Note: Descriptions are shown in the official language in which they were submitted.
Fluid Pressure Pulse Generator for a Telemetry Tool
Field
This disclosure relates generally to a telemetry tool and a fluid pressure
pulse
generator for a telemetry tool, such as a mud pulse telemetry measurement-
while-
drilling ("MWD") tool.
Background
The recovery of hydrocarbons from subterranean zones relies on the process of
drilling wellbores. The process includes drilling equipment situated at
surface, and a
drill string extending from the surface equipment to a below-surface formation
or
subterranean zone of interest. The terminal end of the drill string includes a
drill bit for
drilling (or extending) the wellbore. The process also involves a drilling
fluid system,
which in most cases uses a drilling "mud" that is pumped through the inside of
piping of
the drill string to cool and lubricate the drill bit. The mud exits the drill
string via the drill
bit and returns to surface carrying rock cuttings produced by the drilling
operation. The
mud also helps control bottom hole pressure and prevent hydrocarbon influx
from the
formation into the wellbore, which can potentially cause a blow out at
surface.
Directional drilling is the process of steering a well from vertical to
intersect a
target endpoint or follow a prescribed path. At the terminal end of the drill
string is a
bottom-hole-assembly ("BHA") which comprises 1) the drill bit; 2) a steerable
downhole
mud motor of a rotary steerable system; 3) sensors of survey equipment used in
logging-while-drilling ("LWD") and/or measurement-while-drilling ("MWD") to
evaluate
downhole conditions as drilling progresses; 4) means for telemetering data to
surface;
and 5) other control equipment such as stabilizers or heavy weight drill
collars. The
BHA is conveyed into the wellbore by a string of metallic tubulars (i.e. drill
pipe). MWD
equipment is used to provide downhole sensor and status information to surface
while
drilling in a near real-time mode. This information is used by a rig crew to
make
decisions about controlling and steering the well to optimize the drilling
speed and
trajectory based on numerous factors, including lease boundaries, existing
wells,
CA 2987642 2017-12-04
formation properties, and hydrocarbon size and location. The rig crew can make
intentional deviations from the planned wellbore path as necessary based on
the
information gathered from the downhole sensors during the drilling process.
The ability
to obtain real-time MWD data allows for a relatively more economical and more
efficient
drilling operation.
One type of downhole MWD telemetry known as mud pulse telemetry involves
creating pressure waves ("pulses") in the drill mud circulating through the
drill string.
Mud is circulated from surface to downhole using positive displacement pumps.
The
resulting flow rate of mud is typically constant. The pressure pulses are
achieved by
changing the flow area and/or path of the drilling fluid as it passes the MWD
tool in a
timed, coded sequence, thereby creating pressure differentials in the drilling
fluid. The
pressure differentials or pulses may be either negative pulses or positive
pulses.
Valves that open and close a bypass stream from inside the drill pipe to the
wellbore
annulus create a negative pressure pulse. All negative pulsing valves need a
high
differential pressure below the valve to create a sufficient pressure drop
when the valve
is open, but this results in the negative valves being more prone to washing.
With each
actuation, the valve hits against the valve seat and needs to ensure it
completely closes
the bypass; the impact can lead to mechanical and abrasive wear and failure.
Valves
that use a controlled restriction within the circulating mud stream create a
positive
pressure pulse. Pulse frequency is typically governed by pulse generator motor
speed
changes. The pulse generator motor requires electrical connectivity with the
other
elements of the MWD probe.
One type of valve mechanism used to create mud pulses is a rotor and stator
combination where a rotor can be rotated relative to the fixed stator between
an open
flow position where there is no restriction of mud flowing through the valve
and no pulse
is generated, and a restricted flow position where there is restriction of mud
flowing
through the valve and a pressure pulse is generated.
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Summary
According to a first aspect, there is provided a telemetry tool comprising a
pulser
assembly and a fluid pressure pulse generator. The pulser assembly comprises a
housing enclosing a motor and a driveshaft rotationally coupled to the motor.
The fluid
pressure pulse generator comprises a stator fixedly attached to the housing or
to a drill
collar housing the fluid pressure pulse generator and a rotor fixedly attached
to the
driveshaft. The stator has an angular movement restrictor window with a
central window
segment which axially and rotatably receives a rotatable member comprising at
least a
portion of the driveshaft and/or a portion of the rotor, and an indexing
window segment
in communication with the central window segment which receives an indexer
protruding from the rotatable member received in the central window segment.
The
indexing window segment has an angular span across which the indexer can be
oscillated by the driveshaft, whereby the angular span of the indexing window
segment
defines the range of angular movement of the rotor relative to the stator.
The stator may comprise a stator body comprising the angular movement
restrictor window and a plurality of radially extending stator projections
spaced around
the stator body whereby spaced stator projections define stator flow channels
extending
therebetween. The rotor may comprise a rotor body and a plurality of radially
extending
rotor projections spaced around the rotor body. The rotor projections may be
axially
adjacent and rotatable relative to the stator projections such that the rotor
projections
move in and out of fluid communication with the stator flow channels to create
fluid
pressure pulses in fluid flowing through the stator flow channels.
The stator body may have a bore therethrough with a wall extending across the
bore, and the wall may include the angular movement restrictor window
therethrough. At
least a portion of the rotor body may be received within the bore in the
stator body and
the rotor body may have a bore therethrough which receives a portion of the
driveshaft.
The telemetry tool may further comprise a rotor cap comprising a cap body and
a cap
shaft. The cap shaft may be received in the bore of the rotor body and
configured to
releasably couple the rotor to the driveshaft.
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The angular movement restrictor window may comprise a pair of opposed
indexing window segments and the indexer may comprise a pair of opposed
indexers
each extending from the rotatable member into a respective indexing window
segment.
