EP4735732A1

EP4735732A1 - High frequency injection for breaking energy dissipation

Info

Publication number: EP4735732A1
Application number: EP23947785.4A
Authority: EP
Inventors: David SOK; Federico MIZZON; Ivan ZORIC
Original assignee: Services Petroliers Schlumberger SA; Schlumberger Technology BV
Current assignee: Services Petroliers Schlumberger SA; Schlumberger Technology BV
Priority date: 2023-07-31
Filing date: 2023-07-31
Publication date: 2026-05-06
Also published as: WO2025029286A1

Abstract

A method of operating a downhole motor on a downhole tool includes generating an electrical energy output with the downhole motor. The electrical energy output flows to an electronics system of the downhole tool. The method further includes applying an electrical energy input to the downhole motor with the electronics system. The method further includes reducing the electrical energy output based on the applied electrical energy input in order to maintain the electrical energy output below an operational threshold of the electronics system.

Description

HIGH FREQUENCY INJECTION FOR BREAKING ENERGY DISSIPATION

BACKGROUND

[0001] Wellbores may be drilled into a surface location or seabed for a variety of exploratory or extraction purposes. For example, a wellbore may be drilled to access fluids, such as liquid and gaseous hydrocarbons, stored in subterranean formations and to extract the fluids from the formations. Wellbores used to produce or extract fluids may be formed in earthen formations using earth-boring tools such as drill bits for drilling wellbores and reamers for enlarging the diameters of wellbores.

[0002] In downhole drilling, electric motors are often implemented to drive various components of the drilling system. These motors typically operate at high power levels (e.g., high current and/or voltage), which can subject one or more electrical components of the motor’s electrical system to excess levels and/or prolonged durations of high power when the motors operate in a regeneration mode. This excess power is often dissipated as heat through one or more power dissipating features of the motor system, but such power dissipating components are often limited in their ability to withstand power at elevated levels and/or for longer durations. Additionally, these power dissipating components can typically become damaged or worn from overheat, overcurrent, and/or overvoltage conditions and as such are prone to failure, which may present a risk of damage to one or more other components of the motor system. Therefore, improved techniques for effectively dissipating unwanted quantities of electrical power generated by downhole motors may be advantageous over conventional methods.

SUMMARY

[0003] In some embodiments, a method of operating a downhole motor includes generating an electrical energy output with the downhole motor. The electrical energy output flows to an electronics system of the downhole tool. The method includes applying an electrical energy input to the downhole motor with the electronics system. The method includes reducing the electrical energy output based on the applied electrical energy input in order to maintain the electrical energy output below an operational threshold of the electronics system. [0004] In some embodiments, a method of operating a downhole motor of a downhole tool includes generating an electrical energy output with the downhole motor. The electrical energy output flows to an electronics system of the downhole tool. The method includes, while generating the electrical energy output, selectively decreasing an efficiency of the downhole motor to generate the electrical energy output. The method includes reducing the electrical energy output based on decreasing the efficiency in order to maintain the electrical energy output below an operational threshold of the electronics system.

[0005] In some embodiments, a method of dissipating electrical energy includes identifying a regeneration mode of a downhole motor in a downhole tool. While in the regeneration mode, the downhole motor generates an electrical energy output. The method includes, upon identifying the regeneration mode, applying an electrical energy input to an armature of the downhole motor. The method includes, based on applying the electrical energy input, causing at least a portion of the electrical energy output to dissipate as heat through the downhole motor.

[0006] 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. Additional features and aspects of embodiments of the disclosure will be set forth herein, and in part will be obvious from the description, or may be learned by the practice of such embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to describe the manner in which the above-recited and other features of the disclosure can be obtained, a more particular description will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. For better understanding, the like elements have been designated by like reference numbers throughout the various accompanying figures. While some of the drawings may be schematic or exaggerated representations of concepts, at least some of the drawings may be drawn to scale. Understanding that the drawings depict some example embodiments, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: [0008] FIG. 1 shows an example of a drilling system, according to at least one embodiment of the present disclosure;

[0009] FIGS. 2-1 to 2-3 show an example implementation of a downhole motor system, according to at least one embodiment of the present disclosure;

[0010] FIG. 3 shows an example implementation of a downhole motor system, according to at least one embodiment of the present disclosure;

[0011] FIG. 4 illustrates a flow diagram for a method or a series of acts for operating a downhole motor system as discussed herein, according to at least one embodiment of the present disclosure; [0012] FIG. 5 illustrates a flow diagram for a method or a series of acts for operating a downhole motor system as discussed herein, according to at least one embodiment of the present disclosure; [0013] FIG. 6 illustrates a flow diagram for a method or a series of acts for dissipating electrical energy as discussed herein, according to at least one embodiment of the present disclosure; and [0014] FIG. 7 illustrates certain components that may be included within a computer system, according to at least one embodiment of the present disclosure.

DETAILED DESCRIPTION

[0015] Embodiments of the present disclosure relate to devices, systems, and methods for dissipating energy in a downhole motor system. For instance, a downhole tool may implement a downhole motor system for the purpose of driving one or more functions of the downhole tool, such as a steering or directional drilling tool. The downhole motor system may include a downhole motor as well as various other components such as a power supply for powering the downhole motor and a motor drive for driving and controlling the downhole motor. In some instances, the downhole motor is driven, at least in part, by an external mechanical input, such that the motor operates as a generator and generates an electrical energy output. This may be as part of a designated regeneration mode of the downhole motor system, for example, to regenerate the power supply. Tn some instances, however, the downhole motor may generate too much electrical energy, either too high of a degree or for too long of a duration (or both). In such instances, a motor system will typically implement a brake (e.g., dump) resistor for dissipating an excess quantity of the generated electrical energy, or even all of it. The brake resistor, however, may be limited in its ability to dissipate the electrical energy to a sufficient degree or for a sufficient duration, and may be prone to overheating, damage, wear, failure, etc. As such, in some situations a brake resistor may not be ideal or adequate for dissipating a sufficient amount of the electrical energy output generated by the downhole motor.

[00161 Iⁿ some embodiments, the electronics system, and more specifically the motor drive, is configured to supply and/or inject an electrical energy to the downhole motor in order to intentionally reduce an efficiency of the motor by bringing about or increasing one or more losses associated with the downhole motor. For example, the motor drive may inject and/or supply the downhole motor with electrical energy that has a distorted waveform such that the downhole motor experiences or exhibits an increase in joule losses and/or eddy current losses. The distorted waveform may include one or more alternate frequencies than that of the fundamental frequency of the downhole motor, such as harmonic (e.g., integer multiple) frequencies of the fundamental frequency. This harmonic distortion may contribute to the losses in the motor without substantially contributing to a production or energy output of the downhole motor such that electrical energy may be dissipated based on the downhole motor generating the electrical energy output less efficiently. This energy dissipating mechanism may be in addition to or as an alternative to dissipating electrical energy with the brake resistor. In this way, intentionally induced inefficiencies of the downhole motor may be leveraged by the downhole motor system in order to effectively dissipate some or all of the electrical energy generated by downhole motor. [0017] FIG. 1 shows one example of a drilling system 100 for drilling an earth formation 101 to form a wellbore 102. The drilling system 100 includes a drill rig 103 used to turn a drilling tool assembly 104 which extends downward into the wellbore 102. The drilling tool assembly 104 may include a drill string 105, a bottomhole assembly (BHA) 106, and a bit 110, attached to the downhole end of drill string 105.

[0018] The drill string 105 may include several joints of drill pipe 108 connected end-to-end through tool joints 109. The drill string 105 transmits drilling fluid through a central bore and transmits rotational power from the drill rig 103 to the BHA 106. In some embodiments, the drill string 105 further includes additional components such as subs, pup joints, etc. The drill pipe 108 provides a hydraulic passage through which drilling fluid is pumped from the surface. The drilling fluid discharges through nozzles, jets, or other orifices in the bit 110 for the purposes of cooling the bit 110 and cutting structures thereon, and for lifting cuttings out of the wellbore 102 as it is being drilled. [0019] The BHA 106 may include the bit 110 or other components. An example BHA 106 may include additional or other components (e.g., coupled between the drill string 105 and the bit 110). Examples of additional BHA components include drill collars, stabilizers, measurement-while- drilling (MWD) tools, logging-while-drilling (LWD) tools, downhole motors, underreamers, section mills, hydraulic disconnects, jars, vibration or damping tools, other components, or combinations of the foregoing. The BHA 106 may further include a rotary steerable system (RSS). The RSS may include directional drilling tools that change a direction of the bit 110, and thereby the trajectory of the wellbore 102. In some cases, at least a portion of the RSS maintains a geostationary position relative to an absolute reference frame, such as gravity, magnetic north, or true north. Using measurements obtained with the geostationary position, the RSS may locate the bit 110, change the course of the bit 110, and direct the directional drilling tools on a projected trajectory.

[0020] In general, the drilling system 100 may include additional or other drilling components and accessories, such as special valves (e g., kelly cocks, blowout preventers, and safety valves). Additional components included in the drilling system 100 may be considered a part of the drilling tool assembly 104, the drill string 105, or a part of the BHA 106 depending on their locations in the drilling system 100.

[0021] The bit 110 in the BHA 106 may be any type of bit suitable for degrading downhole materials. For instance, the bit 110 may be a drill bit suitable for drilling the earth formation 101. Example types of drill bits used for drilling earth formations are fixed-cutter or drag bits, and roller cone bits. In other embodiments, the bit 110 may be a mill used for removing metal, composite, elastomer, other downhole materials, or combinations thereof. For instance, the bit 110 may be used with a whipstock to mill into casing 107 lining the wellbore 102. The bit 110 may also be a junk mill used to mill away tools, plugs, cement, other materials within the wellbore 102, or combinations thereof. Swarf or other cuttings formed by use of a mill may be lifted to surface or may be allowed to fall downhole. In still other embodiments, the bit 110 may include a reamer. For instance, an underreamer may be used in connection with a drill bit and the drill bit may bore into the formation while the underreamer enlarges the size of the bore.

[0022] In some embodiments, the drilling system 100 includes a downhole motor system 120. The downhole motor system 120 may be implemented in a downhole tool of the drilling system 100. One or more downhole motor systems 120 may be located or positioned at any location in the drilling system 100, such as in the BHA 106, in the drill string 105, or any other location. The downhole motor system 120 may include a downhole motor 111 and accompanying electronics for powering and controlling (e.g., driving) the downhole motor 111.

[0023] In some embodiments, one or more components of the drilling system implement a downhole motor system 120 including a downhole motor 111 in order to perform various functions of the drilling system 100. For example, the downhole motor 111 may be implemented in a steering system (such as an RSS) for the purpose of steering or directing one or more components of the drilling system 100, such as the bit 110. In another example, the downhole motor 111 may be a motor for driving a rotation of one or more portions of the drilling tool assembly 104. The downhole motor 111 may be implemented in connection with any other component of the drilling system 100, for example, to facilitate an operation of one or more components (e.g., to actuate, rotate, etc.).

[0024] In some embodiments, the downhole motor 111 is an electric motor, and an electrical energy is applied to the downhole motor 111 in order to generate a mechanical motion of the downhole motor 111 to drive a function/feature of the drilling system 100. In some embodiments, a mechanical motion of the downhole motor 111 is driven such that the downhole motor 111 generates electrical energy (e.g., based on an engagement of a downhole component with the borehole and/or based on the general rotation of the drilling tool assembly 104). This may be part of a regeneration mode of the downhole motor 111. As will be discussed herein, in some situations it may be desirable to limit, reduce, restrict, dissipate, etc., the electrical energy generated by the downhole motor 111 and/or an ability of the downhole motor 111 to generate electrical energy.

[0025] FIGS. 2-1 to 2-3 show an example implementation of a downhole motor system 220, according to at least one embodiment of the present disclosure. In some embodiments, the downhole motor system 220 includes a downhole motor 211 and an electronics system 229 including a motor drive 214, and a DC link 213 to a power supply 212.

[0026] As just mentioned, the downhole motor system 220 may include a power supply 212. The power supply 212 may store and/or provide an electrical energy input 215 to the downhole motor system 220. For example, the power supply 212 may include a battery, generator, capacitor, transmission line, grid supply, or any other means for providing and/or supplying the electrical energy input 215. In another example, the power supply 212 may include a store of mechanical, chemical, thermal, nuclear, or any other means for storing energy which may be converted into electrical energy for providing the electrical energy input 215 to the downhole motor system 220. [00271 Iⁿ accordance with at least one embodiment of the present disclosure, the power supply 212 is a battery or battery system including one or more energy cells for storing and providing the electrical energy input 215 to the downhole motor system 220. The power supply 212 may store electrical energy as direct current. The power supply 212 may provide the electrical energy input 215 to the downhole motor system 220 as direct current (“DC”) or alternating current (“AC”) (e.g., a circuitry of the power supply 212 may convert the stored DC electrical energy to AC).

[0028] As mentioned above, the downhole motor system 220 may include a downhole motor 211. The downhole motor 211 may be implemented in connection with a downhole tool and/or component of a drilling system. For example, the downhole motor 211 may be included as part of a steering system (e.g., aRSS) of the drilling system. The downhole motor 211 may be included as part of any component of the drilling system.

[0029] In some embodiments, the downhole motor 211 is an electric motor. For example, the downhole motor 211 may be a DC motor, an AC motor, an induction motor, a single-phase motor, a multi-phase motor (e.g., a 3 -phase motor), any other electric motor, and combinations thereof. The downhole motor 211 may receive and convert the electrical energy input 215 to a mechanical energy output 217 through an output shaft of the downhole motor 211. For example, the electrical energy input 215 may be applied to an armature of the downhole motor 211 which may cause a rotor of the downhole motor 211 to rotate. In this way, the downhole motor 211 may rotate based on receiving the electrical energy input 215.

[0030] The rotation of the downhole motor 211 (e.g., the mechanical energy output 217) may facilitate one or more functions of the drilling system. For example, the mechanical energy output 217 may be used to operate one or more actuators of a downhole component. The mechanical energy output 217 may be used to rotate one or more downhole components or parts of a downhole component. In accordance with at least one embodiment of the present disclosure, the downhole motor 211 (and the mechanical energy output 217) may be implemented in connection with a steering system (e.g., RSS) of the drilling system. For example, the drilling tool assembly of the drilling system may rotate in order to facilitate drilling, degrading, or otherwise removing material from the earth formation to form the borehole. The downhole motor 211 may rotate one or more components of the steering system in accordance with the rotation of the drilling tool assembly. For example, the downhole motor 211 may rotate one or more components of the steering system in a reverse or opposite direction of the rotation of the drilling tool assembly. This may facilitate maintaining one or more components of the steering system substantially rotationally stationary with respect to the earth formation. This may facilitate directing a BHA and/or bit of the drilling system.

[0031] For example, the steering system may include one or more (e.g., extendable) elements that may engage a borehole wall and, in this way, direct the BHA in a direction opposite that of the engagement with the borehole wall (e.g., push the bit systems). In such a case, however, it may be advantageous (or even necessary) that the extendable elements engage the borehole wall without rotating (relative to the borehole) in order to provide a steering force in a uniform direction. In this way, the motor may facilitate preventing the extendable elements from rotating and/or maintaining the extendable elements rotationally stationary.

