Use of Rotary Cutting Elements in Downhole Milling

Abstract

A milling tool includes a milling arm with a rotatable cutting element positioned on the milling arm. The rotatable cutting element may be fixed longitudinally and radially relative to a rotational axis of the rotatable cutting element in the milling arm while being rotatable about the rotational axis.

Description

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 62/916,883 filed Oct. 18, 2019, which is incorporated by reference herein for all purposes.

BACKGROUND

Wellbores may be drilled into a surface location or seabed for a variety of exploratory or extraction purposes. For example, a wellbore may be drilled to access fluids, such as liquid and gaseous hydrocarbons, stored in subterranean formations and to extract the fluids from the formations. Wellbores used to produce or extract fluids may be lined with casing around the walls of the wellbore. A variety of drilling methods may be utilized depending partly on the characteristics of the formation through which the wellbore is drilled.

Some wellbores are reinforced with casing while drilling to stabilize the wellbore. Conventional casing is a steel or other metallic cylinder that provides a durable surface for the interior of the wellbore. The casing allows downhole tools to be tripped into the wellbore with little or no damage to the integrity of the wellbore. The outer diameter of the casing is smaller than the drilled diameter of the initial wellbore, leaving an annular space around the casing and between the casing and wellbore. The annular space is filled with cement or other fluid that can harden and retain the casing in place relative to the wellbore.

The cement is pumped to the bottom of the casing and allowed to flow up the annular space. Filling the annular space from the bottom displaces other material from the annular space and provides more complete filling of the annular space than other delivery methods.

During creation, maintenance, and closing of a wellbore, various materials may be removed by a downhole tool to extend, widen, or redirect the wellbore. For example, downhole tools remove earthen material to extend the wellbore. Downhole tools are also used to remove portions of the metal casing and cement to widen the wellbore or to open a window in the casing to kick off a lateral borehole from the wellbore.

When removing material in a downhole environment, the cuttings are removed by flushing the cuttings upward through the annular space around the downhole tool with drilling fluid. Smaller cuttings are carried away by the drilling fluid more reliably and safely than larger cuttings.

SUMMARY

In some embodiments, a downhole tool includes a milling arm and a rotatable cutting element positioned in the milling arm. The rotatable cutting element is rotatable within the milling arm about a rotational axis of the rotatable cutting element.

In other embodiments, a milling tool includes a milling tool body and a plurality of milling arms. The plurality of milling arms project radially from the body and are configured to move around the milling tool body in a cutting direction. At least one of the milling arms includes a rotatable cutting element and a fixed cutting element. The rotatable cutting element is positioned in arm body of the milling arm and is rotatable about a rotational axis within the arm body. The fixed cutting element is positioned in the arm body of the milling arm.

In yet other embodiments, a milling tool includes a milling tool body and a plurality of milling arms. The plurality of milling arms project radially from the body and are configured to move around the milling tool body in a cutting direction. At least one of the milling arms includes a rotatable cutting element, an inside fixed cutting element, and an outside fixed cutting element. The rotatable cutting element positioned in arm body of the milling arm and is rotatable about a rotational axis within the arm body. The inside fixed cutting element is fixed in the arm body in a downhole direction of the rotatable cutting element. The outside fixed cutting element is fixed relative to the arm body and positioned radially outside of the at least one inside cutting element with a sacrificial region positioned therebetween.

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

Additional features and advantages of embodiments of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of such embodiments. The features and advantages of such embodiments may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features will become more fully apparent from the following description and appended claims, or may be learned by the practice of such embodiments as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 1 is a schematic representation of an embodiment of a drilling system, according to at least one embodiment of the present disclosure;

FIG. 2 is a detail view of the embodiment of a milling tool with a rotatable cutting element, according to at least one embodiment of the present disclosure;

FIG. 3 is a front view of another embodiment of a milling arm with a rotatable cutting element, according to at least one embodiment of the present disclosure;