The indexer may be a coupling key coupling the driveshaft to the rotor. The
driveshaft
may have a keyhole and the rotor may have a receptacle. The coupling key may
comprise a key body with dimensions which extend through the keyhole and
receptacle
and into indexing window segment. The coupling key may comprise at least one
zero
backlash ring extending around the key body and protruding from surfaces of
the key
body and into a gap in between the key body and the keyhole and receptacle,
such that
an interference fit is established between the coupling key, the keyhole, and
the
receptacle when the coupling key is coupling the driveshaft and rotor
together.
The rotor body may be rotatably received in the central window segment and the
indexer may protrude radially from the rotor body. The angular movement
restrictor
window may comprise a pair of opposed indexing window segments and the indexer
may comprise a pair of indexing teeth each extending from the rotor body into
a
respective indexing window segment. The rotor body and the indexer may be
integrally
formed.
The telemetry tool may further comprise a contact sensor at a boundary of the
angular span of the indexing window segment for detecting contact by the
indexer when
the indexer is being oscillated by the driveshaft. The contact sensor may
detect the
force of contact by the indexer and transmit this information to a controller
of the
telemetry tool. An electrical shutoff of the telemetry tool may be initiated
if the contact
sensor detects that the indexer has not made contact with the contact sensor
during
oscillation of the indexer by the driveshaft. An anti-jam sequence may be
initiated if the
contact sensor detects that the indexer has not made contact with the contact
sensor
during oscillation of the indexer by the driveshaft.
According to a second aspect, there is provided a fluid pressure pulse
generator
comprising a stator configured to fixedly attach to a housing of a pulser
assembly of a
telemetry tool or to a drill collar housing the telemetry tool, and a rotor
configured to
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fixedly attach to a driveshaft of the pulser assembly. The rotor is rotatable
relative to the
fixed stator and the stator has an angular movement restrictor window with a
central
window segment which axially and rotatably receives a rotatable member
comprising at
least a portion of the driveshaft and/or a portion of the rotor, and an
indexing window
segment in communication with the central window segment which receives an
indexer
protruding from the rotatable member received in the central window segment.
The
indexing window segment has an angular span across which the indexer can be
oscillated by the driveshaft, whereby the angular span of the indexing window
segment
defines the range of angular movement of the rotor relative to the stator.
The stator may comprise a stator body comprising the angular movement
restrictor window and a plurality of radially extending stator projections
spaced around
the stator body whereby spaced stator projections define stator flow channels
extending
therebetween, and the rotor may comprise a rotor body and a plurality of
radially
extending rotor projections spaced around the rotor body. The rotor
projections may be
axially adjacent and rotatable relative to the stator projections such that
the rotor
projections move in and out of fluid communication with the stator flow
channels to
create fluid pressure pulses in fluid flowing through the stator flow
channels.
The stator body may have a bore therethrough with a wall extending across the
bore, and the wall may include the angular movement restrictor window
therethrough. At
least a portion of the rotor body may be received within the bore in the
stator body and
the rotor body may have a bore therethrough configured to receive a portion of
the
driveshaft. The fluid pressure pulse generator may further comprise a rotor
cap
comprising a cap body and a cap shaft. The cap shaft may be received in the
bore of
the rotor body and configured to releasably couple the rotor to the
driveshaft.
The rotor body may be rotatably received in the central window segment and the
indexer may protrude radially from the rotor body. The angular movement
restrictor
window may comprise a pair of opposed indexing window segments and the indexer
may comprise a pair of indexing teeth each extending from the rotor body into
a
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respective indexing window segment. The rotor body and the indexer may be
integrally
formed.
The fluid pressure pulse generator may further comprise a contact sensor at a
boundary of the angular span of the indexing window segment for detecting
contact by
the indexer when the indexer is being oscillated by the driveshaft.
This summary does not necessarily describe the entire scope of all aspects.
Other aspects, features and advantages will be apparent to those of ordinary
skill in the
art upon review of the following description of specific embodiments.
Brief Description of Drawings
Figure 1 is a schematic of a drill string in an oil and gas borehole
comprising a
MWD telemetry tool.
Figure 2 is a longitudinally sectioned view of a mud pulser section of the MWD
tool that includes a pulser assembly, a fluid pressure pulse generator in
accordance
with a first embodiment, and a flow bypass sleeve that surrounds the fluid
pressure
pulse generator.
Figure 3 is an exploded perspective view of the fluid pressure pulse generator
of
the first embodiment comprising a stator, a rotor and a rotor cap.
Figure 4 is a perspective view of the stator of the fluid pressure pulse
generator
of the first embodiment comprising an angular movement restrictor window.
Figure 5 is a top view of the stator of Figure 4.
Figure 6A is a perspective view and Figure 6B is a top view of the fluid
pressure
pulse generator of the first embodiment with a driveshaft of the pulser
assembly
extending through the angular movement restrictor window and coupled to the
rotor and
the rotor in an open flow position.
Figure 7A is a perspective view and Figure 76 is a top view of the fluid
pressure
pulse generator of the first embodiment with the driveshaft extending through
the
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, .
angular movement restrictor window and coupled to the rotor and the rotor in a
restricted flow position.
Figure 8 is a perspective view of the flow bypass sleeve.
Figure 9 is a perspective view of the downhole end of the flow bypass sleeve.
Figure 10 is an exploded perspective view of a fluid pressure pulse generator
according to a second embodiment comprising a stator, a rotor and a rotor cap.
Figure 11 is a top view of the stator of the fluid pressure pulse generator of
the
second embodiment comprising an angular movement restrictor window.
