USING MAGNETIC FORCE/FIELD FOR DRILL BITS AND OTHER CUTTING TOOLS
A cutting element assembly includes a rotatable cutting element having an axis of rotation extending axially therethrough, a cutting face and a body extending axially downward from the cutting face, at least one retention mechanism disposed adjacent to the rotatable cutting element, and a first magnet disposed at a back face of the rotatable cutting element.
Drill bits used to drill wellbores through earth formations generally are made within one of two broad categories of bit structures. Depending on the application/formation to be drilled, the appropriate type of drill bit may be selected based on the cutting action type for the bit and its appropriateness for use in the particular formation. Drill bits in the first category are generally known as “roller cone” bits, which include a bit body having one or more roller cones rotatably mounted to the bit body. The bit body is typically formed from steel or another high strength material. The roller cones are also typically formed from steel or other high strength material and include a plurality of cutting elements disposed at selected positions about the cones. The cutting elements may be formed from the same base material as is the cone. These bits are typically referred to as “milled tooth” bits. Other roller cone bits include “insert” cutting elements that are press (interference) fit into holes formed and/or machined into the roller cones. The inserts may be formed from, for example, tungsten carbide, natural or synthetic diamond, boron nitride, or any one or combination of hard or superhard materials.
Drill bits of the second category are typically referred to as “fixed cutter” or “drag” bits. Drag bits, include bits that have cutting elements attached to the bit body, which may be a steel bit body or a matrix bit body formed from a matrix material such as tungsten carbide surrounded by a binder material. Drag bits may generally be defined as bits that have no moving parts. However, there are different types and methods of forming drag bits that are known in the art. For example, drag bits having abrasive material, such as diamond, impregnated into the surface of the material which forms the bit body are commonly referred to as “impreg” bits. Drag bits having cutting elements made of an ultra hard cutting surface layer or “table” (typically made of polycrystalline diamond material or polycrystalline boron nitride material) deposited onto or otherwise bonded to a substrate are known in the art as polycrystalline diamond compact (“PDC”) bits.
PDC cutters have been used in industrial applications including rock drilling and metal machining for many years. In PDC bits, PDC cutters are received within cutter pockets, which are formed within blades extending from a bit body, and are typically bonded to the blades by brazing to the inner surfaces of the cutter pockets. The PDC cutters are positioned along the leading edges of the bit body blades so that as the bit body is rotated, the PDC cutters engage and drill the earth formation. In use, high forces may be exerted on the PDC cutters, particularly in the forward-to-rear direction. Additionally, the bit and the PDC cutters may be subjected to substantial abrasive forces. In some instances, impact, vibration, and erosive forces have caused drill bit failure due to loss of one or more cutters, or due to breakage of the blades.
In a typical PDC cutter, a compact of polycrystalline diamond (“PCD”) (or other superhard material, such as polycrystalline cubic boron nitride) is bonded to a substrate material, which is typically a sintered metal-carbide to form a cutting structure. PCD comprises a polycrystalline mass of diamond grains or crystals that are bonded together to form an integral, tough, high-strength mass or lattice. The resulting PCD structure produces enhanced properties of wear resistance and hardness, making PCD materials extremely useful in aggressive wear and cutting applications where high levels of wear resistance and hardness are desired.
An example of a prior art PDC bit having a plurality of cutters with ultra hard working surfaces is shown in
A plurality of orifices 116 are positioned on the bit body 110 in the areas between the blades 120, which may be referred to as “gaps” or “fluid courses.” The orifices 116 are commonly adapted to accept nozzles. The orifices 116 allow drilling fluid to be discharged through the bit in selected directions and at selected rates of flow between the blades 120 for lubricating and cooling the drill bit 100, the blades 120 and the cutters 150. The drilling fluid also cleans and removes the cuttings as the drill bit 100 rotates and penetrates the geological formation. Without proper flow characteristics, insufficient cooling of the cutters 150 may result in cutter failure during drilling operations. The fluid courses are positioned to provide additional flow channels for drilling fluid and to provide a passage for formation cuttings to travel past the drill bit 100 toward the surface of a wellbore (not shown).
