wherein
- one end of the cutting block extends into an opening located on an outer
surface of
the activation element, wherein the one end is moved further into the
activation ele-
ment when the cutting block is moved towards the retracted position.
This configuration also allows for a greater expansion of the cutting blocks
compared
to conventional cutting tools, as the range of expansion is not limited to the
thickness
of the housing. Thus, a simple and compact cutting tool can be formed. This
embodi-
ment differs from the embodiment described above by having the activation
element
arranged in the central through hole of the housing where the cutting block
extends
further through openings located on an inner surface of the housing. In this
embodi-
ment, the cavity/hole of the activation element may have the same
configuration as
described above. In this embodiment, the central through hole of the housing
acts as
the second chamber described above.
In this alternative embodiment, the amount of drilling fluid being led through
the cut-
ting tool is regulated by using a flow regulating unit connected to the
housing.
The amount of drilling fluid being led through the cutting tool is regulated
by using a
flow regulating unit connected to the housing. This allows the activation
level of the
activation element to be adjusted by regulating the amount of drilling fluid
being di-
verted through the cutting tool. The difference pressure across the cutting
tool moves
the activation element when it exceeds the spring force of the spring elements
located
in the housing. An operator is able to pre-set the flow regulating unit prior
to deploy-
ing the cutting tool or able to adjust the configuration of the flow
regulating unit dur-
ing operation. As the force exerted by the difference pressure drops below the
spring
force, the cutting blocks are moved back into the housing by means of the
spring ele-
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
18
ments. This allows the pressure regulating unit to act as the activation unit
described
above.
Description of the Drawing
The invention is described by example only and with reference to the drawings,
wherein:
Fig. 1 shows a first exemplary embodiment of a cutting tool according to the
inven-
tion in a retracted position,
Fig. 2 shows the cutting tool of fig 1 in an expanded position,
Fig. 3 shows a cross sectional view of the cutting tool of fig. 1,
Fig. 4 shows a cross sectional view of a second exemplary embodiment of the
cut-
ting tool
Fig. 5 shows a third exemplary embodiment of the cutting tool in a retracted
posi-
tion,
Fig. 6 shows the cutting tool of fig. 5 in an expanded position,
Fig. 7 shows the cutting tool of fig. 5 seen in the radial direction, and
Fig. 8 shows a cross-section of the cutting tool of fig. 5.
In the following text, the figures will be described one by one and the
different parts
and positions seen in the figures will be numbered with the same numbers in
the dif-
ferent figures. Not all parts and positions indicated in a specific figure
will necessarily
be discussed together with that figure.
Reference list
1 Cutting tool
2 Housing
3 Top end
4 Bottom end
5 Side wall
6 Activation element
7 Sealing element
8 Pressure regulating unit
9 Spring element
10 Cavity
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
19
11 Cutting block
12 Opening
13 Outer surface
14 Cutting elements
15 Mechanical coupling
16 Longitudinal direction, axial movement
17 Transverse direction, radial movement
18 Fluid path, through hole
19 Annular space
20 Stabiliser blade
21 Inner wall
22 Cutting tool
23 Cavity
24 Actuator unit
25 Wall
26 Shaft
27 Linear actuator
28 Control unit
Detailed Description of the Invention
Fig. 1 shows a first exemplary embodiment of a cutting tool 1 in the form of
an un-
derreamer seen from the side. The cutting tool comprises a housing 2 having a
longi-
tudinal direction and a transverse radial direction adapted to be placed in a
borehole.
The housing 2 comprises a top end 3 connected to a bottom end 4 via a
cylindrical
shaped side wall 5. Part of the housing 2 is cut away for illustrative
purposes. The
housing 2 is made of high strength material, such as steel. The longitudinal
direction
extends through the top and bottom ends 3, 4 while the radial direction
extends
through the side wall 5.
The housing 2 forms an internal chamber in which a moveable activation element
6 is
arranged. The activation element 6 in the form of a box is configured to be
moved
axially along the longitudinal direction when activated. One or more sealing
elements
7 are arranged on the inner surface of the housing 2 and/or on the outer
surface of the
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
activation element 6. The sealing element 7 forms a fluid tight seal which
separates
the drilling fluid passing into the fluid path (shown in figs. 3-4).
