Drill bit with electrical power generator

An example drill bit includes a bit body defining at least one pocket, and a support arm attachable to the bit body at the at least one pocket and including a coupling that extends from the support arm. A roller cone defines a cavity for receiving the coupling to rotatably mount the roller cone on the coupling. A direct drive electrical power generator is positioned within the coupling and is operatively coupled to the roller cone such that rotation of the roller cone correspondingly rotates a portion of the direct drive electrical power generator to generate electrical power.

BACKGROUND

The present disclosure is related to downhole power generation systems and, more particularly, to drill bit including devices that generate electrical power.

A wide variety of downhole well tools that require electrical power for operation are used during exploration and production of subterranean hydrocarbons. For example, flow control devices, sensors, samplers, packers, instrumentation within well tools, telemetry devices, and well logging devices are each regularly used and require electricity in performing their respective functions. One common method of supplying electrical power to downhole well tools is to use batteries that can be disposed within the downhole well tools. Unfortunately, some batteries cannot operate for an extended period of time at downhole temperatures, and those batteries that are able to operate in downhole temperatures must still be replaced periodically.

Another common method of supplying electrical power to downhole well tools is extending one or more electrical lines from the surface to the downhole well tools. Electrical lines that extend for long distances downhole, however, can interfere with flow or access if they are positioned within a tubing string, and they can be damaged during run-in if they are positioned outside of the tubing string or cumbersome to deal with when moving pipe in an out of the hole. In addition, rotating such drill strings can result in the need for slip rings to jump the power from a non-rotating part of the drilling system to a rotating part. Such slip rings are often unreliable. Yet another common method to supply power down hole is through the use of a turbine-powered generator positioned in the mud flow, where drilling fluid passes through the turbine, which spins a generator shaft to produce power.

Recently, sensors and other electricity-consuming devices have been placed directly in drill bits of downhole drilling systems to provide various functions, such as monitoring and reporting data relating to the drill bit, the drilling operation, and the surrounding formation being penetrated by the drill bit. It is often difficult to supply electrical power to such electricity-consuming devices from above the drill bit because of the presence of the mechanical connection between the drill bit and the remaining portions of the drill string. Therefore, batteries are often used to power drill bit-mounted devices. As can be appreciated, the electrical energy provided by batteries is often limited due to their size and capacity.

DETAILED DESCRIPTION

The present disclosure is related to downhole power generation systems and, more particularly, to drill bit including devices that generate electrical power.

The embodiments described herein provide an electrical power generator that may be positioned within a cutter cone assembly of a roller cone drill bit. The electrical power generator may comprise a direct drive power generation system configured to generate electrical power as the roller cones of the roller cone drill bit rotate in operation. More particularly, the electrical power generator may include a magnetic flux multiplier assembly that, when properly assembled, may be operatively coupled to a roller cone such that rotation of the roller cone rotates a portion of the magnetic flux multiplier assembly and thereby generates electrical power for consumption. The electrical power generated by the electrical power generator may be conveyed to various electricity-consuming tools or devices within the roller cone drill bit or within a near-bit sub operatively coupled to the roller cone drill bit or any other device positioned above the drill bit where power can be transmitted to that device through a power cable. As opposed to conventional in-the-bit power generation systems, which commonly incorporate a gearing system in generating electrical power, the electrical power generator of the present disclosure uses a direct drive system that bypasses the need for a gearing system, while simultaneously increasing the power efficiency for the available volume of space within the cutter cone assembly. The electrical power generator described herein may be able to provide a greater amount of electrical power through a more efficient electromechanical coupling to a low speed energy source (e.g., the roller cone).

Referring toFIG. 1, illustrated is an exemplary drilling system100that may employ one or more principles of the present disclosure. Boreholes may be created by drilling into the earth102using the drilling system100. The drilling system100may be configured to drive a bottom hole assembly (BHA)104positioned or otherwise arranged at the bottom of a drill string106extended into the earth102from a derrick108arranged at the surface110. The derrick108includes a crane112used to lower and raise the drill string106. The drill string106is rotated by a drive key in the rotary table and a mating faceted kelly pipe diameter to the drive key on surface110. The kelly pipe is integral with the drill string106and when the kelly is rotated, it rotates the drill string106.

The BHA104may include a drill bit114operatively coupled to a tool string116which may be moved axially within a drilled wellbore118as attached to the drill string106. In some instances a mud motor (not shown) such as a positive displacement motor (PDM), a turbine motor (e.g., a turbodrill), or an electric motor can be used to provide the rotational power to the drill bit114in addition to or in place of rotation provided from surface110. During operation, the drill bit114penetrates the earth102and thereby creates the wellbore118. The BHA104provides directional control of the drill bit114as it advances into the earth102. The tool string116can be semi-permanently mounted with various measurement tools (not shown) such as, but not limited to, measurement-while-drilling (MWD) and logging-while-drilling (LWD) tools, that may be configured to take downhole measurements of drilling conditions and earth properties. In other embodiments, the measurement tools may be self-contained within the tool string116, as shown inFIG. 1.

Fluid or “mud” from a mud tank120may be pumped downhole using a mud pump122powered by an adjacent power source, such as a prime mover or motor124. The mud may be pumped from the mud tank120, through a stand pipe126, which feeds the mud into the drill string106and conveys the same to the drill bit114. The mud exits one or more nozzles arranged in the drill bit114and in the process cools the drill bit114. After exiting the drill bit114, the mud circulates back to the surface110via the annulus defined between the wellbore118and the drill string106, and in the process, returns drill cuttings and debris to the surface110. The cuttings and mud mixture are passed through a flow line128and are processed such that a cleaned mud is returned down hole through the stand pipe126once again.

The downhole motor (i.e., a mud motor, a turbine motor, an electric motor, etc.), if used, is generally positioned within the BHA104and often just above the drill bit114or a rotary steerable tool and, in some cases, at or near the top of the BHA104. It is often difficult to run power through such downhole motors from power systems positioned above since there is a rotational difference between the upper and lower end of the assembly, which thereby requires a form of jumping power across two rotationally different bodies. This makes the delivery of power to systems in or near the drill bit114, but below the downhole motor (if used), much more difficult and less reliable. Further, a power cable would need to be routed through bearings and other mechanisms in the downhole motor making it more costly and difficult. Therefore, a power source is needed that does not require a slip ring or inductor pair to jump power across two rotationally different members in the BHA104.

Although the drilling system100is shown and described with respect to a rotary drill system inFIG. 1, those skilled in the art will readily appreciate that many types of drilling systems can be employed in carrying out embodiments of the disclosure. For instance, drills and drill rigs used in embodiments of the disclosure may be used onshore (as depicted inFIG. 1) or offshore (not shown). Offshore oil rigs that may be used in accordance with embodiments of the disclosure include, for example, floaters, fixed platforms, gravity-based structures, drill ships, semi-submersible platforms, jack-up drilling rigs, tension-leg platforms, and the like. It will be appreciated that embodiments of the disclosure can be applied to rigs ranging anywhere from small in size and portable, to bulky and permanent.

