Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
1
Circulating sub with activation mechanism and a method thereof
Field of the Invention
The present invention relates to an activation mechanism for activating a
circulating
sub in a drill string, comprising a sensor sensing at least a pressure of a
drilling fluid
located in a first fluid conduit in the downhole tool when installed, a valve
element
arranged relative to a second fluid conduit in the downhole tool when
installed, and a
control unit connected to the sensor and configured to monitor the sensed
signal and to
electronically control the movement of the valve element based on the sensed
signal.
The present invention also relates to a circulating sub for positioning in a
borehole,
comprising a housing having an outer side surface facing an inner wall of the
bore-
hole, a first fluid conduit connected to a first opening in one end and a
second opening
in the other end for leading a drilling fluid through the circulating sub, and
at least a
second fluid conduit in fluid communication with the first fluid conduit,
wherein the
circulating sub further comprises an activation mechanism as mentioned.
The present invention finally relates to a method for activating a circulating
sub using
an activation mechanism as mentioned above, where the method comprises the
steps
of positioning the circulating sub at a predetermined depth of a borehole,
increasing a
pressure of a drilling fluid located in the first fluid conduit of the
circulating sub, mon-
itoring the pressure of the drilling fluid inside the first fluid conduit, and
activating the
circulating sub when a certain event is detected using a control unit.
Background of the Invention
Today, various activation systems are used to selectively activate downhole
tools,
such as circulating subs, under-reamers and other types of downhole tools used
during
drilling operations. It is known to drop balls of various sizes into the
drilling fluid to
activate or deactivate a circulating sub having a corresponding number of ball
retain-
ers for receiving these balls. Such an activation system only has a limited
number of
activations/deactivations, typically between five to seven times, and
determined by the
size of the ball retainers. Once full, the circulating sub must be retrieved
and the ball
retainers emptied before it can be lowered into the drilling hole again.
Furthermore,
the ball may be stopped in the fluid passageway by accumulated solid
particles, there-
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
2
by blocking the circulation of drilling fluid and causing an increase in
pressure above
the blockage which could damage the downhole tool or even the operation
equipment
located at ground level.
Another activation system solving this problem uses a radio frequency (RF)
receiver
or transceiver arranged in the circulating sub to wirelessly communicate with
one or
more radio frequency identification (RFID) tags being dropped into the
drilling fluid.
Once within communication range of the receiver/transceiver, the RFID device
is able
to communicate with the circulating sub for activating or deactivating a
selected circu-
lating sub. An exemplary solution thereof is disclosed in US 2013/0319767 Al
where-
in active or passive RFID tags are used to activate a desired function of the
circulating
sub based on the command received from the RFID tag. A pressure sensor in the
cir-
culating sub can be used instead to detect mud pulses or flow rate signals for
activat-
ing the circulating sub.
Both types of activation systems provide a slow and time consuming process
since
each ball or RFID tag first has to be pumped via the drilling fluid from the
ground
level to the selected downhole tool before the downhole tool can be activated
or deac-
tivated. It often takes more than one hour for the RFID tag or ball to reach a
downhole
tool located at a depth of about 3000 metres as the speed by which the RFID
tag or
ball travels depends on the pumping speed and the internal diameter of the
drilling
string.
Yet another solution is to use an indexing type activation system in which the
mode of
the downhole tool is changed every time the pumps circulating the drilling
fluid are
turned off and on. The disadvantage of this solution is that the sequence of
modes is
determined by the indexing mechanism, thus the operator must follow the
indexing
sequence to select a desired mode. Furthermore, it is well known that such
indexing
mechanisms have a complex configuration that is prone to mechanical failures.
WO 2013/103907 Al discloses an under-reamer having a pressure activated flow
switch mechanism for activating and deactivating the under-reamer. The flow
switch
mechanism comprises a piston configured to move between an open position and a
closed position based on the different pressures. A spring element pushes the
piston
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
3
towards an upper seat of the housing to form a seal in the closed position.
Once the
differential pressure of the passing drilling fluid exceeds the spring force,
the piston is
axially moved to the open position where it contacts a lower seat of the
housing.
Thereby, allowing drilling fluid to enter an upper chamber while drilling
fluid is venti-
lated from a lower chamber out through an outer opening. The drilling fluid in
the
upper chamber further acts on another piston which radially moves the cutting
block
out of the housing. The spring element forces the piston back to the closed
position
when the spring force exceeds the combined forces of the differential pressure
and the
friction of an annular seal located between the piston and the surrounding
housing.
This activation mechanism has a complex configuration and requires an actual
flow
through the under-reamer tool for activating the cutting block.
There is a need for providing an improved method that allows for a fast and
accurate
activation of a downhole tool, such as a circulating sub, without the use of a
ball or
RFID tag or a complicated downhole link.
US 2013/0284424 Al discloses a circulating sub comprising a housing having a
cen-
tral fluid path in fluid communication with a bypass path in the sidewall of
the hous-
ing. The bypass path has an inlet opening facing the central fluid path and an
outlet
opening facing the annulus surround the sub. A moveable piston is arranged
inside an
interior chamber relative to this bypass path and comprises a plug facing a
plug seat
located in the bypass path. A pressure sensor is used by a controller in the
interior
chamber to detect an activation signal via mud pulses or downlink signals
transferred
through the passing mud in the central fluid path. Upon activation, the
controller ig-
nites a combustible agent wherein the combustion gasses push the piston into
the by-
pass path until the plug comes into contact with the plug seat. This closes
off the by-
pass path. This configuration provides a single-use activation after which the
circulat-
ing sub must be retrieved from the borehole and reset. This activation
mechanism can
only be accessed and reset by taking the sub apart which adds to the
complexity and
costs of the sub.
Object of the Invention
An object of this invention is to provide an activation mechanism that
overcomes the
drawbacks of the prior art.
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
4
An object of this invention is to provide an activation mechanism that allows
for a fast
and accurate activation of a downhole tool.