[0032] In another example, the steering system may have an inner rotating shaft that drives a rotation of the BHA and/or bit. The steering system may apply a biasing force, or may press against the inner rotating shaft which bend the shaft and, in this way, direct the BHA and/or bit in the direction (or in an opposite direction using a fulcrum) of the applied biasing force (e.g., point the bit systems). Similarly, it may be advantageous or necessary to maintain one or more components of the steering system rotationally stationary with respect to the borehole in order that the biasing force may be applied in a uniform direction. In this way, the motor may rotate one or more components of the steering system in order to facilitate the steering and/or directing of the BHA and/or bit.

[0033] As discussed above, the downhole motor 211 may receive the electrical energy input 215 from the power supply 212. In some embodiments, the downhole motor 211 receives the electrical energy input 215 directly from the power supply 212. In some embodiments, the downhole motor 211 receives the electrical energy input 215 indirectly from the power supply 212. For example, the electrical energy input 215 may pass and/or flow through one or more components of the electronics system 229 before flowing to the downhole motor 211. As shown in FIG. 2-1, the downhole motor system 220 includes a motor drive 214 and a DC link 213. The electrical energy input 215 may flow through the DC link 213 and/or the motor drive 214 before flowing to the motor 211. [0034] As just mentioned, the downhole motor system 220 may include a DC link 213 positioned between the power supply 212 and the downhole motor 211. The DC link 213 may facilitate providing a stable supply of electrical energy from the power supply 212. For example, the DC link 213 may connect to multiple nodes, cells, or power sources of the power supply 212 (e.g., multiple power supplies) and may facilitate providing the electrical energy input 215 to the downhole motor system 220 from multiple sources. In some embodiments the DC link 213 acts as a buffer storage for electrical energy. For example, the downhole motor 211 (more specifically the motor drive 214) may demand or require current loads that are changing, irregular, and/or sporadic, and the DC link 213 may facilitate providing stable DC power notwithstanding these changing loads. For example, the DC link 213 may include one or more capacitors that may absorb and/or discharge electrical energy as needed to meet the demands of the downhole motor

211 while maintaining the electrical energy input 215 stable and/or uniform. In this way, the DC link 213 may facilitate providing the electrical energy input 215 to the downhole motor system 220.

[0035] As mentioned above, the downhole motor system 220 may include a motor drive 214. The motor drive 214 may drive and/or control the downhole motor 211 by, for example, controlling and/or regulating the electrical energy input 215 that flows to the motor 211. The motor drive 214 may include control circuitry as well as a processor and executable logic for controlling the control circuitry with the processor. The control circuitry may include and/or define a power inverter/ converter for manipulating the electrical energy that flows through the motor drive 214. [0036] In at least one embodiment of the present disclosure, the motor drive 214 converts DC power that is supplied from the power supply 212 into AC power. This may facilitate powering the downhole motor 211, for example, in implementations where the downhole motor 211 is an AC motor. The motor drive 214 may include a series of power electronic switches, such as insulated gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs), that are controlled by the processor. The processor may control the switching of the power electronic switches to create a controlled AC output that is supplied to the electric motor. [0037] In some embodiments, the motor drive 214 converts the DC power from the power supply

212 into multi-phase (e.g., 3-phase) AC power that is compatible with the downhole motor 211. The motor drive 214 may adjust or vary the frequency and/or amplitude of the AC power and, in this way, provide precise control over the speed and/or torque of the downhole motor 211. In some embodiments, the motor drive 214 receives and/or monitor feedback signals from the downhole motor 211, and may adjust or vary the electrical energy input 215 in order to protect the downhole motor 211 from overvoltage, overcurrent, and over-temperature conditions, etc. In this way, the motor drive 214 may facilitate precise control over the operation of the downhole motor 211. As will be discussed herein in detail, the motor drive 214 may modify, manipulate, and or modulate one or more of a voltage, current, phase, waveform, frequency, magnitude, and a harmonic distortion (and combinations thereof) of the electrical energy input 215 in order to control an operation and/or an efficiency of the downhole motor 211 in accordance with the techniques described herein.

[0038] Operation of the downhole motor 211 may correspond with or may result in one or more energy losses and/or inefficiencies. For example, all of the electrical energy input 215 may not be efficiently or completely converted into the mechanical energy output 217, but some of the electrical energy input 215 may be lost due to the motor inefficiencies and/or losses. The losses of the downhole motor 211 may include mechanical losses 221. The mechanical losses 221 may occur due to friction between moving parts, such as between the bearings and the rotor of the downhole motor 211. The losses of the downhole motor 211 may also include joule losses 222. The joule losses 222 may occur due to current flowing through the armature of the downhole motor 211 encountering resistance and causing the wire in the windings to heat up. The losses of the downhole motor 211 may further include eddy current losses 223. The eddy current losses 223 may occur due to the changing magnetic field (e.g., magnetic flux) produced by the armature inducing eddy currents in the iron core of the downhole motor 211 and generating heat. In this way, the operation of the downhole motor 211 may result in one or more losses, which may affect the mechanical energy output 217.

[0039] Operating the downhole motor 211 with one or more of these inefficiencies or losses may typically increase energy consumption, cost, wear, etc. For example, due to the losses, more electrical power is typically needed to produce an equivalent amount of mechanical power. Similarly, due to the losses, more mechanical power is typically needed to generate an equivalent amount of electrical power when operating as a generator. Thus, it is typically desirable to reduce and/or eliminate losses in a motor system in order to maximize the motor efficiency. For example, the moving parts of a motor may typically be designed in such a way so as to reduce friction, thereby reducing mechanical losses. Additionally, motor systems are conventionally controlled (e g., in real time) by components such as the motor drive 214 to control the electrical energy supplied to the motor (e.g., to control the magnetic rotor field generated by the armature) in order to reduce joule losses and eddy current losses.

[0040] More specifically, the motor drive 214 may conventionally be operated to control the waveform of the electrical energy input 215 to the downhole motor 211 in order to increase the efficiency of the downhole motor 211 and/or reduce losses. For example, one or more of a frequency, phase, magnitude, and harmonic distortion of the (e.g., current of the) electrical energy input may be manipulated in order to affect the efficiency of the downhole motor 211. Motors such as the downhole motor 211 may typically operate at specific operational frequencies, such as 0 Hz-60 Hz. For example, the frequency of the power supplied to the motor may directly correspond to the rotation of the magnetic rotor field generated within the motor which drives the output shaft. Thus, the speed or rotation of the motor may be adjusted or modified based on changing the frequency of the supplied power. However, only this operational (e.g., fundamental) frequency contributes to the average rotation and/or average torque output by the motor (e.g., other frequencies may contribute to torsional oscillations or torque ripple of the rotor, but not necessarily the general rotation when viewed as an average). Electrical energy supplied to the motor at other frequencies (e.g., distorted waveforms), such as harmonics of the fundamental frequency, thus will not contribute to (e.g., increase) the average mechanical energy generation of the motor. Energy at these distorted frequencies (e.g., distorted energy) will, however, generate losses such as joule and/or eddy current losses exhibited by the motor. For example, current flowing through the armature at these other frequencies generates heat through joule losses. Additionally, the distorted current waveform flowing through the armature results in eddy currents in the iron core from a distorted component of the rotor field. However, due to the mismatch in frequency of the distorted energy input waveform with the rotation of the motor (and the fundamental frequency), the distorted energy is not producing an applied torque on the rotor in time with the fundamental frequency and thus is not contributing to the rotation (e.g., average torque output) of the output shaft. In other words, energy inputs with distorted waveforms represent additional energy supplied to the motor without substantially any corresponding return (e.g., increase) in the average mechanical output. Thus, it is typically desirable to eliminate additional frequencies (e.g., harmonics), such as by reducing a total harmonic distortion, in the waveforms in order to provide the electrical energy input 215 to the downhole motor 211 as a near or substantially sinusoidal waveform (e.g., at the fundamental frequency).

[00411 To this end, motor drives are typically operated to optimize one or more aspects of the waveform of the supplied energy, such as a frequency, phase, magnitude, harmonic distortion, and combinations thereof. In some situations, motor drives are typically operated to minimize the total harmonic distortion in the waveform of the energy supplied to a motor. For example, conventional motor drives may be implemented to perform one or more techniques such as pulse width modulation (PWM), or active power factor correction (PFC) to reduce distortion. Conventional motor drives may also include filter circuits, multi-level inverters, or may implement harmonic cancellation algorithms to reduce distortion. In this way, it is typically desirable to implement one or more techniques for providing electrical energy to a motor (such as the downhole motor 211) having a waveform with minimal distortion in order to increase the efficiency of the motor.

[0042] Accordingly, in some embodiments, the electrical energy input 215 is an electrical energy having a waveform that is substantially sinusoidal and/or substantially exhibits only the fundamental frequency (corresponding the downhole motor 211). For example, in some embodiments, the motor drive 214 performs one or more of the optimization and/or distortion minimizing techniques just described above in order to reduce and/or eliminate distortion in the waveform of the electrical energy input 215 and in order to increase an efficiency of the downhole motor 211. This may be in connection with the downhole motor 211 being operated in a motoring mode, or being operated to generate the mechanical energy output 217. As will be discussed herein, however, in some situations the downhole motor system 220 may intentionally induce distortion and/or harmonics into the electrical energy input 215 of the downhole motor 211 in order to reduce an efficiency of the downhole motor 211 (and/or the downhole motor system).

[0043] As described herein, the downhole motor 211 may be implemented in connection with a downhole tool in order to drive one or more functions of the downhole tool and/or to rotate one or more components of the downhole tool. For example, the downhole motor 211 may facilitate rotating one or more components in an opposite direction of a rotation of the drilling tool assembly. To achieve this, the motor system 220 may be implemented as described in connection with FIG. 2-1 in order to generate the mechanical energy output 217 of the downhole motor 211 and drive this rotation. [0044] Tn some situations, the output shaft of the downhole motor 211 may be driven to rotate by an energy input external to the downhole motor system 220. This may be in addition to or in place of the downhole motor 211 being driven by the electrical energy input 215. For example, a mechanical energy input 218 may be applied to the output shaft of the downhole motor 211 and may cause the downhole motor 211 to rotate, as shown in FIG. 2-2. The mechanical energy input 218 may cause the downhole motor 211 to rotate in the same or opposite direction than that in which the electrical energy input 215 causes the downhole motor 211 to rotate. In this way, the mechanical energy input 218 may cause the downhole motor 211 to speed up, or to rotate backwards. The mechanical energy input 218 may be due to or may be caused by, for example, the rotation of the drilling tool assembly (e.g., by an uphole, downhole, or surface motor), an interaction of the drilling tool assembly with the formation (e.g., stick slip, back torque, etc.) or any other mode of mechanically rotating the input shaft of the downhole motor 211. For example, the rotation of the drilling tool assembly and/or the downhole tool (with which the downhole motor 211 is implemented) may produce or generate the mechanical energy input 218 and may cause the downhole motor 211 to rotate. In some embodiments, the rotation of the downhole motor 211 in this way is intentional, such as part of a regeneration mode of the downhole motor system 220.

[0045] The rotation of the downhole motor 211 due to the mechanical energy input 218 may cause the downhole motor system 220 to generate electrical energy. For example, the downhole motor 211 may generate an electrical energy output 219 which may flow from the downhole motor 211 to (or toward) the power supply 212 (e.g., by way of one or more other components of the downhole motor system 220). In this way, the downhole motor 211 may act as a generator. The downhole motor 211 may generate the electrical energy output 219 which may flow to the power supply 212 and may charge, for example, a battery of the power supply 212. In this way, the downhole motor system 220 may operate in a regeneration mode in order to charge and/or maintain a charge in the power supply 212.

[0046] In some embodiments, the downhole motor system 220 operates in the regeneration mode in order to provide a slowing or braking function. For example, the regeneration mode may correspond to a torque generated by the downhole motor 211 that opposes a direction of rotation corresponding to the mechanical energy input 218. In this way, the downhole motor 211 generating the electrical energy output 219 may also correspond to slowing, braking, or decelerating of a rotation of one or more components of the drilling system, such as the drilling tool assembly and/or the BHA.

[00471 Iⁿ some embodiments, the downhole motor system 220 operates in the regeneration mode without the purpose of slowing or braking the drilling tool assembly. For example, while generating the electrical energy output 219 with the downhole motor 211 will inevitably result in the drilling tool assembly somewhat slowing as rotational energy of the drilling tool assembly is converted to electrical energy, the downhole motor system 220 may operate in this manner not necessarily for the purpose of further slowing or stopping the drilling tool assembly from rotating, but for taking advantage of the rotation of the drilling tool assembly to generate the electrical energy output 219 (e.g., to recharge the power supply 212). As such, in some embodiments, the regeneration mode of the downhole motor system 220 operates in a configuration suitable for generating the electrical energy output 219 rather than configured to slow or stop the rotation of the mechanical energy input 218.

[0048] As discussed above, the downhole motor 211 may exhibit one or more inefficiencies or losses. While operating in the regeneration mode, (e.g., when the downhole motor 211 is generating electricity instead of mechanical motion), the downhole motor 211 may also exhibit these inefficiencies. For example, even though the output shaft of the downhole motor 211 is not being driven by the motor, the iron core in the rotor may still experience and/or exhibit the eddy current losses 222 due to a rotating electric field (e.g., magnetic flux) generated by the armature of the downhole motor 211. Additionally, the armature of the downhole motor 211 may still experience and/or exhibit the joule losses 221 as the rotation of the rotor causes a current to flow through the wire windings of the armature. Further, the moving parts of the downhole motor 211 may still experience friction resulting in the mechanical losses 221. One or more of these losses may be manifested as heat generation in the downhole motor 211 (or in one or more components of the downhole motor 211).

[0049] In this way, not all of the mechanical energy input 218 may be converted to the electrical energy output 219, as the inefficiencies of the motor 211 may cause some of the mechanical energy input 218 to be converted to heat. As discussed above, the downhole motor system 220 may operate in a regeneration mode for the purpose of generating the electrical energy output 219, such as to charge the battery. Accordingly, a motor system such as the downhole motor system 220 may typically be tuned or optimized to maximize or optimize the electrical energy output 219. For example, while attempting to regenerate the power supply 212, it may typically be desirable to generate a maximum amount of electricity with the motor and/or the mechanical energy input 218. To this end, the techniques discussed above for improving the efficiency of the motor may typically be implemented to maximize the electrical energy output 219. For example, the armature of the downhole motor 211 may be supplied with electrical energy in order to generate a magnetic field that may interact with a magnetic field of the rotor in order to generate the electrical energy output 219. This electrical energy may typically be provided to the armature with minimal harmonic distortion (e.g., as a substantially sinusoidal waveform) in order to minimize joule losses in the armature and/or eddy current losses in the motor core. Thus, motor systems such as the downhole motor system 220 may typically be configured to improve (or maximize) the efficiency of the motor 211 in order to increase (or maximize) an amount of the electrical energy output 219 generated by the downhole motor 211.

[0050] In some situations, the electrical energy output 219 may exceed an operational threshold of one or more components of the electronics system 229. For example, the power supply 212 may become fully charged and it may become unnecessary or undesirable to continue to provide the electrical energy output 219 to the power supply. In another example, providing the electrical energy output 219 to one or more components of the downhole motor system 220 for a prolonged or sustained period may cause damage or wear to these components, such as from overheating. In another example, the mechanical energy input 218 may be such that the electrical energy output 219 generated by the downhole motor 211 surpasses a threshold level, such as a threshold that one or more electronics components of the downhole motor system 220 is suited to withstand, even for a short period of time. As such, maintaining (or even increasing) this excess level of the electrical energy output 219 to one or more components of the downhole motor system 220 may damage or wear these components, such as through overheating, overcurrent, and/or overvoltage conditions.

