Methods of making earth-boring tools

Abstract

Methods of making earth-boring tools may involve, for each first cutting element of a first earth-boring tool, determining a first slope of a first curve defined by plotting a change in aggressiveness of the first cutting element against a change in velocity of the first cutting element for a range of velocities of the first cutting element. For each second cutting element of a second earth-boring tool, a second slope of a second curve defined by plotting a change in aggressiveness of the second cutting element against a change in velocity of the second cutting element for a range of velocities of the second cutting element may be determined. The second earth-boring tool may be selected for manufacture when a second average of the second slopes for each second cutting element is greater than a first average of the first slopes for each first cutting element.

Description

[0001] METHODS OF MAKING EARTH-BORING TOOLS

[0002] PRIORITY CLAIM

[0003] This application claims the benefit of the filing date of United States Patent Application Serial No. 19 / 075,259, filed March 10, 2025, for “METHODS OF MAKING EARTH-BORING TOOLS,” the disclosure of which is hereby incorporated herein in its ent ire tv by this reference.

[0004] TECHNICAL FIELD

[0005] This disclosure relates generally to methods of making and designing earth-boring tools. More specifically, disclosed examples relate to methods of making and designing earth-boring tools which may mitigate torsional excitability of an earth-boring assembly, increase stability' while engaging in an earth-boring operation, and increase efficiency of an earth-boring operation.

[0006] BACKGROUND

[0007] Wellbores are formed in subterranean formations for various purposes including, for example, extraction of oil and gas from the subterranean formation and extraction of geothermal heat from the subterranean formation. Wellbores may be formed in a subterranean formation using a drill bit such as, for example, an earth-boring rotary’ drill bit. Different types of earth-boring rotary drill bits are known in the art including, for example, fixed-cutter bits (which are often referred to in the art as “drag” bits), rolling-cutter bits (which are often referred to in the art as “rock” bits), diamond-impregnated bits, and hybrid bits (which may include, for example, both fixed cutters and rolling cutters). The drill bit is rotated and advanced into the subterranean formation. As the drill bit rotates, the cutters or abrasive structures thereof cut, crush, shear, and / or abrade away the formation material to form the wellbore. A diameter of the wellbore drilled by the drill bit may be defined by the cutting structures disposed at the largest outer diameter of the drill bit.

[0008] The drill bit is coupled, either directly or indirectly, to an end of what is referred to in the art as a “drill string,” which comprises a series of elongated tubular segments connected end-to-end that extends into the wellbore from the surface of the formation. Often various tools and components, including the drill bit, may be coupled together at the distalend of the drill string at the bottom of the wellbore being drilled. This assembly of tools and components is referred to in the art as a “bottom-hole assembly” (BHA).

[0009] The drill bit may be rotated within the wellbore by rotating the drill string from the surface of the formation, or the drill bit may be rotated by coupling the drill bit to a downhole motor, which is also coupled to the drill string and disposed proximate the bottom of the w ellbore. The downhole motor may comprise, for example, a hydraulic Moineau-type motor having a shaft, to which the drill bit is mounted, that may be caused to rotate by pumping fluid (e.g., drilling mud or fluid) from the surface of the formation down through the center of the drill string, through the hydraulic motor, out from nozzles in the drill bit, and back up to the surface of the formation through the annular space betw een the outer surface of the drill string and the exposed surface of the formation within the wellbore.

[0010] BRIEF SUMMARY

[0011] In some examples, methods of making earth-boring tools may involve, for each first cutting element of a first earth-boring tool, determining a first slope of a first curve defined by plotting a change in aggressiveness of the first cutting element against a change in velocity of the first cutting element for a range of velocities of the first cutting element. For each second cutting element of a second earth-boring tool, a second slope of a second curve defined by plotting a change in aggressiveness of the second cutting element against a change in velocity of the second cutting element for a range of velocities of the second cutting element may be determined. The second earth-boring tool may be selected for manufacture when a second average of the second slopes for each second cutting element is greater than a first average of the first slopes for each first cutting element. The second earth-boring tool may then be made.