An object of this invention is to provide an activation mechanism capable of
activat-
ing the downhole tool without an actual flow of drilling fluid.
An object of the invention is to provide a downhole tool with an integrated
activation
mechanism that reduces the risk of a seal failing during operation.
Description of the Invention
An object of the invention is achieved by an activation mechanism for
activating a
circulating sub in a drill string, comprising:
- at least one sensor configured to sense at least a pressure of a drilling
fluid lo-
cated in a first fluid conduit in the circulating sub when installed,
- a control unit connected to the sensor and configured to monitor the
sensed
signal of the at least one sensor, wherein the control unit is configured to
elec-
tronically activate the movement of at least one moveable valve element in one
direction based on the sensed signal,
- wherein the at least one valve element is configured to be arranged
relative to
at least a second fluid conduit in the circulating sub when installed, the at
least
one valve element is configured to move between an open position and a
closed position,
- wherein the second fluid conduit is in fluid communication with the first
fluid
conduit, and the at least one valve element comprises at least one valve end
configured to close the second fluid conduit in the closed position and to
open
the second fluid conduit in the open position, characterised in that
- the control unit is electrically connected to at least one actuator unit
arranged
relative to the at least one valve element, the at least one actuator unit is
con-
figured to perform a reciprocating movement of the at least one valve element
between the open position and the closed position, wherein the control unit is
further configured to electronically activate the movement of the at least one
moveable valve element in an opposite direction.
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
The term "close" means that the valve element is moved into the conduit and
substan-
tially blocks off (shut) the fluid passageway so that no drilling fluid can
flow through
the conduit. The term "open" means that the valve element is moved out of the
con-
duit so that the drilling fluid can flow through the conduit again.
5
This provides a simple and accurate activation mechanism that does not require
a ball
or RFID tag to be dropped into the drilling fluid for activating or
deactivating the
downhole tool. This allows for a very fast activation/deactivation process
compared to
activation systems using a ball or RFID tag. In example, this configuration
allows a
downhole tool located at a depth of about 3000 metres to be activated within a
few
minutes, e.g. about three minutes. Furthermore, no indexing systems are needed
to
select an operation mode of the downhole tool, as the operation mode can be
selected
during the start-up process of the pumping system, thus no cycling between
start and
stop of the pumping system is needed to select the operation mode.
This configuration allows the activation mechanism to be integrated into the
downhole
tool or arranged as a standalone unit configured to be connected to the
downhole tool.
This configuration is well-suited for any type of circulating subs in which a
bypass of
the main fluid flow is desired. The drilling fluid may be any type of air,
mist, foam,
inert gas, or even any mixture or combination of different gravity fluids or
gasses.
The control unit is configured to control the actuator unit, e.g. first
actuator unit,
which in turn moves the valve element, e.g. first valve element, forwards or
back-
wards along a predetermined direction. The direction of movement may be
parallel
and/or orthogonal to the axial/longitudinal direction of the downhole tool.
Any type of
actuator unit may be used to move the valve element, e.g. a linear actuator, a
piston or
another suitable actuator unit. The actuator unit may be powered by an
electrical, me-
chanical or hydraulic power unit integrated into or connected to the control
unit. This
allows the control unit to control the movement and/or speed of the valve
element.
In one embodiment, the control unit is further configured to apply at least a
first time
window to the sensed signal and to determine whether the sensed signal remains
sta-
ble relative to at least a first threshold value within the at least first
time window or
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
6
not, wherein the at least one valve element is activated if a stable pressure
level is de-
tected.
The terms "stable", "stable level" and "stable pressure level" are defined by
a prede-
termined threshold level or band having an upper and a lower limit value
centred rela-
tive to the threshold value where the sensed parameter, e.g. the pressure,
remains
within the upper and lower limit values for at least the during of the time
window.
The control unit may be any type of analogue, digital or logical electronic
circuit suit-
able of processing and monitoring the electrical signals received from the
sensors, e.g.
the pressure sensor. Alternatively, another type of sensor may be used to
detect a sig-
nal representative of the pressure of the drilling fluid. In a preferred
configuration, the
control unit comprises a controller, e.g. a microprocessor, configured to at
least moni-
tor the sensed pressure within a predetermined/first time window. The control
unit/controller is further configured to compare the sensed pressure with at
least
one/first threshold value defining at least one/first operation mode. This
operation
mode may simply be to activate or deactivate the downhole tool. The control
unit/controller is configured to determine whether the pressure of the
drilling fluid
remains stable within the first time window, i.e. within the upper and lower
limit val-
ues of the respective threshold value. If a stable level is detected, then the
control
unit/controller sends a predetermined control signal or command to the
downhole tool
for activation/deactivation of the tool or selection of an operation mode
thereof. The
control signal may simply be used to activate the actuator unit which then
moves the
valve element in the forward or backward direction depending on the respective
con-
trol signal. The detection of a stable level of the sensed parameter allows a
simpler
and less complex activation process compared to downhole link systems using
mud
pulses or even flow pulses.
The time window may be selected based on the operating flow rate, the
operating
pressure or the dimensions of the borehole. The upper and lower limits may be
deter-
mined based on the respective threshold value and/or the tolerance of the
pumping
system. The operating pressure may be selected between 10bar and 100bar. The
time
windows may be selected between 1 minute and 10 minutes, e.g. between 3
minutes
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
7
and 5 minutes. The upper and lower limit values may be selected between 1% to
10% of the selected activation level/threshold value or the operating level.
In one embodiment, the control unit is further configured to apply at least a
second
time window to the sensed signal, and the control unit is further configured
to deter-
mine whether the sensed signal remains stable relative to at least a second
threshold
value within the at least second time window or not.