[0051] To this end, the downhole motor system 220 may include one or more components for dissipating the electrical energy output 219 (e.g., all of the energy or a portion of the energy in excess of a usable or desired quantity). For example, the downhole motor system 220 may include a brake resistor 216. In some embodiments, the brake resistor 216 is connected and/or coupled to the motor drive 214. For example, the brake resistor 216 may be configured such that an electrical path bypasses the motor drive 214 and passes to the brake resistor 216. The brake resistor 216 may be included in the circuitry of the downhole motor system 220 at any other position or location suitable for providing the energy dissipating functions described herein. The brake resistor 216 may be a resistor (or any other component) that is configured to receive a flow of electrical energy and dissipate some or all of that electrical energy. For example, the brake resistor 216 may be an electrical resistor made of a material that can withstand high temperatures. As electrical energy flows through the brake resistor 216, it is dissipated as heat generated by the brake resistor 216. The brake resistor 216 may be configured such that it may withstand elevated voltages, currents, and/or volumes of electrical energy in order to dissipate the electrical energy. [0052] The downhole motor system 220 may be configured such that some or all of the electrical energy output 219 may flow to the brake resistor 216. For example, when the electrical energy output 219 exceeds a threshold level and/or when it is no longer desirable or necessary to continue providing the electrical energy output 219 to one or more components of the downhole motor system 220, the motor drive 214 may direct an entirety of the flow of the electrical energy output

219 to the brake resistor 216. In another example, it may be desirable to allow or facilitate the flow of the electrical energy output 219 to one or more components of the downhole motor system

220 (e.g., to the power supply 212), but energy of the electrical energy output 219 in excess of an operational threshold or working amount may be directed to the brake resistor 216 in order to maintain a uniform and/or safe level of the electrical energy output 219 to the various components. In this way, the brake resistor 216 may facilitate dissipating some or all of the electrical energy output 219 from the downhole motor system 220. Techniques for dissipating some or all of the electrical energy output 219 in this way may be implemented in connection with a braking, stopping, and/or regeneration mode of the downhole motor 211.

[0053] In some situations, the brake resistor 216 (or equivalent energy dissipating component) may not be suitable for adequately dissipating the electrical energy output 219. For example, in some situations the electrical energy output 219 may exceed a level or quantity that the brake resistor 216 is configured to handle, and the brake resistor 216 may become damaged by receiving the flow of the electrical energy output 219. In another example, a sustained or prolonged flow of the electrical energy output 219 to the brake resistor 216 may damage the brake resistor 216, such as from overheating. In another example, the brake resistor 216 may wear over a (e.g., long) period of use in the downhole motor system 220, and in some situations the brake resistor 216 may accordingly be prone to failure even when operating within its appropriate limits. [0054] The brake resistor 216 failing or performing inadequately may present a risk of serious damage or wear to one or more other components of the downhole motor system 220, such as through overheating, over voltage, over current, etc., for example, due to an excessive or prolonged flow of the electrical energy output 219. Thus, alternative techniques for dissipating the electrical energy output 219 in place of, or in addition to, the brake resistor 216 may be advantageous.

[0055] As shown in FIG. 2-3, in some embodiments, a distorted input 224 is supplied or provided to the downhole motor 211. The distorted input 224 may be electrical energy that is supplied to the motor by the motor drive 214. For example, the motor drive 214 may receive the electrical energy input 215 (e.g., from the power supply 212) and may generate the distorted input 224 from the electrical energy input 215. The motor drive may generate the distorted input 224 by implementing pulse width modulation and/or high frequency modulation. For example, the motor drive may utilize one or more IGBTs or MOSFETs in order to generate the distorted input 224. The distorted input 224 may be supplied to the downhole motor 211 as an alternative to, or in addition to, the electrical energy input 215 being supplied to the downhole motor 211. In this way, the motor drive 214 may inject the distorted input 224 (e.g., inject high-frequency harmonics) into the downhole motor 211.

[0056] The distorted input 224 may be a flow of electrical energy having a waveform that includes at least some distortion. For example, the motor drive 214 may modify and/or manipulate one or more of a frequency, amplitude, phase, or harmonic distortion of the waveform to generate the distorted input 224. In accordance with at least one embodiment of the present disclosure, the distorted input 224 may be an electrical energy supplied to the downhole motor 211 that includes at least some distortion, harmonics, and/or alternate frequencies to that of the fundamental frequency corresponding to a rotation of the downhole motor 211. In some embodiments, the distorted input 224 has a waveform that only contains distortion and/or harmonic frequencies, and does not contain or exhibit the fundamental frequency. For example, the distorted input 224 may be provided to the downhole motor 211 in place of or as an alternative to supplying the electrical energy input 215 to the downhole motor 211. In some embodiments, the distorted input 224 has a waveform that contains distortion and/or harmonic frequencies in addition to the fundamental frequency. For example, the distorted input 224 may be provided to the downhole motor 211 in addition to the electrical energy input 215. In this way, it should be understood that describing the distorted input 224 as a separate energy input from the electrical energy input 215 may be for illustrative purposes, and the distorted input 224 may be representative of distortion and/or harmonics induced or exhibited by, for example the electrical energy input 215. In other words, in some embodiments the distorted input 224 and the electrical energy input 215 may not necessarily be separate or distinct energy inputs to the downhole motor 211, but the distorted input 224 may indicate the presence of at least some distortion and/or harmonics in the electrical energy input 215 supplied to the downhole motor 211. In this way, electrical energy may be supplied or provided to the downhole motor 211 that includes at least some distortion, harmonics, and/or alternative frequencies to that of the fundamental frequency. In some embodiments, the harmonics are high frequency harmonics.

[0057] As described herein, the fundamental (e.g., operating) frequency may be determined and/or based on a speed of the downhole motor 211. In this way, the fundamental frequency may be variable and may be based on a speed (or desired speed) of the downhole motor 211. In some embodiments, the waveform of the distorted input 224 includes harmonics of the fundamental frequency. The harmonics may be frequencies that are integer multiples of the fundamental frequency. In this way, the harmonics of the distorted input 224 may be dependent on or may be functions of the (e.g., variable) fundamental frequency. Thus, the harmonics induced in the waveform of the distorted input 224 may be determined or generated based on a determined or identified frequency of the fundamental frequency of the downhole motor 211 and/or the electrical energy input 215.

[0058] To this end, in some embodiments, the motor drive 214 monitors one or more aspects of the downhole motor 211. For example, the motor drive 214 may receive on or more control and/or feedback signals from the downhole motor 211. The motor drive 214 may monitor one or more of a speed, frequency, torque, current, voltage, induction slip, rotor position, and temperature of the downhole motor 211, or any other aspect of the downhole motor and combinations thereof. This monitoring of the downhole motor 211 by the motor drive 214 may facilitate determining the fundamental frequency, for example, in order to generate the harmonics of the distorted input 224.

[0059] In some embodiments, the distorted input 224 causes and/or results in one or more inefficiencies or losses in or by the downhole motor 211. For example, as discussed herein, the downhole motor 211 may exhibit or experience joule losses and/or eddy current losses. These losses may be worsened or exacerbated by distorted waveforms in the energy applied to the downhole motor 211. Accordingly, supplying the distorted input 224 to the downhole motor 211 may decrease an efficiency of the downhole motor 211. For example, the distorted input 224 may cause and/or result in an increase in the joule losses 222 in the motor, represented by distortion joule losses 225. In another example, the distorted input 224 may cause and/or result in an increase in the eddy current losses 223, represented by distortion eddy current losses 226. While the distortion joule losses 225 and the distortion eddy current losses 226 are represented in FIG. 2-3 as separate or distinct losses from that of the joule losses 222 and eddy current losses 223 (respectively), it should be understood that the distortion joule losses 225 and the distortion eddy current losses 226 are not necessarily separately occurring losses, but may be a same mechanism or means of loss as that of the joule losses 222 and eddy current losses 223 (respectively), but to an increased or greater degree. In this way, the distorted input 224 may result in an increase in losses and/or a decrease in efficiency of the downhole motor 211 (and the downhole motor system 220).

[0060] As discussed herein, losses such as the joule losses 222 and/or the eddy current losses 223 may result in and/or be manifested as heat generated in one or more components of the downhole motor 211. The increase in these losses represented by the distortion joule losses 225 and the distortion eddy current losses 226 may accordingly result in and/or be manifested as an increase in the heat generated by the one or more components of the downhole motor 211. For example, the joule losses 222 may generate heat in the wire windings of the armature of the downhole motor 211, and/or the distortion joule losses 225 may represent an increase in the generated heat. In another example the eddy current losses 223 may generate heat in the iron core of the downhole motor 211, and the distortion eddy current losses 226 may represent an increase in the generated heat.

[0061] As discussed herein, the distortion and/or harmonics in the waveform of an electrical energy supplied to the downhole motor 211 may not produce or contribute to (e.g., increase) an average generation of a mechanical output by the downhole motor 211. Similarly, harmonics and/or distortion in the waveform of an electrical energy supplied to the downhole motor 211 may not produce or contribute to (e.g., increase) the average generation of an electrical energy by the downhole motor 211 (e.g., when acting as a generator). Nevertheless, in either case, distorted waveforms may produce and/or contribute to the losses exhibited by the downhole motor 211 (e g., more electrical power is needed to produce an equivalent amount of mechanical power, or to generate and equivalent amount of electricity). In other words, the distortion in the waveform of an electrical energy supplied to the downhole motor 211 may represent additional energy supplied to the downhole motor 211 without a corresponding return in energy output, or a return in energy converted from electrical to mechanical (or vice versa). This loss of energy (e.g., energy dump) may be leveraged by the downhole motor system 220 to dissipate excess, prolonged, or otherwise unwanted quantities of the electrical energy output 219. In other words, excess electrical power may be dumped into making the downhole motor system 220 less efficient, and thereby generating less electrical energy output 219.

[0062] As discussed herein, when operating in a regeneration mode, the downhole motor system 220 may generate the electrical energy output 219. In some cases, the electrical energy output 219 may be in a quantity, duration, time, etc., that is undesirable (or even damaging) for the downhole motor system 220. In some embodiments, the brake resistor 216 as described herein is inadequate or not equipped to dissipate a sufficient amount of the electrical energy output 219 or for a required duration.

[0063] In some embodiments, the downhole motor system 220 supplies the distorted input 224 to the downhole motor 211 in order to induce (or increase) one or more inefficiencies in the downhole motor 211 and dissipate an unwanted quantity of the electrical energy output 219. For example, the downhole motor system 220 may induce the distortion joule losses 225 and/or the distortion eddy current losses 226 to a degree so as to dissipate at least a portion of the electrical energy output 219 (e.g., as heat). In some embodiments, all of the electrical energy output 219 is dissipated through the induced losses such that the brake resistor 216 does not dissipate any of the electrical energy output 219. For example, the downhole motor 211 may dissipate all or an excess portion of the electrical energy output 219 without the electrical energy output 219 (or the portion) flowing to one or more portions of the electronics system 229, such as the motor drive 214, the DC link 213, the brake resistor 216, the power supply 212, or any other component of the electronics system 229. This may facilitate the downhole motor system 220 and/or the electronics system 229 not including the brake resistor 216 (and/or another energy dissipating component). In some embodiments, only a portion of the electrical energy output 219 is dissipated through the induced losses. For example, the brake resistor 216 may be implemented to dissipate a portion (or the remainder) of the electrical energy output 219 and/or a portion (or the remainder) of the electrical energy output 219 may flow to one or more other components of the downhole motor system 220 (such as to recharge a battery of the power supply 212). In some embodiments, the downhole motor 211 is selectively, periodically, and/or temporarily employed to dissipate some or all of the electrical energy output 219. For example, the motor drive 214 may selectively, periodically, and/or temporarily supply the distorted input 224 to the downhole motor 211 in order to dissipate the electrical energy output 219. This selective dissipation may be implemented based on a charge state of the power supply 212, a temperature of the brake resistor 216, a temperature of the downhole motor 211, an ability of one or more components of the electronics system 229 to handle and/or withstand the electrical energy output 219, any other relevant factor, ability, or function of the electronics system 229, and combinations thereof. In this way, an excess, prolonged, or otherwise unwanted quantity of the electrical energy output 219 may be dissipated by intentionally inducing losses or inefficiencies in the downhole motor 211.

[0064] While the energy dissipating functionality of the downhole motor system 220 has been described primarily with respect to inducing or injecting harmonic distortion to the downhole motor 211, it should be appreciated that the techniques described herein for dissipating energy include decreasing the efficiency of the downhole motor 211 by one or more additional means. These means may be in addition to or as an alternative to inducing harmonic distortion to the downhole motor. For example, the distorted input 224 may include a waveform that has distortion from any number of sources or that have been distorted in any number of ways. For example, the distorted waveform may be the result of one or more of voltage or current spikes, voltage or current surges, voltage or current sags, voltage or current imbalance across motor phases, phase shift between voltage and current, any other form of waveform distortion, and combinations thereof. In some embodiments, the efficiency of the motor 211 may be decreased through DQ motor control, or Clarke and Park transformation control. For example, for a three phase implementation of the motor 211, the three-phase motor variables may be transformed into a two- coordinate, reference frame (d, q) in order to simplify control algorithms and enable independent control of the motor’s active (e.g., torque) and reactive (e.g., magnetizing) components. In this way, the efficiency of the downhole motor may be decreased in any number of ways in addition to harmonic distortion in order to increase an energy dissipation of the downhole motor 211 without an equivalent increase in production, or energy output by the downhole motor 211. [0065] The downhole motor 211 as described herein may be an effective and/or ideal tool for dissipating unwanted electrical energy. For example, the downhole motor 211 may be configured to operate (e.g., in motoring mode) and receive, convert, and/or handle a threshold amount of electrical energy. The operation of the downhole motor 211 in this way may result in the downhole motor 211 generating heat and/or experiencing an increase in temperature. As such, the downhole motor 211 may be configured to withstand a threshold level of heat generation and/or to maintain operation up to a threshold temperature (e.g., corresponding to a quantity or rate of electrical energy supplied to the downhole motor 211). As discussed herein, some or all of the electrical energy output 219 may be dissipated as heat generated in or by the downhole motor 211. In some embodiments, the downhole motor 211 is configured to dissipate the electrical energy output 219 up to an equivalent level or at an equivalent rate to that which the downhole motor 211 is configured to handle as the electrical energy input 215. In some embodiments, the downhole motor 211 is configured to generate heat and/or increase in temperature while dissipating the electrical energy output 219 up to an equivalent level or up to an equivalent degree as that which the downhole motor 211 is configured to experience when operating in motoring mode. In this way, the downhole motor may provide an effective means for dissipating the electrical energy output 219.