Figure 12A is a perspective view and Figure 12B is a top view of the fluid
pressure pulse generator of the second embodiment with a driveshaft of the
pulser
assembly extending through the angular movement restrictor window and coupled
to
the rotor and the rotor in an open flow position.
Figure 13 is a top view of the fluid pressure pulse generator of the second
embodiment with the driveshaft extending through the angular movement
restrictor
window and coupled to the rotor and the rotor in a restricted flow position.
Detailed Description of Embodiments
Directional terms such as "uphole" and "downhole" are used in the following
description for the purpose of providing relative reference only, and are not
intended to
suggest any limitations on how any apparatus is to be positioned during use,
or to be
mounted in an assembly or relative to an environment.
The embodiments described herein generally relate to a telemetry tool with a
fluid pressure pulse generator that can generate pressure pulses. The fluid
pressure
pulse generator may be used for mud pulse ("MP") telemetry used in downhole
drilling,
wherein a drilling fluid (herein referred to as "mud") is used to transmit
telemetry pulses
to surface. The fluid pressure pulse generator may alternatively be used in
other
methods where it is necessary to generate a fluid pressure pulse. The fluid
pressure
pulse generator comprises a stator and a rotor. The stator may be fixed to a
pulser
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=
assembly of the telemetry tool or to a drill collar housing the telemetry
tool, and the rotor
is fixed to a driveshaft coupled to a motor in the pulser assembly. The motor
rotates the
driveshaft and rotor relative to the stator to generate pressure pulses in mud
flowing
through the fluid pressure pulse generator.
Referring to the drawings and specifically to Figure 1, there is shown a
schematic
representation of MP telemetry operation using a fluid pressure pulse
generator 130,
230 according to embodiments disclosed herein. In downhole drilling equipment
1,
drilling mud is pumped down a drill string by pump 2 and passes through a
measurement while drilling ("MWD") tool 20 including the fluid pressure pulse
generator
130, 230. The fluid pressure pulse generator 130, 230 has an open flow
position in
which mud flows relatively unimpeded through the pressure pulse generator 130,
230
and no pressure pulse is generated and a restricted flow position where flow
of mud
through the pressure pulse generator 130, 230 is restricted and a positive
pressure
pulse is generated (represented schematically as block 6 in mud column 10).
Information acquired by downhole sensors (not shown) is transmitted in
specific time
divisions by pressure pulses 6 in the mud column 10. More specifically,
signals from
sensor modules (not shown) in the MWD tool 20, or in another downhole probe
(not
shown) communicative with the MWD tool 20, are received and processed in a
data
encoder in the MWD tool 20 where the data is digitally encoded as is well
established in
the art. This data is sent to a controller in the MWD tool 20 which controls
timing of the
fluid pressure pulse generator 130, 230 to generate pressure pulses 6 in a
controlled
pattern which contain the encoded data. The pressure pulses 6 are transmitted
to the
surface and detected by a surface pressure transducer 7 and decoded by a
surface
computer 9 communicative with the transducer by cable 8. The decoded signal
can then
be displayed by the computer 9 to a drilling operator. The characteristics of
the pressure
pulses 6 are defined by duration, shape, and frequency and these
characteristics are
used in various encoding systems to represent binary data.
Referring to Figure 2, the downhole end of the MWD tool 20 is shown in more
detail. The MWD tool 20 generally comprises fluid pressure pulse generator 130
according to a first embodiment which creates fluid pressure pulses, and a
pulser
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=
assembly 26 which takes measurements while drilling and which drives the fluid
pressure pulse generator 130. The fluid pressure pulse generator 130 and
pulser
assembly 26 are axially located inside a drill collar 27. A flow bypass sleeve
270 is
received inside the drill collar 27 and surrounds the fluid pressure pulse
generator 130.
The pulser assembly 26 is fixed to the drill collar 27 with an annular channel
55
therebetween, and mud flows along the annular channel 55 when the MWD tool 20
is
downhole. The pulser assembly 26 comprises pulser assembly housing 49
enclosing a
motor subassembly and an electronics subassembly 28 electronically coupled
together
but fluidly separated by a feed-through connector (not shown). The motor
subassembly
includes a motor and gearbox subassembly 23, a driveshaft 24 coupled to the
motor
and gearbox subassembly 23, and a pressure compensation device 48. The fluid
pressure pulse generator 130 comprises a stator and a rotor. The stator
comprises a
stator body 141 with a bore therethrough and stator projections 142 radially
extending
around the downhole end of the stator body 141. The rotor comprises generally
cylindrical rotor body 169 with a central bore therethrough and a plurality of
radially
extending projections 162 at the downhole end thereof.
The stator body 141 comprises a cylindrical section at the uphole end and a
generally frusto-conical section at the downhole end which tapers
longitudinally in the
downhole direction. The cylindrical section of stator body 141 is coupled with
the pulser
assembly housing 49. More specifically, a jam ring 158 threaded on the stator
body 141
is threaded onto the pulser assembly housing 49. Once the stator is positioned
correctly, the stator is held in place and the jam ring 158 is backed off and
torqued onto
the stator holding it in place. The stator body 141 surrounds an annular seal
54 which
surrounds the driveshaft 24 and prevents mud from entering the motor
subassembly. In
alternative embodiments (not shown) other means of coupling the stator with
the pulser
assembly housing 49 may be utilized.
The rotor body 169 is received in the downhole end of the bore through the
stator
body 141 and a portion of the driveshaft 24 is received in the uphole end of
the bore
through the rotor body 169. A coupling key 30 extends through the driveshaft
24 and is
received in a coupling key receptacle 164 (shown in Figure 3) at the uphole
end of the
rotor body 169 to couple the driveshaft 24 with the rotor body 169.