In this configuration, the control unit/controller is configured to compare
the sensed
pressure to two or more threshold values each defining an operation mode of
the same
downhole tool or an activation level for individual downhole tools. The
individual
downhole tools may be connected to the same activation mechanism or,
alternatively,
to individual activation mechanisms each designed for a selected threshold
value. The
individual downhole tools may further have the same configuration or different
con-
figurations depending on the desired application and/or position in the
borehole. This
allows multiple operation modes and/or downhole tools to be activated or
deactivated
via the activation mechanism.
The second time window may be the same as the first window or have a different
length and/or shape. The second threshold value may be the same as the first
threshold
value or have a value that is higher or lower than the first threshold value.
The limit
values for the first and second threshold values may be the same or they may
differ for
each threshold value, e.g. define different threshold ranges. This allows the
activation
levels to be optimised for each downhole tool and/or each operation mode for
ena-
bling a better control of multiple operation modes and downhole tools.
The two or more threshold values may be used to simply control the actuator
unit
which selectively extend or retract the valve element, e.g. selectively closes
or opens
the second fluid conduit, dependent on the sensed pressure. In this
configuration, the
controller may monitor the sensed signal, e.g. within another predetermined
time win-
dow, and selective activate the actuator unit each time the sensed pressure
reaches one
of the threshold values. The actuator unit in turn performs a reciprocating
movement
of the valve element according to this selective activation. The control unit
may op-
tionally comprise a timer unit electrically connected to the controller,
wherein the tim-
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
8
er unit may be activated when the valve element is moved into the open or
closed po-
sition. Once a predetermined time period has lapsed, then the controller may
via the
actuator unit move the valve element back into the closed or open position.
This ena-
bles the circulating cub to be activated at regular intervals, if needed, to
provide a pul-
sating fluid flow in the annular space. This pulsating flow may also be used
to dis-
lodge or remove any accumulated cuttings in the annular space.
The control unit/controller may further be configured to detect a temporary
drop or
reduction in the sensed signal, e.g. the sensed pressure. The drop or
reduction may be
defined by a predetermined amplitude and/or time length. This allows the
control unit
to verify that the selected downhole tool or operation mode has been activated
or de-
activated. The second time window may be applied after this temporary drop or
reduc-
tion has been detected, or after the pumping pressure has been increased or
lowered to
the second threshold value.
In exemplary embodiment, the actuator unit comprises at least one solenoid
element
for inductively moving at least one push rod mechanically connected to the at
least
one valve element.
The actuator unit preferably comprises a solenoid element for inductively
moving a
magnetic or magnetic conductive rod or tube, i.e. a push rod, which in turn is
mechan-
ically connected to the valve element. The solenoid element is arranged
relative to the
push rod so that a magnetic field is directed into the material, e.g. steel or
a ferromag-
netic material, of the push rod. The push rod may form part of the valve
element. An
external or internal power unit, e.g. a battery, may be used to supply the
solenoid. De-
pendent on the direction of the current flow in the windings of the solenoid,
the sole-
noid may move the valve element in one or both directions and thus towards the
open
and/or closed position. The control unit/controller may adjust the current
level in the
solenoid which in turn regulates the speed of the valve element. This allows
for a sim-
ple and quick movement of the valve element using a minimum of components.
This
also provides a better control of the movement compared to other activation
mecha-
nism using combustible agents.
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
9
Optionally, a spring element may be arranged relative to the push rod for
biasing the
movement towards the closed position. This provides a failure safe function to
the
activation mechanism in which the valve element is held in the closed position
so no
drilling fluid is led through the second fluid conduit.
In one embodiment, at least one sealing element is arranged in an outer
surface of the
poppet valve, the outer surface is facing an inner surface of the chamber,
wherein the
at least one sealing element remains in contact with the inner surface during
move-
ment of the poppet valve.
The valve element is positioned inside a chamber, e.g. a first chamber, formed
in the
activation mechanism or in the downhole tool where the valve element is able
to move
relative to the chamber when activated. The chamber may be formed in a
sidewall of
the housing of the downhole tool. The valve element is preferably formed as a
poppet
valve where one end is connected to or form part of the push rod mentioned
above.
The valve element may be a solid or hollow element with no internal fluid
conduits or
openings. The other end of the valve element/poppet valve is shaped to be
brought
into contact with a seat, e.g. a valve seat, located relative to the second
fluid conduit,
e.g. a branch thereof. This valve end is configured to substantially close the
second
fluid conduit when placed in the seat, e.g. the closed position.
The chamber comprises at least one inner surface facing a corresponding outer
surface
of the valve element. The chamber further has a first end facing the second
fluid con-
duit and a second end facing away from the second fluid conduit. The sealing
ele-
ments, e.g. one, two or more, are arranged in a dedicated outer surface of the
valve
element/poppet valve and contact a dedicated inner surface of the chamber. The
seal-
ing element may be 0-rings, GT-rings or any other suitable sealing element.
This al-
lows the sealing elements to remain in contact with this inner surface at all
times dur-
ing the movement, thus forming a continuous seal preventing drilling fluid
from enter-
ing the chamber. This reduces the risk of the sealing element failing compared
to con-
ventional downhole units, since no peripheral edges of the valve element are
moved
past the sealing elements, nor is the sealing elements moved past any
peripheral edge
of a bypass opening in the housing.
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
In conventional downhole tools, a bypass conduit in the housing matches a
corre-
sponding bypass opening provided in the body of the centrally placed valve or
sleeve.
Drilling fluid is guided through the sleeve or valve and out through this
bypass open-
ing and further through the bypass conduit of the housing. Sealing elements
located on
5 the housing or on the valve or sleeve seal off the area between these two
units. During
movement, the valve or sleeve is moved relative to the housing so that the
peripheral
edge of the bypass conduit or bypass opening is moved past one or more of the
sealing
elements. This increases the risk of the respective sealing element failing
due to in-
creased wear; the peripheral edge may even force the respective sealing
element out of
10 its seat. The present invention solves this problem by placing the
activation mecha-
nism and thus the valve element in the sidewall of the housing so no fluid
conduits in
the valve element are needed.