[0012] In other examples, methods of making earth-boring tools may involve, for a first earth-boring tool, determining a first slope of a first curve defined by plotting a change in aggressiveness of the first earth-boring tool against a change in rotational velocity' of the first earth-boring tool for a range of rotational velocities of the first earth-boring tool. For a second earth-boring tool, a second slope of a second curve defined by plotting a change in aggressiveness of the second earth-boring tool against a change in rotational velocity of the second earth-boring tool for a range of rotational velocities of the second earth-boring tool may be determined. The second earth-boring tool may be selected for manufacture when thesecond slope for the second earth-boring tool is greater than the first slope for the first earthboring tool. The second earth-boring tool may then be made.

[0013] In other examples, methods of making earth-boring tools may involve, for a first earth-boring tool, determining a first slope of a first curve defined by plotting a change in torque acting on the first earth-boring tool against a rotational velocity of the first cutting earth-boring tool for a range of rotational velocities of the first earth-boring tool. For a second earth-boring tool, a second slope of a second curve defined by plotting a change in torque acting on the second earth-boring tool against a change in rotational velocity of the second earth-boring tool for a range of rotational velocities of the second earth-boring tool may be determined. The second earth-boring tool may be selected for manufacture when the second slope for the second earth-boring tool is greater than the first slope for the first earth-boring tool. The second earth-boring tool may then be made.

[0014] BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0015] While this disclosure concludes with claims particularly pointing out and distinctly claiming specific embodiments, various features and advantages of embodiments within the scope of this disclosure may be more readily ascertained from the following description when read in conjunction with the accompanying drawings. In the drawings:

[0016] FIG. 1 is a schematic diagram of a drilling system;

[0017] FIG. 2 is a perspective view of an earth-boring tool usable wi th the drilling system of FIG. 1;

[0018] FIG. 3 is a cross-sectional side view of a portion of the earth-boring tool of FIG. 2; FIG. 4 is a partially cut-aw ay perspective view of a cutting element usable with the earth-boring tool of FIG. 2;

[0019] FIG. 5 is a simplified cross-sectional view of the cutting element of FIG. 4 engaging an underlying earth formation;

[0020] FIG. 6 is a flow chart illustrating a method of making an earth-boring tool;

[0021] FIG. 7 is a graph showing illustrative values for aggressiveness of various first cutting elements in corresponding positions on an earth-boring tool against velocity;

[0022] FIG. 8 is a graph showing illustrative aggressiveness of an individual cutting element for a variety of velocities;

[0023] FIG. 9 is a graph showing illustrative aggressiveness of another example of an individual cutting element for a variety of velocities;FIG. 10 is a graph showing illustrative aggressiveness of another example of an individual cutting element for a variety of velocities;

[0024] FIG. 11 is a graph showing illustrative aggressiveness of another example of an individual cutting element for a variety of velocities;

[0025] FIG. 12 is a flowchart illustrating another method of making an earth-boring tool; FIG. 13 is a flowchart illustrating another method of making an earth-boring tool; FIG. 14 is a graph showing illustrative first and second torque-rotational velocity curves for first and second earth-boring tools; and

[0026] FIG. 15 is a graph showing illustrative curves for torque against revolutions per minute (RPM) for an earth-boring tool for a variety of applied weights on the earth-boring tool.

[0027] DETAILED DESCRIPTION

[0028] The illustrations presented in this disclosure are not meant to be actual views of any particular drill string, earth-boring tool, component thereof, or act in a method, but are merely idealized representations employed to describe illustrative embodiments. Thus, the drawings are not necessarily to scale.

[0029] Disclosed examples relate generally to methods of making and designing earthboring tools which may mitigate torsional excitability of an earth-boring assembly, increase stability while engaging in an earth-boring operation, and increase efficiency of an earthboring operation. More specifically, disclosed are examples of methods that may enable designers to select and produce earth-boring tools and cutting elements for earth-boring tools which may experience higher cutting forces, and / or exhibit increasing aggressiveness, with increasing velocity.