[0066] In some embodiments, with respect to an electrical energy and/or temperature threshold, the downhole motor 211 is more robust than one or more other electrical components of the downhole motor system 220. For example, the quantity and/or rate of electrical energy that the downhole motor 211 is configured to withstand (e.g., dissipate) may be much more than, for example, what the brake resistor 216 is configured for. In some embodiments, the brake resistor 216 is configured to withstand 10%-30% of the quantity and/or rate of electrical energy that the downhole motor 211 is configured to receive. In another example, the amount of heat generation and/or the temperature which the downhole motor 211 is configured to withstand may be much more than, for example, what the brake resistor 216 is configured for. In some embodiments, the brake resistor is typically configured to withstanding 10%-30% of the heat generation and/or temperature which the downhole motor 211 is configured for. In this way, the downhole motor 211 may facilitate an increased level or rate of energy dissipation compared to conventional techniques, such as with the brake resistor 216. [0067] As discussed herein, waveform distortion such as harmonics may not substantially contribute to (e.g., increase) an average torque output (or an average generation of electricity in regeneration mode) of the downhole motor 211. In some situations, however, distorted waveforms may create or result in torque ripple exhibited by the downhole motor 211. Torque ripple may be a (e.g., instantaneous) variation in the torque and/or rotation of the downhole motor 211. For example, the distortions in the waveforms of an electrical energy supplied to the downhole motor (e.g., distorted input 224) may at times contribute or add to the torque/rotation of the rotor, and may at times inhibit or detract from the torque/rotation of the rotor. These effects may occur periodically and may result in an oscillatory variation on the torque and/or rotation of the rotor (e.g., torsional oscillations). Torque ripple in this way may cause undesired vibrations, noise, and/or other undesirable effects on the downhole motor 211 (or any other component of the drilling system). For example, vibrations by the downhole motor 211 may cause damage or wear to mechanical parts of the downhole motor 211 or any other component coupled to the motor which may experience vibrations from the torque ripple.

[0068] In some embodiments, lower frequency torque ripple corresponds to greater vibrations and/or worse adverse effects than torque ripple of higher frequencies. For example, torque ripple of lower frequencies may exhibit higher amplitudes of vibration than torque ripple of higher frequencies. In some embodiments, supplied waveforms having induced harmonics of lower frequencies correspond to lower frequency torque ripple and/or supplied waveforms having induced harmonics of higher frequencies correspond to higher frequency torque ripple. Lower frequency (e.g., higher amplitude) torque ripple may correspond with increased damage and/or wear on (e.g., the mechanical components) of the downhole motor 211 or any other components of the drilling system. Lower frequency (e.g., higher amplitude) torque ripple may also affect the (e.g., instantaneous) speed and/or torque of the downhole motor 211 to a greater (e.g., undesirable) degree.

[0069] Accordingly, in some embodiments, the distorted input 224 includes and/or exhibit high frequency harmonics in order to reduce and/or mitigate the effects of torque ripple. For example, the waveform of the distorted input 224 may be modulated and/or tuned to reduce the torque ripple. In some embodiments, the resulting torque ripple is in a range having an upper value, a lower value, or upper and lower values including any of 1%, 5%, 10%, 15%, 20%, 25%, 30%, or 50% variation in the average torque, or any value therebetween. For example, the torque ripple may be greater than 1%. Tn another example, the torque ripple may be less than 50%. In yet another example, the torque ripple may be between 1% and 50%. In some embodiments, it is critical that the torque ripple be no more than 15% variation in the average torque to prevent damage and/or wear to the downhole motor 211 (and/or other components of the drilling system) due to torque ripple.

[0070] In some embodiments, the distorted input 224 includes harmonics of the fundamental frequency in a range having an upper value, a lower value, or upper and lower values including any of 5^th order, 7^th order, 9^th, order 11^th order, 13^th order, 15^th order, 17^th order, 19^th order, 21^st order, 23^rd order, or 25^th order harmonics, or any value therebetween. For example, the distorted input 224 may include 5^th order or greater harmonics. In another example, the distorted input 224 may include harmonics of the 25^th order or less. In yet another example, the distorted input 224 may include harmonics between the 5^th order and 25^th order. In some embodiments, it is critical that the distorted input 224 include harmonics of no less than 9^th order in order than the frequencies be high enough to reduce and/or mitigate the effects of torque ripple. The distorted input 224 may include harmonics of any order, such as harmonics of greater than the 25^th order.

[0071] Torque ripple may also result and/or cause damage and/or wear, or an increase in damage and/or wear, when the torque ripple results in vibrations corresponding to a natural frequency of one or more components of the drilling system. For example, the downhole motor 211 and/or any other component may exhibit a natural frequency, and an excitation or applied vibration at that natural frequency may lead to resonance of one or more components. This resonance may lead to an increase in the amplitude of the vibration which may cause excessive motion, stress, or even failure of one or more components. As such, in some embodiments, the distorted input 224 is generated and/or the harmonics in the waveform of the distorted input 224 are selected such that they do not lead to torque ripple that corresponds with vibrations at the natural frequency of the downhole motor 211 (and/or one or more other components of the drilling system). In this way, damage from large amplitude resonant vibrations may be avoided and/or mitigated.

[0072] By injecting the distorted input 224 into the downhole motor 211, it may be inevitable that some torque ripple may result. While it may be desirable to reduce and/or mitigate the effects of torque ripple corresponding with vibrations of certain frequencies (e.g., high amplitude vibrations, resonant vibrations), it should be noted that the resulting vibrations from torque ripple may correspond with an increase in mechanical losses (e g., due to friction) in the downhole motor 21 1 , and thus an increase in the downhole motor 21 1 dissipating the electrical energy output 219. Thus, torque ripple is not necessarily an adverse side effect, but rather contributes to the effectiveness of the energy dissipation techniques described herein.

[0073] The distorted input 224 including higher frequencies in the waveform may also contribute to an increase in the losses exhibited by the downhole motor 211, such as an increase in the distortion joule losses 221 due to skin effect. For example, when an AC current flows through a conductor, such as the wire windings in the armature of the downhole motor 211, the current flow is not uniform across the cross-section of the conductor. This is due to the interaction of the magnetic field generated by the current with the material of the conductor itself. As such, the current density tends to be highest at or near the surface of the conductor and decreases gradually as the distance from the surface increases. This effectively increases the resistance encountered by the current by reducing the effective cross-sectional area of the conductor, which results in increased joule losses. At higher frequencies, the current density near the center of the conductor can be significantly lower than that at or near the surface, as most of the current flows on the surface of the conductor. Thus, including higher frequency distortion (e.g., harmonics) in the distorted input 224 as described herein, may increase the distortion joule losses 221 by increasing the skin effect, which may facilitate dissipating more of the electrical energy output 219 by the downhole motor 211.

[0074] FIG. 3 shows an example implementation of a downhole motor system 320, according to at least one embodiment of the present disclosure. In some embodiments, the downhole motor system 320 includes a power supply 312. The power supply 312 may store and/or provide an electrical energy input to the downhole motor system 320 (such as power supply 212 of FIGS. 2- 1 to 2-3). In some embodiments the downhole motor system 320 includes a downhole motor 311. The downhole motor 311 may be a motor for driving one or more functions of a downhole tool. The downhole motor 311 may be an electric motor, such as a 3-phase AC induction motor. The downhole motor 311 may receive an electrical energy input and may convert it into a mechanical energy output, for example, for driving one or more functions of a downhole tool, as described herein. The downhole motor 311 may be the downhole motor 211 of FIGS. 2-1 to 2-3.

[0075] In some embodiments, the downhole motor system 320 includes a motor drive 314. The motor drive 314 may be coupled to the power supply 312 through a pair of high voltage transmission lines 328. The high voltage transmission lines 328 may facilitate the power supply

15 312 providing an electrical energy input to the motor drive 314. The motor drive 314 may drive and/or control the downhole motor 311. For example, the motor drive 314 may include an IGBT board 314-1 and a motor drive board 314-2. The IGBT board 314-1 may include one or more IGBTs which may modify, modulate, or otherwise convert an electrical energy input received from the power supply 312 in order to provide the electrical energy input to the downhole motor 311 with a certain voltage, current, phase, frequency, magnitude, harmonic distortion, and combinations thereof. For example, the motor drive 314 may be coupled to the downhole motor 311 for providing a 3-phase electrical energy input to the downhole motor 311. The motor drive 314 (e.g., the IGBT board 314-1) may be controlled by a processor and executable logic associated with the motor drive board 314-2 in order to drive the downhole motor 311 as described herein. The motor drive 314 may be the motor drive 214 of FIGS. 2-1 to 2-3.

[0076] In some embodiments, the downhole motor system 320 includes a motor capacitor block 327. The motor capacitor block 327 may be positioned between the motor drive 314 and the power supply 312 (e.g., coupled to the high voltage transmission lines 328). The motor capacitor block 327 may facilitate providing a uniform electrical energy supply from the power supply 312 to the motor drive 314. For example, the motor capacitor block 327 may absorb and/or discharge electrical energy as needed to meet the demands of the motor drive 314 to control the downhole motor 311. The motor capacitor block 327 may perform one or more of the functionalities of the DC link 213 of FIGS. 2-1 to 2-3.

[0077] In some embodiments, the downhole motor system 320 includes a brake resistor 316. The brake resistor 316 may be positioned between the power supply 212 and the downhole motor 311 (e.g., coupled to the high voltage transmission lines). The brake resistor 316 may be configured to dissipate an electrical energy output from the downhole motor 311, for example, when the downhole motor 311 is operating in a regeneration mode. The brake resistor 316 may be the brake resistor 216 of FIGS. 2-1 to 2-3.

[0078] In some embodiments, the downhole motor 311 generates an electrical energy output. For example, the downhole motor 311 may be driven by an external mechanical energy input, as described herein. The downhole motor 311 may, in this way, act as a generator and may generate an electrical energy output. In some embodiments, the electrical energy output flows to the power supply 312, for example, to charge a battery of the power supply 312. In some embodiments, the downhole motor 311 generates the electrical energy output in a quantity or to a degree that is undesirable and/or may be damaging to one or more components of the downhole motor system 320, as described herein. In some embodiments, some or all of the electrical energy output flows to the brake resistor 316, and the brake resistor may dissipate some or all of the electrical energy output as heat.

[0079] In some embodiments, the brake resistor 316 is inadequate for receiving and/or dissipating some or all of the electrical energy output. In some embodiments, the downhole motor system 320 employs the downhole motor 311 for dissipating some or all of the electrical energy output in addition to or as an alternative to the brake resistor 316. For example, the motor drive 314 may supply and/or inject an electrical energy input to the downhole motor 311 with a distorted waveform in order to increase one or more inefficiencies or losses of the downhole motor. The distorted waveform may induce and/or increase one or more of joule losses, eddy current losses, and mechanical losses in the downhole motor 311. The downhole motor (or one or more components of the downhole motor) may generate heat as a result of the losses. In this way, the downhole motor 311 may facilitate dissipating some or all of the electrical energy output, such as according to the techniques described herein in connection with FIGS. 2-1 to 2-3.

[0080] FIG. 4 illustrates a flow diagram for a method 400 or a series of acts for operating a downhole motor system as discussed herein, according to at least one embodiment of the present disclosure. While FIG. 4 illustrates acts according to one embodiment, alternative embodiments may omit, add to, reorder, or modify any of the acts shown in FIG. 4.

[0081] The method 400 may include an act 410 of generating an electrical energy output with a downhole motor. For example, the electrical energy output may flow to an electronics system of the downhole tool. In some embodiments, the electrical energy output is generated without dissipating the electrical energy output through a brake resistor.

[0082] The method 400 may include an act 420 of applying an electrical energy input to the downhole motor. For example, the electrical energy input may be applied to the downhole motor by the electronics system. In some embodiments, a motor drive modulates the electrical energy input, such as with one or more insulated-gate bipolar transistors (IGBTs). For example, the electrical energy input may be a high frequency harmonic of the electrical energy output. In another example, the electrical energy input may be a harmonic of the 9^th order or greater. In another example, the electrical energy input may have an electrical frequency (e.g., current, voltage) that is different than a rotational frequency of the downhole motor. In some embodiments, the electrical energy input results in a torque ripple of no more than 15%. Tn some embodiments, the electrical energy input will not increase an average torque generated by the downhole motor and/or an average speed of the downhole motor. In some embodiments, the downhole motor is a 3 -phase AC motor, such as an induction motor.

[0083] The method 400 may include an act 430 of reducing the electrical energy output based on the applied electrical energy input. For example, the electrical energy input may be maintained below an operational threshold of the electronics system. In some embodiments, the electrical energy output is dissipated by a brake resistor, and reducing the electrical energy output may include reducing an excess portion of the electrical energy output that is not dissipated by the brake resistor. In some embodiments, the electrical energy output is prevented from flowing to one or more components of the electronics system. For example, the electrical energy output may not flow to a DC link of the downhole tool. In another example, the electrical energy output may not flow (dissipate) to a brake resistor. In some embodiments, the electronics system does not include a brake resistor.

[0084] FIG. 5 illustrates a flow diagram for a method 500 or a series of acts for operating a downhole motor system as discussed herein, according to at least one embodiment of the present disclosure. While FIG. 5 illustrates acts according to one embodiment, alternative embodiments may omit, add to, reorder, or modify any of the acts shown in FIG. 5.

[0085] The method 500 may include an act 510 of generating an electrical energy output with a downhole motor. For example, the electrical energy output may flow to an electronics system of the downhole motor system.

[0086] The method 500 may include an act 520 of while generating the electrical energy output, selectively decreasing an efficiency of the downhole motor. For example, the efficiency may be decreased by increasing a total harmonic distortion of the electrical current in an armature of the downhole motor. Decreasing the efficiency may include modifying one or more of a frequency, magnitude, phase, and harmonic distortion of the current in the armature of the downhole motor. Decreasing the efficiency of the downhole motor may include increasing joule losses and/or eddy current losses of the downhole motor.

[0087] The method 500 may include an act 530 of reducing the electrical energy output based on decreasing the efficiency of the downhole motor. For example, the efficiency may be decreased to maintain the electrical energy output below an operational threshold of the electronics system. [0088] FTG. 6 illustrates a flow diagram for a method 600 or a series of acts for dissipating electrical energy as discussed herein, according to at least one embodiment of the present disclosure. While FIG. 6 illustrates acts according to one embodiment, alternative embodiments may omit, add to, reorder, or modify any of the acts shown in FIG. 6.

[0089] The method 600 may include an act 610 of identifying a regeneration mode of a downhole motor. For example, the motor may generate an electrical energy output in the regeneration mode. [0090] The method 600 may include an act 620 of upon identifying the regeneration mode, applying an electrical energy input to an armature of the downhole motor.

[0091] The method 600 may include an act 630 of based on applying the electrical energy input, causing at least a portion of the electrical energy output to dissipate as heat through the downhole motor. For example, at least a portion of the electrical energy output is dissipated as heat through one or more of the armature of the downhole motor and an iron core of the downhole motor. In some embodiments, the electrical energy input results in a net decrease in the electrical energy output. For example, in some situations, an electrical energy input may be applied to a motor, for example, to brake, slow, or decelerate a motor, such as applying an electric current to a motor in order to provide dynamic or regenerative braking to the motor. However, in such a circumstance the motor may generally generate more energy as a result of the braking efforts, resulting in a net increase in an electrical energy output by the motor. The techniques described herein, however, apply an electrical energy input to the downhole motor without affecting an average torque and/or speed of the downhole motor, and without increasing an electrical energy output generated by the downhole motor (e.g., a net decrease).