Referring to
A factor in determining the longevity of PDC cutters is the exposure of the cutter to heat. Exposure to heat can cause thermal damage to the diamond table and eventually result in the formation of cracks (due to differences in thermal expansion coefficients) which can lead to spalling of the polycrystalline diamond layer, delamination between the polycrystalline diamond and substrate, and conversion of the diamond back into graphite causing rapid abrasive wear. The thermal operating range of conventional PDC cutters is typically 700-750° C. or less.
As mentioned, conventional polycrystalline diamond is stable at temperatures of up to 700-750° C. in air, above which observed increases in temperature may result in permanent damage to and structural failure of polycrystalline diamond. This deterioration in polycrystalline diamond is due to the difference in the coefficient of thermal expansion of the binder material, cobalt, as compared to diamond. Upon heating of polycrystalline diamond, the cobalt and the diamond lattice will expand at different rates, which may cause cracks to form in the diamond lattice structure and result in deterioration of the polycrystalline diamond. Damage may also be due to graphite formation at diamond-diamond necks leading to loss of microstructural integrity and strength loss, at extremely high temperatures.
In conventional drag bits, PDC cutters are fixed onto the surface of the bit such that a common cutting surface contacts the formation during drilling. Over time and/or when drilling certain hard but not necessarily highly abrasive rock formations, the edge of the working surface on a cutting element that constantly contacts the formation begins to wear down, forming a local wear flat, or an area worn disproportionately to the remainder of the cutting element. Local wear flats may result in longer drilling times due to a reduced ability of the drill bit to effectively penetrate the work material and a loss of rate of penetration caused by dulling of edge of the cutting element. That is, the worn PDC cutter acts as a friction bearing surface that generates heat, which accelerates the wear of the PDC cutter and slows the penetration rate of the drill. Such flat surfaces effectively stop or severely reduce the rate of formation cutting because the conventional PDC cutters are not able to adequately engage and efficiently remove the formation material from the area of contact. Additionally, the cutters are typically under constant thermal and mechanical load. As a result, heat builds up along the cutting surface, and results in cutting element fracture. When a cutting element breaks, the drilling operation may sustain a loss of rate of penetration, and additional damage to other cutting elements, should the broken cutting element contact a second cutting element.
Additionally, the generation of heat at the cutter contact point, specifically at the exposed part of the PDC layer caused by friction between the PCD and the work material, causes thermal damage to the PCD in the form of cracks which lead to spalling of the polycrystalline diamond layer, delamination between the polycrystalline diamond and substrate, and back conversion of the diamond to graphite causing rapid abrasive wear. The thermal operating range of conventional PDC cutters is typically 750° C. or less.
SUMMARYThis 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.
In one aspect, embodiments disclosed herein relate to a cutting element assembly that includes a rotatable cutting element having an axis of rotation extending axially therethrough, a cutting face and a body extending axially downward from the cutting face, at least one retention mechanism disposed adjacent to the rotatable cutting element, and a first magnet disposed at a back face of the rotatable cutting element.
In another aspect, embodiments disclosed herein relate to a downhole cutting tool that includes a body, a plurality of blades extending radially from the body, a plurality of cutter pockets disposed on the plurality of blades, at least one cutting element assembly disposed in the cutter pockets, wherein the at least one cutting element assembly includes a rotatable cutting element retained in the at least one cutter pocket, the rotatable cutting element comprising an axis of rotation extending axially therethrough, a cutting face and a body extending axially downward from the cutting face, and a first magnet disposed at a back face of the rotatable cutting element.
In yet another aspect, embodiments disclosed herein relate to a downhole tool that includes at least one dynamic component, at least one magnet disposed adjacent to the at least one dynamic component, and a ferrofluid adjacent the at least one magnet and a portion of the at least one dynamic component.
Other aspects and advantages of the disclosure will be apparent from the following description and the appended claims.