[0030] Generally speaking, earth-boring tools may rotate about an axis while performing an earth-boring operation. As a result, cutting elements deployed close to the axis will exhibit a lower velocity than the velocity of cutting elements deployed far from the axis. Because velocity significantly affects cutting dynamics, some attempts have been made to deploy cutting elements having different properties at different distances from the axis. Some approaches for doing so known to the inventors have used efficiency, often as measured by mechanical specific energy (i.e., the amount of energy input required per unit of volume of subterranean material removed), as the standard by which performance may be measured. For some example earth-boring tools, such an approach may result in cutting elements havingcharacteristics tending to produce more aggressive cutting behavior (e.g., those with higher rake angles, those with domed or pointed cutting tips) being deployed close to the axis, so as to remove material with little energy input even at low speeds. Continuing the example, the aforementioned approach may result in cutting elements having less aggressive cutting characteristics (e.g., those with lower rake angles, those with planar cutting faces) being deployed far from the axis, so as to remove material with little energy- input at high speeds.

[0031] Such an approach toward evaluating performance may place an undue focus on energy input at the expense of other factors that may impact the overall efficiency of an earthboring operation. For example, the foregoing approach toward design of an earth-boring tool may produce an earth-boring tool whose design is susceptible to greater impact forces and abrasive wear, which may reduce the useful life of the earth-boring tool. As another example, the foregoing approach toward design of an earth-boring tool may produce an earth-boring tool whose design is susceptible to greater instability, including torsional instability. Exhibiting instability may cause an earth-boring tool to wander away from a planned trajectory-, and may further induce unintended vibrations, rotations, oscillations, and other undesirable dynamic behaviors that may damage or hasten w ear of the earth-boring tool or other components of the drill string.

[0032] In accordance with this disclosure, it is proposed that an alternative approach toyvard evaluating performance look to the aggressiveness exhibited, or to the torque applied, at varying velocities. When selecting a design for an earth-boring tool, cutting element, or combination of earth-boring tool and cutting elements, those designs that may exhibit greater aggressiveness, or that may require greater applied torque, with increasing velocity may be selected over designs exhibiting lower aggressiveness, or requiring lesser applied torque, with increasing velocity. It is expected that doing so may increase stability, and particularly torsional stability, which may increase the useful life of the earth-boring tool and associated cutting elements, and improve ability to remain on a target trajectory. It is further expected that doing so may reduce unstable earth-boring behaviors, and particularly torsional instability (e.g., slip-stick vibrations), reduce impact damage and abrasive wear on the earthboring tool and its components, reduce time spent outside of an intended trajectory, and reduce detours and re-boring when compared to designs resulting from other approaches knoyvn to the inventors.

[0033] As one example, a slope of a curve defined by plotting a change in aggressiveness of a given cutting element for a range of velocities may be utilized to evaluate performance.The curve may be defined by fiting a line to a set of data, which may be generated by simulating the performance of an earth-boring tool or by measuring the relevant parameters while conducting an earth-boring operation (e.g., a sample or experimental earth-boring operation). For example, the curve may be defined by performing a least squares regression on the resulting data.

[0034] One way to implement such an approach is to make a comparison of two designs for first earth-boring tools (e.g., between an existing design and a proposed design, between two existing designs, between two proposed designs), evaluating performance of the earth-boring tools on the basis of overall aggressiveness when selecting which earth-boring tool to manufacture and / or deploy. For example, a first slope of a first curve defined by ploting a change in aggressiveness of a first earth-boring tool against a change in rotational velocity of the first earth-boring tool for a range of rotational velocities of the first earth-boring tool may be determined. For a second earth-boring tool, a second slope of a second curve defined by ploting a change in aggressiveness of the second earth-boring tool against a change in rotational velocity of the second earth-boring tool for a range of rotational velocities of the second earth-boring tool may be determined. The slopes may be compared to one another, and the second earth-boring tool may be selected for manufacture when the second slope is greater than the first slope. Thereafter, the second earth-boring tool may be made.

[0035] Alternatively, the comparison may be made between applied torque against change in velocity. As an example, a first slope of a first curve defined by ploting a change in applied torque on the first earth-boring tool (e.g., a sum of tangential forces acting on the first cutting elements of the first curve) against a change in rotational velocity of the first earth-boring tool for a range of rotational velocities of the first earth-boring tool may be determined. For a second earth-boring tool, a second slope of a second curve defined by ploting a change in applied torque on the second earth-boring tool against a change in rotational velocity of the second earth-boring tool for a range of rotational velocities of the second earth-boring tool may be determined. The second earth-boring tool may be selected for manufacture when the second slope is greater than the first slope. The second earth-boring tool may then be made.