FIG. 4 is a radial end view of the embodiment of a milling arm of FIG. 3, according to at least one embodiment of the present disclosure;

FIG. 5 is a bottom view of the embodiment of a milling arm of FIG. 3, according to at least one embodiment of the present disclosure;

FIG. 6 is a side cross-sectional view of an embodiment of a rotatable cutting element in a housing, according to at least one embodiment of the present disclosure;

FIG. 7 is a side cross-sectional view of another embodiment of a rotatable cutting element in a housing, according to at least one embodiment of the present disclosure;

FIG. 8 is a front view of an embodiment of a rotatable cutting element with an annular cutting portion, according to at least one embodiment of the present disclosure;

FIG. 9 is a front view of another embodiment of a rotatable cutting element with a plurality of cutting portions, according to at least one embodiment of the present disclosure;

FIG. 10 is a side cross-sectional view of an embodiment of a profile of a cutting portion, according to at least one embodiment of the present disclosure;

FIG. 11 is a side cross-sectional view of another embodiment of a profile of a cutting portion, according to at least one embodiment of the present disclosure;

FIG. 12 is a side cross-sectional view of yet another embodiment of a profile of a cutting portion, according to at least one embodiment of the present disclosure; and

FIG. 13 is a front view of an embodiment of a cutting portion with a rotational chipbreaking feature, according to at least one embodiment of the present disclosure.

DETAILED DESCRIPTION

This disclosure generally relates to devices, systems, and methods for improving cutting efficiency in a downhole environment. More particularly, the present disclosure relates to embodiments of milling tools having a rotatable cutting element to distribute wear over the entire edge of the cutting element. Distributing wear on the cutting element may increase a rate of penetration of the tool, reduce the likelihood of a cutting element and/or a tool body failure, or combinations thereof. While a milling bit for cutting through wellbore casing is described herein, it should be understood that the present disclosure may be applicable to other cutting bits such as reamers, hole openers, and other cutting bits, and through other materials, such as cement, concrete, metal, or formations including such materials.

FIG. 1 shows one example of a drilling system 100 for drilling an earth formation 101 to form a wellbore 102. The drilling system 100 includes a drill rig 103 used to turn a tool assembly 104 which extends downward into the wellbore 102. In the embodiment depicted in FIG. 1, the tool assembly 104 is removing a casing 107 of the wellbore 102, for example, to extend or widen the wellbore 102, or to kick off a lateral borehole from the wellbore 102. The tool assembly 104 may include a drill string 105, a bottomhole assembly (“BHA”) 106, a milling tool 110, or combinations thereof. In the depicted embodiment, a milling tool 110 is attached to the downhole end of drill string 105.

The drill string 105 may include several joints of drill pipe 108 a connected end-to-end through tool joints 109. The drill string 105 transmits drilling fluid through a central bore and transmits rotational power from the drill rig 103 to the BHA 106. In some embodiments, the drill string 105 may further include additional components such as subs, pup joints, etc. The drill pipe 108 provides a hydraulic passage through which drilling fluid is pumped from the surface. The drilling fluid may discharge through one or more orifices in the tool assembly 104 for the purposes of cooling the milling tool 110 and cutting structures thereon, and for lifting cuttings out of the wellbore 102 as it the casing 107 is milled.

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

In some embodiments, the BHA 106 may further include any type of bit suitable for degrading downhole materials. For instance, the bit may be a drill bit suitable for drilling the earth formation 101. In the depicted embodiment, the BHA 106 may include a milling tool 110 to mill into the casing 107 lining the wellbore 102 and a bit may then start a lateral borehole in the earth formation 101. The milling tool 110 may also be a junk mill used to mill away tools, plugs, cement, other materials within the wellbore 102, or combinations thereof. Swarf or other cuttings formed by use of the milling tool 110 may be lifted to surface, or may be allowed to fall downhole.

As shown in FIG. 1, the milling tool 110 may have a plurality of milling arms that are deployable from a body of the milling tool 110 to remove material from the casing 107 and/or earth formation 101 to expand the wellbore 102.

