EP4731868A1

EP4731868A1 - Magnetic brake for an mwd rotary pulser

Info

Publication number: EP4731868A1
Application number: EP23944516.6A
Authority: EP
Inventors: Edward Richards
Original assignee: Services Petroliers Schlumberger SA; Schlumberger Technology BV
Current assignee: Services Petroliers Schlumberger SA; Schlumberger Technology BV
Priority date: 2023-07-05
Filing date: 2023-07-05
Publication date: 2026-04-29
Also published as: WO2025010081A1

Abstract

A magnetic parking brake for use in a downhole telemetry tool includes first and second magnets disposed, or spring biased into magnetic engagement with one another. An electromagnetic and/or mechanical mechanism is configured to reduce the magnetic engagement and thereby release the brake.

Description

MAGNETIC BRAKE FOR AN MWD ROTARY PULSER

BACKGROUND

[0001] Petroleum drilling operations commonly employ a number of techniques to gather information about the wellbore and the formation through which it is drilled. Such techniques are commonly referred to in the art as measurement while drilling (MWD) and logging while drilling (LWD). MWD and LWD techniques may be used, for example, to obtain information about the wellbore (e.g., information about the size, shape, and direction thereof) and the properties of the surrounding formation (e.g., the density, porosity, and resistivity thereof which may be related to the hydrocarbon bearing potential). Transmission of data from a downhole tool in the drill string to the surface is a difficulty common to many MWD and LWD operations.

[0002] Mud pulse and mud siren telemetry are commonly used to transmit data from a downhole tool in a wellbore to a receiver at the surface. Mud pulse techniques encode a series of pressure pulses while mud siren techniques encode a very low frequency (VLF) carrier signal. Both techniques commonly utilize a rotary pulser including a rotor/stator mechanism that restricts the flow of drilling fluid in the bottom hole assembly. The flow is restricted in such a way as to generate a pressure signal including a series of pressure pulses or a modulated pressure wave. The pressure signal may be detected at the surface, for example, via one or more pressure transducers deployed in the standpipe.

[0003] MWD tools commonly make use of a magnetic parking brake to prevent the rotor from stopping in the closed position (e.g., when electrical power to the tool is turned off). While the use of a magnetic parking brake effectively secures the rotor in the open position it can also increase peak power demand during operation of the rotary pulser and may further add to the complexity of the control system used to rotate and modulate the rotor, particularly in quadrature phase shift keying (QPSK) and octal phase shift keying (OPSK) encoding. There is a need for an improved magnetic brake mechanism for an MWD rotary pulser.

SUMMARY

[0004] In one example embodiment, a magnetic brake for a rotary pulser may include a first permanent magnet deployed on and rotationally fixed to a shaft, the shaft being configured to rotate in a housing; a second permanent magnet deployed on and rotationally fixed to the housing; an electromagnetic coil deployed about the first permanent magnet or the second permanent magnet, the electromagnetic coil configured, when energized with an electrical current, to generate a magnetic field that opposes a magnetic field generated by the first permanent magnet or the second permanent magnet; wherein the first permanent magnet and the second permanent magnet are disposed and configured to magnetically engage one another and thereby resist rotation of the shaft in the housing; and wherein energizing the electromagnetic coil with an electrical current reduces said magnetic engagement of the first permanent magnet and the second permanent magnet. Disclosed downhole telemetry tools may include the example of the magnetic brake embodiment. [0005] In another example embodiment, a magnetic brake for a rotary pulser may include a first permanent magnet deployed on and rotationally fixed to a shaft, the shaft being configured to rotate in a housing; a solenoid deployed about the shaft and rotationally fixed to the housing, the solenoid including a solenoid coil and a solenoid plate; a second permanent magnet deployed on the solenoid plate, the solenoid plate being spring biased axially away from the solenoid coil such that the first permanent magnet and the second permanent magnet magnetically engage one another when the solenoid coil is deenergized and thereby resist rotation of the shaft in the housing; and wherein energizing the solenoid coil with an electrical current translates the solenoid plate and the second permanent magnet axially away from the first permanent magnet against the spring bias and thereby reduces said magnetic engagement of the first permanent magnet and the second permanent magnet. Disclosed downhole telemetry tools may include the example of the magnetic brake embodiment.

[0006] In still another example embodiment, a magnetic brake for a rotary pulser may include a first permanent magnet deployed on and rotationally fixed to a shaft, the shaft being configured to rotate in a housing; an iris mechanism including at least one iris blade, the iris mechanism deployed about the shaft and rotationally fixed to the housing, the iris mechanism including a rotary actuator configured to open and close the at least one iris blade; a second permanent magnet deployed on the at least one iris blade, the at least one iris blade being spring biased towards a closed position such that the first permanent magnet and the second permanent magnet magnetically engage one another; and wherein energizing the rotary actuator rotates the at least one iris blade and the second permanent magnet against the spring bias from the closed position to an open position away from the first permanent magnet and thereby reduces said magnetic engagement of the first permanent magnet and the second permanent magnet. Disclosed downhole telemetry tools may include the example of the magnetic brake embodiment.