Further, although described herein with respect to oil drilling, various embodiments of the disclosure may be used in many other applications. For example, disclosed methods can be used in drilling for mineral exploration, environmental investigation, natural gas extraction, underground installation, mining operations, water wells, geothermal wells, and the like. Further, embodiments of the disclosure may be used in weight-on-packers assemblies, in running liner hangers, in running completion strings, casing drilling strings, liner drilling strings, pipe in pipe drilling systems, coil tubing drilling systems, etc., without departing from the scope of the disclosure.

As will be appreciated by those skilled in the art, various types of drill bits may be used to form the wellbore118. Examples of such drill bits include roller cone bits, also commonly referred to as rotary cone bits. Referring toFIGS. 2A and 2B, with continued reference toFIG. 1, illustrated are views of an exemplary roller cone drill bit200that may be used in accordance with the principles of the present disclosure. More particularly,FIG. 2Adepicts a side view of the roller cone drill bit200(hereafter “the drill bit200”) andFIG. 2Bdepicts an exploded cross-sectional view of a portion of the drill bit200. The drill bit200may be the same as or similar to the drill bit114ofFIG. 1and, therefore, may be used to drill the wellbore118. As illustrated, the drill bit200may include a threaded pin connection202for use in attaching the drill bit200to a drill string204. The pin connection202and the corresponding threaded connections of the drill string204are designed to allow rotation of the drill bit200in response to rotation of the drill string204.

As the drill bit200operates, an annulus206is formed between the exterior of the drill string204and an inner wall208of the wellbore118. In addition to rotating the drill bit200, the drill string204may also be used as a conduit for communicating drilling fluids (not shown) from the well surface to the drill bit200at the bottom of the wellbore118. Such drilling fluids or “mud” may be ejected out of the drill bit200via various nozzles210provided in the drill bit200. Cuttings (not shown) formed by the drill bit200and any other debris at the bottom of the wellbore118will mix with the drilling fluid exiting the nozzles210and return to the well surface via the annulus206. Cutting or drilling action for the drill bit200occurs as one or more cutter cone assemblies212are rolled around the bottom of the wellbore118by rotation of the drill string204. The cutter cone assemblies212cooperate with each other to form the wellbore118in response to rotation of the drill bit200.

Each cutter cone assembly212may include cutting edges214with protruding inserts216configured to scrape and gouge against the sides and bottom of the wellbore118in response to the weight and rotation applied to the drill bit200from the drill string204. The position of the cutting edges214and the inserts216for each cutter cone assembly212may be varied to provide the desired downhole cutting action. As will be appreciated, other types of cutter cone assemblies212may alternatively be used in accordance with the scope of the present disclosure including, but not limited to, cutter cone assemblies having milled teeth instead of the inserts216.

The drill bit200may include a one-piece or unitary bit body218and one or more support arms220(typically three) that can be removably attached but are generally permanently welded to the bit body218. The threaded pin connection202may be used to connect the bit body218to the BHA104(FIG. 1) and may be a pin connection, as shown, or alternatively a female box connection. The bit body218may provide or otherwise define one or more pockets224(FIG. 2B) spaced radially from each other and configured to receive a corresponding one of the support arms220to be secured therein. As will be appreciated by those skilled in the art, there are many different kinds of configurations for securing the support arms220to the bit body218, without departing from the scope of the disclosure. Following a drilling operation, in some embodiments, the support arms220may be detached and otherwise removable from the bit body218to replace, rebuild or otherwise rehabilitate the drill bit200. In other embodiments, however, the drill bit200is scrapped or discarded and a new drill bit is used.

Referring specifically toFIG. 2B, illustrated is an exploded view showing the relationship between the bit body218and one of the support arms220with its associated cutter cone assembly212. Each support arm220may include a coupling222extending from the respective support arm220. Each cutter cone assembly212of the drill bit200is constructed and mounted on its associated coupling222in a substantially identical manner, and each support arm220is constructed and mounted in its associated pocket224in substantially the same manner. Accordingly, only one support arm220and cutter cone assembly212will be described herein since the same description applies generally to the other support arms220and their associated cutter cone assemblies212.

The cutter cone assembly212includes a roller cone226that, as illustrated, may exhibit a generally frustoconical shape. The roller cone226may provide or otherwise define a cavity228configured to receive the coupling222such that the roller cone226may be mounted on the coupling222. One or more bearing assemblies230may be positioned within the cavity228and otherwise configured to interpose the inner walls of the cavity228and an annular bearing surface232of the coupling222. As illustrated, the coupling222may be angled downwardly and inwardly with respect to the projected axis of rotation of the drill bit200. This orientation of the coupling222results in the roller cone226and the associated cutting edges214and inserts216engaging the side and bottom of the wellbore118during drilling operations.

A ball retaining assembly including one or more ball bearings234may be used to secure the cutter cone assembly212to the coupling222. More particularly, the roller cone226may be retained on the coupling222by inserting a plurality of ball bearings234through a ball passageway236defined through a portion of the support arm220and into a ball race238defined in the coupling222. A matching or opposing ball race (not labeled) may be provided on the interior of cutter cone assembly212. Once inserted, the ball bearings234, in cooperation with the ball races, will prevent disengagement of the roller cone226from the coupling222. The ball passageway236may subsequently be plugged by welding or other known techniques, such as by inserting a ball plug (not shown) in the ball passageway236.

A lubricant chamber240may be provided or otherwise defined within the support arm220and may be sealed with a diaphragm242. An opening244to the exterior of the drill bit200is defined in the support arm220and used to access and provide lubricant to the lubricant chamber240via the diaphragm242. A lubricant conduit246may extend from the lubricant chamber240to the ball passageway236to provide lubrication to the ball bearings234disposed within the ball race238.

As will be appreciated, the drill bit200and its foregoing description are merely provided for illustrative purposes in explaining the principles of the present disclosure. Indeed, those skilled in the art will readily recognize that other types and designs of roller cone drill bits and numerous structural variations and different configurations of drill bit200may be had, without departing from the scope of the disclosure. Accordingly, the foregoing description of the drill bit200should not be considered as limiting the scope of the present disclosure.

According to embodiments of the present disclosure, the drill bit200may further include an electrical power generator248positioned within the cutter cone assembly212and the coupling222. The electrical power generator248may comprise a direct drive power generation system configured to generate electrical power as the drill bit200operates in rotation. More particularly, the electrical power generator248may include a magnetic flux multiplier assembly250that may be secured within the coupling222. When the cutter cone assembly212is properly assembled, the magnetic flux multiplier assembly250may be operatively coupled to the roller cone226such that rotation of the roller cone226rotates a portion of the magnetic flux multiplier assembly250, such as a rotor shaft (not shown), and thereby generates electrical power for consumption. In some embodiments, the magnetic flux multiplier assembly250may be operatively coupled to the roller cone226by being directly coupled to an inner wall of the cavity228. In other embodiments, as illustrated, the magnetic flux multiplier assembly250may be operatively coupled to the roller cone226via a torque coupling252. As illustrated, the torque coupling252may include a stem that is secured to and extends from the back wall of the cavity228. The stem of the torque coupling252may be configured to matingly engage the end of the magnetic flux multiplier assembly250when the roller cone226is properly mounted on the coupling222. In at least one embodiment, the stem of the torque coupling252may be splined, but may equally be any other type of coupling that appropriately mates the magnetic flux multiplier assembly250with the roller cone226for rotation therewith.