At least a second valve element may be arranged in the first chamber or in at
least a
second chamber. The second valve element may be arranged relative to the
second
fluid conduit, e.g. another branch thereof, or at least another/third fluid
conduit in flu-
id communication with the first fluid conduit. Optionally, a second actuator
unit may
be connected to the second valve element for moving that valve element where
this
actuator unit is controlled by the control unit/controller. The at least two
valve ele-
ments and actuator units may have the same configuration or different
configurations.
The individual valve elements may be activated at the same pressure level or
at differ-
ent pressure levels. This allows the activation mechanism to control the fluid
bypass
of two or more fluid conduits, thus allowing for an improved control of the
bypass of
the drilling fluid.
Alternatively, the first valve element as described above may be arranged
relative to
two or more branches of the second fluid conduit and/or two or more fluid
conduits in
fluid communication with the first fluid conduit. This allows for an increased
bypass
of the drilling fluid. The individual branches and/or fluid conduits used to
bypass the
drilling fluid are designed to reduce any 'dead end' areas between the
respective inner
and outer openings. In example, the seat may be positioned parallel or
perpendicular
to the flow direction in the branch/conduit. The side or sides of the seat may
be sloped
or curved and/or have a minimal surface area to prevent solids from
accumulating on
the seat which otherwise would render the valve element inoperable. The
internal sur-
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
11
faces of the branch/conduit and optionally the seat are preferably shaped so
that they
do not form any significant or large restrictions along the flow path which
otherwise
would cause an increase in the flow velocity and, thus, an accelerated wear.
In one embodiment, a valve housing is arranged inside the chamber, wherein the
pop-
pet valve extend at least partly into the valve housing via an opening in one
end of the
valve housing.
The chamber may comprise a narrow portion and a large portion. The narrow
portion,
e.g. an internal hole, is at one end in communication with the second fluid
conduit.
The narrow portion is at the other end in communication with the large
portion. The
inner dimensions of the narrow portion substantially correspond to the outer
dimen-
sions of the valve element, thus forming a relative tight fit around the valve
element.
This increases the structural strength of the sidewall of the housing near the
second
fluid conduit as only a minimum amount of material is removed. The large
portion,
e.g. a cavity having an opening located in an outer side surface of the
sidewall, is con-
figured to receive and hold the remaining components of the activation
mechanism.
A valve housing or retainer may be arranged in the chamber, e.g. in the large
portion,
and comprises one end facing the second fluid conduit and another end facing
the ac-
tuator unit. The push rod may extend at least partly into the valve housing
via an
opening in this other end. This opening may be sealed off using suitable
sealing
means. The valve element/poppet valve may also extend at least partly into the
valve
housing via an opening in this one end. This opening may be also sealed off
using
suitable sealing means. The valve housing may be partly or fully filled with a
lubri-
cant, e.g. oil. This reduces the amount of air inside the valve housing and
reduces the
energy required to move the valve element. This also keeps the sealing
elements in-
tact.
The valve housing may comprise guiding means, e.g. a bearing, for guiding the
valve
element is it moves relative to the valve housing. When placed in the closed
position,
a contact surface on the valve element, e.g. a thickened or thinned portion,
is optional-
ly brought into contact with a corresponding contact surface on the valve
housing, e.g.
a protrusion. Likewise when placed in the open position, a contact surface on
the
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
12
valve element, e.g. a thickened or thinned portion, is optionally brought into
contact
with a corresponding contact surface on the valve housing, e.g. a protrusion.
This lim-
its the movement of the valve element relative to the valve housing.
Alternatively, the push rod may be connected to this other end of the valve
housing
and thus the valve housing may be moved relative to the chamber. As the valve
hous-
ing is moved towards the second fluid conduit, a contact surface on the valve
housing
may be brought into contact with a corresponding contact surface on the valve
ele-
ment. The valve housing and valve element are then moved together towards the
closed position. Likewise, as the valve housing is moved away the second fluid
con-
duit, another contact surface on the valve housing may be brought into contact
with
another corresponding contact surface on the valve element. The valve housing
and
valve element are then moved together towards the open position.
In one embodiment, the control unit is further connected to an activation
circuit, e.g. a
pressure switch, which is configured to activate the control unit at a
predetermined
pressure level.
The control unit is electrically connected to an activation circuit for
reducing the pow-
er consumption of the electrical components. The activation circuit is
configured to
wake up the control unit, e.g. turn power on, when the pressure inside the
first fluid
conduit exceeds a predetermined/third threshold level. Any suitable activation
circuit
may be used to wake up the control unit, such as a simple pressure switch. The
control
unit/controller then monitors the internal pressure of the drilling fluid in
the first fluid
conduit and activates a desired operation mode or downhole tool or the
actuator unit
as described above if a stable pressure level is detected. Once the activation
circuit
determines, e.g. simply by detection, that the pressure drops below the third
threshold
value, the control unit enters a sleep mode, e.g. power is turned off. This
allows the
control unit to only be activated when the internal pressure of the drilling
fluid reaches
a predetermined pressure level, thus reducing the power consumption and
increasing
the operation time.
The control unit may also be configured to enter sleep mode after completing
one or
more task, such as activation of the selected operation mode or downhole tool
and
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
13
optionally verifying the activation as described above. The control unit may
be further
configured to activate the downhole tool or actuator unit when a certain event
is de-
tected, such as excessive vibrations or cocking of a jarring tool.
In one embodiment, the activation mechanism is configured to be implemented in
a
cavity located in an outer side surface of a housing of the circulating sub.
The activation mechanism according to the invention has a small enough
configura-
tion for implementation or installation in an outer cavity located in the
housing of the
downhole tool, while most conventional activation mechanisms are designed for
im-
plementation/installation in a central cavity of the downhole tool. This
allows for a
more optimal fluid passageway in the central through hole, i.e. the first
fluid conduit,
of the downhole tool, since there are no flow restrictions or at least a
reduced number
of flow restrictions in the downhole tool. Also, this provides quick and easy
access to
the various components of the activation mechanism whereas other activation
mecha-
nisms are only accessible by taking the entire downhole tool apart.
