CA2987642C - Fluid pressure pulse generator for a telemetry tool - Google Patents

Abstract

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.

Description

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, 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.

2 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.

3 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

4 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

5 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

6 , .
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

7 =
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, 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

8 =
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 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

9 =
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 =
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 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 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 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 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 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.

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 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.

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 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 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, 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.

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 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 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.

Claims (23)

Claims

1. A telemetry tool comprising:
(a) a pulser assembly comprising a housing enclosing a motor, and a driveshaft rotationally coupled to the motor;
(b) a fluid pressure pulse generator comprising:
(i) a stator fixedly attached to the housing or to a drill collar housing the fluid pressure pulse generator, the stator comprising a stator body and a plurality of radially extending stator projections spaced around the stator body whereby spaced stator projections define stator flow channels extending therebetween; and (ii) a rotor fixedly attached to the driveshaft, the rotor comprising a rotor body and a plurality of radially extending rotor projections spaced around the rotor body, wherein the rotor projections are 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, and wherein the stator body 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 having 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.

2. The telemetry tool of claim 1, wherein the stator body has a bore therethrough with a wall extending across the bore, and the wall includes the angular movement restrictor window therethrough.

3. The telemetry tool of claim 2, wherein at least a portion of the rotor body is received within the bore in the stator body and the rotor body has a bore therethrough which receives a portion of the driveshaft.

4. The telemetry tool of claim 3 further comprises a rotor cap comprising a cap body and a cap shaft, the cap shaft being received in the bore of the rotor body and configured to releasably couple the rotor to the driveshaft.

5. The telemetry tool of any one of claims 1 to 4, wherein the angular movement restrictor window comprises a pair of opposed indexing window segments and the indexer comprises a pair of opposed indexers each extending from the rotatable member into a respective indexing window segment.

6. The telemetry tool of claim 5, wherein the indexer is a coupling key coupling the driveshaft to the rotor.

7. The telemetry tool of claim 6, wherein the driveshaft has a keyhole and the rotor has a receptacle, and the coupling key comprises a key body with dimensions which extend through the keyhole and receptacle and into the indexing window segments.

8. The telemetry tool of claim 7, wherein the coupling key comprises 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.

9. The telemetry tool of any one of claims 1 to 4, wherein the rotor body is rotatably received in the central window segment and the indexer protrudes radially from the rotor body.

10. The telemetry tool of claim 9, wherein the angular movement restrictor window comprises a pair of opposed indexing window segments and the indexer comprises a pair of indexing teeth each extending from the rotor body into a respective indexing window segment.

11. The telemetry tool of claim 9 or 10, wherein the rotor body and the indexer are integrally formed.

12. The telemetry tool of any one of claims 1 to 11, further comprising 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.

13. The telemetry tool of claim 12, wherein the contact sensor detects the force of contact by the indexer and transmit this information to a controller of the telemetry tool.

14. The telemetry tool of claim 12 or 13, wherein an electrical shutoff of the telemetry tool is 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.

15. The telemetry tool of any one of claims 12 to 14, wherein an anti-jam sequence is 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.

16. A fluid pressure pulse generator comprising:
(i) 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, the stator comprising a stator body and a plurality of radially extending stator projections spaced around the stator body whereby spaced stator projections define stator flow channels extending therebetween; and (ii) a rotor configured to fixedly attach to a driveshaft of the pulser assembly, the rotor comprising a rotor body and a plurality of radially extending rotor projections spaced around the rotor body, wherein the rotor projections are 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, and wherein the stator body 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 having 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.

17. The fluid pressure pulse generator of claim 16, wherein the stator body has a bore therethrough with a wall extending across the bore, and the wall includes the angular movement restrictor window therethrough.

18. The fluid pressure pulse generator of claim 17, wherein at least a portion of the rotor body is received within the bore in the stator body and the rotor body has a bore therethrough configured to receive a portion of the driveshaft.

19. The fluid pressure pulse generator of claim 18 further comprises a rotor cap comprising a cap body and a cap shaft, the cap shaft being received in the bore of the rotor body and configured to releasably couple the rotor to the driveshaft.

20. The fluid pressure pulse generator of any one of claims 16 to 19, wherein the rotor body is rotatably received in the central window segment and the indexer protrudes radially from the rotor body.

21. The fluid pressure pulse generator of claim 20, wherein the angular movement restrictor window comprises a pair of opposed indexing window segments and the indexer comprises a pair of indexing teeth each extending from the rotor body into a respective indexing window segment.

22. The fluid pressure pulse generator of claim 20 or 21, wherein the rotor body and the indexer are integrally formed.

23. The fluid pressure pulse generator of any one of claims 16 to 22 further comprising 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.