As opposed to conventional in-the-bit power generation systems, which commonly incorporate a gearing system in generating electrical power, the electrical power generator248of the present disclosure uses a direct drive system that bypasses the need for a gearing system, while simultaneously increasing the power efficiency for the available volume of space within the cutter cone assembly212. As will be appreciated by those of skill in the art, the input shaft of the magnetic flux multiplier assembly250eliminates the need for an outside gear to speed up the rotor shaft, thus leaving more room for power generation capacity in the available volume. However, in some embodiments, a gearing system may alternatively be included to increase the power generator shaft speed, without departing from the scope of the disclosure. In general, however, using that same volume for just direct drive power conversion may be far more efficient than what space would be used to step up the generator shaft speed using a gearing system, since the torque density of the generator volume with a flux multiplier system will generally surpass any torque density gains offered by any known gearing system, including mechanical harmonic gearing and planetary gearing systems.

As will be described in more detail below, the magnetic flux multiplier assembly250uses concentric magnetic rings that create harmonic varying flux linkages to increase the overall rate of change of magnetic flux in the armature coil windings. Such systems have the potential to approach power factors of 0.9 or higher (90% efficiency of mechanical to electrical power conversion) at low input rotations per minute (RPMs) while capable of very high torque densities. The presently disclosed embodiments may be advantageous over prior art mechanical gearing power generators for a variety of reasons. For instance, the electrical power generator248, and its various embodiments described herein, may be able to generate twenty times (or higher) increased torque density over power generators that use planetary gearing. In addition, as described below, the magnetic flux multiplier assembly250comprises a harmonic flux multiplier that uses an interference ring partly made of highly magnetically permeable material, which increases the number of magnetic poles in the electrical power generator248by a high multiplier. Lastly, the electrical power generator248, and its various embodiments described herein, provide a greater amount of electrical power through a more efficient electromechanical coupling to a low speed energy source (e.g., the roller cones226).

Electric current generated by a magnetic field can be generalized by a variant of Maxwell's equation:

where V is the stator coil output voltage or electric potential (in volts); B is the magnetic flux density (in Teslas or Webbers/meter2); and t is time (in seconds). Essentially the voltage V generated is proportional to the rate of change of magnetic flux B in a winding verses time t.

Electrical power is described as:
Pe=V2·(Rloss+RL)  Equation (2)

where Peis electrical power (in Watts); Rlossis electrical resistance to/from a load, such as winding resistance (in Ohms); and RLis electrical load resistance (in Ohms).

Substituting terms provides the following:

Hence, the power produced is a function of the rate of change of magnetic flux density in the stator coils of the power generator. A 5× increase in rotor speed with a planetary gear, for instance, will result in a 5× increase in power output by the stator.

By being able to increase the torque density of a power generator, it is possible to increase the power coupled from rotation of the roller cone226to the electrical power generator248. Mechanical power, according to the presently described embodiments, may be described as follows:
Pm=ω·TEquation (4)

where ρtis torque density (in Newton meter/meter3); and Vol is the volume of generator space (in meters3) within the cutter cone assembly212. Hence, for a fixed volume of space in which the electrical power generator248is positioned, if the torque density is increased higher than a conventional mechanical gearing system, more electrical power may be extracted from the same volume of space.

Due to conservation of energy, the power conversion between mechanical and electrical systems can be described as follows:
Pe=PF·PmEquation (6)

where PF is the power factor or the power conversion efficiency (unitless). The power factor PF is an efficiency ratio that describes efficiency of the energy conversion. It represents the losses experienced in the system during the conversion, which is wattage that is generally dissipated as heat due to a number of inefficiencies in the power conversion process.

Re-organizing and combining Equations (5) and (6) renders the following general expression for the power output of any particular generator volume:

To facilitate a better understanding of the present disclosure, the following example is given, but in no way should the following example be read to limit, or to define, the scope of the disclosure. In this example, the torque density=30,000 Nm/m3; RPM=100; power factor=0.9; generator diameter=0.75 inches (0.01905 meters); generator radius=0.375 inches (0.009525 meters); and generator length=2.25 inches (0.05715 meters). The expected power output may be calculated as follows:

Conventional geared power generators exhibit a power factor and torque density that are lower than the embodiments described herein, thereby rendering the following:

Accordingly, the presently described embodiments may be able to generate several watts of power out of a generator that is able to fit in the support arm220of the cutter cone assembly212. The magnetic flux multiplier assembly250may comprise a magnetic pole multiplier, which translates into a higher flux coupling rate of change as between the permanent magnet rotor and the windings on the associated stator. As described below, the magnetic pole multiplier is achieved by adding an interference ring of ferrous material to the magnetic flux multiplier assembly250, which creates more fluctuations in the magnetic field per shaft rotation than would normally be achievable thus an overall higher rate of change of flux versus time.

The premise of the increase in power generation is primarily due to the increase in the torque density of the direct drive power generator. The generator requires a great deal more torque to rotate the shaft than a conventional generator, due to the increase in magnetic flux change per arc length of rotation. Since power is a function of torque multiplied by rotary speed, by increasing the input torque of the generator, one can increase the input mechanical power required to turn the shaft, which results in a higher output power in the form of electrical power.

Referring now toFIGS. 3A and 3B, with continued reference toFIGS. 2A and 2B, illustrated are side and enlarged cross-sectional views, respectively, of the electrical power generator248as positioned within the cutter cone assembly212ofFIG. 2B, according to one or more embodiments. More particularly, the cutter cone assembly212is depicted in an assembled configuration, where the roller cone226is mounted on the coupling222. Similar reference numerals fromFIGS. 2A-2Bthat are used inFIGS. 3A-3Brepresent like elements or components not described again in detail.

In the illustrated embodiment, a ball plug302is positioned within the ball passageway236and may be configured to help maintain the ball bearings234within the ball races238for operation. In some embodiments, the cutter cone assembly212may further include one or more seals304(two shown inFIG. 3A) positioned between an inner surface of the roller cone226and an outer surface of the coupling222. In at least one embodiment, the seals304may be elastomeric seals, such as O-rings or the like, and may be configured to prevent the migration of fluids and/or debris into the cavity228that receives the coupling222, which may otherwise contaminate the bearing surfaces of the cutter cone assembly212.

Referring toFIG. 3B, the magnetic flux multiplier assembly250may, in at least one embodiment, include a rotor shaft306that extends out one end to operatively couple the magnetic flux multiplier assembly250to the roller cone226such that rotation of the roller cone226generates electricity in the magnetic flux multiplier assembly250. In the illustrated embodiment, the rotor shaft306may have a head308that may be operatively coupled to the roller cone226via the torque coupling252. As mentioned above, in at least one embodiment, the torque coupling252may comprise a stem309that is secured to and otherwise extends from a base311provided in the cavity228of the roller cone226. In some embodiments, the stem309may be a flexible shaft configured to matingly engage the rotor shaft306at the head308. In at least one embodiment, the stem309may be splined and the head308may define an opening310configured to receive the stem309. In such embodiments, the opening310may include a corresponding splined engagement surface to receive the stem309as extended from the base311. As the roller cone226rotates, the stem309correspondingly rotates and urges the rotor shaft306to rotate via the mated engagement within the head308.