In one embodiment, the at least one sensor comprises a first sensor configured
to
sense a first pressure of the drilling fluid in the first fluid conduit and a
second sensor
configured to sense a second pressure of the drilling fluid in a returning
drilling fluid
when installed, wherein the control unit is configured to determine a
differential pres-
sure by using the first and second pressures.
The activation mechanism may comprise at least two pressure sensors
electrically
connected to the control unit/controller. A first pressure sensor is arranged
relative to
the first fluid conduit for measuring an internal/first pressure of the
drilling fluid, e.g.
via an opening in the inner surface of the through hole. A second pressure
sensor is
arranged relative to the annulus for measuring an external/second pressure of
the re-
turning drilling fluid, e.g. via an opening in the outer side surface of the
housing or in
the removable cover. The control unit may be configured to determine a
differential
pressure using the pressure signals from the first and second pressure
sensors. The
differential pressure may be compared to a predetermined threshold value, e.g.
be-
tween 40 bar and 60 bar, e.g. 50 bar. If the measured differential pressure
exceeds this
threshold value, then the control unit may activate the downhole tool or
simply the
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
14
valve element. This enables the downhole tool to maintain a predetermined
differen-
tial pressure regardless of the operating depth, hydrostatic pressure, and mud
weight.
This differential pressure may also be used to determine if there is an actual
flow in-
side the drilling string, e.g. by detecting if the first pressure is greater
than the second
pressure.
An object of the invention is also achieved by a circulating sub for
positioning in a
borehole, comprising:
- a housing having an outer side surface facing an inner wall of the
borehole,
where the housing is configured to be placed inside the borehole,
- a first fluid conduit connected to a first opening in one end of the
circulating
sub and a second opening in the other end of the circulating sub for leading a
drilling fluid through the circulating sub,
- at least a second fluid conduit in fluid communication with the first
fluid con-
duit via at least one inner opening, and connected to at least one outer
opening
located in the outer side surface of the housing, characterised in that
- at least one cavity is provided in the outer side surface of the housing,
in which
at least one activation mechanism as described above is arranged.
This provides a downhole tool with a simple and accurate activation mechanism
that
does not require a ball retainer for receiving one or more dropped balls, or a
RF trans-
ceiver or receiver for communication with a dropped RFID tag. This reduces the
com-
plexity and number of components needed to activate the downhole tool. The
activa-
tion mechanism described above allows for an activation of the downhole tool
or the
bypass function by means of the internal pressure of the drilling fluid only;
no fluid
flow is required. The downhole tool is activated by means of the pressure of
the drill-
ing fluid, this allows for a much faster activation compared to conventional
indexing
systems and ball or RFID tag systems.
The downhole tool comprises a central through hole, e.g. the first fluid
conduit, ex-
tending from a first end, e.g. the top end, to a second end, e.g. the bottom
end, for
leading the drilling fluid being pumped into the drilling string through the
downhole
tool. The housing has a smaller diameter than the inner diameter of the
borehole so
that an annular is formed along the outer surface for leading the drilling
fluid and cut-
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
tings back to the ground level. At least one bypass conduit, e.g. the second
fluid con-
duit, is provided in the housing and connected to an outer opening and an
inner open-
ing for bypassing at least some of the drilling fluid.
5 A cavity is formed in the outer side surface in which the activation
mechanism is
placed. The valve element is positioned relative to the second fluid conduit
and a seat
located at the second fluid conduit. The seat and second fluid conduit are
arranged so
that the valve element, when placed in the seat, closes this fluid conduit so
substantial-
ly no drilling fluid is led through the second fluid conduit. By placing the
activation
10 mechanism within the housing of the downhole tool, e.g. between the
inner and outer
side surfaces, the number of flow restricting elements in the fluid passageway
can be
reduced or even eliminated so that substantially a full-bore can be achieved,
i.e. oper-
ating at maximum power or operation speed.
15 In one embodiment, a removable cover is arranged at an opening of the at
least one
cavity for closing off the at least one cavity, wherein an optional seal is
provided be-
tween said cover and the housing.
The cavity is closed off by means of a cover or hatch for preventing drilling
fluid or
cuttings from entering the activation mechanism and potentially causing a
failure in
the activation mechanism. The cover and surfaces of the cavity define the
chamber in
which the activation mechanism is arranged. The cover/hatch may be fastened to
the
outer side surface by suitable fastening means, such bolts, screws, a snap-fit
coupling
or another arrangement. A seal or sealing element, e.g. a rubber element, an 0-
ring or
another suitable seal, may be arranged between the cover/hatch and the housing
for
sealing off the chamber. This allows for easy access to the activation
mechanism in
the event of servicing or replacement of the activation mechanism. This also
allows
for a fast and simply installation of the activation mechanism as the
activation mecha-
nism can be assembled and installed as a single unit. Furthermore, no sealing
elements
have to be guided into and then installed inside the internal hole in which
the valve
element is situated. This significantly reduces the installation time and
complexity
thereof. This also eliminates the need for a specialised insertion tool to
position the
sealing elements inside the internal hole.
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
16
One or more balancing arrangements, e.g. balance pistons, may be located at
the top
end or bottom end of the downhole tool. The balancing arrangement may be
config-
ured to regulate or balance the pressure inside the downhole relative to the
pressure of
the drilling fluid located above or below the downhole tool.
In one embodiment, at least one of the inner and outer openings of the second
fluid
conduit comprises a nozzle configured to regulate the speed of the drilling
fluid enter-
ing or exiting the second conduit.
Two or more outer openings may be arranged in the outer side surface for
distributing
the bypassed fluid and/or optimizing the bypass of drilling fluid. The outer
openings
may form branches of the same fluid conduit or different fluid conduits as
described
above. Alternatively, two or more cavities may be arranged in the outer
surface for
receiving and holding two or more activation mechanisms which each is arranged
relative to at least a second or third fluid conduit.