Embodiments disclosed herein relate generally to rotatable structures including roller cones and rotatable cutting elements, also referred to as rolling cutters, and methods of retaining such rotatable structures on a drill bit or other downhole tools. For example, according to embodiments of the present disclosure, a magnetic force or magnetic field may be used alone or in combination with other retention mechanisms to retain a rotatable structure to a drill bit. Advantageously, retaining mechanisms described herein allow a rolling cutter to rotate as it contacts the formation to be drilled, while at the same time retaining the rolling cutter on the drill bit. A magnetic force or field may be used to provide additional features, such as providing a dampening effect to a rotatable structure, to help retain a ferrofluid within a bearing space of a rotatable structure, and to aid in rotation of a rotatable structure.
According to embodiments of the present disclosure, one or more magnets may be used to retain a rotatable cutting element to a drill bit or other cutting tool by placing the one or more magnets along the rotatable cutting element axis of rotation and opposite from the cutting face of the rotatable cutting element. For example,
Further, the magnetic force may be used alone or in addition to other retention methods. For example, a rotatable cutting element may be retained in a sleeve using at least one retention mechanism disposed between the rotatable cutting element and the sleeve and at least one magnet disposed at the back face of the rotatable cutting element. Referring again to
According to embodiments of the present disclosure, a rotatable cutting element assembly may be retained directly to a cutter pocket formed in a cutting tool, without the use of a sleeve. For example, U.S. Provisional Application No. 61/834,264 and U.S. Publication No. 2011/0297454, which are incorporated herein by reference, include embodiments of retaining a cutting element directly to a cutter pocket.
The retention element 362 may be retained within retention pocket 314 by a screw 364 or other fastener, or may be brazed in place in yet other embodiments. In the illustrated embodiment, the screw 364 is inserted through a thru-hole in the retention element 362 and engages with blade 310 (such as by threaded engagement) or a threaded bolt infiltrated into blade 310. The rotatable cutting element 360, magnet 320, and retention element 362 may be assembled together in the cutter pocket 312 by disposing the magnet 320 at the bottom side of the cutter pocket 312, fitting a projection or lip 368 formed in the retention element 362 into a corresponding groove 366 formed around the rotatable cutting element 360, placing the rotatable cutting element 360 and retention element 362 into the cutter pocket 312 (and retention pocket 314) to cover the magnet 320, and finally, securing the retention element 362 to the cutting tool 310. By mating the lip 368 formed in the retention element 362 with the groove 366 formed around the rotatable cutting element 360, the retention element 362 may help to axially retain the rotatable cutting element 360 within the cutter pocket 312 without covering a portion of the cutting face 370 of the rotatable cutting element 360.
Various retention mechanisms may be used in combination with a magnetic force retention mechanism described herein. For example, a retention mechanism may include retention balls, springs, pins, retaining rings, or mating non-planar geometry. Retention mechanisms using retention balls may have a plurality of retention balls disposed between corresponding grooves formed around the outer surface of the rotatable cutting element body and the inner side surface of a sleeve, which is attached to a cutter pocket. Retention mechanisms using springs may include at least one spring and at least one ball or pin disposed between at least one blind hole and/or groove, such that the retention mechanism may be compressed when the rotatable cutting element is being fitted into the sleeve and may expand into the corresponding blind holes and/or grooves to retain the rotatable cutting element in a certain axial position within the sleeve. Retention mechanisms using mating non-planar geometry may include at least one corresponding groove and protrusion formed in an inner surface of the sleeve and an outer side surface of the rotatable cutting element. In such embodiments, the sleeve may be formed by joining two or more pieces together around the rotatable cutting element. For example, a rotatable cutting element may have a groove and/or a protrusion formed around its circumference. A sleeve having a mating protrusion and/or groove formed around the inner surface of the sleeve may be split along the length of the sleeve into at least two pieces. The at least two pieces may be assembled around the inner cutter such that the mating groove(s) and protrusion(s) are aligned, and the at least two pieces may be bonded together.