Alternative means of
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=
coupling the rotor body 169 to the driveshaft 24 may be used as are would be
known to
a person skilled in the art.
A rotor cap comprising a cap body 191 and a cap shaft 192 is positioned at the
downhole end of the fluid pressure pulse generator 130. The cap shaft 192 is
received
in the downhole end of the bore through the rotor body 169 and threads onto
the
driveshaft 24 to lock (torque) the rotor body 169 to the driveshaft 24. The
cap body 191
includes a hexagonal shaped opening 193 dimensioned to receive a hexagonal
Allen
key which is used to torque the rotor body 169 to the driveshaft 24.
Rotation of the driveshaft 24 by the motor and gearbox subassembly 23 rotates
the rotor relative to the fixed stator. The electronics subassembly 28
includes downhole
sensors, control electronics, and other components required by the MWD tool 20
to
determine direction and inclination information and to take measurements of
drilling
conditions, to encode this telemetry data using one or more known modulation
techniques into a carrier wave, and to send motor control signals to the motor
and
.. gearbox subassembly 23 to rotate the driveshaft 24 and rotor in a
controlled pattern to
generate pressure pulses 6 representing the carrier wave for transmission to
surface.
The motor subassembly is filled with a lubricating liquid such as hydraulic
oil or
silicon oil and this lubricating liquid is fluidly separated from mud flowing
along the
annular channel 55 by annular seal 54. The pressure compensation device 48
comprises a flexible membrane (not shown) in fluid communication with the
lubrication
liquid on one side and with mud on the other side via ports 50 in the pulser
assembly
housing 49; this allows the pressure compensation device 48 to maintain the
pressure
of the lubrication liquid at about the same pressure as the mud in the annular
channel
55.
The fluid pressure pulse generator 130 is located at the downhole end of the
MWD tool 20. In alternative embodiments (not shown), the fluid pressure pulse
generator 130 may be positioned at the uphole end of the MWD tool 20. Mud
pumped
from the surface by pump 2 flows along annular channel 55 between the outer
surface
of the pulser assembly 26 and the inner surface of the drill collar 27. When
the mud
reaches the fluid pressure pulse generator 130 it flows along an annular
channel 56
CA 2987642 2017-12-04
=
between the external surface of the stator body 141 and the internal surface
of the flow
bypass sleeve 270. The rotor rotates between an open flow position where mud
flows
freely through the fluid pressure pulse generator 130 resulting in no pressure
pulse and
a restricted flow position where flow of mud is restricted to generate
pressure pulse 6 as
described in more detail below.
Referring now to Figures 3 to 7 the fluid pressure pulse generator 130
comprising
stator 140, rotor 160 and rotor cap 190 is shown in more detail. The stator
projections
142 have a radial profile with an uphole end 146 and a downhole face 145, with
two
opposed side faces 147 extending therebetween. Mud flowing along the external
surface of the stator body 141 contacts the uphole end 146 of the stator
projections 142
and flows through stator flow channels 143 defined by the side faces 147 of
adjacently
positioned stator projections 142. The radially extending rotor projections
162 are
equidistantly spaced around the downhole end of the rotor body 169 and are
axially
adjacent and downhole relative to the stator projections 142 in the assembled
fluid
pressure pulse generator 130. The rotor projections 162 have a radial profile
including
an uphole face 166 and a downhole face 165, with two opposed side faces 167
extending between the uphole face 166 and the downhole face 165. Rotor flow
channels 163 are defined by side faces 167 of adjacent rotor projections 162.
The uphole cylindrical section of the stator body 141 includes a mechanical
stop
wall 180 extending across the bore through the stator body 141. The mechanical
stop
wall 180 has an angular movement restrictor window comprising a central window
segment 187 flanked by two 180 opposed indexing window segments 188. The
mechanical stop wall 180 may be an integral part of the stator body 141 or it
may be
fixed or coupled to the stator body 141 during assembly. The angular movement
restrictor window may be machined into the mechanical stop wall 180 or the
mechanical
stop wall 180 may be formed with the angular movement restrictor window
included
therein. As shown in Figures 6 and 7, the central window segment 187 of the
angular
movement restrictor window rotatably receives the driveshaft 24 and the
opposed
indexing window segments 188 allow opposed ends of the coupling key 30 to
oscillate
within the indexing window segments 188. The coupling key 30 comprises a key
body
with a pair of zero backlash rings 31 which are seated in grooves (not shown)
formed
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CA 2987642 2017-12-04
around the outer surface of the key body. The zero backlash rings 31 may
create an
interference fit between the driveshaft 24 and the rotor 160 with zero
backlash.
Avoiding such backlash may be desirable to reduce the risk of premature wear
and
fatigue of components and inaccurate telemetry caused by play between the
driveline
components. Coupling keys with zero backlash rings are described in more
detail in WO
2014/071519. In alternative embodiments, the
coupling key 30 may be any type of coupling key.
In the embodiment of the fluid pressure pulse generator 130 shown in Figures 3
to 7, the angular span a of the indexing window segments 188 allows the rotor
160 to
oscillate 30 degrees in either the clockwise or counter-clockwise direction.