In other embodiments, as mentioned above, the rotor shaft306may alternatively be operatively coupled directly to the roller cone226in a variety of configurations, such as being inserted into a corresponding receiver opening or the like defined in the base311of the roller cone226. Such a receiver opening may be configured to receive a portion of the rotor shaft306to engage the rotor shaft306to the roller cone226. In any case, operatively coupling the rotor shaft306to the roller cone226provides for a direct drive from the rotation of the roller cone226into the magnetic flux multiplier assembly250, such that rotation of the roller cone226correspondingly rotates the rotor shaft306and thereby bypasses the need for a gear assembly. In other embodiments, however, a gear assembly, such as a planetary gearing system, may interpose the roller cone226and the magnetic flux multiplier assembly250, without departing from the scope of the disclosure.

In some embodiments, the electrical power generator248may include one or more radial bearings312configured to stabilize rotation of the rotor shaft306. Moreover, in some embodiments, the electrical power generator248may also include one or more thrust bearings314to reduce the thrust loads assumed by the magnetic flux multiplier assembly250during operation.

The electrical power generator248may also include one or more electrical conductors316(one shown) that extend from the magnetic flux multiplier assembly250to provide power to electricity-consuming devices positioned in the drill bit200(FIGS. 2A-2B) or, as described below, in a near-bit sub. As will be described below, as the magnetic flux multiplier assembly250operates, electrical power is generated and conveyed by the electrical conductor316to various sensors and other electricity-consuming devices for consumption. In some embodiments, one or more of the electricity-consuming devices318may be arranged or otherwise positioned within the cutter cone assembly212itself, such as within the coupling222or the roller cone226. The electricity-consuming device(s)318in the cutter cone assembly212may be a variety of sensors such as, but not limited to, a temperature sensor, a pressure sensor, a gamma ray sensor, a resistivity sensor, a mud viscosity sensor, a seismic sensor, a strain sensor, an RPM sensor, a formation sensor, and any combination thereof.

Referring now toFIG. 4, with continued reference to the prior figures, illustrated is a partial cut-away view of the electrical power generator248ofFIGS. 3A-3B, according one or more embodiments. As illustrated, the electrical power generator248includes the magnetic flux multiplier assembly250, which provides an elongate stator body402having a first or input end404aand a second or output end404b. The rotor shaft306is depicted as extending between the first and second ends404a,b, and the head308extends out of the first end404aa short distance. The opening310in the head308is depicted as providing a splined engagement that may be configured to receive the stem309ofFIG. 3B, for example.

At the second end404b, the magnetic flux multiplier assembly250may include an end cap406, a journal arm connector408, a centralizer bearing410, a retaining nut412, and a bushing414. The end cap406may be configured to secure the journal arm connector408to the stator body402with one or more mechanical fasteners416. In other embodiments, the end cap406may alternatively be secured to the stator body402using other attachment means including, but not limited to, welding, brazing, adhesives, shrink fitting, and any combination thereof. The journal arm connector408may be secured within the end cap406and may provide axial support to the rotor shaft306in conjunction with the centralizer bearing410. As illustrated, the centralizer bearing410may be a ball bearing or the like, and may be configured to allow the rotor shaft306to rotate about a central axis418during rotation. The centralizer bearing410may also serve as a thrust bearing from the rotor shaft306. The retaining nut412may be configured to help axially retain the rotor shaft306within the stator body402, and the bushing414may help mitigate radial and thrust loads assumed within the magnetic flux multiplier assembly250.

At the first end404a, the magnetic flux multiplier assembly250may include a retaining ring420configured to secure the components of the magnetic flux multiplier assembly250within the stator body402. In some embodiments, as illustrated, the stator body402may have one or more anti-rotation keys422defined longitudinally along the outer surface of the stator body402. The anti-rotation key(s)422may be configured to mate with complimentary slots (not shown) defined in the coupling222(FIG. 3B) to prevent the stator body402from rotating during operation.

Referring now toFIGS. 5A and 5B, with continued reference toFIG. 4, illustrated are partial cut-away views of the first and second ends404a,bof the magnetic flux multiplier assembly250, respectively. Similar reference numerals fromFIGS. 2A-2B,FIGS. 3A-3B, andFIG. 4that are used inFIGS. 5A-5Brepresent like elements or components not described again in detail.

InFIG. 5A, the first end404aof the stator body402is shown, with the rotor shaft306(FIGS. 3B and 4) omitted for ease of viewing the internal components of the magnetic flux multiplier assembly250. As illustrated, the magnetic flux multiplier assembly250may include a first or inner magnetic ring502, a second or outer magnetic ring504, and an interference ring506that interposes the inner and outer magnetic rings502,504. The inner and outer magnetic rings502,504and the interference ring506each form concentric, cylindrical rings that extend longitudinally between the first and second ends404a,bof the stator body402.

In the illustrated embodiment, the inner magnetic ring502may comprise a plurality of magnets508athat are attached to the rotor shaft306(FIGS. 3B and 4) such that rotation of the rotor shaft306results in rotation of the magnets508aof the inner magnetic ring502relative to the outer magnetic ring504. In some embodiments, the magnets508aof the inner magnetic ring502may be mechanically fastened to the rotor shaft306, such as being screwed or bolted onto the outer radial surface of the rotor shaft306. In other embodiments, the magnets508aof the inner magnetic ring502may be secured to the rotor shaft306with an adhesive. In at least one embodiment, the rotor shaft306may define or otherwise provide corresponding pockets or recesses (not shown) configured to receive the magnets508aof the inner magnetic ring502.

The outer magnetic ring504may also comprise a plurality of magnets508b. In the illustrated embodiment, the outer magnetic ring504may be secured to the inner surface of the stator body402and, therefore, may be prevented from rotation. In other embodiments, however, the outer magnetic ring504may rotate with respect to the inner magnetic ring502, as described in more detail below.

The magnets508a,bmay be any type of permanent magnet. Suitable magnets508a,bthat may be used include, but are not limited to, neodymium iron boron (NdFeB) magnets, bonded NdFeB magnets, samarium cobalt magnets, alnico magnets, ceramic (hard ferrite) magnets, and any combination thereof. The type of magnet508a,bemployed may depend on temperature conditions where the magnetic flux multiplier assembly250may be used. For instance, samarium cobalt magnets may be used in most applications, but for lower temperature applications, NdFeB magnets or bonded NdFeB magnets may be used and may result in an increase in generator performance.

The arrows depicted on each magnet508a,bindicate the magnetic dipole direction, which is usually in the direction of the North pole of the given magnet508a,b. While the magnets508a,bof each of the inner and outer rings502,504are depicted as engaging angularly adjacent magnets508a,bon either side, in some embodiments, a small gap (not shown) may be defined between angularly adjacent magnets508a,b. Such a gap may encourage more flux leakage along the dipole axis of the given magnet508a,b.