FIG. 2 illustrates an embodiment of a milling arm 112 deployed from the body of the milling tool 110. In some embodiments, the milling arm 112 may have an arm body that is oriented in a cutting direction of the milling arm 112 around the body of the milling tool 110. The arm body 114 may have one or more features thereon to remove material from a formation 101 and/or casing 107 as the milling arm 112 and milling tool 110 rotates relative to the formation 101 and/or casing 107. While one or more embodiments of a milling arm will be described in relation to milling a casing in a downhole direction, it should be understood that at least one of embodiments described herein may be inverted and used in an uphole milling direction. Any directional references, such as downhole, uphole, etc., should be understood to be in reference to a downhole milling direction.

In some embodiments, a milling arm 112 may include a rotatable cutting element 116 located on the arm body 114. In other embodiments, a milling arm 112 may include and inside cutting element 118. The rotatable cutting element 116 may be positioned on the arm body of the milling arm 112 to contact an end of the casing 107 and mill casing 107 material while the inside cutting element 118 may be positioned on the milling arm 112 to remove material from an inside surface of the formation 101 and/or casing 107 and/or protect the milling arm 112 from erosion and/or damage from contact with the formation 101 and/or casing 107.

In some embodiments, at least a portion of the rotatable cutting element 116 may be an ultrahard material. As used herein, the term “ultrahard” is understood to refer to those materials known in the art to have a grain hardness of about 1,500 HV (Vickers hardness in kg/mm²) or greater. Such ultra-hard materials can include those capable of demonstrating physical stability at temperatures above about 750° C., and for certain applications above about 1,000° C., that are formed from consolidated materials. Such ultrahard materials can include but are not limited to diamond or polycrystalline diamond (PCD) including leached metal catalyst PCD, non-metal catalyst PCD, binderless PCD, nanopolycrystalline diamond (NPD), or hexagonal diamond (Lonsdaleite); cubic boron nitride (cBN); polycrystalline cBN (PcBN); Q-carbon; binderless PcBN; diamond-like carbon; boron suboxide; aluminum manganese boride; metal borides; boron carbon nitride; and other materials in the boron-nitrogen-carbon-oxygen system which have shown hardness values above 1,500 HV, as well as combinations of the above materials. In at least one embodiment, a portion of the rotatable cutting element 116 may be a monolithic carbonate PCD. For example, a portion of the rotatable cutting element 116 may consist of a PCD compact without an attached substrate or metal catalyst phase. In some embodiments, the ultrahard material may have a hardness values above 3,000 HV. In other embodiments, the ultrahard material may have a hardness value above 4,000 HV. In yet other embodiments, the ultrahard material may have a hardness value greater than 80 HRa (Rockwell hardness A).

In some embodiments, the rotatable cutting element 116 may rotate relative to the milling arm 112 and the inside cutting element 118 may be fixed relative to the milling arm 112. The rotatable cutting element 116 may rotate relative to the milling arm 112 due at least partially to the contact between the rotatable cutting element 116 and the formation 101 and/or casing 107. For example, the rotatable cutting element 116 may be oriented in the milling arm 112 relative to the direction of movement of the milling arm 112 to contact the casing 107 askew, thereby driving a net torque on the rotatable cutting element 116. The rotation of the rotatable cutting element 116 may limit and/or prevent excessive wear on one location of the rotatable cutting element 116 relative to other portions of the rotatable cutting element 116. In other words, the rotation of the rotatable cutting element 116 allows exposure of a “new” portion of the rotatable cutting element 116 to wear the rotatable cutting element 116 evenly during use to increase the operational lifetime of the milling tool 110.