To generate
fluid pressure pulses 6 a controller (not shown) in the electronics
subassembly 28 sends
motor control signals to the motor and gearbox subassembly 23 to rotate the
driveshaft
24 and rotor 160 in a controlled pattern between an open flow position and a
restricted
flow position. More specifically, the rotor 160 starts in the open flow
position shown in
Figure 6A and 6B where the rotor flow channels 163 align with the stator flow
channels
143 and there is unrestricted flow of mud through the flow channels 143, 163
with zero
pressure. In the open flow position, protruding ends of the coupling key 30
contact a
side of each of the indexing window segments 188. As the two indexing window
segments 188 are 180 degrees apart and have the same angular span a, contact
by
one end of the coupling key 30 against one side of one indexing window segment
188
should result in the other end of the coupling key 30 contacting the opposite
side of the
other indexing window segment 188.The driveshaft 24 and rotor 160 are then
rotated 30
degrees clockwise from the open flow position to the restricted flow position
shown in
Figure 7A and 7B where the rotor projections 162 align with the stator flow
channels
143 and flow of mud through the fluid pressure pulse generator 130 is
restricted thereby
generating pressure pulse 6. In the restricted flow position, protruding ends
of the
coupling key 30 contact the opposite side of each of the indexing window
segments 188
to the side contacted in the open flow position. The driveshaft 24 and rotor
160 can then
be rotated 30 degrees counter-clockwise back to the open flow position. A
precise
pattern of pressure pulses may therefore be generated through rotation of the
rotor 160
between the open flow position and the restricted flow position (i.e. 30
degrees in a
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clockwise direction and 30 degrees in a counter-clockwise direction) with the
protruding
ends of the coupling key 30 contacting both of the opposed sides of the
indexing
window segments 188 with each clockwise/counter-clockwise rotation.
In alternative embodiments (not shown) more or less rotor projections 162 and
stator projections 142 may be present on the fluid pressure pulse generator
130 and the
span of rotation of the described oscillation method and the angular span a
the indexing
window segments 188 may vary depending on the amount of rotation required to
rotate
the rotor 160 between the open flow position and the restricted flow position.
The
frequency of pressure pulses 6 that can be generated may be increased with a
reduced
span of rotation of the rotor 160 and, as a result, the data acquisition rate
may be
increased. In an alternative embodiment, the driveshaft 24 and rotor 160 may
rotate
counter-clockwise from the open flow position to the restricted flow position
and
clockwise back to the open flow position. In this alternative embodiment, in
the open
flow position, the protruding ends of the coupling key 30 will contact the
opposite side of
each of the indexing window segments 188 than the side contacted in Figure 6A
and
6B, and in the restricted flow position, the protruding ends of the coupling
key 30 will
contact the opposite side of each of the indexing window segments 188 than the
side
contacted in Figure 7A and 7B. In further alternative embodiment, the angular
span a of
the indexing window segments 188 may be greater than the rotational span of
the rotor
between the open flow and restricted flow positions.
In the embodiment of the fluid pressure pulse generator 130 shown in Figures 3
to 7, the driveshaft 24 is received in central window segment 187 and the
coupling key
functions as an indexer and is constrained to oscillate between the angular
span a
defined by the indexing window segments 188 of the stator 140; in other words,
25 movement of the coupling key 30 within the indexing window segments 188
provides a
mechanical indication of an angular movement limit. The coupling key 30
extends
through the indexing window segments 188 of the stator 140 and is received in
the
coupling key receptacle 164 of the rotor 160 to couple the rotor 160 to the
driveshaft 24.
In alternative embodiments, an indexer may be included in addition to or as an
30 alternative to the coupling key 30. The indexer may be integrally formed
with the
driveshaft 24 and/or rotor 160. In alternative embodiments the angular
restrictor window
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may have a single or more than two indexing window segments 188 and there may
be a
corresponding number of indexers received therein. The number of indexing
window
segments 188 that may be present may depend on the angular span a of each
indexing
window segment 188.
In an alternative embodiment (not shown), the rotor 160 may be rotated from
the
open flow (start) position either clockwise or counter-clockwise to a
restricted flow
position to generate a pattern of pressure pulses. For example, the rotor 160
may have
a 60 degree rotational span and rotate 30 degrees clockwise from the open flow
(start)
position to a first restricted flow position to generate a first pressure
pulse or 30 degrees
counter-clockwise from the open flow (start) position to a second restricted
flow position
to generate a second pressure pulse, each time returning to the open flow
(start)
position before generating the next pulse. The first and second restricted
flow positions
may allow substantially the same amount of mud to flow through the fluid
pressure
generator 130 such that the first and second pressure pulses are substantially
the same
height, or alternatively, the first and second restricted flow positions may
allow a
different amount of mud to flow through the fluid pressure generator such that
the first
and second pressure pulses are different heights. For example, the fluid
pressure pulse
generator may be a dual height pressure pulse generator as described in
PCT/0A2015/050587 where
the rotor rotates in one
direction from the open flow (start) position to a partial restricted flow
position and in the
opposite direction to a full restricted flow position to respectively generate
a partial and
full pressure pulse, with the partial pressure pulse being reduced compared to
the full
pressure pulse. In these alternative embodiments, the angular span a of the
indexing
window segments 188 of the angular restrictor window may be the same as the
angular
.. span of the rotor 160 and the indexer (e.g. coupling key 30) may be
positioned at a
central point in the indexing window segments 188 when the rotor 160 is in the
open
flow (start) position and contact opposite sides of each of the indexing
window
segments 188 when the rotor 160 is rotated clockwise or counter-clockwise from
the
open flow (start) position to the first and second restricted flow positions
respectively.