[0092] Turning now to FIG. 7, this figure illustrates certain components that may be included within a computer system 700. One or more computer systems 700 may be used to implement the various devices, components, and systems described herein.

[0093] The computer system 700 includes a processor 701. The processor 701 may be a general-purpose single- or multi-chip microprocessor (e.g., an Advanced RISC (Reduced Instruction Set Computer) Machine (ARM)), a special purpose microprocessor (e.g., a digital signal processor (DSP)), a microcontroller, a programmable gate array, etc. The processor 701 may be referred to as a central processing unit (CPU). Although just a single processor 701 is shown in the computer system 700 of FIG. 7, in an alternative configuration, a combination of processors (e.g., an ARM and DSP) could be used. [0094] The computer system 700 also includes memory 703 in electronic communication with the processor 701. The memory 703 may be any electronic component capable of storing electronic information. For example, the memory 703 may be embodied as random-access memory (RAM), read-only memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM) memory, registers, and so forth, including combinations thereof.

[0095] Instructions 705 and data 707 may be stored in the memory 703. The instructions 705 may be executable by the processor 701 to implement some or all of the functionality disclosed herein. Executing the instructions 705 may involve the use of the data 707 that is stored in the memory 703. Any of the various examples of modules and components described herein may be implemented, partially or wholly, as instructions 705 stored in memory 703 and executed by the processor 701. Any of the various examples of data described herein may be among the data 707 that is stored in memory 703 and used during execution of the instructions 705 by the processor 701.

[0096] A computer system 700 may also include one or more communication interfaces 709 for communicating with other electronic devices. The communication interface(s) 709 may be based on wired communication technology, wireless communication technology, or both. Some examples of communication interfaces 709 include a Universal Serial Bus (USB), an Ethernet adapter, a wireless adapter that operates in accordance with an Institute of Electrical and Electronics Engineers (IEEE) 802.11 wireless communication protocol, a Bluetooth® wireless communication adapter, and an infrared (IR) communication port.

[0097] A computer system 700 may also include one or more input devices 711 and one or more output devices 713. Some examples of input devices 711 include a keyboard, mouse, microphone, remote control device, buttonjoystick, trackball, touchpad, and lightpen. Some examples of output devices 713 include a speaker and a printer. One specific type of output device that is typically included in a computer system 700 is a display device 715. Display devices 715 used with embodiments disclosed herein may utilize any suitable image projection technology, such as liquid crystal display (LCD), light-emitting diode (LED), gas plasma, electroluminescence, or the like. A display controller 717 may also be provided, for converting data 707 stored in the memory 703 into text, graphics, and/or moving images (as appropriate) shown on the display device 715.

[00981 The various components of the computer system 700 may be coupled together by one or more buses, which may include a power bus, a control signal bus, a status signal bus, a data bus, etc. For the sake of clarity, the various buses are illustrated in FIG. 7 as a bus system 719.

[0099] The techniques described herein may be implemented in hardware, software, firmware, or any combination thereof, unless specifically described as being implemented in a specific manner. Any features described as modules, components, or the like may also be implemented together in an integrated logic device or separately as discrete but interoperable logic devices. If implemented in software, the techniques may be realized at least in part by a non-transitory processor-readable storage medium comprising instructions that, when executed by at least one processor, perform one or more of the methods described herein. The instructions may be organized into routines, programs, objects, components, data structures, etc., which may perform particular tasks and/or implement particular data types, and which may be combined or distributed as desired in various embodiments.

[0100] Computer-readable media can be any available media that can be accessed by a general purpose or special purpose computer system. Computer-readable media that store computerexecutable instructions are non-transitory computer-readable storage media (devices). Computer-readable media that carry computer-executable instructions are transmission media. Thus, by way of example, and not limitation, embodiments of the disclosure can comprise at least two distinctly different kinds of computer-readable media: non-transitory computer- readable storage media (devices) and transmission media.

[0101] In some embodiments, a drilling system includes a drill rig used to turn a drilling tool assembly which extends downward into the wellbore. The drilling tool assembly may include a drill string, a bottomhole assembly (BHA), and a bit, attached to the downhole end of drill string. [0102] The drill string may include several j oints of drill pipe connected end-to-end through tool joints. The drill string transmits drilling fluid through a central bore and transmits rotational power from the drill rig to the BHA. In some embodiments, the drill string further includes additional components such as subs, pup joints, etc. The drill pipe provides a hydraulic passage through which drilling fluid is pumped from the surface. The drilling fluid discharges through nozzles, jets, or other orifices in the bit for the purposes of cooling the bit and cutting structures thereon, and for lifting cuttings out of the wellbore as it is being drilled.

[01031 The BHA may include the bit or other components. An example BHA may include additional or other components (e.g., coupled between the drill string and the bit). Examples of additional BHA components include drill collars, stabilizers, measurement-while-drilling (MWD) tools, logging-while-drilling (LWD) tools, downhole motors, underreamers, section mills, hydraulic disconnects, jars, vibration or damping tools, other components, or combinations of the foregoing. The BHA 106 may further include a rotary steerable system (RSS). The RSS may include directional drilling tools that change a direction of the bit, and thereby the trajectory of the wellbore. In some cases, at least a portion of the RSS maintains a geostationary position relative to an absolute reference frame, such as gravity, magnetic north, or true north. Using measurements obtained with the geostationary position, the RSS may locate the bit, change the course of the bit, and direct the directional drilling tools on a projected trajectory.

[0104] In general, the drilling system may include additional or other drilling components and accessories, such as special valves (e.g., kelly cocks, blowout preventers, and safety valves). Additional components included in the drilling system may be considered a part of the drilling tool assembly, the drill string, or a part of the BHA depending on their locations in the drilling system.

[0105] The bit in the BHA may be any type of bit suitable for degrading downhole materials. For instance, the bit may be a drill bit suitable for drilling the earth formation. Example types of drill bits used for drilling earth formations are fixed-cutter or drag bits, and roller cone bits. In other embodiments, the bit may be a mill used for removing metal, composite, elastomer, other downhole materials, or combinations thereof. For instance, the bit may be used with a whipstock to mill into casing lining the wellbore. The bit may also be a junk mill used to mill away tools, plugs, cement, other materials within the wellbore, or combinations thereof. Swarf or other cuttings formed by use of a mill may be lifted to surface or may be allowed to fall downhole. In still other embodiments, the bit may include a reamer. For instance, an underreamer may be used in connection with a drill bit and the drill bit may bore into the formation while the underreamer enlarges the size of the bore.

[0106] In some embodiments, the drilling system includes a downhole motor system. The downhole motor system may be implemented in a downhole tool of the drilling system. One or more downhole motor systems may be located or positioned at any location in the drilling system, such as in the BHA, in the drill string, or any other location. The downhole motor system may include a downhole motor and accompanying electronics for powering and controlling (e.g., driving) the downhole motor.

[0107] In some embodiments, one or more components of the drilling system implements a downhole motor system including a downhole motor in order to perform various functions of the drilling system. For example, the downhole motor may be implemented in a steering system (such as an RSS) for the purpose of steering or directing one or more components of the drilling system, such as the bit. In another example, the downhole motor may be a motor for driving a rotation of one or more portions of the drilling tool assembly. The downhole motor may be implemented in connection with any other component of the drilling system, for example, to facilitate an operation of one or more components (e.g., to actuate, rotate, etc.).

[0108] In some embodiments, the downhole motor is an electric motor, and electrical energy may be applied to the downhole motor in order to generate a mechanical motion of the downhole motor to drive a function/feature of the drilling system. In some embodiments, a mechanical motion of the downhole motor is driven such that the downhole motor generates electrical energy (e.g., based on an engagement of a downhole component with the borehole and/or based on the general rotation of the drilling tool assembly). This may be part of a regeneration mode of the downhole motor. As will be discussed herein, in some situations it may be desirable to limit, reduce, restrict, dissipate, etc., the electrical energy generated by the downhole motor and/or an ability of the downhole motor to generate electrical energy.

[0109] In some embodiments, a downhole motor system includes a downhole motor and an electronics system including a motor drive, and a DC link to a power supply.

[0110] As just mentioned, the downhole motor system may include a power supply. The power supply may store and/or provide an electrical energy input to the downhole motor system. For example, the power supply may include a battery, generator, capacitor, transmission line, grid supply, or any other means for providing and/or supplying the electrical energy input. In another example, the power supply may include a store of mechanical, chemical, thermal, nuclear, or any other means for storing energy which may be converted into electrical energy for providing the electrical energy input to the downhole motor system. [0111] Tn accordance with at least one embodiment of the present disclosure, the power supply is a battery or battery system including one or more energy cells for storing and providing the electrical energy input to the downhole motor system. The power supply may store electrical energy as direct current. The power supply may provide the electrical energy input to the downhole motor system as direct current (“DC”) or alternating current (“AC”) (e.g., a circuitry of the power supply may convert the stored DC electrical energy to AC).

[0112] As mentioned above, the downhole motor system may include a downhole motor. The downhole motor may be implemented in connection with a downhole tool and/or component of a drilling system. For example, the downhole motor may be included as part of a steering system (e.g., a RSS) of the drilling system. The downhole motor may be included as part of any component of the drilling system.

[0113] In some embodiments, the downhole motor is an electric motor. For example, the downhole motor may be a DC motor, an AC motor, an induction motor, a single-phase motor, a multi-phase motor (e.g., a 3-phase motor), any other electric motor, and combinations thereof. The downhole motor may receive and convert the electrical energy input to a mechanical energy output through an output shaft of the downhole motor. For example, the electrical energy input may be applied to an armature of the downhole motor which may cause a rotor of the downhole motor to rotate. In this way, the downhole motor may rotate based on receiving the electrical energy input.

[0114] The rotation of the downhole motor (e.g., the mechanical energy output) may facilitate one or more functions of the drilling system. For example, the mechanical energy output may be used to operate one or more actuators of a downhole component. The mechanical energy output may be used to rotate one or more downhole components or parts of a downhole component. In accordance with at least one embodiment of the present disclosure, the downhole motor (and the mechanical energy output) may be implemented in connection with a steering system (e.g., RSS) of the drilling system. For example, the drilling tool assembly of the drilling system may rotate in order to facilitate drilling, degrading, or otherwise removing material from the earth formation to form the borehole. The downhole motor may rotate one or more components of the steering system in accordance with the rotation of the drilling tool assembly. For example, the downhole motor may rotate one or more components of the steering system in a reverse or opposite direction of the rotation of the drilling tool assembly. This may facilitate maintaining one or more components of the steering system substantially rotationally stationary with respect to the earth formation. This may facilitate directing a BHA and/or bit of the drilling system.

[01151 For example, the steering system may include one or more (e.g., extendable) elements that may engage a borehole wall and, in this way, direct the BHA in a direction opposite that of the engagement with the borehole wall (e.g., push the bit systems). In such a case, however, it may be advantageous (or even necessary) that the extendable elements engage the borehole wall without rotating (relative to the borehole) in order to provide a steering force in a uniform direction. In this way, the motor may facilitate preventing the extendable elements from rotating and/or maintaining the extendable elements rotationally stationary.

[0116] In another example, the steering system may have an inner rotating shaft that drives a rotation of the BHA and/or bit. The steering system may apply a biasing force, or may press against the inner rotating shaft which bend the shaft and, in this way, direct the BHA and/or bit in the direction (or in an opposite direction using a fulcrum) of the applied biasing force (e.g., point the bit systems). Similarly, it may be advantageous or necessary to maintain one or more components of the steering system rotationally stationary with respect to the borehole in order that the biasing force may be applied in a uniform direction. In this way, the motor may rotate one or more components of the steering system in order to facilitate the steering and/or directing of the BHA and/or bit.

[0117] As discussed above, the downhole motor may receive the electrical energy input from the power supply. In some embodiments, the downhole motor receives the electrical energy input directly from the power supply. In some embodiments, the downhole motor receives the electrical energy input indirectly from the power supply. For example, the electrical energy input may pass and/or flow through one or more components of the electronics system before flowing to the downhole motor. The downhole motor system may include a motor drive and a DC link. The electrical energy input may flow through the DC link and/or the motor drive before flowing to the motor.

[0118] As just mentioned, the downhole motor system may include a DC link positioned between the power supply and the downhole motor. The DC link may facilitate providing a stable supply of electrical energy from the power supply. For example, the DC link may connect to multiple nodes, cells, or power sources of the power supply (e.g., multiple power supplies) and may facilitate providing the electrical energy input to the downhole motor system from multiple sources. Tn some embodiments the DC link acts as a buffer storage for electrical energy. For example, the downhole motor (more specifically the motor drive) may demand or require current loads that are changing, irregular, and/or sporadic, and the DC link may facilitate providing stable DC power notwithstanding these changing loads. For example, the DC link may include one or more capacitors that may absorb and/or discharge electrical energy as needed to meet the demands of the downhole motor while maintaining the electrical energy input stable and/or uniform. In this way, the DC link may facilitate providing the electrical energy input to the downhole motor system.

[0119] As mentioned above, the downhole motor system may include a motor drive. The motor drive may drive and/or control the downhole motor by, for example, controlling and/or regulating the electrical energy input that flows to the motor. The motor drive may include control circuitry as well as a processor and executable logic for controlling the control circuitry with the processor. The control circuitry may include and/or define a power inverter/converter for manipulating the electrical energy that flows through the motor drive.

[0120] In at least one embodiment of the present disclosure, the motor drive converts DC power that is supplied from the power supply into AC power. This may facilitate powering the downhole motor, for example, in implementations where the downhole motor is an AC motor. The motor drive may include a series of power electronic switches, such as insulated gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs), that are controlled by the processor. The processor may control the switching of the power electronic switches to create a controlled AC output that is supplied to the electric motor.

[0121] In some embodiments, the motor drive converts the DC power from the power supply into multi-phase (e.g., 3-phase) AC power that is compatible with the downhole motor. The motor drive may adjust or vary the frequency and/or amplitude of the AC power and, in this way, provide precise control over the speed and/or torque of the downhole motor. In some embodiments, the motor drive receives and/or monitor feedback signals from the downhole motor, and may adjust or vary the electrical energy input in order to protect the downhole motor from overvoltage, overcurrent, and over-temperature conditions, etc. In this way, the motor drive may facilitate precise control over the operation of the downhole motor. As will be discussed herein in detail, the motor drive may modify, manipulate, and or modulate one or more of a voltage, current, phase, waveform, frequency, magnitude, and a harmonic distortion (and combinations thereof) of the electrical energy input in order to control an operation and/or an efficiency of the downhole motor in accordance with the techniques described herein.

[01221 Operation of the downhole motor may correspond with or may result in one or more energy losses and/or inefficiencies. For example, all of the electrical energy input may not be efficiently or completely converted into the mechanical energy output, but some of the electrical energy input may be lost due to the motor inefficiencies and/or losses. The losses of the downhole motor may include mechanical losses. The mechanical losses may occur due to friction between moving parts, such as between the bearings and the rotor of the downhole motor. The losses of the downhole motor may also include joule losses. The joule losses may occur due to current flowing through the armature of the downhole motor encountering resistance and causing the wire in the windings to heat up. The losses of the downhole motor may further include eddy current losses. The eddy current losses may occur due to the changing magnetic field (e.g., magnetic flux) produced by the armature inducing eddy currents in the iron core of the downhole motor and generating heat. In this way, the operation of the downhole motor may result in one or more losses, which may affect the mechanical energy output.