In the illustrated embodiment, the interference ring506may float between the inner and outer magnetic rings502,504and may include a plurality of alternating ferromagnetic pole pieces510and spacers512. The ferromagnetic pole pieces510may be made of a ferromagnetic material such as, but not limited to, a nickel-iron magnetic alloy (e.g., permalloy) or iron. Ideally, the material may exhibit the highest magnetic relative permeability possible while still retaining the mechanical strength required for the interference ring506. When using iron, for example, the best kind of iron would be fully annealed iron or soft iron as which is often used in the making of transformer cores. Permalloy presents some of the highest relative magnetic permeability ranging up to 20,000-50,000 while very soft (annealed) pure iron of 99.95% can range up to 200,000. Further, stacks of Metglas, which is an amorphous metal alloy ribbon that exhibits a relative permeability of over 1,000,000, could also conceivably be used. However, the most practical material to work with is strips of annealed iron given the need to carry mechanical loadings from the reactions to the magnetic attraction and repulsion forces present in the generator assembly. The permeability of the ferromagnetic pole pieces510may be in the range of about 3,000 for iron alloys having the mechanical strength properties required, and much higher for nickel-iron magnetic alloys.

The spacers512may be made of or comprise a variety of materials that are non-conductive and/or non-magnetic. Suitable materials for the spacers512include, but are not limited to, a polymer (e.g., polyether ether ketone (PEEK)), tin, copper, brass, beryllium-copper alloys, titanium, aluminum, monel, austenitic stainless steel (e.g., NITRONIC® 50 or 60), a cobalt-nickel alloy (e.g., AERMET®), a carbon composite material or other composite, and any combination thereof. Further, the spacers512can serve as a partial or continuous carrier for the ferromagnetic pole pieces510by providing mounting and support for the ferromagnetic pole pieces510. In some embodiments, the spacers512may comprise empty spaces that interpose angularly adjacent ferromagnetic pole pieces510about the circumference of the interference ring506.

The plurality of alternating ferromagnetic pole pieces510and spacers512may be held together mechanically or chemically. In some embodiments, for instance, angularly adjacent ferromagnetic pole pieces510and spacers512may be secured together with complimentary butterfly or dovetail slots. In other embodiments, the interference ring506may be encased in a magnetically-permeable and non-magnetic carrier or casing, such as a polymer (e.g., PEEK) casing molded about the interference ring506. In other embodiments, a polymer (e.g., PEEK) may be injection molded around the ferromagnetic pole pieces510and, therefore, the polymer may comprise the spacers512. In yet another embodiment, the non-magnetic portion of the interference ring506may be shaped with a continuous or semi-continuous diameter to act as a support or tray for the ferromagnetic pole pieces510.

The magnetic flux multiplier assembly250may further include a plurality of coil windings514disposed within the stator body402, also referred to herein as an “armature.” In the illustrated embodiment, the magnets508bof the outer magnetic ring504may be communicably coupled to the coil windings514for electrical power generation. In some embodiments, as illustrated, there may be six coil windings514positioned on the armature (the stator body402) and configured for three-phase power. As will be appreciated, however, the design of the magnetic flux multiplier assembly250may be altered to produce two-phase power or four-phase power, without departing from the scope of the disclosure.

In exemplary operation of the magnetic flux multiplier assembly250, as the rotor shaft306(FIGS. 3B and 4) rotates, the magnets508aof the inner magnetic ring502correspondingly rotate relative to the outer magnetic ring504. The ferromagnetic pole pieces510may be configured to modulate the magnetic fields exhibited by the inner and outer magnetic rings502,504. Interaction of the magnetic fields of the inner and outer magnetic rings502,504induces electrical power (current) in the coil windings514, which, as discussed below, can be captured and used to power one or more electricity-consuming devices. In a preferred embodiment, the interference ring506may float freely between the inner and outer magnetic rings502,504. The magnetic forces generally keep the interference ring506centralized and thereby allow it to rotate within a magnetic bearing structure created by the repulsion and attraction of the various magnetic dipoles created within the ferromagnetic material.

In the illustrated embodiment, the inner magnetic ring502includes four magnets508aor two pole-pairs arranged to produce a spatially varying magnetic field. Moreover, the outer magnetic ring504includes forty-four magnets508bor twenty-two pole-pairs arranged to also produce a spatially varying magnetic field. It will be appreciated, however, that the number of magnets508a,b, ferromagnetic pole pieces510, and coil windings514may vary depending on the application and depending on various optimizations intended to enhance operation of the magnetic flux multiplier assembly250.

InFIG. 5B, the rotor shaft306, the inner and outer magnetic rings502,504and the interference ring506are each depicted as extending toward the second end404bof the stator body402where the end cap406is secured. The centralizer bearing410is depicted as interposing the axial end of the rotor shaft306and the journal arm connector408.

In some embodiments, the magnetic flux multiplier assembly250may further include a rectifier board516arranged at or near the second end404bof the stator body402. Each coil winding514(one shown) may loop around at the second end404bto complete the coil loop, and the ends518of each coil winding514may be connected to the rectifier board516, which converts the alternating current (AC) derived from operation of the magnetic flux multiplier assembly250to direct current (DC). The rectifier board516may be a standard bridge rectifier set up for three-phase power, and may convert the AC into a rectified positive voltage line520aand a negative voltage line520b. As illustrated, the positive and negative voltage lines520a,bmay run to corresponding plunger connector rings522, which allow electrical communication into the journal arm connector408.

While this embodiment is optional, it may prove advantageous in permitting only the need for a minimum of one voltage line520a,bto lead from the magnetic flux multiplier assembly250and the other voltage line520a,bcould be grounded to the stator body402. Ideally, though, it is better to run both voltage lines520a,bback to the power conditioning system elsewhere in the system. Accordingly, two voltage lines520a,bare shown. If the windings were not rectified, then at least one wire from each winding would have to be run to the power conditioning system elsewhere in the drill bit. The additional power conditioning circuitry can consist of smoothing capacitors, step up or down voltage transformers, switch power supply circuits and other semiconductors used to condition the power, voltage and current into a desirable format. To maximize power generation, the rectifiers could be dropped entirely from the generator section and one could ground to the stator body402one end518of each armature coil winding514, thus using the bit body218(FIG. 2A-2B) as a ground, assuming the stator body402is in electrical contact with the bit body218, and run the other end518of the armature coil winding514wire to the power conditioning circuits elsewhere in the system. This would maximize the available volume in the cone area solely for power generation capacity only. In all cases, current carrying cables, such as the voltage lines520a,b, may have a dielectric insulator around them to prevent electrical shorting to other electrically conductive paths in the magnetic flux multiplier assembly250, the drill bit200(FIGS. 2A-2B), or other conductor cables or wires.