In an alternative embodiment (not shown), the angular span a of the indexing
window segments 188 of the angular restrictor window may be greater than the
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rotational span of the rotor. For example, the angular span a of the indexing
window
segments 188 may be 70 degrees allowing rotation of the rotor 160 across its
angular
span with a gap of 5 degrees on either side. Provision of a 70 degree angular
span a for
the indexing window segments 188 allows the rotor 160 to rotate between the
restricted
flow positions without the indexer contacting or hitting the sides of the
indexing window
segments 188. In this alternative embodiment, the rotor position may be
calibrated by
programming a controller (not shown) in the electronics subassembly 28 to
control the
motor of the motor and gearbox subassembly 23 to rotate the driveshaft 24 and
rotor
160 such that the indexer contacts one side of the indexing window segment
188, and
.. then the opposite way until the indexer contacts the opposite side of the
indexing
window segment 188. The central position of the indexer in the indexing window
segment 188 can be determined by the controller and the driveshaft 24 and
rotor 160
can be readily positioned at the open flow (start) position by controlling the
motor of the
motor and gearbox subassembly 23 to rotate the driveshaft 24 such that the
indexer is
positioned at the mid or central point of the indexing window segment 188,
i.e. move 35
degrees towards the centre after the indexer has made contact with one side of
the
indexing window segment 188. When the indexer is in the central position the
rotor 160
will be in the open flow (start) position with zero pressure as described
above. The rotor
160 can then be rotated 30 degrees clockwise or counter-clockwise from the
open flow
position to the first or second restricted flow positions respectively. A
memory (not
shown) in the electronics subassembly 28 may be encoded with instructions
executable
by the controller to move the motor in this manner and monitor motor current
feed rate
which indicates when contact is made. This provides a simple approach to
calibrate the
driveshaft 24 angular position after each oscillation or multiple series of
oscillations, with
the indexer providing angular movement feedback and without the need for
electronic
sensors and associated circuitry to track the angular position of the
driveshaft 24.
Further, the memory can be programmed with a value for the rotational span of
the rotor
(for example 60 degrees) and to record a fault when the distance traveled by
the
indexer during calibration does not match the stored rotational span value;
such lack of
match can occur for example when some part of the driveline is jammed and the
indexer is unable to traverse the entire angular span.
CA 2987642 2017-12-04
In alternative embodiments the rotational span of the rotor 160 may be more
than
or less than 60 degrees, and the angular span a of the indexing window
segments 188
of the angular restrictor window may be selected to correspond to the desired
range of
oscillation for the rotor 160 that provides a full range of motion between the
open flow
position and the restricted flow position(s) and optionally an additional
amount so that
the indexer does not contact the sides of the indexing window segments 188 as
described above. For example, the angular span a of the indexing window
segments
188 may be between about 60-180 degrees, or between about 10-60 degrees or any
amount therebetween. It will be evident from the foregoing that provision of
more stator
projections 142 and rotor projections 162 will reduce the amount of rotation
required to
move the rotor 160 between the open and restricted flow position(s), thereby
increasing
the speed of data transmission. The angular span a of the indexing window
segments
188 may be reduced when more stator and rotor projections 142, 162 are present
as
the rotation span of the rotor 160 is reduced. The number of stator
projections 142 and
rotor projections 162 may be limited by the circumferential area of the stator
body 141
and rotor body 169 being able to accommodate the stator projections 142 and
rotor
projections 162 respectively. In order to accommodate more stator projections
142 and
rotor projections 162 if data transmission speed is an important factor, the
width of the
stator projections 142 and rotor projections 162 can be decreased to allow for
more
stator projections 142 and rotor projections 162 to be present.
Referring to Figures 10 to 13, there is shown a fluid pressure pulse generator
230 according to a second embodiment comprising stator 240, rotor 260 and
rotor cap
290. Rotor cap 290 is positioned at the downhole end of fluid pressure pulse
generator
230 and comprises a cap body 291 and a cap shaft 292. The rotor 260 comprises
rotor
body 269 and a plurality of radially extending rotor projections 262
equidistantly spaced
around the downhole end of the rotor body 269. The rotor body 269 has a bore
therethrough and an uphole section of the bore through the rotor body 269
receives the
driveshaft 24 of the pulser assembly 26 and the downhole section of the bore
through
the rotor body 269 receives the cap shaft 292. The cap shaft 292 threads onto
the
driveshaft 24 to lock (torque) the rotor body 269 to the driveshaft 24 as
described above
in more detail with reference to Figure 2. Coupling key 30 extends through the
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CA 2987642 2017-12-04
driveshaft 24 and is received in a coupling key receptacle 264 at the uphole
end of the
rotor body 269 to couple the driveshaft 24 with the rotor body 269.
Alternative means of
coupling the rotor body 269 to the driveshaft 24 may be used as are would be
known to
a person skilled in the art. A pair of opposed indexing teeth 235 protrude
radially from
the rotor body 269. The indexing teeth 235 extend longitudinally along the
length of the
rotor body 269. The indexing teeth 235 may be integrally formed with the rotor
body 269
or they may be attached to the rotor body 269.
The rotor projections 262 have a radial profile including an uphole face 266
and a
downhole face 265, with two opposed side faces 267 extending therebetween.
Rotor
flow channels 263 are defined by side faces 267 of adjacent rotor projections
262. The
stator 240 comprises a stator body 241 with a bore therethrough and a
plurality of stator
projections 242 radially extending around the downhole end of the stator body
241. The
stator projections 242 have a radial profile with an uphole end 246 and a
downhole face
245 and opposed side faces 247 extending therebetween. Mud flowing along the
external surface of the stator body 241 contacts the uphole end 246 of the
stator
projections 242 and flows through stator flow channels 243 defined by the side
faces
247 of adjacently positioned stator projections 242. The rotor projections 262
are axially
adjacent and downhole relative to the stator projections 242 in the assembled
fluid
pressure pulse generator 230. The rotor projections 262 rotate in and out of
fluid
communication with the stator flow channels 243 to generate pressure pulses 6.