FIG. 3 illustrates another embodiment of a milling arm 212 according to the present disclosure. The milling arm 212 may have an arm body 214 similar to that described in relation to FIG. 2, with a rotatable cutting element 216 positioned thereon. In some embodiments, the milling arm 212 may include at least one inside cutting element 218 and at least one outside cutting element 220. As described in relation to FIG. 2, the inside cutting element 218 may be positioned on the milling arm 212 in a downhole direction relative to the rotatable cutting element 216 to remove material from an inside surface of the casing and/or protect the milling arm 212 from erosion and/or damage from contact with the formation and/or casing.

In some embodiments, the outside cutting element(s) 220 may be positioned on the milling arm 212 in a downhole direction relative to the rotatable cutting element 216 to remove material from the formation and/or an outside surface of casing and/or protect the milling arm 212 from erosion and/or damage from contact with the formation and/or casing. In other embodiments, the outside cutting elements 220 may be positioned at a radial end of the milling arm 212 and configured to remove at least a portion of the cement radially outside the casing that holds the casing in position in the wellbore.

In some embodiments, the inside cutting elements 218 and/or the outside cutting elements 220 may include an ultrahard material. In other embodiments, the inside cutting elements 218 and/or the outside cutting elements 220 may include a material having a higher hardness than the constituent material of the arm body 214. For example, the inside cutting elements 218 and/or the outside cutting elements 220 may include a tungsten carbide and the arm body 214 may include a steel alloy. In other embodiments, the inside cutting elements 218 and/or the outside cutting elements 220 may include a PCD and the arm body 214 may include a titanium alloy.

In some embodiments, the milling arm 212 may include a sacrificial region 219 positioned downhole of the rotatable cutting element 216. In some embodiments, the sacrificial region 219 may be positioned adjacent to an inside cutting element 218. In other embodiments, the sacrificial region 219 may be positioned adjacent to an outside cutting element 218. In yet other embodiments, the sacrificial region 219 may be positioned adjacent to and between an inside cutting element 218 and an outside cutting element 220.

In some embodiments, the sacrificial region 219 may be a different material from the remainder of the arm body 214. For example, the sacrificial region 219 may include an aluminum alloy and the remainder of the arm body 214 may include a steel alloy. In other examples, the sacrificial region 219 may include a soft steel alloy and the remainder of the milling arm may include a tool steel. In at least one example, the sacrificial region 219 may include a softer material than the remainder of the milling arm 212 such that the sacrificial region 219 preferentially wears in contact with the casing and/or formation to create a channel that may direct the casing to the rotatable cutting element 216.

FIG. 4 illustrates the embodiment of a milling arm 212 of FIG. 3 in an end view. In some embodiments, the rotatable cutting element 216 may rotate relative to the arm body 214 about a rotational axis 222 of the rotatable cutting element 216.

The milling arm 212 may be moved in a cutting direction 224 by the body of the milling tool (such as milling tool 110 of FIG. 2) to move around the edge of the wellbore as the milling tool advances longitudinally through the wellbore. In some embodiments, the rotational axis 222 may be oriented with a declination 226 (e.g., oriented in a downhole direction relative to the cutting direction 224. In some embodiments, the declination 226 may be in a range having an upper value, a lower value, or upper and lower values including any of 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, or any values therebetween. For example, the rotational axis 222 of the rotatable cutting element 216 may be oriented with a declination 226 of greater than 0° relative to the cutting direction 224. In other examples, the rotational axis 222 may be oriented with a declination of less than 45° relative to the cutting direction 224. In yet other examples, the declination 226 may be between 5° and 40°. In further examples, the declination 226 may be between 10° and 35°.

FIG. 5 is a bottom view illustrating the perpendicular orientation of the rotatable cutting element 216 relative to the cutting direction 224 of the arm body 214 during milling operations. In some embodiments, the rotatable cutting element 216 may be oriented in a radially outward direction (e.g., away from the arm body 214) an radial angle 228 in a range having an upper value, a lower value, or upper and lower values including any of 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, or any values therebetween. For example, the rotational axis 222 of the rotatable cutting element 216 may be oriented radially outward at a radial angle 228 of greater than 0° relative to the cutting direction 224. In other examples, the rotational axis 222 may be oriented radially outward at a radial angle 228 of less than 45° relative to the cutting direction 224. In yet other examples, the radial angle 228 may be between 5° and 40°. In further examples, the radial angle 228 may be between 10° and 35°.