The activation element 6 is at a top end connected to a pressure regulating
unit 8
5 which is configured to regulate the different pressure across the cutting
tool 1. The
pressure regulating unit 8 may comprise fixed regulating elements or
adjustable regu-
lating elements for diverting a drilling fluid into one or more fluid paths
(shown in
figs. 3 and 4) located in the housing 2 or the activation element 6. The fluid
paths may
be through holes which at the other end are connected to an outlet (not
shown). If the
10 cutting tool 1 comprises active regulating elements, an actuator element
(not shown)
may be connected to the regulating elements for adjusting their position. The
actuator
element may be controlled by a control unit (shown in fig. 5).
The activation element 6 is at a bottom end connected to a spring element 9,
e.g. a
15 compression spring, arranged inside the chamber. The spring element 9 is
further con-
nected to the bottom end 4 of the housing 2. The spring element 9 is
configured to
generate a spring force when it is deformed which is used to bias the
differential pres-
sure of the drilling fluid.
20 The activation element 6 comprises a cavity 10 (not shown in fig. 1 and
2) configured
to receive and hold at least a part of a moveable cutting block 11. The cavity
10 is
connected to at least one opening located in the outer surface 6a of the
activation ele-
ment 6. The opening faces an opening 12, e.g. a through hole, located in the
outer sur-
face 13 of the housing 2. The cutting block 11 comprises a longitudinal
direction par-
allel to the radial direction of the housing 2. The cutting block 11 comprises
a plurality
of cutting elements 14 at one end configured to perform an underreaming
process
when brought into contact with the inner surface of the borehole. The other
end is con-
figured to extend into the cavity 10 of the activation element 6. For
illustrative pur-
poses, only one cutting block 11 is shown.
A mechanical coupling 15 is arranged between the cutting block 11 and the
activation
element 6 for transferring the axial movement of the activation element 6 into
a radial
movement of the cutting blocks 11. The mechanical coupling 15 comprises a
first set
of coupling elements (not shown) arranged on a side surface of the activation
element
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
21
6 and a second set of coupling elements (not shown) arranged on a side surface
of the
cutting block 11. The first coupling elements are grooves configured to engage
com-
plementary tracks defining the second set of coupling elements. The track and
grooves
are placed in an inclined angle, e.g. 45 degrees, relative to the respective
longitudinal
directions of the elements 6, 11, or any other angle capable of providing a
radial ex-
pansion rate (travel-to-expansion ratio) from 1:1 and 1:100.
The method of operation will now be described in reference to figs. 1 and 2.
Fig. 2
shows the cutting tool 1 in an expanded position while fig. 1 shows the
cutting tool in
a retracted position. The cutting tool 1 is mounted to a drill string or
bottom hole as-
sembly and located into position in the borehole. The pressure in the drilling
fluid is
increased. As the differential pressure exceeds the activation level of the
activation
element 6, e.g. the spring force, the activation element 6 is moved/pushed
axially
downwards (marked with arrow 16) towards a stopping position, thereby
compressing
the spring element 9. The second coupling elements then slide along the first
coupling
elements in the mechanical coupling 15 which in turn cause the cutting block
11 to
move radially outwards (marked with arrow 17) of the housing 2 and the cavity
10.
When the reaming process is completed, the pressure in the drilling fluid is
reduced.
The spring force causes the activation element 6 to move axially upwards
(marked
with arrow 16) towards its starting position as the differential pressure
drops below
the activation level of the activation element 6. The first coupling elements
are then
slid along the second coupling elements which in turn cause the cutting block
11 to
move back into the housing 2 and further into the cavity 10. The cutting tool
1 may
then be raised to the ground level or moved to a new position.
Fig. 3 shows a cross sectional view of the cutting tool l' where the cutting
block 11 is
placed in its retracted position. The outer surface of the activation element
6 is shaped
to substantially match the inner contour of the housing 2 so they form a more
or less
tight fit. One or more optional guiding elements configured to limit the
movement of
the activation element 6 to an axial movement may be arranged between the
inner
surface of the housing 2 and the outer surface of the activation element 6.