The uphole cylindrical section of the stator body 241 includes a mechanical
stop
wall 280 extending across the bore through the stator body 241. The mechanical
stop
wall 280 has an angular movement restrictor window comprising a central window
segment 287 flanked by two 1800 opposed indexing window segments 288. As shown
in Figures 12 and 13, the central window segment 287 of the angular movement
restrictor window rotatably receives the driveshaft 24 and rotor body 269 with
the
coupling key 30 extending therethrough, and the opposed indexing window
segments
288 receive the opposed indexing teeth 235. The indexing window segments 288
have
an angular span a across which the indexing teeth 235 can oscillate and this
angular
span a limits the range of angular movement of the rotor 260 relative to the
stator 240.
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CA 2987642 2017-12-04
In order to generate pressure pulses 6, the rotor 260 oscillates between an
open
flow position (shown in Figure 12A) where the rotor flow channels 263 are
aligned with
the stator flow channels 243 and there is unrestricted flow of mud through the
fluid
pressure pulse generator 230, and a restricted flow position where the rotor
projections
262 align with the stator flow channels 243 and there is restriction of flow
of mud
through the fluid pressure pulse 230 as described in more detail above with
reference to
Figures 3 to 7. In the open flow position the indexing teeth 235 contact one
side of the
indexing window segments 288 as shown in Figure 12B. As the two indexing
window
segments 288 are 180 degrees apart and have the same angular span a, contact
by
.. one of indexing tooth 235 against one side of one indexing window segment
288 should
result in the other indexing tooth 235 contacting the opposite side of the
other indexing
window segment 288. In the restricted flow position, the indexing teeth 235
contact the
other side of the indexing window segments 288 to the side contacted in the
open flow
position, as shown in Figure 13.
In the second embodiment of the fluid pressure pulse generator 230 shown in
Figures 10 to 13, the angular span a of the indexing window segments 288 limit
rotation
of the rotor 260 to 30 degrees in either clockwise or counter-clockwise
direction. In
alternative embodiments (not shown) more or less rotor projections 262 and
stator
projections 242 may be present on the fluid pressure pulse generator 230 and
the span
of rotation of the described oscillation method and the angular span a the
indexing
window segments 288 may vary depending on the amount of rotation required to
rotate
the rotor 260 between the open and restricted flow positions. In further
alternative
embodiments, the angular span a of the indexing window segments 288 may be
greater
than the rotational span of the rotor 260 between the open flow and restricted
flow
positions. In other embodiments, the indexing teeth 235 may only be present on
the
uphole portion of the rotor body 269 received in the central window segment
287 of the
angular movement restrictor window, and/or there may be a single or more than
two
indexing teeth 235 radially protruding from the rotor body 269 and a
corresponding
number of indexing window segments 288.
In an alternative embodiment (not shown), the indexer may be provided by one
or more indexing teeth formed directly on the driveshaft by machining out
angular
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CA 2987642 2017-12-04
portions of the driveshaft on each side of each indexing tooth to define a
smaller
diameter circular pin (rotatable member) which is rotatable within the central
window
segment of the angular restrictor window. The stator may include a pair of
protrusions
extending radially inwards towards the central window segment of the angular
restrictor
window and these protrusions may define the boundaries of the indexing window
segments thereby limiting rotation of the indexing teeth within the indexing
window
segments. The indexing teeth may be wider than the coupling key 30 of the
first
embodiment of the fluid pressure pulse generator 130 shown in Figures 3-7, and
the
indexing window segments may therefore have a greater angular span a to
accommodate the wider indexing teeth and still provide the same rotation span
for the
rotor (e.g. 30 degrees).
In alternative embodiments (not shown) the fluid pressure pulse generator may
be any rotor/stator type fluid pressure pulse generator where the stator
includes flow
channels or orifices through which mud flows and the rotor rotates relative to
the fixed
stator to move in and out of fluid communication with the flow channels or
orifices to
generate pressure pulses 6. The fluid pressure pulse generator may be
positioned at
either the downhole or uphole end of the MWD tool 20. In these alternative
embodiments, the stator may be fixed to the pulser assembly housing 49 or to
the drill
collar 27 and includes the angular movement restrictor window with a central
window
segment which axially and rotatably receives a rotatable member comprising at
least a
portion of the driveshaft 24 and/or a portion of the rotor, and an indexing
window
segment in communication with the central window segment which receives an
indexer
protruding from the rotatable member received in the central window segment.
The
indexing window segment has an angular span across which the indexer can be
oscillated by the driveshaft 24 and the angular span of the indexing window
segment
defines the angular range of the rotor's angular movement relative to the
stator. The
indexing window segment may include one or more electrical contact sensors
which can
sense contact by the indexer. This information may be transmitted to a
controller in the
electronics subassembly 28. The electrical contact sensors may detect the
force of
impact by the indexer and transmit this information to the controller and the
information
may be used by the controller to control rotation of the rotor. The electrical
contact
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CA 2987642 2017-12-04
sensors may be used to sense contact by the indexer and trigger an electrical
shutoff if
the indexer does not contact the contact sensor. Failure of the indexer to
contact the
contact sensors may indicate that the rotor has become jammed by debris in the
mud,
therefore if the indexer fails to make contact with the contact sensor during
normal
oscillation of the indexer an anti-jam sequence may be initiated to try and
clear the
blockage.
In the embodiments disclosed herein, the mechanical stop mechanism is
provided by the stator 140, 240 in combination with the coupling key 30,
indexing teeth
235 or other indexer and does not require a separate mechanical stop
mechanism, such
as the mechanical stop collar described in WO 2014/071519; this may reduce the
size
of the MWD tool 20. Furthermore, the stator 140, 240 and rotor 160, 260 may be
automatically aligned as a result of the indexer being coupled to the rotor
160, 260 and
received in the indexing window segments 188, 288 of the stator 140, 240. It
may
therefore not be necessary to align the rotor high side to the stator high
side for correct
alignment of the rotor 160, 260 and stator 140, 240 which may reduce the time
and cost
required to mount the fluid pressure pulse generator 130, 230. As the rotor
160, 260 is
rotated in both clockwise and counter-clockwise directions, there is less
likelihood of
wear than if the rotor 160, 260 is only rotated in one direction. Furthermore,
the span of
rotation is limited by the angular span a of the indexing window segments 188,
288
thereby reducing wear of the motor, seals, and other components associated
with
rotation.