In other embodiments, a rotatable cutting element may be rotatably retained in a cutter pocket using changes in the rotatable cutting element body's diameter. For example, a rotatable cutting element body may have a first diameter proximate to the cutting end of the rotatable cutting element and a second diameter axially distant from the cutting end, wherein the second diameter is larger than the first diameter. A sleeve surrounding the rotatable cutting element body may have a first inner diameter corresponding with the first diameter of the rotatable cutting element. Thus, when the rotatable cutting element is assembled within the corresponding sleeve or pocket, the larger second diameter retains the rotatable cutting element. Various examples of retention mechanisms also include those disclosed in U.S. Patent Publication Nos. 2012/0132471, 2012/0273281, and 2010/0314176, and U.S. Pat. Nos. 7,703,559 and 8,091,655, all of which are assigned to the present assignee and herein incorporated by reference in their entirety.
Referring again to
A diamond or other ultra-hard material table forming the cutting face of a rotatable cutting element may be disposed on a substrate formed of a variety of hard or ultra hard particles. In one embodiment, the substrate may be formed from a suitable material such as tungsten carbide, tantalum carbide, or titanium carbide. Additionally, various binding metals may be included in the substrate, such as cobalt, nickel, iron, metal alloys, or mixtures thereof. In the substrate, metal carbide grains are supported within the metallic binder, such as cobalt. Additionally, the substrate may be formed of a sintered tungsten carbide composite structure. It is well known that various metal carbide compositions and binders may be used, in addition to tungsten carbide and cobalt. Thus, references to the use of tungsten carbide and cobalt are for illustrative purposes only, and no limitation on the type substrate or binder used is intended. In another embodiment, the substrate may also be formed from a diamond ultra-hard material such as polycrystalline diamond and thermally stable diamond. While the illustrated embodiments show the cutting face and substrate as two distinct pieces, one of skill in the art should appreciate that it is within the scope of the present disclosure the cutting face and substrate may be integral, identical compositions. For example, some embodiments may have a single diamond composite forming the cutting face and substrate or distinct layers. In some embodiments having diamond at the cutting face, the diamond may be layered or form a gradient having different diamond size and/or composition. For example, diamond at the cutting edge (around the circumference of the cutting face) may have a relatively finer grain size with a relatively higher wear resistance than the diamond away from the cutting edge having a coarser grain size with a higher toughness.
According to embodiments of the present disclosure, a magnet may be at least partially disposed within a sleeve or may be disposed axially behind the sleeve. For example, as shown in
According to embodiments of the present disclosure, one or more magnets may be used in combination with a ferrofluid in a bearing system for a rotatable structure. A ferrofluid may include ferromagnetic nanoparticles disposed in a fluid. For example, ferromagnetic nanoparticles may include coated nanoparticles of ferrite. The fluid carrying the ferromagnetic nanoparticles may include regular or high temperature grease used in downhole drilling operations. By using ferrofluid in combination with at least one magnet in rotatable structure assemblies of the present disclosure, the ferrofluid may accumulate around the at least one magnet and rotatable structure to provide damping for the rotatable structure and thereby reduce friction. For example, ferrofluid disposed around at least one magnet used in a cutting element assembly may provide damping between the rotatable cutting element and surrounding sleeve, and thereby reduce the amount of friction occurring during rotation of the rotatable cutting element within the sleeve. Ferrofluid disposed within a bearing space of a rotatable structure assembly of the present disclosure may also act as a coolant for frictional heat caused by the rotation of the rotatable structure. Further, the magnetic field from magnets used with rotatable structure assemblies of the present disclosure may keep ferrofluid from leaking out of the cutting element assemblies, especially when the grease/fluid loses viscosity at elevated temperature.