The electrical conductor316or “power cable” may extend from the journal arm connector408to, for example, a power controller board (not shown) or the like elsewhere in the drill bit200(FIGS. 2A-2B). In other embodiments, as described below, the electrical conductor316may extend to a near-bit sub that may be connected to the drill bit200. At the power controller board, the voltage provided by the electrical conductor316may be smoothed through the use of one or more capacitors (not shown) to make it more usable for electronic circuits and, more particularly, for downhole electricity-consuming devices. The capacitors used to condition the voltage may be, for example, tantalum capacitors, which may not be able to withstand high-pressure environments. The rectifiers of the rectifier board516, however, may be able to withstand high-pressure environments and, therefore, may be placed in a non-pressurized cavity, such as is shown inFIG. 5B. In at least some embodiments, the magnetic flux multiplier assembly250may be immersed in a dielectric fluid, such as the lubrication oil provided from the lubricant chamber240(FIG. 2B). In other embodiments, however, the magnetic flux multiplier assembly250may be sealed and otherwise isolated from mixing with the lubrication oil, which may result in improving reliability and longevity of the magnetic flux multiplier assembly250by keeping debris from wearing wear out the generator. In such an embodiment, a rotary seal or magnetic coupling (not shown) on the input shaft would be required to isolate the two areas within the cone while permitting the transference of rotational energy from the cone into the magnetic flux multiplier assembly250.

Referring now toFIGS. 6A-6C, illustrated are cross-sectional end views of the magnetic flux multiplier assembly250, according to at least three embodiments. More particularly,FIGS. 6A-6Cdepict end views of different configurations of the magnetic flux multiplier assembly250as looking at the first end404aof the stator body402(FIGS. 4 and 5A). As will be appreciated, the configurations of the internal components of the magnetic flux multiplier assembly250may vary depending on the application. Indeed, the concentric position and location of the first and second magnetic rings502,504and the interference ring506may vary, and the position of the coil windings514may also vary, without departing from the scope of the disclosure.

InFIG. 6A, a first exemplary configuration of the magnetic flux multiplier assembly250is depicted. The first configuration is similar to or the same as the configuration shown and described above with reference toFIG. 5A. As illustrated, the first magnetic ring502and associated magnets508aare mounted to or otherwise form part of the rotor shaft306, and the second magnetic ring504and associated magnets508bare secured to the inner wall of the stator body402. The interference ring506, including its associated ferromagnetic pole pieces510and spacers512, interposes the first and second magnetic rings502,504. In the illustrated embodiment, the spacers512comprise corresponding empty spaces between angularly adjacent ferromagnetic pole pieces510. Moreover, the coil windings514are arranged within corresponding armatures positioned within the stator body402. The crosses and points depicted with respect to the coil windings514illustrate the polarity of the coils.

In exemplary operation, the rotor shaft306and the first magnetic ring502rotate relative to the second magnetic ring504, and the interference ring506floats between the first and second magnetic rings502,504to modulate the corresponding magnetic fields. Electrical power (current) is generated in the coil windings514as the magnetic fields of the inner and outer magnetic rings502,504interact. In the illustrated embodiment, the rotor shaft306may be directly driven from rotation of the roller cone226(FIGS. 2B and 3A-3B). As a result, no mechanical gearing is required since the magnetic flux multiplier assembly250is able to modulate the flux through the coil windings514at a higher rate that is usually a harmonic of the input speed.

InFIG. 6B, a second exemplary configuration of the magnetic flux multiplier assembly250is depicted. Similar to the first configuration, the first magnetic ring502and associated magnets508aare mounted to or otherwise form part of the rotor shaft306in the second configuration. Unlike the first configuration, however, the second magnetic ring504and associated magnets508bmay be secured to a rotatable substrate602, which, in some embodiments, may be the inner wall of the stator body402. Moreover, the interference ring506, including its associated ferromagnetic pole pieces510and spacers512, interposes the first and second magnetic rings502,504but may be a stationary member within the magnetic flux multiplier assembly250. In the illustrated embodiment, the coil windings514are looped around the angularly adjacent ferromagnetic pole pieces510.

InFIG. 6C, a third exemplary configuration of the magnetic flux multiplier assembly250is depicted. In the third configuration, a central armature or stator604is provided and affords a location to position the coil windings514. The first magnetic ring502and associated magnets508aare mounted to the stator604and, as a result, do not move during operation. Similar to the second configuration, the second magnetic ring504and associated magnets508bmay be secured to the rotatable substrate602, which, in some embodiments, may be the inner wall of the stator body402. Moreover, the interference ring506, including its associated ferromagnetic pole pieces510and spacers512, interposes the first and second magnetic rings502,504but may float to modulate the corresponding magnetic fields within the magnetic flux multiplier assembly250.

Referring now toFIGS. 7 and 8, illustrated are exploded cross-sectional views of the portion of the drill bit200ofFIG. 2B, according to at least two embodiments. More particularly,FIGS. 7 and 8depict exemplary embodiments where the electrical power generator248positioned within the cutter cone assembly212is able to provide electrical power to various electricity-consuming devices. Similar reference numerals fromFIG. 2Bthat are used inFIGS. 7 and 8represent like elements or components that will not be described again.

In each ofFIGS. 7 and 8, the electrical conductor316extending from the magnetic flux multiplier assembly250may extend to a sealable connector702positioned on the support arm220. In some embodiments, as illustrated, the electrical conductor316may extend to the sealable connector702via the pressure compensator system of the drill bit200, which may include the lubricant chamber240, the lubricant conduit246, and the ball passageway236. Accordingly, the electrical conductor316may extend to the sealable connector702by extending through each of the lubricant chamber240, the lubricant conduit246, and the ball passageway236. In other embodiments, however, a conduit (not shown) may be drilled or otherwise formed within the support arm220that extends directly to the sealable connector702, without departing from the scope of the disclosure.

The sealable connector702may be a male connector configured to mate with a corresponding female connector704positioned or otherwise arranged within the pocket224on the bit body218. Upon attaching the support arm220to the bit body218at the associated pocket224, the sealable connector702and the female connector704may matingly engage to provide an electrical connection therebetween. Communicably coupling the sealable connector702and the female connector704may effectively extend the electrical conductor316into the bit body218and, more particularly, into a conduit706defined in the bit body218that extends to a drilling fluid cavity708formed in the bit body218.

InFIG. 7, the electrical conductor316may extend and provide electrical power to an electronics unit710arranged or otherwise positioned within the drilling fluid cavity708. The electronics unit710may include one or more electricity-consuming devices configured to consume the electrical power provided by the electrical power generator248via the electrical conductor316. In some embodiments, for instance, the electronics unit710may include power-conditioning circuitry, such as one or more capacitors712and/or one or more rectifiers714. The electronics unit710may further include one or more power storage devices716, such as a battery or the like, that may be charged by the electrical power provided by the electrical conductor316. In other embodiments, the power storage devices716may be used for powering the electricity-consuming devices in the electronics unit710when the magnetic flux multiplier assembly250is not producing power, such as is the case when the drill bit200is off of the bottom of the hole during trips. However, in some embodiments, the magnetic flux multiplier assembly250may be able to provide power simultaneously to both the electronics unit710and the power storage devices716. This stored energy can then be used when the magnetic flux multiplier assembly250is not able to produce electrical power when the drill bit200is off bottom. Further, electrical power can be transmitted from the drill bit200to any other point in the drill string over a power transmission cable or electrical conductive path, such as an electric cable, electric connectors, an inductive coupling, or any combination thereof, to power other devices in the drill string, such as a rotary steerable tool, an MWD tool or an LWD tool.