[0007] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a more complete understanding of the disclosed subject matter, and advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0009] FIG. 1 depicts an example drilling rig including a telemetry tool having a disclosed magnetic parking brake.

[0010] FIG. 2 depicts an example telemetry tool including a disclosed magnetic parking brake.

[0011] FIG. 3 depicts a prior art magnetic parking brake.

[0012] FIG. 4 depicts a schematic plot of the torque required to rotate the shaft at a constant velocity versus angular position for a shaft including the prior art magnetic brake.

[0013] FIG. 5 depicts one embodiment of a disclosed magnetic brake.

[0014] FIG. 6 depicts a schematic plot of the torque required to rotate the shaft at a constant velocity versus angular position for a shaft including the magnetic brake shown on FIG. 5.

[0015] FIGS. 7A and 7B (collectively FIG. 7) depict another disclosed magnetic brake embodiment.

[0016] FIGS. 8A and 8B (collectively FIG. 8) depict still another disclosed magnetic brake embodiment.

[0017] FIG. 9 depicts a schematic plot of the torque required to rotate the shaft at a constant velocity versus angular position for shafts including the magnetic brakes shown on FIGS 7 and 8.

DETAILED DESCRIPTION

[0018] FIG. 1 depicts an example drilling rig 20 including a telemetry tool 70 having a disclosed magnetic parking brake (not shown in FIG. 1). As described in more detail below, the telemetry tool 70 includes a rotary pulser configured to transmit a mud pulse telemetry or mud siren telemetry signal to the surface. The drilling rig 20 may be positioned over a subterranean formation (not shown). The rig 20 may include, for example, a derrick and a hoisting apparatus (also not shown) for raising and lowering a drill string 30, which, as shown, extends into wellbore 40 and includes, for example, a drill bit 32 and telemetry tool 70. The drill string 30 may include various other tools, for example, including a downhole drilling motor, a steering tool such as a rotary steerable tool or a bent sub, and one or more MWD and/or LWD tools including various sensors for sensing downhole characteristics of the wellbore and the surrounding formation. The disclosed embodiments are not limited with regards to these other tools in the drill string.

[0019] Drilling rig 20 further includes a surface system 50 for controlling the flow of drilling fluid used on the rig (e.g., used in drilling the wellbore 40). In the example rig depicted, drilling fluid 35 is pumped downhole (as depicted at 62), for example, via a conventional mud pump 57. The drilling fluid 35 may be pumped, for example, through a standpipe 58 and mud hose 59 in route to the drill string 30. The drilling fluid 35 typically emerges from the drill string 30 at or near the drill bit 32 and creates an upward flow 64 of mud through the wellbore annulus 42 (the annular space between the drill string and the wellbore wall). The drilling fluid 35 then flows through a return conduit 52 and solids control equipment 55 to a mud pit system 56 where it may be recirculated. It will be appreciated that the terms drilling fluid and mud are used synonymously herein.

[0020] With continued reference to FIG. 1, telemetry tool 70 may be configured, for example, to receive data from another tool, such as an MWD tool and/or LWD tool (not shown) and to prepare the data for transmission to the surface. As is known to those of ordinary skill, such data preparation may include filtering, compressing, encoding, and/or digitizing the data. The encoding and digitizing may include, for example, any suitable modulation method to superimpose a digital bit pattern on a carrier wave, for example, phase shift keying (PSK), quadrature phase shift keying (QPSK), frequency shift keying, continuous phase modulation, quadrature amplitude modulation, orthogonal frequency division multiplexing, and the like. The disclosed embodiments are, of course, not limited to any particular data preparation or encoding methods.

[0021] The telemetry tool 70 may further includes one or more valves (e.g., a rotary valve) to create positive pressure pulses in the drilling fluid. For example, the telemetry tool 70 may include a rotary pulser or a rotary disc valve pulser that is rotated relative to a stator. In example embodiments, the rotor and stator may each include at least one aperture (window) that permits fluid flow when rotationally aligned (opened) and restrict fluid flow when rotationally misaligned (closed). In other example embodiments, the rotor may include blades that restrict fluid flow when rotationally aligned with stator apertures (closed) and permit fluid flow when rotationally misaligned with the apertures (opened). In such example embodiments, rotation of the rotor periodically restricts the flow of drilling fluid (via periodic alignment and misalignment of the rotor and stator) and thereby generates a positive pressure signal in the downwardly flowing drilling fluid 62. The rotor may be rotated continuously in one direction (e.g., as in a mud siren), incrementally in one direction only, or incrementally by oscillating the rotor in one direction and then back to its original position. The disclosed embodiments are expressly not limited in this regard.