According to embodiments of the present disclosure, a ferrofluid may be disposed around at least one magnet in a cutting element assembly. For example, referring to
Referring now to
As mentioned above, magnets used in cutting element assemblies according to embodiments of the present disclosure have a magnetic force that may be used to attract and hold ferrofluid within the cutting element assembly. For example,
Ferrofluid may be used in combination with at least one magnet with other rotatable structure assemblies on drill bits to provide at least one of the advantages described herein. For example, according to embodiments of the present disclosure, a drill bit may have a bit body and at least one rotatable structure retained to a journal extending from the drill bit. At least one bearing system may be disposed between the at least one rotatable structure and the journal to allow rotation of the rotatable structure around the axis of journal. The bearing space may include at least one magnet and a ferrofluid disposed between the at least one rotatable structure and the journal.
Further, the roller cone 14 is retained to the journal 14 using a retention ball system. As shown, the retention ball system includes corresponding circumferential grooves 32, 43 formed in the bore bearing surface 30 and the journal bearing surface 42, respectively, to form a race that receives and holds a plurality of retention balls 37. The retention balls 37 may be inserted into the race via a ball passageway 36 formed through the journal 18 to intersect with the race. A ball retainer 39 is disposed within the ball passageway 36, and a ball hole plug 38 is secured behind the ball retainer 39 to close the ball passageway 36 and keep the retention balls 37 within the race.
According to embodiments of the present disclosure, ferrofluid may be used in addition to grease in a bearing system of a drill bit. For example,
According to some embodiments of the present disclosure, grease used in a bearing system of a drill bit may include a ferrofluid grease. For example,
Although roller cones are shown in
According to embodiments of the present disclosure, ferrofluid used with rotatable structures may include ferrofluid grease and/or ferrofluid lubricant. Ferrofluid grease may be formed by mixing dry ferropowder with grease, such as a lithium and calcium based grease, and optimized for drill bit and/or borehole environment performances.
In some embodiments, a second magnet may be used adjacent to and in combination with a first magnet in a cutting element assembly to create a damping effect. For example,
Further, as shown in
Magnets used in embodiments of the present disclosure may include permanent magnets, electromagnets, or superconducting magnets, and may include other mechanisms to create a magnetic field or magnetize otherwise non-magnetic components, for example, through application of a magnetic coating on an otherwise non-magnetic component. Permanent magnets may include, for example, neodymium magnets (neodymium iron boron based), samarium cobalt, alnico (aluminum, nickel and cobalt based magnets), ceramic and ferrite materials. Further, permanent magnets may be formed, for example, by injection molding, which may include mixing magnetic material with a matrix/binder material, such as resin, vinyl, etc. In embodiments using electromagnets, the strength of the electromagnet may be tuned based on the amount of load applied to the rotatable cutting element during operation.
Further, the size of magnets used in embodiments of the present disclosure may vary. For example,
In some embodiments, one or more permanent magnets may be attached or joined to a substrate of a rotatable cutting element with, for example, an adhesive, solder, or low temperature braze, wherein the solder or braze alloy melting point are lower than the permanent magnet Currie temperature. In other embodiments, a portion of a substrate of a rotatable cutting element may be magnetized, such that a magnet is formed as part of the rotatable cutting element. For example, the portion of a carbide substrate forming the back face of a rotatable cutting element may be magnetized such that a magnet is formed as part of the rotatable cutting element at the back face of the rotatable cutting element.
Further, according to embodiments of the present disclosure, a sleeve used in cutting element assemblies may be formed from a variety of materials. In one embodiment, a sleeve used in a cutting element assembly may be formed of a suitable material such as tungsten carbide, tantalum carbide, or titanium carbide. Additionally, various binding metals may be included in the sleeve, such as cobalt, nickel, iron, metal alloys, or mixtures thereof, such that metal carbide grains may be supported within the metallic binder. In a particular embodiment, the sleeve is a cemented tungsten carbide with a cobalt content ranging from 6 to 13 percent. It is also within the scope of the present disclosure that the sleeve may also include more lubricious materials to reduce the coefficient of friction. The sleeve may be formed of such materials in its entirety or have a portions thereof (such as the inner surface) including such lubricious materials. For example, the sleeve may include diamond, diamond-like coatings, or other solid film lubricant. In other embodiments, the sleeve may be formed of steel or alloy composites, such as alloy steels, carbon steel, nickel-based alloys, cobalt-based alloys, and/or high speed cutting tool steels.