In one or more embodiments, the electronics unit710may also include a sensor controller718and one or more sensors720communicably coupled to and otherwise controlled by the sensor controller718. Suitable sensors720may include, but are not limited to, a temperature sensor, a pressure sensor, a gamma ray sensor, a resistivity sensor, a mud viscosity sensor, a seismic sensor, a strain sensor, an RPM sensor, a drilling force sensor (e.g., a rotary speed sensor), a rotary position sensor, a rotary acceleration sensor, a rotary jerk sensor (i.e., a rate of change of acceleration), an axial load sensor, a cross-axis load sensor, a torque sensor, a bend sensor, a bend direction sensor, a formation sensor, and any combination thereof.

In yet other embodiments, the electronics unit710may also include a telemetry module722. The telemetry module722may be communicably coupled to the sensors720and/or the sensor controller718and may be configured to transmit data obtained by the sensors720to a BHA telemetry module (not shown) positioned uphole from the drill bit200. In other embodiments, the telemetry module722may be configured to transmit the data directly to a surface location for consideration. The telemetry module722may be any downhole telemetering device known to those skilled in the art including, but not limited to, mud pulse telemetry, electromagnetic telemetry, acoustic telemetry, ultrasonic telemetry, electrical lines, fiber optic lines, radio frequency transmission, or any combination thereof. The electronics unit710may further include a toroid724. The toroid724may be configured to create an electrical dipole voltage across at least a portion of the drill string to generate electrical current used for electromagnetic telemetry. In this instance one could use the toroid724to bi-directionally communicate with a long haul telemetry system elsewhere in the BHA104(FIG. 1), thereby reducing the amount of space required near the bit that would be required to support a long haul telemetry system that communicates with the surface.

InFIG. 8, the drill bit200may have a near-bit sub802coupled thereto and otherwise attached at the threaded pin connection202. The electrical conductor316inFIG. 8may extend from the conduit706to a center-supported rotary connector804positioned within the drilling fluid cavity708at or near the top of the drill bit200. In some embodiments, the rotary connector804may comprise a female fitting configured to receive a male circular plunger connector806that is operatively coupled to an electronics unit808arranged or otherwise positioned within the near-bit sub802. Communicably coupling the rotary connector804and the circular plunger connector806may effectively extend the electrical conductor316into the near-bit sub802and, more particularly, to the electronics unit808to provide electrical power thereto.

Similar to the electronics unit710ofFIG. 7, the electronics unit808may include one or more electricity-consuming devices configured to consume the electrical power provided by the electrical power generator248via the electrical conductor316. More particularly, for instance, the electronics unit808may include power-conditioning circuitry810, such as one or more capacitors and/or one or more rectifiers. The electronics unit808may further include one or more power storage devices812, such as a battery or the like, that may be charged by the electrical power provided by the electrical conductor316. In one or more embodiments, the electronics unit808may also include a sensor controller814and one or more sensors816that may be controlled by the sensor controller814. Suitable sensors816are the same as the sensors720mentioned above. In yet other embodiments, the electronics unit808may also include and power a telemetry module818similar to the telemetry module722ofFIG. 7. Lastly, the electronics unit808may further include a toroid818.

It will be appreciated that, while the magnetic flux multiplier assembly250is shown associated with only one roller cone226on the drill bit200, other embodiments are contemplated where the magnetic flux multiplier assembly250may be associated with some or all of the roller cones226. In such an embodiment, a centralized power conditioning system may be able to condition the power from the power feed from all power generating roller cones226in the drill bit200.

Moreover, it will be appreciated that the magnetic flux multiplier assembly250may be retrievable and otherwise reusable in multiple types or configurations of drill bits, such as a drill bit other than the drill bit200. More particularly, when the drill bit200has reached its usable lifespan, the drill bit200may be retrieved to a surface location, and the roller cone226may be disassembled to access the magnetic flux multiplier assembly250. The magnetic flux multiplier assembly250may then be removed from the drill bit200, refurbished in any manner necessary as needed and potentially used in another drill bit, while the drill bit200is discarded or otherwise scrapped. Furthermore, the electronics units710,808ofFIGS. 7 and 8, respectively, and their various electricity-consuming devices, may also be removable, refurbishable and reusable in other drilling tool applications. In some embodiments, the electricity-consuming devices in the electronics units710,808may be removable and otherwise able to be extracted for servicing, rehabilitation, or replacement.

A. A drill bit that includes a bit body defining at least one pocket, a support arm attachable to the bit body at the at least one pocket and including a coupling that extends from the support arm, a roller cone defining a cavity for receiving the coupling to rotatably mount the roller cone on the coupling, and a direct drive electrical power generator positioned within the coupling and operatively coupled to the roller cone such that rotation of the roller cone correspondingly rotates a portion of the direct drive electrical power generator to generate electrical power.

B. A method that includes introducing a drill string into a wellbore, the drill string having a drill bit positioned at a distal end thereof and the drill bit including a bit body defining at least one pocket, a support arm attachable to the bit body at the at least one pocket and including a coupling that extends from the support arm, the drill bit further including a roller cone that defines a cavity for receiving the coupling to rotatably mount the roller cone on the coupling, rotating the drill string within the wellbore and thereby rotating the roller cone on the coupling, rotating a portion of a direct drive electrical power generator positioned within the coupling as the roller cone rotates, the portion of the direct drive electrical power generator being operatively coupled to the roller cone, and generating electrical power with the direct drive electrical power generator as the portion of the direct drive electrical power generator rotates.

C. A rotary cone drill bit that includes a bit body defining at least one pocket, a cutter cone assembly attachable to the bit body at the at least one pocket and including a roller cone, and a magnetic flux multiplier assembly positioned within the cutter cone assembly and operatively coupled to a roller cone such that rotation of the roller cone correspondingly rotates a rotor shaft of the magnetic flux multiplier assembly to generate electrical power, wherein the magnetic flux multiplier assembly includes a first magnetic ring, a second magnetic ring, an interference ring that interposes the first and second magnetic rings, and a plurality of coil windings communicably coupled to one of the first and second magnetic rings, and wherein the first and second magnetic rings and the interference ring are concentrically-located and, of the first and second magnetic rings and the interference ring, one is a rotating member operatively coupled to the roller cone for rotation therewith, one is a floating member, and one is a stationary member.