In some embodiments, the rotational rate of the rotatable cutting element 216 about the rotational axis 222 may be related to the declination 226 and/or the radial angle 228 in the radial direction. For example, contacting the casing with the rotatable cutting element 216 with a rotational axis 222 parallel to the cutting direction 224 of the milling arm about the milling tool may result in little to no rotation of the rotatable cutting element 216. In other embodiments, a rotational axis 222 with a 30° declination (such as declination 226 in FIG. 4) and a 30° radial angle 228 in the radial direction may result in one or more revolutions of the rotatable cutting element 216 about the rotational axis 222 for each rotation of the milling tool about the wellbore.

In some embodiments, an arm body 214 may have a bottom surface 230 that is tapered toward rotatable cutting element 216 to provide clearance for the rotatable cutting element 216 to contact the casing and/or formation. For example, the bottom surface 230 may have less area than an opposite top surface to accommodate the declination of the rotatable cutting element 216. In other examples, the bottom surface 230 may have less area than an opposite top surface to provide clearance for cuttings or other debris to be flushed from the cutting area.

FIG. 6 and FIG. 7 illustrate different embodiments of retention mechanisms for retaining the rotatable cutting element in a milling arm while allowing rotation of the rotatable cutting element within the arm body. FIG. 6 is a cross-sectional view of an embodiment of a rotatable cutting element 316 inside a housing 336. In some embodiments, the housing 336 may be an arm body (such as the arm body 114, 214 described in relation to FIG. 2 through 5). In other embodiments, the housing 336 may be a discrete part that may be fixed to the arm body. For example, the housing 336 may be fixed to the arm body by welding, brazing, adhesive, mechanical interlock, friction fit, snap fit, one or more mechanical fasteners (e.g., pins, clips, clamps, bolts, etc.), or combinations thereof.

In some embodiments, the rotatable cutting element 316 may include a cutting portion 332 and a base 334. In some embodiments, the base 334 may be substantially cylindrical and received within a complimentarily sized space in the housing 336. For example, the base 334 may be configured to rotate freely within the housing 336 about the rotational axis 322.

In some embodiments, the cutting portion 332 may be integrally formed with the base 334. For example, the cutting portion 332 may be sintered with the base 334, such that the cutting portion 332 and base 334 are bonded together microstructurally. In other embodiments, the cutting portion 332 may be affixed to the base 334 by brazing, adhesive, mechanical interlock, friction fit, snap fit, one or more mechanical fasteners (e.g., pins, clips, clamps, bolts, etc.), or combinations thereof.

In some embodiments, at least a portion of the rotatable cutting element 316 may be positioned inside the housing 336. The rotatable cutting element 316 may be rotatable relative to the housing 336 while being longitudinally fixed relative to the housing 336. For example, the movement of the rotatable cutting element 316 in the direction of the rotational axis 322 may be limited and/or prevented by a retention member.

In some embodiments, the retention member may be an expansion ring 338. For example, the expansion ring 338 may be positioned in a circumferential groove 340 about the base 334, as the base 334 is inserted into the housing 336. The expansion ring 338 may expand upon reaching a notch 342 or shoulder in the housing 336, limiting the longitudinal movement of the rotatable cutting element 316 relative to the housing 336. In other embodiments, the retention member may be compression ring that is snapped around the base 334 and into the groove 340 from the rear of the housing 336.

In other embodiments, the rotatable cutting element may be retained in the housing by a plurality of retention members. FIG. 7 illustrates an embodiment of a rotatable cutting element 416 in a housing 436 with at least part of the housing 436 positioned in the rotatable cutting element 416. For example, the rotatable cutting element 416 may have a cutting portion 432 and a base 434, and at least a portion of the housing 436 may protrude into the base 434. The housing 436 and base 434 may have a plurality of fasteners, such as pins 444, inserted between.