[0123] Operating the downhole motor with one or more of these inefficiencies or losses may typically increase energy consumption, cost, wear, etc. For example, due to the losses, more electrical power is typically needed to produce an equivalent amount of mechanical power. Similarly, due to the losses more mechanical power is typically needed to generate an equivalent amount of electrical power when operating as a generator. Thus, it is typically desirable to reduce and/or eliminate losses in a motor system in order to maximize the motor efficiency. For example, the moving parts of a motor may typically be designed in such a way so as to reduce friction, thereby reducing mechanical losses. Additionally, motor systems are conventionally controlled (e.g., in real time) by components such as the motor drive to control the electrical energy supplied to the motor (e.g., to control the magnetic rotor field generated by the armature) in order to reduce joule losses and eddy current losses.

[0124] More specifically, the motor drive may conventionally be operated to control the waveform of the electrical energy input to the downhole motor in order to increase the efficiency of the downhole motor and/or reduce losses. For example, one or more of a frequency, phase, magnitude, and harmonic distortion of the (e.g., current of the) electrical energy input may be manipulated in order to affect the efficiency of the downhole motor. Motors such as the downhole motor may typically operate at specific operational frequencies, such as 0 Hz-60 Hz. For example, the frequency of the power supplied to the motor may directly correspond to the rotation of the magnetic rotor field generated within the motor which drives the output shaft. Thus, the speed or rotation of the motor may be adjusted or modified based on changing the frequency of the supplied power. However, only this operational (e.g., fundamental) frequency contributes to the average rotation and/or average torque output by the motor (e.g., other frequencies may contribute to torsional oscillations or torque ripple of the rotor, but not necessarily the general rotation when viewed as an average). Electrical energy supplied to the motor at other frequencies (e.g., distorted waveforms), such as harmonics of the fundamental frequency, thus will not contribute to (e.g., increase) the average mechanical energy generation of the motor. Energy at these distorted frequencies (e.g., distorted energy) will, however, generate losses such as joule and/or eddy current losses exhibited by the motor. For example, current flowing through the armature at these other frequencies generates heat through joule losses. Additionally, the distorted current waveform flowing through the armature results in eddy currents in the iron core from a distorted component of the rotor field. However, due to the mismatch in frequency of the distorted energy input waveform with the rotation of the motor (and the fundamental frequency), the distorted energy does not produce an applied torque on the rotor in time with the fundamental frequency and thus does not contribute to the rotation (e.g., average torque output) of the output shaft. In other words, energy inputs with distorted waveforms represent additional energy supplied to the motor without substantially any corresponding return (e.g., increase) in the average mechanical output. Thus, it is typically desirable to eliminate additional frequencies (e.g., harmonics), such as by reducing a total harmonic distortion, in the waveforms in order to provide the electrical energy input to the downhole motor as a near or substantially sinusoidal waveform (e.g., at the fundamental frequency).

[0125] To this end, motor drives are typically operated to optimize one or more aspects of the waveform of the supplied energy, such as a frequency, phase, magnitude, harmonic distortion, and combinations thereof. In some situations, motor drives are typically operated to minimize the total harmonic distortion in the waveform of the energy supplied to a motor. For example, conventional motor drives may be implemented to perform one or more techniques such as pulse width modulation (PWM), or active power factor correction (PFC) to reduce distortion. Conventional motor drives may also include filter circuits, multi-level inverters, or may implement harmonic cancellation algorithms to reduce distortion. Tn this way, it is typically desirable to implement one or more techniques for providing electrical energy to a motor (such as the downhole motor) having a waveform with minimal distortion in order to increase the efficiency of the motor.

[0126] Accordingly, in some embodiments, the electrical energy input is an electrical energy having a waveform that is substantially sinusoidal and/or substantially exhibits only the fundamental frequency (corresponding to the downhole motor). For example, in some embodiments, the motor drive performs one or more of the optimization and/or distortion minimizing techniques just described above in order to reduce and/or eliminate distortion in the waveform of the electrical energy input and in order to increase an efficiency of the downhole motor. This may be in connection with the downhole motor being operated in a motoring mode, or being operated to generate the mechanical energy output. As will be discussed herein, however, in some situations the downhole motor system intentionally induces distortion and/or harmonics into the electrical energy input of the downhole motor in order to reduce an efficiency of the downhole motor (and/or the downhole motor system).

[0127] As described herein, the downhole motor may be implemented in connection with a downhole tool in order to drive one or more functions of the downhole tool and/or to rotate one or more components of the downhole tool. For example, the downhole motor may facilitate rotating one or more components in an opposite direction of a rotation of the drilling tool assembly. To achieve this, the motor system may be implemented as described above in order to generate the mechanical energy output of the downhole motor and drive this rotation.

[0128] In some situations, the output shaft of the downhole motor is driven to rotate by an energy input external to the downhole motor system. This may be in addition to or in place of the downhole motor being driven by the electrical energy input. For example, a mechanical energy input may be applied to the output shaft of the downhole motor and may cause the downhole motor to rotate. The mechanical energy input may cause the downhole motor to rotate in the same or opposite direction than that in which the electrical energy input causes the downhole motor to rotate. In this way, the mechanical energy input may cause the downhole motor to speed up, or to rotate backwards. The mechanical energy input may be due to or may be caused by, for example, the rotation of the drilling tool assembly (e.g., by an uphole, downhole, or surface motor), an interaction of the drilling tool assembly with the formation (e g., stick slip, back torque, etc.) or any other mode of mechanically rotating the input shaft of the downhole motor. For example, the rotation of the drilling tool assembly and/or the downhole tool (with which the downhole motor is implemented) may produce or generate the mechanical energy input and may cause the downhole motor to rotate. In some embodiments, the rotation of the downhole motor in this way is intentional, such as part of a regeneration mode of the downhole motor system.

[0129] The rotation of the downhole motor due to the mechanical energy input may cause the downhole motor system to generate electrical energy. For example, the downhole motor may generate an electrical energy output which may flow from the downhole motor to (or toward) the power supply (e.g., by way of one or more other components of the downhole motor system). In this way, the downhole motor may act as a generator. The downhole motor may generate the electrical energy output which may flow to the power supply and may charge, for example, a battery of the power supply. In this way, the downhole motor system may operate in a regeneration mode in order to charge and/or maintain a charge in the power supply.

[0130] In some embodiments, the downhole motor system operates in the regeneration mode in order to provide a slowing or braking function. For example, the regeneration mode may correspond to a torque generated by the downhole motor that opposes a direction of rotation corresponding to the mechanical energy input. In this way, the downhole motor generating the electrical energy output may also correspond to slowing, braking, or decelerating of a rotation of one or more components of the drilling system, such as the drilling tool assembly and/or the BHA. [0131] In some embodiments, the downhole motor system operates in the regeneration mode without the purpose of slowing or braking the drilling tool assembly. For example, while generating the electrical energy output with the downhole motor this will inevitably result in the drilling tool assembly somewhat slowing as rotational energy of the drilling tool assembly is converted to electrical energy, the downhole motor system may operate in this manner not necessarily for the purpose of further slowing or stopping the drilling tool assembly from rotating, but for taking advantage of the rotation of the drilling tool assembly to generate the electrical energy output (e.g., to recharge the power supply). As such, in some embodiments, the regeneration mode of the downhole motor system operates in a configuration suitable for generating the electrical energy output rather than configured to slow or stop the rotation of the mechanical energy input. [0132] As discussed above, the downhole motor may exhibit one or more inefficiencies or losses. While operating in the regeneration mode, (e.g., when the downhole motor is generating electricity instead of mechanical motion), the downhole motor may also exhibit these inefficiencies. For example, even though the output shaft of the downhole motor is not being driven by the motor, the iron core in the rotor may still experience and/or exhibit the eddy current losses due to a rotating electric field (e.g., magnetic flux) generated by the armature of the downhole motor. Additionally, the armature of the downhole motor may still experience and/or exhibit the joule losses as the rotation of the rotor causes a current to flow through the wire windings of the armature. Further, the moving parts of the downhole motor may still experience friction resulting in the mechanical losses. One or more of these losses may be manifested as heat generation in the downhole motor (or in one or more components of the downhole motor).

[0133] In this way, not all of the mechanical energy input may be converted to the electrical energy output, as the inefficiencies of the motor may cause some of the mechanical energy input to be converted to heat. As discussed above, the downhole motor system may operate in a regeneration mode for the purpose of generating the electrical energy output, such as to charge the battery. Accordingly, a motor system such as the downhole motor system may typically be tuned or optimized to maximize or optimize the electrical energy output. For example, while attempting to regenerate the power supply, it may typically be desirable to generate a maximum amount of electricity with the motor and/or the mechanical energy input. To this end, the techniques discussed above for improving the efficiency of the motor may typically be implemented to maximize the electrical energy output. For example, the armature of the downhole motor may be supplied with electrical energy in order to generate a magnetic field that may interact with a magnetic field of the rotor in order to generate the electrical energy output. This electrical energy may typically be provided to the armature with minimal harmonic distortion (e.g., as a substantially sinusoidal waveform) in order to minimize joule losses in the armature and/or eddy current losses in the motor core. Thus, motor systems such as the downhole motor system may typically be configured to improve (or maximize) the efficiency of the motor in order to increase (or maximize) an amount of the electrical energy output generated by the downhole motor.

[0134] In some situations, the electrical energy output exceeds an operational threshold of one or more components of the electronics system. For example, the power supply may become fully charged and it may become unnecessary or undesirable to continue to provide the electrical energy output to the power supply. In another example, providing the electrical energy output to one or more components of the downhole motor system for a prolonged or sustained period may cause damage or wear to these components, such as from overheating. In another example, the mechanical energy input may be such that the electrical energy output generated by the downhole motor surpasses a threshold level, such as a threshold that one or more electronics components of the downhole motor system is suited to withstand, even for a short period of time. As such, maintaining (or even increasing) this excess level of the electrical energy output to one or more components of the downhole motor system may damage or wear these components, such as through overheating, overcurrent, and/or overvoltage conditions.

[0135] To this end, the downhole motor system may include one or more components for dissipating the electrical energy output (e g., all of the energy or a portion of the energy in excess of a usable or desired quantity). For example, the downhole motor system may include a brake resistor. In some embodiments, the brake resistor is connected and/or coupled to the motor drive. For example, the brake resistor may be configured such that an electrical path bypasses the motor drive and passes to the brake resistor. The brake resistor may be included in the circuitry of the downhole motor system at any other position or location suitable for providing the energy dissipating functions described herein. The brake resistor may be a resistor (or any other component) that is configured to receive a flow of electrical energy and dissipate some or all of that electrical energy. For example, the brake resistor may be an electrical resistor made of a material that can withstand high temperatures. As electrical energy flows through the brake resistor, it is dissipated as heat generated by the brake resistor. The brake resistor may be configured such that it may withstand elevated voltages, currents, and/or volumes of electrical energy in order to dissipate the electrical energy.

[0136] The downhole motor system may be configured such that some or all of the electrical energy output may flow to the brake resistor. For example, when the electrical energy output exceeds a threshold level and/or when it is no longer desirable or necessary to continue providing the electrical energy output to one or more components of the downhole motor system, the motor drive may direct an entirety of the flow of the electrical energy output to the brake resistor. In another example, it may be desirable to allow or facilitate the flow of the electrical energy output to one or more components of the downhole motor system (e g., to the power supply), but energy of the electrical energy output in excess of an operational threshold or working amount may be directed to the brake resistor in order to maintain a uniform and/or safe level of the electrical energy output to the various components. In this way, the brake resistor may facilitate dissipating some or all of the electrical energy output from the downhole motor system. Techniques for dissipating some or all of the electrical energy output in this way may be implemented in connection with a braking, stopping, and/or regeneration mode of the downhole motor.

[0137] In some situations, the brake resistor (or equivalent energy dissipating component) is not suitable for adequately dissipating the electrical energy output. For example, in some situations the electrical energy output may exceed a level or quantity that the brake resistor is configured to handle, and the brake resistor may become damaged by receiving the flow of the electrical energy output. In another example, a sustained or prolonged flow of the electrical energy output to the brake resistor may damage the brake resistor, such as from overheating. In another example, the brake resistor may wear over a (e.g., long) period of use in the downhole motor system, and in some situations the brake resistor may accordingly be prone to failure even when operating within its appropriate limits.

[0138] The brake resistor failing or performing inadequately may present a risk of serious damage or wear to one or more other components of the downhole motor system, such as through overheating, over voltage, over current, etc., for example, due to an excessive or prolonged flow of the electrical energy output. Thus, alternative techniques for dissipating the electrical energy output in place of, or in addition to, the brake resistor may be advantageous.

[0139] In some embodiments, a distorted input is supplied or provided to the downhole motor. The distorted input may be electrical energy that is supplied to the motor by the motor drive. For example, the motor drive may receive the electrical energy input (e.g., from the power supply) and may generate the distorted input from the electrical energy input. The motor drive may generate the distorted input by implementing pulse width modulation and/or high frequency modulation. For example, the motor drive may utilize one or more IGBTs or MOSFETs in order to generate the distorted input. The distorted input may be supplied to the downhole motor as an alternative to, or in addition to, the electrical energy input being supplied to the downhole motor. In this way, the motor drive may inject the distorted input (e.g., inject high-frequency harmonics) into the downhole motor. [0140] The distorted input may be a flow of electrical energy having a waveform that includes at least some distortion. For example, the motor drive may modify and/or manipulate one or more of a frequency, amplitude, phase, or harmonic distortion of the waveform to generate the distorted input. In accordance with at least one embodiment of the present disclosure, the distorted input may be an electrical energy supplied to the downhole motor that includes at least some distortion, harmonics, and/or alternate frequencies to that of the fundamental frequency corresponding to a rotation of the downhole motor. In some embodiments, the distorted input has a waveform that only contains distortion and/or harmonic frequencies, and is not containing or exhibiting the fundamental frequency. For example, the distorted input may be provided to the downhole motor in place of or as an alternative to supplying the electrical energy input to the downhole motor. In some embodiments, the distorted input has a waveform that contains distortion and/or harmonic frequencies in addition to the fundamental frequency. For example, the distorted input may be provided to the downhole motor in addition to the electrical energy input. In this way, it should be understood that describing the distorted input as a separate energy input from the electrical energy input may be for illustrative purposes, and the distorted input may be representative of distortion and/or harmonics induced or exhibited by, for example the electrical energy input. In other words, in some embodiments the distorted input and the electrical energy input are not necessarily separate or distinct energy inputs to the downhole motor, but the distorted input indicates the presence of at least some distortion and/or harmonics in the electrical energy input supplied to the downhole motor. In this way, electrical energy may be supplied or provided to the downhole motor that includes at least some distortion, harmonics, and/or alternative frequencies to that of the fundamental frequency. In some embodiments, the harmonics are high frequency harmonics.

[0141] As described herein, the fundamental (e.g., operating) frequency may be determined and/or based on a speed of the downhole motor. In this way, the fundamental frequency may be variable and may be based on a speed (or desired speed) of the downhole motor. In some embodiments, the waveform of the distorted input includes harmonics of the fundamental frequency. The harmonics may be frequencies that are integer multiples of the fundamental frequency. In this way, the harmonics of the distorted input may be dependent on or may be functions of the (e.g., variable) fundamental frequency. Thus, the harmonics induced in the waveform of the distorted input may be determined or generated based on a determined or identified frequency of the fundamental frequency of the downhole motor and/or the electrical energy input.