A nozzle is provided at the inner and/or outer opening of the second fluid
conduit for
regulating the speed of the drilling fluid. An inner/first nozzle may be
configured to
increase the speed of the drilling fluid entering the conduit. An outer/second
nozzle
may be configured to further increase the speed of the drilling fluid exiting
the con-
duit. The nozzles may be placed at a predetermined angle relative to the
longitudinal
direction of the downhole tool, e.g. in an angle of 90 degrees or in an acute
angle
where the nozzle at least partly faces the first/top end of the downhole tool.
The noz-
zles may be mounted at the openings or integrated into the openings. The
nozzles may
be made of a wear resistant material, such as tungsten carbide or another
suitable ma-
terial. This allows the pressure of the drilling fluid inside the drilling
string to be re-
duced as well as an increase in the flow of the circulating drilling fluid, if
needed. The
increase in the flow in the annular space may be used to dissolve or break up
any
packed off areas or remove accumulated cuttings from areas likely to get
packed off or
blocked by the cuttings, such as the transition area between two different
liners.
The inner/first nozzle may be accessed and installed from the outside through
a selec-
tive conduit in the housing. This selective conduit may be a separate conduit
or one of
the fluid conduits for bypassing the first fluid conduit. The selective
conduit may be
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
17
closed off by means of plug mounted at the outer opening. Alternatively, a
nozzle for
regulating the speed of the drilling fluid exiting this fluid conduit may be
mounted at
the outer opening. This further simplifies the installation and servicing
process as all
the nozzles can be accessed from outside the downhole tool. One or more of
these
bypass conduits may thus be used for multiple purposes.
The downhole tool may be any type of a circulating sub or packoff assembly
(packoff
buster) used in drilling applications in which a bypass function is desired.
The circu-
lating sub or packoff assembly may advantageously be placed in positions along
the
borehole where packoffs are likely to form, such as in areas where changes in
the di-
ameter of the borehole occur, e.g. at the transition area between different
liners. Alter-
natively, the activation mechanism described above may be connected to or
integrated
into a jarring tool for releasing a stuck or lodged downhole tool, such as the
jarring
tool described in US 2012/0227970 Al.
An object of the invention is finally achieved by a method for activating a
circulating
sub using an activation mechanism as described above, where the method
comprises
the steps of:
- positioning the circulating sub at a predetermined depth of a borehole,
- increasing a pressure of a drilling fluid located in the first fluid conduit
of the
circulating sub,
- monitoring the pressure of the drilling fluid inside the first fluid
conduit using
at least one pressure sensor,
- activating the circulating sub when a certain event is detected using a
control
unit, characterised in that
- the step of activating the circulating sub comprises moving a valve
element ar-
ranged in a chamber of the activation mechanism from a closed position to an
open position so that at least a second fluid conduit is open for leading at
least
a part of the drilling fluid through the second fluid conduit.
This provides a fast and accurate method for activating or deactivating a
downhole
tool without the use of balls or RFID tags being dropped into the drilling
fluid. This
method allows for a very fast action process compared to activation systems
using
balls or RFID tags. As example, the process for activating a downhole tool at
a depth
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
18
of about 3000 metres takes several hours, e.g. more than one hour, while the
present
invention enables the activation process to be completed within minutes, e.g.
three
minutes. Furthermore, the complexity as well as the number of components
needed to
activate the downhole tool can be reduced compared to conventional activation
sys-
tems, thus reducing costs.
This configuration enables the downhole tool to be activated without requiring
an ac-
tual flow through the downhole tool, thus allowing it to be operated in packed
off
boreholes or situations where no circulating flow can be established.
In one embodiment, the sensed pressure is monitored within at least one time
window,
and the circulating sub is activated by the control unit if it is determined
that the
sensed pressure has remained stable relative to at least one threshold value
within the
at least one time window.
This enables the downhole tool to be activated once the pressure has reached a
prede-
termined activation level for that downhole tool or an operation mode thereof.
When
the control unit has determined that a stable pressure level has been
detected, a control
signal is sent to an actuator unit for initiating the movement of the valve
element. The
actuator unit then moves the valve element from the closed position where the
second
fluid conduit is closed to the open position where the second fluid conduit is
open, or
vice versa if that mode or tool is deactivated. This allows at least some of
the drilling
fluid to be bypassed from the first fluid conduit to a pressure chamber
located inside
the downhole tool or to the annular spacing located at the outer surface of
the housing
of the downhole tool. This also allows for an endless number of activations or
deacti-
vations without having to retrieve the downhole tool to empty a ball retainer
or to re-
set the activation mechanism.
The control unit may continue to monitor the sensed pressure for detecting a
change,
e.g. a drop, in the pressure which indicates that the downhole tool or the
selected op-
eration mode has been activated. The pressure of the pumped drilling fluid may
then
be increased to the operation level or another activation level for another
mode or
downhole tool.
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
19
In one embodiment, the sensed pressure is monitored within at least a second
time
window, and a second downhole tool or another operation mode of the first
downhole
tool is activated by the control unit if it is determined that the pressure
has remained
stable relative to at least a second threshold value within the at least
second time win-
dow.
This provides a simple and accurate method for activating or deactivating
multiple
operation modes of a downhole tool and/or multiple downhole tools by using the
same
activation mechanism or individual activation mechanisms. This configuration
allows
the multiple operation modes and/or multiple downhole tools to be activat-
ed/deactivated by simply regulating the pressure of the drilling fluid, no
indexing sys-
tem is needed. Furthermore, the operation modes and/or downhole tools can be
acti-
vated or deactivated using different threshold levels as described above. The
activa-
tion or threshold levels may be selected so that they do not interfere with
the operation
of other downhole tools of the drilling string.
The control unit may monitor vibrations sensed by at least one vibration
sensor, and
activate the downhole tool if excessive vibrations is detected, and/or monitor
the
sensed pressure for determining whether a jarring tool has been cocked or not
and
activate the jarring tool when a certain event is detected.