Each of embodiments A, B, and C may have one or more of the following additional elements in any combination: Element 1: wherein the direct drive electrical power generator is directly coupled to an inner wall of the cavity when the roller cone is mounted on the coupling. Element 2: further comprising a stem extending from a wall of the cavity, wherein the stem is engageable with a rotor shaft of the direct drive electrical power generator. Element 3: wherein an electrical conductor extends from the direct drive electrical power generator to convey the electrical power to one or more electricity-consuming devices. Element 4: wherein the one or more electricity-consuming devices are selected from the group consisting of a sensor controller, a temperature sensor, a pressure sensor, a gamma ray sensor, a resistivity sensor, a mud viscosity sensor, a seismic sensor, a strain sensor, an RPM sensor, a formation sensor, an electronics unit, a capacitor, a rectifier, a power storage device, a battery, a rechargeable battery, a telemetry module, and a toroid. Element 5: wherein the one or more electricity-consuming devices are positioned within at least one of the coupling, the support arm, and the roller cone. Element 6: wherein the one or more electricity-consuming devices are positioned within a drilling fluid cavity defined within the bit body. Element 7: further comprising a lubricant chamber defined within the support arm, a lubricant conduit in fluid communication with the lubricant chamber and defined in the support arm, and a ball passageway in fluid communication with the lubricant conduit and defined in the coupling, wherein the electrical conductor extends through at least the ball passageway, the lubricant conduit, and the lubricant chamber to reach the drilling fluid cavity. Element 8: wherein the one or more electricity-consuming devices are positioned within a near-bit sub coupled to the bit body at a threaded pin connection. Element 9: wherein the direct drive electrical power generator is a magnetic flux multiplier assembly comprising a first magnetic ring having a first plurality of magnets, a second magnetic ring having a second plurality of magnets, wherein a number of the first plurality of magnets is different than a number of the second plurality of magnets, an interference ring that interposes the first and second magnetic rings and includes a plurality of ferromagnetic pole pieces alternating with a plurality of spacers, the interference ring being configured to modulate magnetic fields exhibited by the first and second magnetic rings, and a plurality of coil windings communicably coupled to one of the first and second magnetic rings and operable to conduct electrical power through interaction of the magnetic fields of the first and second magnetic rings, wherein the first and second magnetic rings and the interference ring are concentrically-located, and wherein, of the first and second magnetic rings and the interference ring, one is a rotating member, one is a floating member, and one is a stationary member, and wherein the rotating member is operatively coupled to the roller cone for rotation therewith. Element 10: wherein the first and second pluralities of magnets are permanent magnets selected from the group consisting of a neodymium iron boron magnet, a bonded neodymium iron boron magnet, a samarium cobalt magnet, an alnico magnet, a ceramic (hard ferrite) magnet, and any combination thereof. Element 11: wherein the first magnetic ring is the rotating member and is coupled to a rotor shaft, the second magnetic ring is the stationary member and is coupled to a stator body, and the interference ring is the floating member. Element 12: wherein the first magnetic ring is the rotating member and coupled to a rotor shaft, the second magnetic ring is the floating member and coupled to a rotatable substrate, and the interference ring is the stationary member. Element 13: wherein the first magnetic ring is the stationary member and coupled to a stator that houses the plurality of coil windings, the second magnetic ring is the rotating member and is coupled to a rotatable substrate, and the interference ring is the floating member.

Element 14: wherein the portion of the direct drive electrical power generator comprises a rotor shaft, and wherein rotating the portion of the direct drive electrical power generator comprises rotating the rotor shaft as engaged with a stem extending from a wall of the cavity. Element 15: further comprising conveying the electrical power to one or more electricity-consuming devices with an electrical conductor that extends from the direct drive electrical power generator, wherein the one or more electricity-consuming devices are selected from the group consisting of a sensor controller, a temperature sensor, a pressure sensor, a gamma ray sensor, a resistivity sensor, a mud viscosity sensor, a seismic sensor, a strain sensor, an RPM sensor, a formation sensor, an electronics unit, a capacitor, a rectifier, a power storage device, a telemetry module, a battery, a rechargeable battery, and a toroid. Element 16: wherein conveying the electrical power to the one or more electricity-consuming devices comprises conveying the electrical power to the one or more electricity-consuming devices as positioned within at least one of the coupling, the support arm, and the roller cone. Element 17: wherein conveying the electrical power to the one or more electricity-consuming devices comprises conveying the electrical power to the one or more electricity-consuming devices as positioned within a drilling fluid cavity defined within the bit body. Element 18: wherein the drill bit further includes a lubricant chamber defined within the support arm, a lubricant conduit in fluid communication with the lubricant chamber and defined in the support arm, and a ball passageway in fluid communication with the lubricant conduit and defined in the coupling, the method further comprising extending the electrical conductor through at least the ball passageway, the lubricant conduit, and the lubricant chamber to reach the drilling fluid cavity. Element 19: wherein conveying the electrical power to the one or more electricity-consuming devices comprises conveying the electrical power to the one or more electricity-consuming devices as positioned within a near-bit sub coupled to the bit body at a threaded pin connection. Element 20: further comprising retrieving the drill bit to a surface location, and accessing the one or more electricity-consuming devices for at least one of servicing, rehabilitation, and replacement of the one or more electricity-consuming devices. Element 21: further comprising retrieving the drill bit to a surface location, disassembling the roller cone to access the direct drive electrical power generator, and removing the direct drive electrical power generator from the roller cone; and installing the direct drive electrical power generator in a secondary drill bit for use.

Element 22: wherein the first magnetic ring has a first plurality of magnets and the second magnetic ring has a second plurality of magnets, and wherein a number of the first plurality of magnets is different than a number of the second plurality of magnets. Element 23: wherein the interference ring includes a plurality of ferromagnetic pole pieces alternating with a plurality of spacers, the interference ring being configured to modulate magnetic fields exhibited by the first and second magnetic rings. Element 24: wherein the first magnetic ring is the rotating member and is coupled to the rotor shaft, the second magnetic ring is the stationary member and is coupled to a stator body, and the interference ring is the floating member. Element 25: wherein the rotor shaft is directly coupled to an inner wall of the cavity when the roller cone is mounted on the coupling. Element 26: further comprising a stem extending from a wall of the cavity, wherein the stem is engageable with the rotor shaft. Element 27: wherein an electrical conductor extends from the magnetic flux multiplier assembly to convey the electrical power to one or more electricity-consuming devices. Element 28: wherein the one or more electricity-consuming devices are selected from the group consisting of a sensor controller, a temperature sensor, a pressure sensor, a gamma ray sensor, a resistivity sensor, a mud viscosity sensor, a seismic sensor, a strain sensor, an RPM sensor, a formation sensor, an electronics unit, a capacitor, a rectifier, a power storage device, a telemetry module, a battery, a rechargeable battery, and a toroid. Element 29: wherein the one or more electricity-consuming devices are positioned within the cutter cone assembly. Element 30: wherein the one or more electricity-consuming devices are positioned within a drilling fluid cavity defined within the bit body. Element 31: wherein the one or more electricity-consuming devices are positioned within a near-bit sub coupled to the bit body at a threaded pin connection.

By way of non-limiting example, exemplary combinations applicable to A, B, and C include: Element 3 with Element 4; Element 3 with Element 5; Element 3 with Element 6; Element 6 with Element 7; Element 3 with Element 8; Element 9 with Element 10; Element 9 with Element 11; Element 9 with Element 12; Element 9 with Element 13; Element 15 with Element 16; Element 15 with Element 17; Element 17 with Element 18; Element 15 with Element 19; Element 15 with Element 20; Element 27 with Element 28; Element 27 with Element 29; Element 27 with Element 30; and Element 27 with Element 31.

The use of directional terms such as above, below, upper, lower, upward, downward, left, right, uphole, downhole and the like are used in relation to the illustrative embodiments as they are depicted in the figures, the upward direction being toward the top of the corresponding figure and the downward direction being toward the bottom of the corresponding figure, the uphole direction being toward the surface of the well and the downhole direction being toward the toe of the well.