[0036] As yet another example, metrics for evaluating performance in accordance with this disclosure may be applied directly on a cuting-element-by-cuting-element basis. This approach may be taken with the aggressiveness-velocity or with the torque-velocity curves discussed above. For example, cuting elements of an earth-boring tool may be evaluated for potential replacement individually across the group of cuting elements. More specifically, afirst slope of a first curve defined by plotting a change in aggressiveness of a first cutting element against a change in veloci ty of the first cutting element for a range of velocities of the first cutting element may be determined for each first cutting element of an earth-boring tool. An aggressiveness-velocity curve defined by plotting a change in aggressiveness of each first cutting element against a velocity of the respective first cutting element for a range of velocities of the respective first cutting element may be determined. A design of the earthboring tool may be changed, by performing at least the following actions for each first cutting element of the earth-boring tool. The first cutting element may be at least temporarily replaced with a second cutting element exhibiting a difference in shape, rake angle, position on the earth-boring tool, profile shape of a blade on which the second cutting element is supported, or any combination of these. A second slope of a second curve defined by plotting a change in aggressiveness of the second cutting element against a change in velocity of the second cutting element for a range of velocities of the second cutting element may be determined. The second cutting element may be selected for deployment on the earth-boring tool when the second slope of the second curve is greater than the first slope of the first curve. The earth-boring tool may be made when each first cutting element has been replaced or when the first slope for each first cutting element is greater than the second slope of a corresponding second cutting element.

[0037] Earth-boring tools designed and manufactured in accordance with this disclosure may improve efficiency of earth-boring operations performed with such earth-boring tools. For example, such earth-boring tools may experience less impact damage and abrasive wear, resulting in fewer trips out of and back into a borehole to repair and / or replace the earthboring tool. Such earth-boring tools may spend less time boring away from a target trajectory’, requiring less redirection and re-boring. When evaluated wholistically, including these factors and not just mechanical specific energy, such earth-boring tools may exhibit improved efficiency when compared to other designs for earth-boring tools known to the inventors.

[0038] As used in this disclosure, the term “earth-boring tool” means and includes any type of tool having cutting elements secured to the tool used for material removal during the creation or enlargement of a wellbore in a subterranean formation. For example, earth-boring tools include fixed-cutter bits, rolling cone bits, percussion bits, core bits, eccentric bits, bicenter bits, mills, drag bits, hybrid bits, reamers, and other drilling bits and tools known in the art.As used in this disclosure, the terms “poly crystalline table” and “polycrystalline material” mean and include any structure or material comprising grains (e.g., crystals) of a material (e.g., a superabrasive material) that are bonded directly together by inter-granular bonds. The crystal structures of the individual grains of the material may be randomly oriented in space within the poly crystalline table. For example, polycrystallinc tables include poly crystalline diamond compacts (PDCs) characterized by diamond grains that are directly bonded to one another to form a matrix of diamond material with interstitial spaces among the diamond grains.

[0039] As used herein, the term “inter-granular bond” and “interbonded” mean and include any direct atomic bond (e g., covalent, metallic, etc.) between atoms in adjacent grains of superabrasive material.

[0040] As used herein, the term “superhard” means and includes any material having a Knoop hardness value of about 3,000 Kgf / mm2(29,420 MPa) or more. Superhard materials include, for example, diamond and cubic boron nitride. Superhard materials may also be characterized as “superabrasive” materials.

[0041] As used herein, the term “aggressiveness,” as applied to an earth-boring tool, means and includes a value calculated by dividing a torque acting on an earth-boring tool (i.e., the sum of all moments of the tangential forces acting on the earth-boring tool) by a weight applied to the earth-boring tool (e.g., axial force expressed in weight, weight-on-bit (WOB)). As applied to a cutting element, the term “aggressiveness,” as used herein, means and includes a value calculated by dividing a tangential force acting on the given cutting element during an earth-boring operation by an axial force acting on the cutting element.

[0042] As used herein, the terms “storage device” and “memory” shall be interpreted to exclude transitory signals.

[0043] As used herein, the terms “substantially” and “about” in reference to a given parameter, property, or condition means and includes to a degree that one of ordinary skill in the art would understand that the given parameter, property', or condition is met with a degree of variance, such as within acceptable manufacturing tolerances. For example, a parameter that is substantially’ or about a specified value may be at least about 90% the specified value, at least about 95% the specified value, at least about 99% the specified value, or even at least about 99.9% the specified value.