[0022] With still further reference to FIG. 1, the telemetry signals in the downwardly flowing drilling fluid 62 may be received, for example, via one or more pressure transducers 54 deployed on the standpipe 58. While not depicted on FIG. 1 it will be appreciated that conventional drilling rigs commonly further include a pulsation dampener (a desurger) that evens out the flow in the standpipe 58 and tends to improve the signal to noise ratio of the transmitted telemetry signal. The disclosed embodiments are not limited to the use of such a pulsation dampener.

[0023] It will of course be appreciated that while FIG. 1 depicts a land rig 20, that the disclosed embodiments are equally well suited for land rigs or offshore rigs. As is known to those of ordinary skill, offshore rigs commonly include a platform deployed atop a riser that extends from the sea floor to the surface. The drill string extends downward from the platform, through the riser, and into the wellbore through a blowout preventer (BOP) located on the sea floor. The disclosed embodiments are expressly not limited in these regards.

[0009] FIG. 2 depicts an example telemetry tool 70 including a disclosed magnetic parking brake 100. In the example embodiment depicted, telemetry tool 70 includes a rotary pulser 80 having a rotor 82 rotationally coupled to a shaft 72 and a stator 84 rotationally coupled to an outer housing 74 (e.g., a drill collar or an MWD tool housing) such that rotation of the shaft 72 with respect to the housing 74 rotates the rotor 82 with respect to the stator 84. The stator may include flow apertures (or flow channels) 85 in fluid communication with flow channel 75 (which is radially interposed between the shaft and housing). As described above, the rotor 82 may include a rotary disc valve including apertures (not shown) that permit fluid flow when rotationally aligned with the stator apertures 85 and restrict fluid flow when rotationally misaligned with the stator apertures. The rotor 82 may alternatively include a plurality of blades (not shown) that restrict fluid flow when rotationally aligned with stator apertures 85 and permit fluid flow when rotationally misaligned with the stator apertures 85.

[0010] The telemetry tool 70 may further include a controller (not shown) configured to cause electric motor 78 to rotate the shaft 72 (and rotor) with respect to the housing 74 (and stator).

Rotation of the shaft is intended to generate a series of pressure pulses or a modulated pressure wave (modulated carrier signal) in the drilling fluid 35 (FIG. 1) and thereby transmit information to the surface. In mud siren embodiments, the controller may be configured to modulate the rotation rate of the motor 78 and shaft 72 to encode a carrier wave (pressure wave). As noted above, the encoding may include substantially any suitable encoding scheme such as PSK, QPSK, and the like.

[0011] FIG. 3 depicts a cross sectional schematic view of a prior art magnetic parking brake 90 including a first set of inner magnets 92 rotationally coupled with a shaft 93 and a second set of outer magnets 94 rotationally coupled with an outer housing 95. The magnets 92, 94 are arranged and configured to resist the shaft (and the rotationally coupled rotor) from stopping in the closed position (restricting fluid flow) when electrical power is removed from the telemetry motor. In one common configuration, the magnets in each set 92, 94 have alternating polarities (N, S, N, S, and so on). As depicted on FIG. 3, the parking brake is “locked” (with the rotor in the open position) when N and S poles on the inner magnets 92 facing corresponding S and N poles on the outer magnets 94.

[0012] As described above, the use of a prior art magnetic parking brake is intended to secure the rotor in the open position. However, the use of such a brake can significantly increase peak power demand during operation of the rotary pulser and may further add to the complexity of the control system used to rotate and modulate the rotor. It may also require a more powerful (and therefore more expensive) electric motor to rotate the shaft.

[0013] FIG. 4 depicts a schematic plot of the required torque needed to rotate the shaft at a constant velocity versus the angular position of the shaft (or time since the rotation rate is constant) for a shaft including prior art brake 90. Note that the force (torque) profile is essentially sinusoidal with maxima 98 occurring when the rotor is in the open position (and when attracting NS and SN poles face one another in the brake) and minima 99 occurring when the rotor is in the closed position (and when opposing NN and SS poles face one another in the brake). One negative consequence of the depicted torque profile is that a high peak power is required to overcome the magnetic resistance of the prior art brake to rotate and modulate the rotor. High power is also required to accurately position the rotor.