Embodiments of the present disclosure may provide cutting element assemblies with a higher resistance to chipping and wear between a rotatable cutting element and sleeve when compared with cutting element assemblies that do not have at least one magnet. Particularly,
According to embodiments of the present disclosure, at least one magnet may be used with a rotatable structure assembly. For example, at least one magnet may be used in addition to one or more other retention mechanisms to hold a rotatable cutting element within a sleeve. The magnetic force or field created by the at least one magnet may be used to pull the rotatable cutting element into the sleeve, and thus maintain full contact with the sleeve and prevent any foreign particles from getting into the cutting element assembly. By pulling the rotatable cutting element within the sleeve, the magnetic force or field may also reduce erosion along the interface between the rotatable cutting element and sleeve. The magnetic force or field may also help prolong the fatigue life of the cutting element by providing more front impact support for the rotatable cutting element and less yanking movement on the rotatable cutting element.
According to embodiments of the present disclosure, a magnetic force or field positioned at the back of a cutting element assembly may be used to provide damping effects on the back of the rotatable cutting element, thereby also reducing friction between the rotatable cutting element and the sleeve. The magnetic force may be used to create damping effects by placing the same poles of two magnets adjacent to each other and/or by using a ferrofluid. For example, in embodiments having ferrofluid disposed around at least on magnet positioned at the back face of a rotatable cutting element in a cutting element assembly, the ferrofluid may be pulled around the at least one magnet to create a compressible damping layer. Using a magnet in combination with ferrofluid in a rotatable structure assembly may also provide a means of minimizing leakage of the ferrofluid. According to embodiments of the present disclosure, ferrofluid may act as a lubricant for the rotatable structure, such as within a bearing space of a rotatable structure assembly, a damper for a rotatable structure, and/or a coolant for frictional heat created during rotation of the rotatable structure.
Another rotatable cutting structure in which the ferrofluid and magnet may be used is a roller reamer, illustrated in
In the depicted example shown in
However, the use of the ferrofluids of the present disclosure is not limited to rotatable cutting structures, such as rolling cutters, roller cones, or roller reamers. Rather, it is envisioned that the ferrofluids of the present disclosure may be used in combination with a magnet on any dynamic component of a downhole tool. For example, such downhole tools may include a percussion bit that includes grease between sliding or percussive surfaces, an indexable bit with indexable (but not freely rotating cutting structures), open bearing (sealless) bits or other tools), jars, reamers (including rolling reamers, expandable reamers with a movable arm, etc), rotating control devices, mills, drilling motors, stabilizers, measurement while drilling tools, logging while drilling tools, steering tools, turbines, alternators, production pumps, under-reamers, hole-openers, turbine-alternators, whipstocks (including adjustable whipstocks), bent subs, and the like. In addition, it is also envisioned that the ferrofluids may also be used in combination with static downhole applications in which grease is conventionally used, and which may benefit from the grease having reduced washout or reduced contamination between two static surfaces. Such examples may include tools in which grease is used for assembly and/or disassembly, including, for examples, turbines, threaded connections, packers, etc. In such applications, the combination of a ferrofluid as grease with a magnet may beneficially allow for the grease (ferrofluid) to remain, to a greater extent than conventional greases, in the desired space upon use of the tool. Specifically, the magnet may attract the ferrofluid grease so that the ferrofluid grease has a reduced amount washout or displacement as compared to conventional greases.
Another example of a downhole tool that may use the ferrofluids of the present disclosure is a rotary steerable tool.
Referring to
Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.
Claims
1. A cutting element assembly, comprising:
- a rotatable cutting element comprising an axis of rotation extending axially therethrough, a cutting face and a body extending axially downward from the cutting face;
- at least one retention mechanism disposed adjacent to the rotatable cutting element; and
- a first magnet disposed at a back face of the rotatable cutting element.