In some embodiments, the base 434 may have a circumferential groove 446 therein, which may receive the plurality of pins 444. The pins 444 may be positioned in the groove 446 adjacent to the base 434 to limit and/or prevent longitudinal movement of the rotatable cutting element 416 in the direction of the rotational axis 422. In some embodiments, the pins 444 may further limit the movement of the rotatable cutting element 416 perpendicular to the rotational axis 422 without inhibiting the rotational movement of the rotatable cutting element 416. In some embodiments, the pins 444 may be removed from the housing 436 to allow removal and/or replacement of the rotatable cutting element 416 for repair of the rotatable cutting element 416 and/or a milling arm.

FIG. 6 and FIG. 7 illustrate embodiments of a rotatable cutting element 316, 416 including a cutting portion 332, 432 that may be a monolithic disc that is continuous about a circumferential edge. FIG. 8 is an end view of a front face of another embodiment of a rotatable cutting element 516 with a cutting portion with a continuous circumferential edge. In some embodiments, the cutting portion 532 of a rotatable cutting element 516 may positioned at the edge of the front face annularly about the rotational axis 522 of the rotatable cutting element 516. For example, the cutting portion 532 may be an annular disc around the base 534 in the center of the rotatable cutting element 516.

In some embodiments, the cutting portion 532 may be a percentage of the surface area of the front face shown of the rotatable cutting element 516 in a range having an upper value, a lower value, or upper and lower values including any of 5%, 10%, 15%, 20%, 25%, 50%, 75%, 80%, 85%, 90%, 95%, 100%, or any values therebetween. For example, the cutting portion 532 may be greater than 5% of the surface area of the front face of the rotatable cutting element 516. In other examples, the cutting portion 532 may be less than 100% of the surface area of the front face of the rotatable cutting element 516. In yet other examples, the cutting portion 532 may be between 10% and 60% of the surface area of the front face of the rotatable cutting element 516. In further examples, the cutting portion 532 may be between 15% and 50% of the surface area of the front face of the rotatable cutting element 516.

In some embodiments, the cutting portion 532 may have a width that is a percentage of the radius of the rotatable cutting element 516 in a range having an upper value, a lower value, or upper and lower values including any of 5%, 10%, 15%, 20%, 25%, 50%, 75%, 80%, 85%, 90%, 95%, 100%, or any values therebetween. For example, the cutting portion 532 may be an annulus with a width that is greater than 5% of the radius of the rotatable cutting element 516. In other examples, the cutting portion 532 may be an annulus with a width that is between 5% and 95% of the radius of the rotatable cutting element 516. In yet other examples, the cutting portion 532 may be an annulus with a width that is between 10% and 60% of the radius of the rotatable cutting element 516. In further examples, the cutting portion 532 may be an annulus with a width that is between 15% and 40% of the radius of the rotatable cutting element 516.

FIG. 9 is an end view of yet another embodiment of a rotatable cutting element 616. The rotatable cutting element 616 may have a plurality of cutting portions 632 affixed to a base 634. In some embodiments, the rotatable cutting element 616 may have a plurality of cutting portions 632 that are spaced circumferentially around the rotatable cutting element 616 at equal angular intervals around the rotational axis 622. In other embodiments, the rotatable cutting element 616 may have a plurality of cutting portions 632 positioned at unequal angular intervals around the rotational axis 622. In some embodiments, at least one of the cutting portions 632 may be removable and/or replaceable to facilitate repair of a part of the rotatable cutting element 616 without having to replace the entire rotatable cutting element 616.