[0014] Based on the foregoing, it is evident that there is a need for an improved magnetic braking mechanism for an MWD rotary pulser. The disclosed embodiments may advantageously provide an improved magnetic brake and are intended to address the above-described difficulties inherent with prior art magnetic brakes. In first example embodiments, an improved magnetic brake includes a plurality of coils wrapped around a corresponding plurality of the magnets (e.g., each of the outer magnets). In such embodiments, energizing the coils is intended to buckle and/or fully or partially neutralize the magnetic field and thereby reduce the attractive force when the rotor is in the closed position. In second example embodiments, one of the inner or outer sets of magnets are disposed (and configured) to move with respect to and away from the other set of magnets and thereby reduce the attractive force when the rotor is in the closed position.

[0015] Turning now to FIG. 5, and with further reference to FIG. 2, magnetic parking brake 100 is shown in cross section. The example embodiment depicted includes a first set of inner magnets 102 rotationally coupled with shaft 72 and a second set of outer magnets 104 rotationally coupled with the outer housing 74. The magnets 102, 104 are arranged and configured to inhibit the shaft (and the rotationally coupled rotor) from stopping in the closed position when electric power is removed (disconnected) from the telemetry motor 78. As depicted, the magnets in each set 102, 104 have alternating polarities (N, S, N, S, and so on). The parking brake is “locked” (with the rotor in the open position) when N and S poles on the inner magnets 102 face corresponding S and N poles on the outer magnets 104.

[0016] In the depicted example embodiment, at least one electromagnetic coil 110 is/are wrapped around the magnets in the outer set 104. The coil(s) 110 are disposed and configured such that energizing the coil(s) with an electrical current buckles or neutralizes the magnetic fields about the individual magnets. By buckles or neutralizes it will be understood that the energized coils 110 generate corresponding magnetic fields that oppose the magnetic fields around each of the individual magnets in the outer set 104. It will be appreciated that the disclosed embodiments are not limited to any particular number of the coil(s) 110. For example, in one embodiment, a single (continuous) coil may be wrapped around each of the plurality of magnets in the outer set. In another example embodiment, a distinct coil may be wrapped around each of the plurality of magnets.

[0017] It will be further appreciated that while the electromagnetic coils 110 are shown wrapped around the outer magnets 104, that the coils may alternatively and/or additionally be wrapped around the inner magnets 102. While the disclosed embodiments are not limited in this regard, deployment of the coils about the outer magnets may be advantageous since there is generally more space available near the periphery of the telemetry tool (and away from the rotating shaft).

[0018] With continued reference to FIGS. 3 and 5, telemetry tool 70 may further include or be connected to a downhole power supply (such as a downhole turbine alternator). In example embodiments, the power supply may be configured to provide electrical power to both the telemetry motor 78 and the coil(s) 110 (e.g., simultaneously). For example, when power is provided to the motor to rotate the shaft during a telemetry operation, such power may also be provided to the coils to buckle the magnetic fields about the magnets 104 (and thereby magnetically release the brake). When power is removed from the motor (e.g., when the flow of drilling fluid stops), such power may also be removed from the coils, thereby locking the brake as described above.

[0019] FIG. 6 depicts a schematic plot of the torque required to rotate the shaft at a constant velocity versus the angular position of the shaft (or time since the rotation rate is constant) for a shaft including magnetic brake 100. Note that the force (torque) profile is approximately constant (as compared with the dotted force profile for the prior art brake). Use of the disclosed magnetic brake including the electromagnetic coils may therefore advantageously reduce the peak power required to rotate and position the shaft. It will be appreciated that the torque profile may have a small amplitude sinusoidal shape if the coils do not perfectly cancel the permanent magnetic field of magnets 104.

[0020] Turning now to FIGS. 7A and 7B (collectively FIG. 7), and with continued reference to FIG. 2, another disclosed magnetic parking brake 100' is depicted. Magnetic brake 100' is similar to magnetic brake 100 in that it includes inner and outer sets of magnets 102', 104' configured to lock the rotary pulser in the open position when power is removed from the pulser. As described previously, the inner set of magnets 102' is rotationally fixed (e.g., keyed) to the shaft 72 and the outer set of magnets 104' is rotationally fixed (e.g., keyed) to the housing 74. In this example embodiment, the magnetic brake 100' further includes a solenoid 120, having a solenoid coil 122 and a solenoid plate 124, deployed about the shaft 72 and rotationally coupled to the tool housing 74. The outer set of magnets 104' may be deployed on the solenoid plate 124 and is translated in an axial direction with the plate between first and second axial positions.