The sealing
element (shown in figs. 1-2) forms a fluid tight seal which separates the
drilling fluid
passing into the fluid path 18 from the drilling fluid passing through the
annular space
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
22
19. The fluid path 18 is formed by a central through hole in the activation
element 6 in
fluid connection with an inlet and outlet (not shown) located at the ends 3, 4
respec-
tively.
The cavity 10 extends in a longitudinal direction parallel to the longitudinal
direction
of the activation element. The mechanical coupling 15 is arranged in the
cavity 10
between two opposite facing surfaces of the two elements 6, 11. The cutting
elements
14 are in the retracted position flushed with or placed in a retracted
position relative to
the outer surface 13 of the housing 2.
One or more stabiliser blades 20 are arranged in a second opening located on
the outer
surface 13 of the tool 1'. The stabiliser blade 20 extends into the housing 2
and into a
second cavity in the activation element 6, as shown in fig. 3. The stabiliser
blade 20 is
moveable connected to the activation element 6 by a second mechanical coupling
15.
Instead of cutting elements, the stabiliser blade 20 comprises a curved
guiding surface
20a or a plurality of rollers for contacting the inner wall 21 of the borehole
(marked
with a dotted line). The stabiliser blade 20 is expanded and retracted in the
same man-
ner as the cutting blocks 11. This stabilises the tool 1 during movement in
the expand-
ed borehole.
Fig. 4 shows a cross sectional view of a second exemplary embodiment of the
cutting
tool 1. In this embodiment the tool 1" comprises two or more cutting blocks
11a, lib,
11c, here three blocks are shown, each of which is arranged in an individual
opening
12a, 12b, 12c and cavity 10a, 10b, 10c. The cutting blocks 11 are angled
relative to
each other, e.g. in 120 degrees intervals and are simultaneously activated,
e.g. moved
radially, when the activation element 6 is moved axially downwards as
described
above.
Fig. 5 shows a third exemplary embodiment of the cutting tool 22 in a
retracted posi-
tion where fig. 6 shows the cutting tool 22 in an expanded position. The
cutting tool
22 has a cavity 23 formed in the outer surface 13 of the housing 2' in which
the acti-
vation element 6 and the cutting block 11 are arranged. An activation unit 24
is further
arranged in the cavity 23 and connected to the activation element 6 via a
shaft 25. An
inner wall 26 separates the cavity 23 into a first chamber and a second
chamber,
wherein the shaft 25 extends through the inner wall 26.
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
23
The activation unit 24 comprises a linear actuator 27 connected to a control
unit 28
which controls the operation of the cutting tool 22. The activation unit 24 is
accessible
via a cover removable connected to the housing 2'. The control unit 28
communicates
with a remote unit (dotted lines) via a communications module arranged in the
cavity
23.
When activated, the control unit 28 send a control signal to the linear
actuator 27
which in turn moves the activation element 6 and the cutting block to their
expanded
position as described in figs. 1 and 2. After completing the underreamer
process, the
control unit 28 then sends another control signal to the linear actuator 27
which moves
the activation element 6 and the cutting block to their retracted position as
described
in figs. 1 and 2.
In this configuration, the drilling fluid is able to pass freely through the
cutting tool 22
as the central trough hole of the housing 2' acts as the fluid passageway 18'.
Fig. 7 shows the cutting tool 22 seen in the radial direction where the
housing 2' is
omitted for illustrative purposes. As illustrated, the cavity 23 is connected
to three
openings which can be closed off by a cover or hatch (not shown). The coupling
ele-
ments 15 are here shown as a through hole in the cutting block 11 and a pin
extending
through the hole. The pin is connected to two opposite facing surfaces on the
activa-
tion element 6.
The cavity 10' of the activation element 6 is an elongated cavity which at
least corre-
sponds to the axial movement of the activation element 6.
Fig. 8 shows a cross-section of the cutting tool 22 and the cavity 23 in which
the acti-
vation element 6 and the cutting block 11 are arranged. The inner diameter of
the
through hole 18' is greater than the inner diameter of the through hole 18
shown in
figs. 3 and 4. Thus, more drilling fluid may be led through the cutting tool
22 without
any significant loss of pressure.
CA 02954444 2017-01-06
WO 2016/004954 PCT/DK2015/050205
24
The invention is not limited to the embodiments described herein, and may be
modi-
fied or adapted without departing from the scope of the present invention as
described
in the patent claims below.