FIG. 10 through FIG. 12 are cross-sectional views of various embodiments of profiles of rotatable cutting elements 716, 816, 916. FIG. 10 is a side cross-sectional view of an embodiment of a rotatable cutting element 716 with a cutting portion 732 fixed to a base 734. The cutting portion 732 may have a bevel 748 located at the edge of the cutting portion 732. In some embodiments, the bevel 748 may reduce fracturing of the cutting portion 732 near the edge. In other embodiments, the bevel 748 may correspond to the declination and/or radial angle (such as declination 226 and radial angle 228 described in relation to FIG. 4 and FIG. 5, respectively) to allow the bevel 748 to contact flush against the casing being milled. For example, the bevel 748 may be a complementary angle to the declination (such as declination 226 described in relation to FIG. 4). In other examples, the bevel 748 may be a complimentary angle to the radial angle (such as radial angle 228 described in relation to FIG. 5).

In some embodiments, the bevel 748 may be in a range having an upper value, a lower value, or upper and lower values including any of 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, 90°, or any values therebetween. For example, the bevel 748 may be greater than 0°. In other examples, the bevel 748 may be less than 90°. In yet other examples, the bevel 748 may be between 5° and 85°. In further examples, the bevel 748 may be between 10° and 80°.

FIG. 11 is a side cross-sectional view of another embodiment of a profile of a rotatable cutting element 816 with a cutting portion 832 fixed to a base 834. The cutting portion 832 may have a first bevel 848 located at the edge of the cutting portion 832 and a second bevel 850 inward of the first bevel 848. In some embodiments, the combination of the first bevel 848 and second bevel 850 may reduce fracturing of the cutting portion 832 near the edge. In other embodiments, the first bevel 848 may correspond to the declination and/or angle (such as declination 226 and radial angle 228 described in relation to FIG. 4 and FIG. 5, respectively) to allow the first bevel 848 to contact flush against the casing being milled. In some embodiments, the first bevel 848 may be in a range having an upper value, a lower value, or upper and lower values including any of 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, or any values therebetween. For example, the first bevel 848 may be greater than 0°. In other examples, the first bevel 848 may be less than 45°. In yet other examples, the first bevel 848 may be between 5° and 40°. In further examples, the first bevel 848 may be between 10° and 35°.

In some embodiments, the second bevel 850 may be higher than the first bevel 848 and may be in a range having an upper value, a lower value, or upper and lower values including any of 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, or any values therebetween. For example, the first bevel 848 may be greater than 10°. In other examples, the first bevel 848 may be less than 85°. In yet other examples, the first bevel 848 may be between 15° and 80°. In further examples, the first bevel 848 may be between 45° and 80°.

In some embodiments, a rotatable cutting element may have one or more chipbreaking features on a surface thereof. For example, FIG. 12 illustrates an embodiment of a rotatable cutting element 916 with a bevel 948 and a chipbreaking feature 952 in a cutting portion 932. The cutting portion 932 is fixed to a base 934. In some embodiments, the chipbreaking feature 952 may be configured to break the cutting of the casing by bending and/or work hardening the cutting. The cutting may, therefore, break into a series of smaller pieces that are more easily flushed away.

In some embodiments, the chipbreaking feature 952 may be a concave feature in the cutting portion 932 that will bend the cutting formed by the cutting portion 932. For example, the cutting portion 932 may cut material from a casing at a point on the cutting portion 932 between the chipbreaking feature 952 and the bevel 948, urging material from the casing toward the chipbreaking feature 952. The chipbreaking feature 952 may then direct the cutting along the concave surface of the chipbreaking feature to fracture the cutting.

In other embodiments, a chipbreaking feature may include one or more facets or angles to promote the fracturing of the cuttings into smaller pieces. FIG. 13 illustrates another embodiment of a rotatable cutting element 1016 with a faceted cutting portion 1032 within a bevel 1048 at the edge. In some embodiments, the chipbreaking feature 1052 may include a plurality of facets which, when the rotatable cutting element 1016 rotates, may interact to deflect and/or bend a cutting in a plurality of directions to work harden and/or break the cutting into smaller pieces. For example, a faceted chipbreaking feature 1052 may include a plurality of ridges 1054 angularly spaced about the cutting portion 1032. The plurality of ridges 1054 may rotationally separate concave chipbreaking features 1052, similar to the concave chipbreaking features 952 described in relation to FIG. 12.