[0021] In FIG. 7A, the solenoid plate 124 and the outer set of magnets 104' is biased into the first axial position by one or more springs 130 (e.g., one or more coil springs off-axis or coaxial with the shaft). The shaft may then rotate such that the N and S poles on the inner magnets 102' face the corresponding S and N poles on the outer magnets 104' and the rotor is secured (locked) in the open position. Energizing the solenoid coil 122 with an electrical current draws the plate 124 and the outer set of magnets 104' towards the second axial position against the bias of the spring(s) 130 as depicted on FIG. 7B. It will be appreciated that moving the outer set of magnets 104' away from the inner set of magnets 102' reduces the attractive force between the magnets and thereby reduces the braking force that must be overcome by the telemetry motor 78 during a telemetry operation.

[0022] As described above, telemetry tool 70 may further include or be connected to a downhole power supply (such as a downhole turbine alternator). In example embodiments, the power supply may be configured to provide electrical power to both the telemetry motor 78 and the solenoid coil 122 (e.g., simultaneously). For example, when power is provided to the motor to rotate the shaft during a telemetry operation, such power may also be provided to the solenoid coils to retract the solenoid plate against the bias of springs 130 and thereby translate the outer magnets 104' away from the inner magnets 102' (and thereby release the brake). When power is removed from the motor (e.g., when the flow of drilling fluid stops), such power may also be removed from the solenoid coil 122, thereby allowing the spring(s) 130 to translate the solenoid plate 124 and outer magnets 104' to the first position (thereby locking the brake as described above).

[0023] Turning now to FIGS. 8 A and 8B (collectively FIG. 8), and with continued reference to FIG. 2, still another magnetic brake embodiment 100" is depicted. Magnetic brake 100" is similar to magnetic brakes 100, 100' in that it includes inner and outer sets of magnets 102", 104" configured to lock the rotary pulser in the open position when power is removed from the pulser.

As described previously, the inner set of magnets 102" is rotationally fixed (e.g., keyed) to the shaft 72 and the outer set of magnets 104" is rotationally fixed (e.g., keyed or pinned) to an outer housing 74. Magnetic brake 100" similar to magnetic brake 100' in that one set of magnets (e.g., the outer set) is configured to move with respect to the other set of magnets (e.g., the inner set).

[0024] In this example embodiment, the magnetic brake 100" includes an iris mechanism 140 that enables the outer magnets 104" to pivot between first and second positions with respect to an inner set of magnets 102". Each of the outer set of magnets 104" may be deployed on a corresponding iris blade 142. A first end of each iris blade 142 is pivotably coupled (e.g., pinned) at 144 to a drive plate 150 (only an inner portion of which is shown) that is configured to rotate between first and second rotational positions when the iris mechanism is actuated. In the disclosed example, the magnetic brake 100" is closed (FIG. 8A) when the drive plate 150 is in the first rotational position and open (FIG. 8B) when the drive plate is in the second rotational position.

[0025] In FIG. 8A, the drive plate 150 is biased into the first rotational position by a spring 162 (such as a torsion spring), which is depicted schematically. Such bias rotates the iris blades 142 and outer set of magnets 104" into proximity with the inner magnets 102". As described above, the shaft is then free to rotate such that the N and S poles on the inner magnets 102" face the corresponding S and N poles on the outer magnets 104" and thereby magnetically secure the rotor in the open position. Energizing a rotary actuator 160 with an electrical current rotates the drive plate 150 to the second rotational position (against the bias of the spring). Such rotation opens the iris mechanism 140, thereby rotating the blades 142 and outer magnets 104" out and away from the inner magnets 102" as shown on FIG. 8B.

[0026] It will be understood that iris mechanism 140 may include substantially any suitable iris mechanism in which iris blades 142 and outer magnets 104" are configured (and constrained) to rotate into and out of magnetic engagement with the inner magnets 102". In the depicted example embodiment, the drive plate 150 is disposed behind and configured to rotate with respect to a guide plate 152. A first end of each iris blade 142 is pivotably coupled 144 to the drive plate 150 and rotates therewith. A second opposing end of each blade 142 includes a guide pin 146 that is constrained to move in a guide channel 154 in the guide plate 152. Rotation of the drive plate 150 (and pivot 144) constrains the guide pins 146 to move in corresponding guide channels 154 thereby rotating the blades 142 and outer magnets 104" out and away from the inner magnets 102".

[0027] FIG. 9 depicts a schematic plot of the torque required to rotate the shaft at a constant velocity versus the angular position of the shaft (or time since the rotation rate is constant) for a shaft including one of magnetic brakes 100' or 100". Note that the force (torque) profile is a low amplitude sinusoid as compared with the dotted force profile for the prior art brake (owing to the movement of the outer magnets away from the inner magnets). Use of the disclosed magnetic brakes 100', 100" including moveable magnets may therefore advantageously reduce the peak power required to rotate and position the shaft during a telemetry operation.

[0028] It will be understood that the present disclosure includes numerous embodiments. These embodiments include, but are not limited to, the following embodiments.