[0044] FIG. 1 through FIG. 5 depict example sy stems and apparatuses on which methods in accordance with this disclosure may be utilized to improve the design of the system,apparatus, or component thereof. Thus, FIG. 1 through FIG. 5 are intended to provide context and enabling information to ensure that those of ordinary skill in the art have familiarity with the hardware that may be improved utilizing methods in accordance with this disclosure. Additional detail regarding the methods themselves is provided in connection with FIG. 6 through FIG. 11.

[0045] FIG. 1 is a schematic diagram of an illustrative earth-boring system 100 that may utilize earth-boring tools 200 made according to the disclosure herein. FIG. 1 shows a wellbore 102 having an upper section 104 with a casing 106 installed therein and a lower section 108 being drilled with a drill string 110. The drill string 110 is shown to include a tubular member 112 with a bottom-hole-assembly 114 (BHA) attached at its leading end. The tubular member 112 may be made up by joining drill pipe sections or it may be a coiled-tubing. An earth-boring tool 200 (e.g., a drill bit) is shown attached to the bottom end of the BHA 114 for disintegrating the rock formation 116 to drill the wellbore 102 to a selected diameter.

[0046] Drill string 110 is shown conveyed into the wellbore 102 from a rig 118 at the surface 120. The illustrative rig 118 shown is a land rig for ease of explanation. The apparatus and methods disclosed herein may also be utilized with an offshore rig used for drilling wellbores under w ater. A rotary table 122 or a top drive (not shown) coupled to the drill string 110 may be utilized to rotate the drill string 110 to rotate the BHA 114 and thus the earth-boring tool 200 to drill the wellbore 102. A drilling motor 124 (also referred to as the “mud motor”) may be provided in the BHA 114 to rotate the earth-boring tool 200. The drilling motor 124 may be used alone to rotate the earth-boring tool 200 or to superimpose the rotation of the drill bit by the drill string 110. A control unit (or controller) 126, which may be a computer-based unit, may be placed at the surface 120 to receive and process data transmitted by the sensors in the earth-boring tool 200 and the sensors in the BHA 114, and to control selected operations of the various devices and sensors in the BHA 114. The surface controller 126, in one embodiment, may include a processor 128, a data storage device (or a computer-readable medium) 130 for storing data, algorithms and computer programs 132. The data storage device 130 may be any suitable device including, but not limited to, a read-only memory (ROM), a random-access memory (RAM), a flash memory, a magnetic tape, a hard disk and an optical disk. During drilling, a drilling fluid 134 from a source thereof is pumped under pressure into the tubular member 112. The drilling fluid discharges at the leading end of theearth-boring tool 200 and returns to the surface via the annular space (also referred as the “annulus”) between the drill string 110 and the inside wall 136 of the wellbore 102.

[0047] Still referring to FIG. 1, the earth-boring tool 200 includes a face section (or bottom section) 138. The face section 138, or a portion thereof, faces the formation in front of the drill bit or the wellbore bottom during drilling. The BHA 114 may further include one or more downhole sensors (collectively designated by numeral 140). The sensors 140 may include any number and type of sensors including, but not limited to. sensors generally known as the measurement-while-drilling (“MWD”) sensors or the logging-while-drilling (“LWD”) sensors, and sensors that provide information relating to the behavior of the BHA 114, such as drill bit rotation (revolutions per minute or “RPM”), tool face, pressure, vibration, whirl, bending, and stick-slip.

[0048] The BHA 114 may further include a control unit (or controller) 142 configured to control the operation of components of the BHA 114 and for at least partially processing data received from the sensors 140. The controller 142 may include, among other things, circuits to process the sensor 140 signals (e.g., amplify and digitize the signals), a processor 144 (such as a microprocessor) to process the digitized signals, a data storage device 146 (such as a solid-state-memory ), and a computer program 148. The processor 144 may process the digitized signals, control the operation of the components of the BHA 114, process data from other sensors downhole, control other downhole devices and sensors, and communicate data information with the controller 126 at the surface 120 via a two-way telemetry unit 150.