In at least one embodiment, a milling arm with a rotatable cutting element therein may allow for longer operational lifetimes and/or more efficient cutting of casing by distributing wear across a rotational edge of the rotatable cutting element. The rotation of the rotatable cutting element may provide a greater wear area, increasing the cutting efficiency of the cutting element compared to a conventional fixed cutting element. In at least one other embodiment, the rotatable cutting element may include a chipbreaking feature, and the rotation of the rotatable cutting element may assist in breaking chips of the cutting.

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

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

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

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

The terms “approximately,” “about,” and “substantially” as used herein represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the terms “approximately,” “about,” and “substantially” may refer to an amount that is within less than 5% of, within less than 1% of, within less than 0.1% of, and within less than 0.01% of a stated amount. Further, it should be understood that any directions or reference frames in the preceding description are merely relative directions or movements. For example, any references to “up” and “down” or “above” or “below” are merely descriptive of the relative position or movement of the related elements.

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

Claims

1. A downhole tool, the downhole tool comprising:

a milling arm, and

a rotatable cutting element positioned in the milling arm and rotatable within the milling arm about a rotational axis.

2. The downhole tool of claim 1, further comprising at least one inside cutting element positioned in the milling arm in a downhole direction of the rotatable cutting element.

3. The downhole tool of claim 2, further comprising at least one outside cutting element positioned in the milling arm in a downhole direction of the rotatable cutting element.

4. The downhole tool of claim 3, the milling arm having a sacrificial region between the at least one inside cutting element and the at least one outside cutting element.

5. The downhole tool of claim 1, the rotatable cutting element having a front face including a cutting portion including an ultrahard material.

6. The downhole tool of claim 5, less than 50% of the front face being the ultrahard material.

7. The downhole tool of claim 5, the ultrahard material being a continuous circumferential edge of the rotatable cutting element.

8. The downhole tool of claim 5, the rotatable cutting element have a chipbreaking feature on the front face.

9. The downhole tool of claim 1, the rotatable cutting element being retained in a housing by one or more fasteners.

10. The downhole tool of claim 9, wherein at least a portion of the housing is positioned within the rotatable cutting element.

11. The downhole tool of claim 1, the rotatable cutting element being retained in a housing by at least one ring.

12. A milling tool, the milling device comprising:

a milling tool body; and

a plurality of milling arms projecting radially from the body and configured to move about the milling tool body in a cutting direction, at least one milling arm of the plurality of milling arms including,

a rotatable cutting element positioned in an arm body of the milling arm and rotatable about a rotational axis, and

at least one fixed cutting element positioned in the arm body of the milling arm.

13. The milling tool of claim 12, the rotational axis being non-parallel to the cutting direction.

14. The milling tool of claim 12, the rotational axis being oriented at a declination from the cutting direction between 0° and 45°.

15. The milling tool of claim 14, the rotatable cutting element having a bevel that is complimentary to the declination.

16. The milling tool of claim 12, the rotational axis being oriented radially outward from the cutting direction at a radial angle between 0° and 45°.

17. The milling tool of claim 16, the rotatable cutting element having a bevel that is complimentary to the radial angle.

18. The milling tool of claim 12, the plurality of milling arms being deployable from the body.

19. A milling tool, the milling device comprising:

a milling tool body; and

a plurality of milling arms projecting radially from the body and configured to move about the milling tool body in a cutting direction, at least one milling arm of the plurality of milling arms including,

a rotatable cutting element positioned in an arm body of the milling arm and rotatable about a rotational axis,

at least one inside fixed cutting element fixed relative to the arm body and positioned in a downhole direction of the rotatable cutting element, and

at least one outside fixed cutting element fixed relative to the arm body and positioned radially outside of the at least one inside cutting element with a sacrificial region positioned therebetween.

20. The milling tool of claim 19, the at least one outside cutting element positioned at a radial end of the arm body.