[0029] In a first embodiment, a magnetic brake for a rotary pulser comprises a first permanent magnet deployed on and rotationally fixed to a shaft, the shaft being configured to rotate in a housing; a second permanent magnet deployed on and rotationally fixed to the housing; an electromagnetic coil deployed about the first permanent magnet or the second permanent magnet, the electromagnetic coil configured, when energized with an electrical current, to generate a magnetic field that opposes a magnetic field generated by the first permanent magnet or the second permanent magnet; wherein the first permanent magnet and the second permanent magnet are disposed and configured to magnetically engage one another and thereby resist rotation of the shaft in the housing; and wherein energizing the electromagnetic coil with an electrical current reduces said magnetic engagement of the first permanent magnet and the second permanent magnet.

[0030] A second embodiment may include the first embodiment, wherein the first permanent magnet comprises a first plurality of permanent magnets deployed about an outer surface of the shaft; the second permanent magnet comprises a second plurality of permanent magnets deployed about the first plurality of permanent magnets; and the electromagnetic coil is deployed about the first plurality of magnets or the second plurality of magnets.

[0031] A third embodiment may include the second embodiment, wherein the electromagnetic coil comprises a plurality of electromagnetic coils, at least one of which is deployed about each of the first plurality of magnets or the second plurality of magnets; and energizing the plurality of electromagnetic coils with corresponding electrical currents generates corresponding magnetic fields that oppose the magnetic fields generated by each of the first plurality of magnets or the second plurality of magnets.

[0032] A fourth embodiment may include any one of the second through third embodiments, wherein the electromagnetic coil is deployed about the second plurality of magnets.

[0033] In a fifth embodiment a downhole telemetry tool comprises the magnetic brake of any one of second through fourth embodiments; a drilling fluid flow channel disposed between the shaft and the housing; a stator rotationally fixed to the housing, the stator including at least one aperture in fluid communication with the drilling fluid flow channel; a rotor rotationally fixed to the shaft; and an electrical motor configured to rotate the shaft and rotor in the housing and thereby generate pressure pulses or a pressure wave in the drilling fluid flow channel.

[0034] A sixth embodiment may include the fifth embodiment, wherein the electromagnetic coil and the electrical motor are connected to a common electrical power source such that interruption of electrical power from the power source automatically engages the magnetic brake by deenergizing the electromagnetic coil.

[0035] In a seventh embodiment, a magnetic brake for a rotary pulser comprises a first permanent magnet deployed on and rotationally fixed to a shaft, the shaft being configured to rotate in a housing; a solenoid deployed about the shaft and rotationally fixed to the housing, the solenoid including a solenoid coil and a solenoid plate; a second permanent magnet deployed on the solenoid plate, the solenoid plate being spring biased axially away from the solenoid coil such that the first permanent magnet and the second permanent magnet magnetically engage one another when the solenoid coil is deenergized and thereby resist rotation of the shaft in the housing; and wherein energizing the solenoid coil with an electrical current translates the solenoid plate and the second permanent magnet axially away from the first permanent magnet against the spring bias and thereby reduces said magnetic engagement of the first permanent magnet and the second permanent magnet.

[0036] An eighth embodiment may include the seventh embodiment, wherein the spring bias is provided by at least one coil spring deployed axially between the solenoid coil and the solenoid plate.

[0037] A ninth embodiment may include any one of the seventh through eighth embodiments, wherein the first permanent magnet comprises a first plurality of permanent magnets deployed about an outer surface of the shaft; and the second permanent magnet comprises a second plurality of permanent magnets deployed on the solenoid plate.

[0038] A tenth embodiment may include the ninth embodiment, wherein the second plurality of permanent magnets is disposed about the first plurality of permanent magnets when the solenoid coil is deenergized. [0039] In an eleventh embodiment, a downhole telemetry tool comprises the magnetic brake of any one of the ninth through tenth embodiments; a drilling fluid flow channel disposed between the shaft and the housing; a stator rotationally fixed to the housing, the stator including at least one aperture in fluid communication with the drilling fluid flow channel; a rotor rotationally fixed to the shaft; and an electrical motor configured to rotate the shaft and rotor in the housing and thereby generate pressure pulses or a pressure wave in the drilling fluid flow channel.

[0040] A twelfth embodiment may include the eleventh embodiment, wherein the solenoid coil and the electrical motor are connected to a common electrical power source such that interruption of electrical power from the power source automatically engages the magnetic brake by deenergizing the solenoid coil.