[0049] Referring to FIG. 2, a perspective view' of an earth-boring tool 200 is shown. The particular earth-boring tool 200 show n may be characterized as, for example, a fixed-cutter drill bit (e.g., a drag bit). The earth-boring tool 200 may include a body 202 having a leading end 204 and a trailing end 206. At the trailing end 206, the body 202 may include a connection member 208 (e.g., an American Petroleum Institute (API) threaded connection) configured to connect the earth-boring tool 200 to a drill string. At the leading end 204, the body 202 may include blades 210 extending axially outw ardly from a remainder of the body 202 and radially outwardly from a rotational axis 212, which may also be a central axis, of the body 202 across the leading end 204. A crown 214 of the body 202 of the earth-boring tool 200 may comprise an outer surface defined by the blades 210 and the remainder of the body 202 at the leading end 204 of the body 202. Cutting elements 216 may be secured to the body 202. For example, the cutting elements 216 may be partially located in pockets 218 formed in rotationally leading surfaces of the blades 210 and brazed to the surfaces of theblades 210 defining the pockets 218 to secure the cutting elements 216 to the body 202. The cutting elements 216 may be distributed over the crown 214 to form a cutting structure configured to engage with and remove an underlying earth formation as the earth-boring tool 200 is rotated during use. Gage pads 220 may be located at a periphery 222 of the body 202 and may define a radially outermost portion of the earth-boring tool 200 in some embodiments. In other embodiments, additional cutting elements 216 may be secured to the body 202 at the periphery 222 to define the radially outermost portion of the earth-boring tool 200.

[0050] Referring to FIG. 3, a cross-sectional side view of a portion of the earth-boring tool 200 of FIG. 2 is shown. The crown 214 may be defined by a series of regions extending radially outwardly from the rotational axis 212 of the body 202 to the periphery 222. For example, the crown 214 may be defined by a first, cone region 302 located at and immediately surrounding the rotational axis 212. The cone region 302 may be characterized by a sloping surface extending downwardly (when the rotational axis 212 is oriented vertically with the leading end 204 facing down) located at and immediately surrounding the rotational axis 212, which may generally resemble an inverted cone shape. A second, shoulder region 304 may be located radially outward from the cone region 302 adjacent the periphery' 222 of the body 202. The shoulder region 304 may be characterized by a rounded, upwardly curving surface transitioning to the periphery 222 of the body 202. A third, nose region 306 may be interposed between and adjacent to both the cone region 302 and the shoulder region 304. The nose region 306 may be characterized by a transition from the sloping surface of the cone region 302 curving toward horizontal and beginning to curve upwardly into the shoulder region 304. A fourth, gage region 308 may be located radially outward from and adjacent to the shoulder region 304 and may define the periphery 222 of the body 202.

[0051] Cutting elements 216 may be distributed radially across at least a portion of the crown 214 at the leading end 204 of the body 202. In some examples, the cutting elements 216 may be limited to cutting elements located at the rotationally leading face of a blade 210, as shown in FIG. 2. In other examples, the cutting elements 216 may include backup cutting elements rotationally trailing leading cutting elements secured to the same blade 210.

[0052] Drilling conditions in the different regions 302, 304, 306, and 308 may significantly differ from one another. For example, cutting elements 216 in the cone region 302 may be subjected to high axial forces (i.e., forces acting in a direction parallel to the rotational axis212 of the earth-boring tool 200) resulting from the weight forcing the earth-boring tool 200 toward the underlying earth formation (e.g., weight-on-bit (W.O.B.)) or a combination of high axial forces and high tangential forces (i. e. , forces acting in a direction perpendicular to the rotational axis 212 of the earth-boring tool 200) resulting from engagement of the cutting elements 216 with the underlying earth formation, may traverse relatively short helical cutting paths with each rotation of the earth-boring tool 200, and may have a high depth of cut. Cutting elements 216 in the shoulder region 304, by contrast, may be subjected to low axial forces and high tangential forces, may traverse relatively long helical cutting paths with each rotation of the earth-boring tool 200, and may have a low7depth of cut. Cutting elements 216 in the nose region 306 may experience use conditions intermediate those present in the cone region 302 and shoulder region 304. Cutting elements in the gage region 308 may not be subjected to significant axial forces, may traverse relatively long helical paths with each rotation of the earth-boring tool 200, and may have a low depth of cut. Such differences in drilling conditions produce stresses at different levels and oriented in different directions and operational temperatures at different intensities in the cutting elements 216 in different regions 302, 304, 306, and 308 of the crown 214 of the earth-boring tool 200.