Referring now to Figures 8 and 9 there is shown a flow bypass sleeve 270 which
may be used to receive and surround the fluid pressure pulse generator 130,
230. The
flow bypass sleeve 270 comprises a generally cylindrical sleeve body with a
central
bore therethrough made up of an uphole body portion 271a and a downhole body
portion 271b. A plurality of apertures 275 extend longitudinally through the
uphole body
portion 271a of the flow bypass sleeve 270. The apertures 275 are circular and
equidistantly spaced around uphole body portion 271a. The internal surface of
the
downhole body portion 271b includes a plurality of spaced grooves 278 which
align with
the apertures 275 in the assembled flow bypass sleeve 270.
CA 2987642 2017-12-04
During assembly of the flow bypass sleeve 270, the uphole and downhole body
portions 271a, 271b are axially aligned and a lock down sleeve 81 is received
on the
downhole end of downhole body portion 271b and moved towards the uphole end of
the
uphole body portion 271a until the uphole end of the lock down sleeve 81 abuts
an
annular shoulder (not shown) on the external surface of uphole body portion.
The
assembled flow bypass sleeve 270 can then be inserted into the downhole end of
drill
collar 27. The external surface of uphole body portion 271a includes an
annular
shoulder 280 which abuts a downhole shoulder of a keying ring (not shown) that
is
press fitted into the drill collar 27. A keying notch 284 on the external
surface of uphole
body portion 271a mates with a projection (not shown) on the keying ring to
correctly
align the flow bypass sleeve 270 with the pulser assembly 26. A threaded ring
(not
shown) fixes the flow bypass sleeve 270 within the drill collar 27. A groove
285 on the
external surface of the uphole body portion 271a receives an o-ring (not
shown) and a
rubber back-up ring (not shown) such as a parbak to help seat the flow bypass
sleeve
270 and reduce fluid leakage between the flow bypass sleeve 270 and the drill
collar 27.
In alternative embodiments the flow bypass sleeve 270 may be assembled or
fitted
within the drill collar 27 using alternative fittings as would be known to a
person of skill
in the art.
As shown in Figure 2, the uphole body portion 271a of the sleeve body
surrounds
the frusto-conical section of stator body 141 with the annular channel 56
extending
therebetween. The uphole body portion 271a also surrounds the rotor and stator
projections 162, 142. The downhole body portion 271b of the flow bypass sleeve
270
surrounds the rotor cap body 191. Mud flows along annular channel 56 and
through the
apertures 275 and into the grooves 278 of the flow bypass sleeve 270 thereby
bypassing the rotor and stator projections 162, 142.
The external dimensions of flow bypass sleeve 270 may be adapted to fit any
sized drill collar 27. It is therefore possible to use a one size fits all
fluid pressure pulse
generator 130, 230 with multiple sized flow bypass sleeves 270, with each flow
bypass
sleeve 270 having the same internal dimensions to receive the one size fits
all fluid
pressure pulse generator 130, 230 but a different external diameter
dimensioned to fit
different sized drill collars 27. In larger diameter drill collars 27 the
volume of mud
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CA 2987642 2017-12-04
flowing through the drill collar 27 will generally be greater than the volume
of mud
flowing through smaller diameter drill collars 27, however the apertures 275
of the flow
bypass sleeve 270 may be dimensioned to accommodate this greater volume of
mud.
The apertures 275 of the different sized flow bypass sleeves 270 may therefore
be
dimensioned such that the volume of mud flowing through the one size fits all
fluid
pressure pulse generator 130, 230 fitted within any sized drill collar 27 is
within an
optimal range for generation of pressure pulses 6 which can be detected at the
surface
without excessive pressure build up. It may therefore be possible to control
the flow
rate of mud through the fluid pressure pulse generator 130, 230 using
different sized
flow bypass sleeves 270 rather than having to fit different sized fluid
pressure pulse
generators 130, 230 to the pulser assembly 26.
In alternative embodiments, the flow bypass sleeve may be any sleeve with flow
bypass channels that allows flow of mud to bypass the fluid pressure pulse
generator,
such as the different embodiments of flow bypass sleeves disclosed in
PCT/CA2015/050586 .
In alternative embodiments (not shown), the fluid pressure pulse generator
130,
230 may be present in the drill collar 27 without the flow bypass sleeve 270.
In these
alternative embodiments, the stator projections 142, 242 and rotor projections
162, 262
may be radially extended to have an external diameter that is greater than the
external
diameter of the cylindrical section of the stator body 141, 241, such that mud
following
along annular channel 55 impinges on the stator projections 142, 242 and is
directed
through the stator flow channels 143, 243. The stator projections 142, 242 and
rotor
projections 162, 262 may radially extend to meet the internal surface of the
drill collar
27. There may be a small gap between the rotor projections 162, 262 and the
internal
surface of the drill collar 27 to allow rotation of the rotor projections 162,
262. The
innovative aspects apply equally in embodiments such as these.
While particular embodiments have been described in the foregoing, it is to be
understood that other embodiments are possible and are intended to be included
herein. It will be clear to any person skilled in the art that modifications
of and
adjustments to the foregoing embodiments, not shown, are possible.
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