[0041] In a thirteenth embodiment, a magnetic brake for a rotary pulser comprises a first permanent magnet deployed on and rotationally fixed to a shaft, the shaft being configured to rotate in a housing; an iris mechanism including at least one iris blade, the iris mechanism deployed about the shaft and rotationally fixed to the housing, the iris mechanism including a rotary actuator configured to open and close the at least one iris blade; a second permanent magnet deployed on the at least one iris blade, the at least one iris blade being spring biased towards a closed position such that the first permanent magnet and the second permanent magnet magnetically engage one another; and wherein energizing the rotary actuator rotates the at least one iris blade and the second permanent magnet against the spring bias from the closed position to an open position away from the first permanent magnet and thereby reduces said magnetic engagement of the first permanent magnet and the second permanent magnet.

[0042] A fourteenth embodiment may include the thirteenth embodiment, wherein the first permanent magnet comprises a first plurality of permanent magnets deployed about an outer surface of the shaft; and the second permanent magnet comprises a second plurality of permanent magnets deployed on a corresponding plurality of the iris blades.

[0043] A fifteenth embodiment may include the fourteenth embodiment, wherein the second plurality of permanent magnets is spring biased into the closed position about the first plurality of permanent magnets when the rotary actuator is deenergized.

[0044] A sixteenth embodiment may include any one of the fourteenth through fifteenth embodiments, wherein the iris mechanism further comprises a drive plate and a guide plate, the rotary actuator being configured to rotate the drive plate against the spring bias from the closed position to the open position.

[0045] A seventeenth embodiment may include the sixteenth embodiment, wherein a first end of each of the plurality of iris blades is pivotably coupled to the drive plate; and a second end of the each of the plurality of iris blades includes a guide pin that is constrained to a corresponding guide channel in the guide plate such that rotation of the drive plate with respect to the guide plate opens and closes the plurality of iris blades.

[0046] An eighteenth embodiment may include any one of the sixteenth through seventeenth embodiments, wherein the spring bias is provided by a torsion spring deployed between the drive plate and the guide plate.

[0047] In a nineteenth embodiment, a downhole telemetry tool comprises the magnetic brake of any one of the fourteenth through eighteenth embodiments; a drilling fluid flow channel disposed between the shaft and the housing; a stator rotationally fixed to the housing, the stator including at least one aperture in fluid communication with the drilling fluid flow channel; a rotor rotationally fixed to the shaft; and an electrical motor configured to rotate the shaft and rotor in the housing and thereby generate pressure pulses or a pressure wave in the drilling fluid flow channel. [0048] A twentieth embodiment may include the nineteenth embodiment, wherein the rotary actuator and the electrical motor are connected to a common electrical power source such that interruption of electrical power from the power source automatically engages the magnetic brake by deenergizing the rotary actuator.

[0049] Although magnetic parking brakes for a rotary pulser and certain advantages thereof have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the spirit and scope of the disclosure.

Claims

1. A magnetic brake for a rotary pulser, the magnetic brake comprising: a first permanent magnet deployed on and rotationally fixed to a shaft, the shaft being configured to rotate in a housing; a second permanent magnet deployed on and rotationally fixed to the housing; an electromagnetic coil deployed about the first permanent magnet or the second permanent magnet, the electromagnetic coil configured, when energized with an electrical current, to generate a magnetic field that opposes a magnetic field generated by the first permanent magnet or the second permanent magnet; wherein the first permanent magnet and the second permanent magnet are disposed and configured to magnetically engage one another and thereby resist rotation of the shaft in the housing; and wherein energizing the electromagnetic coil with an electrical current reduces said magnetic engagement of the first permanent magnet and the second permanent magnet.

2. The magnetic brake of claim 1, wherein the first permanent magnet comprises a first plurality of permanent magnets deployed about an outer surface of the shaft; the second permanent magnet comprises a second plurality of permanent magnets deployed about the first plurality of permanent magnets; and the electromagnetic coil is deployed about the first plurality of magnets or the second plurality of magnets.

3. The magnetic brake of claim 2, wherein: the electromagnetic coil comprises a plurality of electromagnetic coils, at least one of which is deployed about each of the first plurality of magnets or the second plurality of magnets; and energizing the plurality of electromagnetic coils with corresponding electrical currents generates corresponding magnetic fields that oppose the magnetic fields generated by each of the first plurality of magnets or the second plurality of magnets.

4. The magnetic brake of claim 2, wherein the electromagnetic coil is deployed about the second plurality of magnets.

5. A downhole telemetry tool comprising: the magnetic brake of claim 2; a drilling fluid flow channel disposed between the shaft and the housing; a stator rotationally fixed to the housing, the stator including at least one aperture in fluid communication with the drilling fluid flow channel; a rotor rotationally fixed to the shaft; and an electrical motor configured to rotate the shaft and rotor in the housing and thereby generate pressure pulses or a pressure wave in the drilling fluid flow channel.