In this configuration, the downhole tool further comprises at least one
vibration sensor
connected to the control unit which monitors the vibrations of the downhole
tool and
in part the drilling string. The control unit compares the sensed vibrations
to one or
more threshold parameters, e.g. a reference frequency, pattern, amplitude or
any other
relevant parameters. If the sensed vibrations exceed the threshold parameters,
then the
control signal is sent to the actuator unit for moving the valve element so
that the sec-
ond fluid conduit is open. This allows the pressure of the pumped drilling
fluid to be
reduced while increasing the flow. This warns the operator at ground level
that the
drilling vibrations are out of range without using measure-while-drilling
(MWD) sig-
nals.
In another configuration, the downhole tool is configured as a jarring tool or
is con-
nected to a jarring tool. The control unit compares the sensed pressure to one
or more
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
reset levels for determining if the jarring tool is recocked or not. The
control unit may
generate another control signal once the pressure reaches a selected reset
level or if the
sensed pressure remains stable at the reset level within another time window.
The con-
trol unit may be configured to detect a drop having a predetermined amplitude
and/or
5 time length which indicates that the jarring tool has been cocked.
In one embodiment, an action circuit activates the control unit when the
pressure of
the drilling fluid exceeds a predetermined pressure level.
10 The electrical components are powered by an external or internal power
source, such
as a battery. Power to the electrical components is controlled by an optional
activation
circuit, e.g. a pressure switch, which turns on power when the pressure of the
drilling
fluid exceeds an activation level/the third threshold value. The control unit
then
switches from a sleep mode to a normal mode in which it monitors the pressure
of the
15 drilling fluid located in the first fluid conduit. The control unit
activates or deactivates
a selected operation mode or downhole tool if a stable pressure level has been
detected
as described above. The control unit enters sleep mode again and the power is
turned
off if once the activation or deactivation process is completed or if the
sensed pressure
drops below the activation level/the third threshold level. This saves power
as the
20 downhole tool is only activated at a predetermined pressure level,
thereby reducing
the power consumption and increasing the operation time.
Description of the Drawing
The invention is described by example only and with reference to the drawings,
wherein:
Fig. 1 shows an activation mechanism according to the present invention
integrated
into a downhole tool seen from a top end;
Fig. 2 shows a downhole tool with three activation mechanisms seen from a top
end;
Fig. 3 shows a longitudinal cross-section of the activation mechanism of fig.
1 in a
closed position;
Fig. 4 shows a longitudinal cross-section of the activation mechanism of fig.
1 in an
open position;
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
21
Fig. 5 shows an exemplary application of the downhole tool placed in a
borehole in
a deactivated state; and
Fig. 6 shows the downhole tool of fig. 5 in an activated state.
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.
List of reference numbers
1 Activation mechanism
2 Downhole tool
3 Housing
4 Outer side surface
5 Cavity
6 First fluid conduit, first hole
7 Second fluid conduit
8 Inner opening
9 Inner surface
10 Inner wall of borehole
11 Pressure sensor
12 Control unit
13 Pressure switch
14 Actuator unit
15 Valve element
16 Push rod
17 Chamber
18 Valve housing
19 Seat for valve element
20 Sealing elements
21 Annular spacing
22 Top end
23 Bottom end
24 Outer opening
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
22
25 Plug
26 Cover
27 Drill string
28 Borehole
29 Cuttings
30 Transition area
Detailed Description of Embodiments of the Invention
Fig. 1 shows an exemplary embodiment of an activation mechanism 1 according to
the
present invention. The activation mechanism 1 is integrated into a downhole
tool 2 in
the form of a circulating sub. The downhole tool 2 and the activation
mechanism 1 are
seen from a top end (shown in figs. 3-4) where the top end, a bottom end
(shown in
figs. 3-4) and other components of the downhole tool 2 are omitted for
illustrative
purposes.
The downhole tool 2 comprises a housing 3 configured to be placed in a
borehole
where an outer side surface 4 of the housing 3 faces an inner wall (shown in
figs. 3-4)
of the borehole. A cavity 5 is formed in the outer surface 4 for receiving and
holding
the activation mechanism 1. The cavity 5 is closed off by a cover (shown in
figs. 3-4)
so the drilling fluid in the borehole does not come into contact with the
electrical
components.
A first hole 6 is formed inside the housing 3, e.g. at the centre, extending
in the longi-
tudinal direction of the downhole tool 2. The first hole 6 forms a first fluid
conduit for
leading drilling from the top end, through the downhole tool 2 and out of the
bottom
end.
A second hole 7 is formed in the wall of the housing 3 and forms a second
fluid con-
duit for bypassing at least some of the drilling fluid. The second fluid
conduit 7 is flu-
id communication with the first fluid conduit 6 via an inner opening 8 and
with an
annular spacing (shown in figs. 3-4) via an outer opening (shown in figs. 3-
4). The
activation mechanism 1 is arranged relative to the second fluid conduit 7 so
that a
valve element (shown in figs. 3-4) is able to control the fluid flow through
the second
fluid conduit 7.
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
23
Fig. 2 shows another exemplary embodiment of the downhole tool 2' having three
activation mechanisms 1, 1', 1" arranged in individual cavities 5, 5', 5" in
the outer
surface 4. Each of the activation mechanisms 1, 1', 1" is arranged relative to
a second
fluid conduit 7, 7', 7" for bypassing at least some of the drilling fluid in
the first fluid
conduit 6. The activation mechanisms 1, 1', 1" may each have the same or
different
configurations, e.g. they can be activated simultaneously or individually.
Fig. 3 shows a longitudinal cross-section of the activation mechanism 1 in a
deactivat-
ed state. The activation mechanism 1 is positioned within the sidewall of the
housing
3 between the outer surface 4 and an inner surface 9. The inner surface 9
faces the first
fluid conduit 6. The outer surface 4 faces the inner wall 10 of the borehole.