[01421 To this end, in some embodiments, the motor drive monitors one or more aspects of the downhole motor. For example, the motor drive may receive one or more control and/or feedback signals from the downhole motor. The motor drive may monitor one or more of a speed, frequency, torque, current, voltage, induction slip, rotor position, and temperature of the downhole motor, or any other aspect of the downhole motor and combinations thereof. This monitoring of the downhole motor by the motor drive may facilitate determining the fundamental frequency, for example, in order to generate the harmonics of the distorted input.

[0143] In some embodiments, the distorted input causes and/or results in one or more inefficiencies or losses in or by the downhole motor. For example, as discussed herein, the downhole motor may exhibit or experience joule losses and/or eddy current losses. These losses may be worsened or exacerbated by distorted waveforms in the energy applied to the downhole motor. Accordingly, supplying the distorted input to the downhole motor may decrease an efficiency of the downhole motor. For example, the distorted input may cause and/or result in an increase in the joule losses in the motor, represented by distortion joule losses. In another example, the distorted input may cause and/or result in an increase in the eddy current losses, represented by distortion eddy current losses. While the distortion joule losses and the distortion eddy current losses may be described as separate or distinct losses from that of the joule losses and eddy current losses (respectively), it should be understood that the distortion joule losses and the distortion eddy current losses are not necessarily separately occurring losses, but may be a same mechanism or means of loss as that of the joule losses and eddy current losses (respectively), but to an increased or greater degree. In this way, the distorted input may result in an increase in losses and/or a decrease in efficiency of the downhole motor (and the downhole motor system). [0144] As discussed herein, losses such as the joule losses and/or the eddy current losses may result in and/or be manifested as heat generated in one or more components of the downhole motor. The increase in these losses represented by the distortion joule losses and the distortion eddy current losses may accordingly result in and/or be manifested as an increase in the heat generated by the one or more components of the downhole motor. For example, the joule losses may generate heat in the wire windings of the armature of the downhole motor, and/or the distortion joule losses may represent an increase in the generated heat. In another example the eddy current losses may generate heat in the iron core of the downhole motor, and the distortion eddy current losses may represent an increase in the generated heat.

[01451 As discussed herein, the distortion and/or harmonics in the waveform of electrical energy supplied to the downhole motor may not produce or contribute to (e.g., increase) an average generation of a mechanical output by the downhole motor. Similarly, harmonics and/or distortion in the waveform of electrical energy supplied to the downhole motor may not produce or contribute to (e.g., increase) the average generation of electrical energy by the downhole motor (e.g., when acting as a generator). Nevertheless, in either case, distorted waveforms may produce and/or contribute to the losses exhibited by the downhole motor (e.g., more electrical power is needed to produce an equivalent amount of mechanical power, or to generate an equivalent amount of electricity). In other words, the distortion in the waveform of electrical energy supplied to the downhole motor may represent additional energy supplied to the downhole motor without a corresponding return in energy output, or a return in energy converted from electrical to mechanical (or vice versa). This loss of energy (e.g., energy dump) may be leveraged by the downhole motor system to dissipate excess, prolonged, or otherwise unwanted quantities of the electrical energy output. In other words, excess electrical power may be dumped into making the downhole motor system less efficient, and thereby generating less electrical energy output.

[0146] As discussed herein, when operating in a regeneration mode, the downhole motor system 220 may generate the electrical energy output. In some cases, the electrical energy output may be in a quantity, duration, time, etc., that is undesirable (or even damaging) for the downhole motor system. In some embodiments, the brake resistor as described herein is inadequate or not equipped to dissipate a sufficient amount of the electrical energy output or for a required duration.

[0147] In some embodiments, the downhole motor system supplies the distorted input to the downhole motor in order to induce (or increase) one or more inefficiencies in the downhole motor and dissipate an unwanted quantity of the electrical energy output. For example, the downhole motor system may induce the distortion joule losses and/or the distortion eddy current losses to a degree so as to dissipate at least a portion of the electrical energy output (e.g., as heat). In some embodiments, all of the electrical energy output is dissipated through the induced losses such that the brake resistor is not dissipating any of the electrical energy output. For example, the downhole motor may dissipate all or an excess portion of the electrical energy output without the electrical energy output (or the portion) flowing to one or more portions of the electronics system, such as the motor drive, the DC link, the brake resistor, the power supply, or any other component of the electronics system. This may facilitate the downhole motor system and/or the electronics system not including the brake resistor (and/or another energy dissipating component). In some embodiments, only a portion of the electrical energy output is dissipated through the induced losses. For example, the brake resistor may be implemented to dissipate a portion (or the remainder) of the electrical energy output and/or a portion (or the remainder) of the electrical energy output may flow to one or more other components of the downhole motor system (such as to recharge a battery of the power supply). In some embodiments, the downhole motor is selectively, periodically, and/or temporarily employed to dissipate some or all of the electrical energy output. For example, the motor drive may selectively, periodically, and/or temporarily supply the distorted input to the downhole motor in order to dissipate the electrical energy output. This selective dissipation may be implemented based on a charge state of the power supply, a temperature of the brake resistor, a temperature of the downhole motor, an ability of one or more components of the electronics system to handle and/or withstand the electrical energy output, any other relevant factor, ability, or function of the electronics system, and combinations thereof. In this way, an excess, prolonged, or otherwise unwanted quantity of the electrical energy output may be dissipated by intentionally inducing losses or inefficiencies in the downhole motor.

[0148] While the energy dissipating functionality of the downhole motor system has been described primarily with respect to inducing or injecting harmonic distortion to the downhole motor, it should be appreciated that the techniques described herein for dissipating energy include decreasing the efficiency of the downhole motor by one or more additional means. These means may be in addition to or as an alternative to inducing harmonic distortion to the downhole motor. For example, the distorted input may include a waveform that has distortion from any number of sources or that have been distorted in any number of ways. For example, the distorted waveform may be the result of one or more of voltage or current spikes, voltage or current surges, voltage or current sags, voltage or current imbalance across motor phases, phase shift between voltage and current, any other form of waveform distortion, and combinations thereof. In some embodiments, the efficiency of the motor may be decreased through DQ motor control, or Clarke and Park transformation control. For example, for a three phase implementation of the motor, the three-phase motor variables may be transformed into a two-coordinate, reference frame (d, q) in order to simplify control algorithms and enable independent control of the motor’s active (e g., torque) and reactive (e.g., magnetizing) components Tn this way, the efficiency of the downhole motor may be decreased in any number of ways in addition to harmonic distortion in order to increase an energy dissipation of the downhole motor without an equivalent increase in production, or energy output by the downhole motor.

[0149] The downhole motor as described herein may be an effective and/or ideal tool for dissipating unwanted electrical energy. For example, the downhole motor may be configured to operate (e.g., in motoring mode) and receive, convert, and/or handle a threshold amount of electrical energy. The operation of the downhole motor in this way may result in the downhole motor generating heat and/or experiencing an increase in temperature. As such, the downhole motor may be configured to withstand a threshold level of heat generation and/or to maintain operation up to a threshold temperature (e.g., corresponding to a quantity or rate of electrical energy supplied to the downhole motor). As discussed herein, some or all of the electrical energy output may be dissipated as heat generated in or by the downhole motor. In some embodiments, the downhole motor is configured to dissipate the electrical energy output up to an equivalent level or at an equivalent rate to that which the downhole motor is configured to handle as the electrical energy input. In some embodiments, the downhole motor is configured to generate heat and/or increase in temperature while dissipating the electrical energy output up to an equivalent level or up to an equivalent degree as that which the downhole motor is configured to experience when operating in motoring mode. In this way, the downhole motor may provide an effective means for dissipating the electrical energy output.

[0150] In some embodiments, with respect to an electrical energy and/or temperature threshold, the downhole motor is more robust than one or more other electrical components of the downhole motor system. For example, the quantity and/or rate of electrical energy that the downhole motor is configured to withstand (e.g., dissipate) may be much more than, for example, what the brake resistor is configured for. In some embodiments, the brake resistor is configured to withstand 10%-30% of the quantity and/or rate of electrical energy that the downhole motor is configured to receive. In another example, the amount of heat generation and/or the temperature which the downhole motor is configured to withstand may be much more than, for example, what the brake resistor is configured for. In some embodiments, the brake resistor is typically configured to withstanding 10%— 30% of the heat generation and/or temperature which the downhole motor is configured for. Tn this way, the downhole motor may facilitate an increased level or rate of energy dissipation compared to conventional techniques, such as with the brake resistor.

[01511 As discussed herein, waveform distortion such as harmonics may not substantially contribute to (e.g., increase) an average torque output (or an average generation of electricity in regeneration mode) of the downhole motor. In some situations, however, distorted waveforms may create or result in torque ripple exhibited by the downhole motor. Torque ripple may be a (e.g., instantaneous) variation in the torque and/or rotation of the downhole motor. For example, the distortions in the waveforms of an electrical energy supplied to the downhole motor (e.g., distorted input) may at times contribute or add to the torque/rotation of the rotor, and may at times inhibit or detract from the torque/rotation of the rotor. These effects may occur periodically and may result in an oscillatory variation on the torque and/or rotation of the rotor (e.g., torsional oscillations). Torque ripple in this way may cause undesired vibrations, noise, and/or other undesirable effects on the downhole motor (or any other component of the drilling system). For example, vibrations by the downhole motor may cause damage or wear to mechanical parts of the downhole motor or any other component coupled to the motor which may experience vibrations from the torque ripple.

[0152] In some embodiments, lower frequency torque ripple corresponds to greater vibrations and/or worse adverse effects than torque ripple of higher frequencies. For example, torque ripple of lower frequencies may exhibit higher amplitudes of vibration than torque ripple of higher frequencies. In some embodiments, supplied waveforms having induced harmonics of lower frequencies correspond to lower frequency torque ripple and/or supplied waveforms having induced harmonics of higher frequencies correspond to higher frequency torque ripple. Lower frequency (e.g., higher amplitude) torque ripple may correspond with increased damage and/or wear on (e.g., the mechanical components) of the downhole motor or any other components of the drilling system. Lower frequency (e.g., higher amplitude) torque ripple may also affect the (e.g., instantaneous) speed and/or torque of the downhole motor to a greater (e.g., undesirable) degree.

[0153] Accordingly, in some embodiments, the distorted input includes and/or exhibits high frequency harmonics in order to reduce and/or mitigate the effects of torque ripple. For example, the waveform of the distorted input may be modulated and/or tuned to reduce the torque ripple. In some embodiments, the resulting torque ripple is in a range having an upper value, a lower value, or upper and lower values including any of 1%, 5%, 10%, 15%, 20%, 25%, 30%, or 50% variation in the average torque, or any value therebetween. For example, the torque ripple may be greater than 1%. In another example, the torque ripple may be less than 50%. In yet another example, the torque ripple may be between 1% and 50%. In some embodiments, it is critical that the torque ripple be no more than 15% variation in the average torque to prevent damage and/or wear to the downhole motor (and/or other components of the drilling system) due to torque ripple. The distorted input may include harmonics of any order, such as harmonics of greater than the 25^th order.

[0154] In some embodiments, the distorted input includes harmonics of the fundamental frequency in a range having an upper value, a lower value, or upper and lower values including any of 5^th order, 7^th order, 9^th, order 11^th order, 13^th order, 15^th order, 17^th order, 19^th order, 21^st order, 23^rd order, or 25^th order harmonics, or any value therebetween. For example, the distorted input may include 5^th order or greater harmonics. In another example, the distorted input may include harmonics of the 25^th order or less. In yet another example, the distorted input may include harmonics between the 5^th order and 25^th order. In some embodiments, it is critical that the distorted input include harmonics of no less than 9^th order in order than the frequencies be high enough to reduce and/or mitigate the effects of torque ripple.

[0155] Torque ripple may also result and/or cause damage and/or wear, or an increase in damage and/or wear, when the torque ripple results in vibrations corresponding to a natural frequency of one or more components of the drilling system. For example, the downhole motor and/or any other component may exhibit a natural frequency, and an excitation or applied vibration at that natural frequency may lead to resonance of one or more components. This resonance may lead to an increase in the amplitude of the vibration which may cause excessive motion, stress, or even failure of one or more components. As such, in some embodiments, the distorted input is generated and/or the harmonics in the waveform of the distorted input are selected such that they do not lead to torque ripple that corresponds with vibrations at the natural frequency of the downhole motor (and/or one or more other components of the drilling system). In this way, damage from large amplitude resonant vibrations may be avoided and/or mitigated.

[0156] By injecting the distorted input into the downhole motor, it may be inevitable that some torque ripple may result. While it may be desirable to reduce and/or mitigate the effects of torque ripple corresponding with vibrations of certain frequencies (e g., high amplitude vibrations, resonant vibrations), it should be noted that the resulting vibrations from torque ripple may correspond with an increase in mechanical losses (e.g., due to friction) in the downhole motor, and thus an increase in the downhole motor dissipating the electrical energy output. Thus, torque ripple is not necessarily an adverse side effect, but rather contributes to the effectiveness of the energy dissipation techniques described herein.

[0157] The distorted input including higher frequencies in the waveform may also contribute to an increase in the losses exhibited by the downhole motor, such as an increase in the distortion joule losses due to skin effect. For example, when an AC current flows through a conductor, such as the wire windings in the armature of the downhole motor, the current flow is not uniform across the cross-section of the conductor. This is due to the interaction of the magnetic field generated by the current with the material of the conductor itself. As such, the current density tends to be highest at or near the surface of the conductor and decreases gradually as the distance from the surface increases. This effectively increases the resistance encountered by the current by reducing the effective cross-sectional area of the conductor, which results in increased joule losses. At higher frequencies, the current density near the center of the conductor can be significantly lower than that at or near the surface, as most of the current flows on the surface of the conductor. Thus, including higher frequency distortion (e.g., harmonics) in the distorted input as described herein, may increase the distortion joule losses by increasing the skin effect, which may facilitate dissipating more of the electrical energy output by the downhole motor.

[0158] In some embodiments a downhole motor system includes a power supply. The power supply may store and/or provide an electrical energy input to the downhole motor system. In some embodiments the downhole motor system includes a downhole motor. The downhole motor may be a motor for driving one or more functions of a downhole tool. The downhole motor may be an electric motor, such as a 3 -phase AC induction motor. The downhole motor may receive an electrical energy input and may convert it into a mechanical energy output, for example, for driving one or more functions of a downhole tool, as described herein.

[0159] In some embodiments, the downhole motor system includes a motor drive. The motor drive may be coupled to the power supply through a pair of high voltage transmission lines. The high voltage transmission lines may facilitate the power supply providing an electrical energy input to the motor drive. The motor drive may drive and/or control the downhole motor. For example, the motor drive may include an IGBT board and a motor drive board. The IGBT board may include one or more TGBTs which may modify, modulate, or otherwise convert an electrical energy input received from the power supply in order to provide the electrical energy input to the downhole motor with a certain voltage, current, phase, frequency, magnitude, harmonic distortion, and combinations thereof. For example, the motor drive may be coupled to the downhole motor for providing a 3 -phase electrical energy input to the downhole motor. The motor drive (e.g., the IGBT board) may be controlled by a processor and executable logic associated with the motor drive board in order to drive the downhole motor as described herein.