6. The downhole telemetry tool of claim 5, wherein the electromagnetic coil and the electrical motor are connected to a common electrical power source such that interruption of electrical power from the power source automatically engages the magnetic brake by deenergizing the electromagnetic coil.

7. A magnetic brake for a rotary pulser, the magnetic brake comprising: a first permanent magnet deployed on and rotationally fixed to a shaft, the shaft being configured to rotate in a housing; a solenoid deployed about the shaft and rotationally fixed to the housing, the solenoid including a solenoid coil and a solenoid plate; a second permanent magnet deployed on the solenoid plate, the solenoid plate being spring biased axially away from the solenoid coil such that the first permanent magnet and the second permanent magnet magnetically engage one another when the solenoid coil is deenergized and thereby resist rotation of the shaft in the housing; and wherein energizing the solenoid coil with an electrical current translates the solenoid plate and the second permanent magnet axially away from the first permanent magnet against the spring bias and thereby reduces said magnetic engagement of the first permanent magnet and the second permanent magnet.

8. The magnetic brake of claim 7, wherein the spring bias is provided by at least one coil spring deployed axially between the solenoid coil and the solenoid plate.

9. The magnetic brake of claim 7 , wherein the first permanent magnet comprises a first plurality of permanent magnets deployed about an outer surface of the shaft; and the second permanent magnet comprises a second plurality of permanent magnets deployed on the solenoid plate.

10. The magnetic brake of claim 9, wherein the second plurality of permanent magnets is disposed about the first plurality of permanent magnets when the solenoid coil is deenergized.

11. A downhole telemetry tool comprising: the magnetic brake of claim 9; a drilling fluid flow channel disposed between the shaft and the housing; a stator rotationally fixed to the housing, the stator including at least one aperture in fluid communication with the drilling fluid flow channel; a rotor rotationally fixed to the shaft; and an electrical motor configured to rotate the shaft and rotor in the housing and thereby generate pressure pulses or a pressure wave in the drilling fluid flow channel.

12. The downhole telemetry tool of claim 11, wherein the solenoid coil and the electrical motor are connected to a common electrical power source such that interruption of electrical power from the power source automatically engages the magnetic brake by deenergizing the solenoid coil.

13. A magnetic brake for a rotary pulser, the magnetic brake comprising: a first permanent magnet deployed on and rotationally fixed to a shaft, the shaft being configured to rotate in a housing; an iris mechanism including at least one iris blade, the iris mechanism deployed about the shaft and rotationally fixed to the housing, the iris mechanism including a rotary actuator configured to open and close the at least one iris blade; a second permanent magnet deployed on the at least one iris blade, the at least one iris blade being spring biased towards a closed position such that the first permanent magnet and the second permanent magnet magnetically engage one another; and wherein energizing the rotary actuator rotates the at least one iris blade and the second permanent magnet against the spring bias from the closed position to an open position away from the first permanent magnet and thereby reduces said magnetic engagement of the first permanent magnet and the second permanent magnet.

14. The magnetic brake of claim 13, wherein the first permanent magnet comprises a first plurality of permanent magnets deployed about an outer surface of the shaft; and the second permanent magnet comprises a second plurality of permanent magnets deployed on a corresponding plurality of the iris blades.

15. The magnetic brake of claim 14, wherein the second plurality of permanent magnets is spring biased into the closed position about the first plurality of permanent magnets when the rotary actuator is deenergized.

16. The magnetic brake of claim 14, wherein the iris mechanism further comprises a drive plate and a guide plate, the rotary actuator being configured to rotate the drive plate against the spring bias from the closed position to the open position.

17. The magnetic brake of claim 16, wherein: a first end of each of the plurality of iris blades is pivotably coupled to the drive plate; and a second end of the each of the plurality of iris blades includes a guide pin that is constrained to a corresponding guide channel in the guide plate such that rotation of the drive plate with respect to the guide plate opens and closes the plurality of iris blades.

18. The magnetic brake of claim 16, wherein the spring bias is provided by a torsion spring deployed between the drive plate and the guide plate.

19. A downhole telemetry tool comprising: the magnetic brake of claim 14; a drilling fluid flow channel disposed between the shaft and the housing; a stator rotationally fixed to the housing, the stator including at least one aperture in fluid communication with the drilling fluid flow channel; a rotor rotationally fixed to the shaft; and an electrical motor configured to rotate the shaft and rotor in the housing and thereby generate pressure pulses or a pressure wave in the drilling fluid flow channel.

20. The downhole telemetry tool of claim 19, wherein the rotary actuator and the electrical motor are connected to a common electrical power source such that interruption of electrical power from the power source automatically engages the magnetic brake by deenergizing the rotary actuator.