2. The cutting element assembly of claim 1, further comprising a sleeve, wherein the rotatable cutting element is partially disposed within the sleeve.
3. The cutting element assembly of claim 2, further comprising a ferrofluid disposed between the rotatable cutting element and the sleeve.
4. The cutting element assembly of claim 1, further comprising a second magnet disposed adjacent to the first magnet and opposite the back face.
5. The cutting element assembly of claim 4, wherein the first magnet and the second magnet each have poles, and wherein the same poles of the first and second magnets are positioned facing each other.
6. The cutting element assembly of claim 1, wherein the first magnet comprises an electromagnet.
7. The cutting element assembly of claim 1, wherein the first magnet comprises a permanent magnet.
8. The cutting element assembly of claim 3, wherein the ferrofluid comprises a plurality of ferromagnetic nanoparticles.
9. A downhole cutting tool, comprising:
- a body;
- a plurality of blades extending radially from the body;
- a plurality of cutter pockets disposed on the plurality of blades;
- at least one cutting element assembly disposed in the cutter pockets, wherein the at least one cutting element assembly comprises: a rotatable cutting element retained in the at least one cutter pocket, the rotatable cutting element comprising an axis of rotation extending axially therethrough, a cutting face and a body extending axially downward from the cutting face; and a first magnet disposed at a back face of the rotatable cutting element.
10. The downhole cutting tool of claim 9, wherein a bottom side of the cutter pocket comprises a ferromagnetic material.
11. The downhole cutting tool of claim 10, wherein the cutting element assembly further comprises a sleeve and at least one retention mechanism disposed between the rotatable cutting element and the sleeve.
12. The downhole cutting tool of claim 11, further comprising a ferrofluid disposed between the rotatable cutting element and the sleeve.
13. The downhole cutting tool of claim 9, further comprising a second magnet disposed adjacent to the first magnet and opposite the back face.
14. The downhole cutting tool of claim 13, wherein the first magnet and the second magnet each have poles, and wherein the same poles of the first and second magnets are positioned facing each other.
15. The downhole cutting tool of claim 9, wherein the first magnet comprises an electromagnet.
16. The downhole cutting tool of claim 9, wherein the first magnet comprises a permanent magnet.
17. A downhole tool, comprising:
- at least one dynamic component;
- at least one magnet disposed adjacent to the at least one dynamic component; and
- a ferrofluid adjacent the at least one magnet and a portion of the at least one dynamic component.
18. The downhole tool of claim 17, wherein the downhole cutting tool is a drill bit, comprising:
- a bit body;
- a journal extending from the bit body, wherein the at least one rotatable structure is retained to the journal;
- wherein the bearing system is disposed between the at least one rotatable structure and the journal;
- wherein the at least one magnet is disposed between the at least one rotatable structure and the journal; and
- wherein the ferrofluid is disposed between the at least one rotatable structure and the journal.
19. The downhole tool of claim 20, wherein the bearing system comprises an o-ring seal and the at least one magnet comprises a ring magnet disposed proximate to the o-ring seal.
20. The downhole tool of claim 20, wherein the ferrofluid is a ferrofluid grease comprising ferropowder and grease.
21. The downhole tool of claim 17, wherein the tool comprises a reamer, an indexable bit, a percussion bit, a hole opener, a turbine, a drilling motor, a stabilizer, a measurement while drilling tool, a logging while drilling tool, a steering tool, turbine, an alternator, a production pump, an under-reamer, a hole-opener, a turbine-alternator, an adjustable whipstock, or a bent sub.
Type: Application
Filed: Aug 14, 2014
Publication Date: Feb 19, 2015
Inventors: Yuri Burhan (Spring, TX), Youhe Zhang (Spring, TX), Joseph Swinehart (Houston, TX), Chen Chen (Houston, TX)
Application Number: 14/459,828
International Classification: E21B 10/60 (20060101);