[0160] In some embodiments, the downhole motor system includes a motor capacitor block. The motor capacitor block may be positioned between the motor drive and the power supply (e.g., coupled to the high voltage transmission lines). The motor capacitor block may facilitate providing a uniform electrical energy supply from the power supply to the motor drive. For example, the motor capacitor block may absorb and/or discharge electrical energy as needed to meet the demands of the motor drive to control the downhole motor.

[0161] In some embodiments, the downhole motor system includes a brake resistor. The brake resistor may be positioned between the power supply and the downhole motor (e.g., coupled to the high voltage transmission lines). The brake resistor may be configured to dissipate an electrical energy output from the downhole motor, for example, when the downhole motor is operating in a regeneration mode.

[0162] In some embodiments, the downhole motor generates an electrical energy output. For example, the downhole motor may be driven by an external mechanical energy input, as described herein. The downhole motor may, in this way, act as a generator and may generate an electrical energy output. In some embodiments, the electrical energy output flows to the power supply, for example, to charge a battery of the power supply. In some embodiments, the downhole motor generates the electrical energy output in a quantity or to a degree that is undesirable and/or may be damaging to one or more components of the downhole motor system, as described herein. In some embodiments, some or all of the electrical energy output flows to the brake resistor, and the brake resistor dissipates some or all of the electrical energy output as heat.

[0163] In some embodiments, the brake resistor is inadequate for receiving and/or dissipating some or all of the electrical energy output. In some embodiments, the downhole motor system employs the downhole motor for dissipating some or all of the electrical energy output in addition to or as an alternative to the brake resistor. For example, the motor drive may supply and/or inject an electrical energy input to the downhole motor with a distorted waveform in order to increase one or more inefficiencies or losses of the downhole motor. The distorted waveform may induce and/or increase one or more of joule losses, eddy current losses, and mechanical losses in the downhole motor. The downhole motor (or one or more components of the downhole motor) may generate heat as a result of the losses. In this way, the downhole motor may facilitate dissipating some or all of the electrical energy output.

[0164] In some embodiments, a method of operating a downhole motor system includes an act of generating an electrical energy output with a downhole motor. For example, the electrical energy output may flow to an electronics system of the downhole tool. In some embodiments, the electrical energy output is generated without dissipating the electrical energy output through a brake resistor.

[0165] The method may include an act of applying an electrical energy input to the downhole motor. For example, the electrical energy input may be applied to the downhole motor by the electronics system. In some embodiments, a motor drive modulates the electrical energy input, such as with one or more insulated-gate bipolar transistors (IGBTs). For example, the electrical energy input may be a high frequency harmonic of the electrical energy output. In another example, the electrical energy input may be a harmonic of the 9^th order or greater. In another example, the electrical energy input may have an electrical frequency (e.g., current, voltage) that is different than a rotational frequency of the downhole motor. In some embodiments, the electrical energy input results in a torque ripple of no more than 15%. In some embodiments, the electrical energy input does not increase an average torque generated by the downhole motor and/or an average speed of the downhole motor. In some embodiments, the downhole motor is a 3 -phase AC motor, such as an induction motor.

[0166] The method may include an act of reducing the electrical energy output based on the applied electrical energy input. For example, the electrical energy input may be maintained below an operational threshold of the electronics system. In some embodiments, the electrical energy output is dissipated by a brake resistor, and reducing the electrical energy output may include reducing an excess portion of the electrical energy output that is not dissipated by the brake resistor. In some embodiments, the electrical energy output is prevented from flowing to one or more components of the electronics system. For example, the electrical energy output may not flow to a DC link of the downhole tool. In another example, the electrical energy output may not flow (dissipate) to a brake resistor Tn some embodiments, the electronics system will not include a brake resistor.

[01671 Iⁿ some embodiments, a method of operating a downhole motor includes an act of generating an electrical energy output with a downhole motor. For example, the electrical energy output may flow to an electronics system of the downhole motor system.

[0168] The method may include an act of while generating the electrical energy output, selectively decreasing an efficiency of the downhole motor. For example, the efficiency may be decreased by increasing a total harmonic distortion of the electrical current in an armature of the downhole motor. Decreasing the efficiency may include modifying one or more of a frequency, magnitude, phase, and harmonic distortion of the current in the armature of the downhole motor. Decreasing the efficiency of the downhole motor may include increasing joule losses and/or eddy current losses of the downhole motor.

[0169] The method may include an act of reducing the electrical energy output based on decreasing the efficiency of the downhole motor. For example, the efficiency may be decreased to maintain the electrical energy output below an operational threshold of the electronics system. [0170] In some embodiments, a method of dissipating electrical energy includes an act of identifying a regeneration mode of a downhole motor. For example, the motor may generate an electrical energy output in the regeneration mode.

[0171] The method may include an act of upon identifying the regeneration mode, applying an electrical energy input to an armature of the downhole motor.

[0172] The method may include an act of based on applying the electrical energy input, causing at least a portion of the electrical energy output to dissipate as heat through the downhole motor. For example, at least a portion of the electrical energy output is dissipated as heat through one or more of the armature of the downhole motor and an iron core of the downhole motor. In some embodiments, the electrical energy input results in a net decrease in the electrical energy output. For example, in some situations, an electrical energy input may be applied to a motor, for example, to brake, slow, or decelerate a motor, such as applying an electric current to a motor in order to provide dynamic or regenerative braking to the motor. However, in such a circumstance the motor may generally generate more energy as a result of the braking efforts, resulting in a net increase in an electrical energy output by the motor. The techniques described herein, however, apply an electrical energy input to the downhole motor without affecting an average torque and/or speed of the downhole motor, and without increasing an electrical energy output generated by the downhole motor (e.g., a net decrease).

[01731 Iⁿ some embodiments, a computer system includes a processor. The processor may be a general-purpose single- or multi-chip microprocessor (e.g., an Advanced RISC (Reduced Instruction Set Computer) Machine (ARM)), a special purpose microprocessor (e.g., a digital signal processor (DSP)), a microcontroller, a programmable gate array, etc. The processor may be referred to as a central processing unit (CPU). Although just a single processor has been described, in an alternative configuration, a combination of processors (e.g., an ARM and DSP) could be used.

[0174] The computer system also includes memory in electronic communication with the processor. The memory may be any electronic component capable of storing electronic information. For example, the memory may be embodied as random-access memory (RAM), read-only memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor, erasable programmable readonly memory (EPROM), electrically erasable programmable read-only memory (EEPROM) memory, registers, and so forth, including combinations thereof.

[0175] Instructions and data may be stored in the memory. The instructions may be executable by the processor to implement some or all of the functionality disclosed herein. Executing the instructions may involve the use of the data that is stored in the memory. Any of the various examples of modules and components described herein may be implemented, partially or wholly, as instructions stored in memory and executed by the processor. Any of the various examples of data described herein may be among the data that is stored in memory and used during execution of the instructions by the processor.

[0176] A computer system may also include one or more communication interfaces for communicating with other electronic devices. The communication interface(s) may be based on wired communication technology, wireless communication technology, or both. Some examples of communication interfaces include a Universal Serial Bus (USB), an Ethernet adapter, a wireless adapter that operates in accordance with an Institute of Electrical and Electronics Engineers (IEEE) 802.11 wireless communication protocol, a Bluetooth® wireless communication adapter, and an infrared (IR) communication port. [0177] A computer system may also include one or more input devices and one or more output devices. Some examples of input devices include a keyboard, mouse, microphone, remote control device, button joystick, trackball, touchpad, and lightpen. Some examples of output devices include a speaker and a printer. One specific type of output device that is typically included in a computer system is a display device. Display devices used with embodiments disclosed herein may utilize any suitable image projection technology, such as liquid crystal display (LCD), light-emitting diode (LED), gas plasma, electroluminescence, or the like. A display controller may also be provided, for converting data stored in the memory into text, graphics, and/or moving images (as appropriate) shown on the display device.

[0178] The various components of the computer system may be coupled together by one or more buses, which may include a power bus, a control signal bus, a status signal bus, a data bus, etc.

[0179] The techniques described herein may be implemented in hardware, software, firmware, or any combination thereof, unless specifically described as being implemented in a specific manner. Any features described as modules, components, or the like may also be implemented together in an integrated logic device or separately as discrete but interoperable logic devices. If implemented in software, the techniques may be realized at least in part by a non-transitory processor-readable storage medium comprising instructions that, when executed by at least one processor, perform one or more of the methods described herein. The instructions may be organized into routines, programs, objects, components, data structures, etc., which may perform particular tasks and/or implement particular data types, and which may be combined or distributed as desired in various embodiments.

[0180] Computer-readable media can be any available media that can be accessed by a general purpose or special purpose computer system. Computer-readable media that store computerexecutable instructions are non-transitory computer-readable storage media (devices). Computer-readable media that carry computer-executable instructions are transmission media. Thus, by way of example, and not limitation, embodiments of the disclosure can comprise at least two distinctly different kinds of computer-readable media: non-transitory computer- readable storage media (devices) and transmission media.

[0181] The embodiments of the downhole motor system have been primarily described with reference to wellbore drilling operations. The downhole motor system described herein may be used in applications other than the drilling of a wellbore. Tn other embodiments, the downhole motor system according to the present disclosure may be used outside a wellbore or other downhole environment used for the exploration or production of natural resources. For instance, the downhole motor system of the present disclosure may be used in a borehole used for placement of utility lines. Accordingly, the terms “wellbore,” “borehole” and the like should not be interpreted to limit tools, systems, assemblies, or methods of the present disclosure to any particular industry, field, or environment.

[0182] One or more specific embodiments of the present disclosure are described herein. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, not all features of an actual embodiment may be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous embodiment-specific decisions will be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vary from one embodiment to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0183] Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. For example, any element described in relation to an embodiment herein may be combinable with any element of any other embodiment described herein. Numbers, percentages, ratios, or other values stated herein are intended to include that value, and also other values that are “about” or “approximately” the stated value, as would be appreciated by one of ordinary skill in the art encompassed by embodiments of the present disclosure. A stated value should therefore be interpreted broadly enough to encompass values that are at least close enough to the stated value to perform a desired function or achieve a desired result. The stated values include at least the variation to be expected in a suitable manufacturing or production process, and may include values that are within 5%, within 1%, within 0.1%, or within 0.01% of a stated value.

[0184] A person having ordinary skill in the art should realize in view of the present disclosure that equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations may be made to embodiments disclosed herein without departing from the spirit and scope of the present disclosure. Equivalent constructions, including functional “means-plus-function” clauses are intended to cover the structures described herein as performing the recited function, including both structural equivalents that operate in the same manner, and equivalent structures that provide the same function. It is the express intention of the applicant not to invoke means-plus-function or other functional claiming for any claim except for those in which the words ‘means for’ appear together with an associated function. Each addition, deletion, and modification to the embodiments that falls within the meaning and scope of the claims is to be embraced by the claims.

[0185] The terms “approximately,” “about,” and “substantially” as used herein represent an amount close to the stated amount that is within standard manufacturing or process tolerances, or which still performs a desired function or achieves a desired result. For example, the terms “approximately,” “about,” and “substantially” may refer to an amount that is within less than 5% of, within less than 1% of, within less than 0. 1% of, and within less than 0.01% of a stated amount. Further, it should be understood that any directions or reference frames in the preceding description are merely relative directions or movements. For example, any references to “up” and “down” or “above” or “below” are merely descriptive of the relative position or movement of the related elements.

[0186] Various features are described herein in alternative format in order to emphasize that features may be combined in any number of combinations. Each feature should be considered to be combinable with each other feature unless such features are mutually exclusive. The term “or” as used herein is not exclusive unless the contrary is clearly expressed. For instance, having A or B encompasses A alone, B alone, or the combination of A and B. In contrast, having only A or B encompasses A alone or B alone, but not the combination of A or B. Even if not expressly recited in multiple independent form, the description provides support for each claim being combined with each other claim (or any combination of other claims).

[0187] The present disclosure may be embodied in other specific forms without departing from its spirit or characteristics. The described embodiments are to be considered as illustrative and not restrictive. The scope of the disclosure is, therefore, indicated by the appended claims rather than by the foregoing description. Changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

CLAIMS What is claimed is:

1. A method of operating a downhole motor on a downhole tool, comprising: generating an electrical energy output with the downhole motor, wherein the electrical energy output flows to an electronics system of the downhole tool; applying an electrical energy input to the downhole motor with the electronics system; and reducing the electrical energy output based on the applied electrical energy input in order to maintain the electrical energy output below an operational threshold of the electronics system.

2. The method of claim 1, wherein the electrical energy input is a high frequency harmonic of the electrical energy output.

3. The method of claim 1, wherein the electrical energy input is a harmonic of the electrical energy output of a 9^th order or greater.

4. The method of claim 1, wherein the electrical energy input has an electrical frequency that is different than a rotational frequency of the downhole motor.

5. The method of claim 1, wherein the electrical energy input is modulated by a motor drive of the downhole motor.

6. The method of claim 5, wherein the electrical energy input is modulated by one or more insulated-gate bipolar transistors (TGBTs) of the motor drive.

7. The method of claim 1, wherein the electrical energy input results in a torque ripple of no more than 15%.

8. The method of claim 1, further comprising: preventing the electrical energy output from flowing to a DC link of the downhole tool.

9. The method of claim 1, wherein the electrical energy output is dissipated by a brake resistor, and wherein reducing the electrical energy output includes reducing an excess portion of the electrical energy output that is not dissipated by the brake resistor.

10. The method of claim 1, wherein the electronics system does not include a brake resistor.

11. The method of claim 1, wherein the electrical energy input does not increase an average torque generated by the downhole motor.

12. The method of claim 1, wherein the electrical energy input does not affect an average speed of the downhole motor.

13. The method of claim 1, wherein the downhole motor is a 3-phase AC motor.

14. A method of operating a downhole motor of a downhole tool, comprising: generating an electrical energy output with the downhole motor, wherein the electrical energy output flows to an electronics system of the downhole tool; while generating the electrical energy output, selectively decreasing an efficiency of the downhole motor to generate the electrical energy output; and reducing the electrical energy output based on decreasing the efficiency in order to maintain the electrical energy output below an operational threshold of the electronics system.

15. The method of claim 14, wherein decreasing the efficiency of the downhole motor includes increasing a total harmonic distortion of an electrical current in an armature of the downhole motor.

16. The method of claim 15, wherein decreasing the efficiency of the downhole motor includes modifying one or more of a frequency, magnitude, phase, and harmonic distortion of a current in an armature of the downhole motor.

17. The method of claim 14, wherein decreasing the efficiency of the downhole motor includes increasing a joule loss and/or an eddy current loss of the downhole motor.

18. A method of dissipating electrical energy, comprising: identifying a regeneration mode of a downhole motor in a downhole tool, wherein, in the regeneration mode, the downhole motor generates an electrical energy output; upon identifying the regeneration mode, applying an electrical energy input to an armature of the downhole motor; and based on applying the electrical energy input; causing at least a portion of the electrical energy output to dissipate as heat through the downhole motor.

19. The method of claim 18, wherein the at least a portion of the electrical energy output is dissipated as heat through one or more of the armature of the downhole motor and an iron core of the downhole motor.

20. The method of claim 18, wherein the electrical energy input results in a net decrease in the electrical energy output.