The activation mechanism 1 comprises a pressure sensor 11 configured to sense
the
pressure of the drilling fluid located in the first fluid conduit 6. The
pressure sensor 11
is electrically connected to a control unit 12 comprising a controller, e.g. a
micropro-
cessor, a memory unit, a communication interface for communicating with other
downhole tools 2 or other external devices or tools, and other components for
control-
ling the internal communication between the individual components of the
activation
mechanism 1. A pressure switch 13 configured to sense the pressure of the
drilling
fluid located in the first fluid conduit 6 is further connected to the control
unit 12, e.g.
a power unit thereof. The pressure switch 13 is configured to turn on or off
power to
the electrical components of the activation mechanism 1.
An actuator unit 14 in the form of a solenoid is electrically connected to the
control
unit 12. The actuator unit 14 is configured to control the movement of the
valve ele-
ment 15 by generating a magnetic field in its wires which influences a push
rod 16
mechanically connected to the valve element 15. The push rod 16 is made of a
mag-
netic conductive material, e.g. steel or a ferromagnetic material. The valve
element 15
is moveably arranged inside a chamber 17, e.g. formed in the activation
mechanism or
the housing 3. One end of the valve element 15 is positioned inside a valve
housing 18
which forms a retainer for the valve element 15. The valve housing 18 is
connected to
the push rod 16. The other end of the valve element 15 is configured to rest
against a
seat 19 arranged relative to the second fluid conduit 7 in a closed position
as shown in
fig. 3, thus closing the second fluid conduit 7 so that no drilling fluid is
bypassed via
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
24
this conduit. This allows the drilling fluid to pass from the top end 22 of
the downhole
tool 2 and out of the bottom end 23 of the downhole tool 2 via the first fluid
conduit 6.
One or more sealing elements 20, two is shown here, are arranged in an outer
surface
of the valve element 15 as shown in figs. 3-4, thereby forming a seal between
the
chamber 17 and the second fluid conduit 7. The sealing elements 20, e.g. 0-
rings,
remain in contact with the inner surface of the chamber 17 at all times during
the mov-
ing of the valve element 15. Thus, no bypass openings or peripheral edges are
moved
past either one of the sealing elements 20, thereby reducing the risk that the
sealing
elements 20 are forced out of its seat or otherwise gets damaged.
Another conduit connected to another outer opening 24 in the outer side
surface 4 is
arranged in the sidewall of the housing 3. The outer opening 24 of this
conduit is
aligned with the inner opening 8. Here this conduit is closed off by means of
a plug
25. This conduit provides access to the inner opening 8 and allows for the
installation
of a nozzle as shown in figs. 3-4. The plug 25 may be replaced by another
nozzle, thus
allowing this conduit to acts as another second fluid conduit 7 for bypassing
the first
fluid conduit 6.
The chamber 17 is closed off by means of a remove cover 26 which secured to
the
housing 3. The cover 26 is sealed off using suitable sealing means to prevent
drilling
fluid from entering the chamber 17.
Fig. 4 shows the activation mechanism 1 in an activated state where the
actuator unit
14 is activated to move the valve element, e.g. in the longitudinal direction,
from the
closed position shown in fig. 3 to an open position as shown in fig. 4.
The actuator unit 14 is configured to retract the valve element 15 further
into the
chamber 17 so that the other end of the valve element 15 is brought out of
contact
with the seat 19. This opens the second fluid conduit 7, thus allowing at
least some of
the drilling fluid to bypass the first fluid conduit 6 and enter the annular
spacing 21.
This allows the drilling fluid to pass from the top end 22 of the downhole
tool 2 and to
partly bypass the first fluid conduit 6 via the second fluid conduit 7.
CA 02968427 2017-05-19
WO 2016/078671 PCT/ K2015/050356
Figs. 5-6 show an exemplary application of the downhole tool 2 with the
activation
mechanism (shown in fig. 3-4) installed in a drill string 27 or borehole
assembly
(BHA) which is positioned in a borehole 28. In exemplary embodiment, the
downhole
tool 2 is positioned above an under-reamer and/or a drill bit which are
configured to
5 widen the borehole and/or extend the borehole.
Cuttings 29 are led towards the top of the borehole 28 via the annular spacing
21 be-
tween the drill string 27 and the inner wall 10 of the borehole (here
indicated by dot-
ted lines). The cuttings 29 accumulate in the transition area 30 at which the
speed of
10 the returning drilling fluid containing the cuttings 29 is slowed down,
e.g. due to a
widening of the inner diameter of the borehole 28. This causes the cuttings 29
to form
a packoff as shown in fig. 5.
The activation mechanism 1 and thus downhole tool 2 remains inactive until the
pres-
15 sure switch 13 turns on power to the electrical components, including
the control unit
12. Drilling fluid is then led through the first fluid conduit 6 and back up
via the annu-
lar spacing 21 as indicated by the arrows in figs. 3-4.
The pressure switch 13 is activated when the internal pressure inside the
first fluid
20 conduit 6 exceeds a predetermined pressure level. The control unit 12
then wakes up
and monitor the internal pressure inside the first fluid conduit 6 within one
or more
predetermined time windows. If the control unit 12 determines that the
pressure has
remained stable within at least one time window, a control signal is generated
and is
sent to the actuator unit 14. The actuator unit 14 then moves the valve
element 15
25 from the closed position to the open position, thus allows at least some
of the drilling
fluid to bypass the first fluid conduit 6. This activates the downhole tool 2
and drilling
fluid is led through the second fluid conduit 7 (indicated by arrows in fig.
6) and out
into the annular spacing 21. This increases the speed of the returning
drilling fluid,
thereby forcing the packoff to break up so that circulation of the drilling
fluid can be
resumed.
The present invention is not limited to the illustrated embodiment or the
described
embodiments herein, and may be modified or adapted without departing from the
scope of the present invention as described in the patent claims below.