[0053] Referring to FIG. 4, a partially cut-aw ay perspective view of a cutting element 216 is shown. Cutting element 216 includes a substrate 402 having a table 404 of superabrasive material, such as a polycrystalline superhard material (e.g., polycrystalline diamond material), thereon. The table 404 may be formed on the substrate 402. or the table 404 and the substrate 402 may be separately formed and subsequently attached together. In some examples, the table 404 may have a chamfered edge 406. The chamfered edge 406 of the cutting element 216 in FIG. 4 is depicted as a single chamfer surface 408, although the chamfered edge 406 also may have additional chamfer surfaces, and such chamfer surfaces may be oriented at chamfer angles that differ from the chamfer angle of the chamfer surface 408 shown in FIG. 4. The table 404 also has a side surface 410 extending from the chamfer surface 408 to the interface betw een the table 404 and the substrate 402.

[0054] The substrate 402 may have a generally cylindrical shape. A face 412 of the cutting element defined by the table 404 and located at a rotationally leading end of the cutting element 21 may be at least substantially planar in some examples. In lieu of the chamfered edge 406, or in addition to the chamfered edge 406, the face may be have a non-planar shape (e.g., rounded, domed, chisel-shaped) in other examples.The substrate 402 may be formed from a material that is relatively hard and resistant to wear. For example, the substrate 402 may be formed from and include a ceramic-metal composite material (which are often referred to as '‘cermet” materials). More specifically, the substrate 402 may include a cemented carbide material, such as a cemented tungsten carbide material, in which tungsten carbide particles are cemented together in a metallic binder material. The metallic binder material may include, for example, cobalt, nickel, iron, or alloys and mixtures thereof. Alternatively, other substrate materials may be used.

[0055] Referring to FIG. 5, a simplified cross-sectional view of a cutting element 216 engaging an underlying earth formation 502 is shown. Cutting elements 216 attached to blades 210 of earth-boring tools 200 may be oriented at rake angles 504 with respect to such earth formations 502. The rake angle 504 may be a smallest angle at which the cuting element 216 engages the earth formation 502 relative to a vertical line at the point of engagement. When the cuting elements 216 are oriented such that the rake angle 504 trails the vertical line at the point of engagement, the rake angle 504 may be said to be negative, which generally produces a less aggressive cuting action. When the cuting elements 216 are onented such that the rake angle 504 leads the vertical line at the point of engagement, the rake angle 504 may be said to be positive, which generally produces a more aggressive cuting action.

[0056] As the earth-boring tool 200 rotates within the borehole, at least some of the cuting elements 216 may engage the underlying earth formation 502 to facilitate its removal. Cuting actions by the cuting elements 216 may involve gouging, crushing, and / or shearing aw ay the earth formation 502, depending on the shape, rake angle 504, depth of cut, and other characteristics affecting the aggressiveness of the cuting elements 216.

[0057] FIG. 6 is a flowchart illustrating a method 600 of making an earth-boring tool. The method 600 may involve determining a first slope of a first curve defined by plotting a change in aggressiveness of the first cuting element against a change in velocity of the first cuting element for a range of velocities of the first cuting element for each first cuting element of a first earth-boring tool, as indicated at act 602. In some examples, the first slope may further be determined against change in velocity for a range of velocities and a range of depths of cut.

[0058] The aggressiveness of each first cuting element may be calculated by dividing a tangential force acting on the respective cuting element (e.g.. the reactive lateral force from engagement with the underlying earth formation) by a penetration actual force acting on thecuting element (e.g., the proportion of the weight-on-bit (WOB) acting on the cuting element). The tangential and axial forces, including proportion of WOB, acting on each first cuting element may be determined by direct measurement utilizing sensors (e.g., stress sensors, strain sensors) deployed on or in each first cuting element, a hanger of a drilling rig, a top drive of a drilling rig, or elsewhere in the drill string for sensing forces during an actual earth-boring operation.

[0059] Alternatively, the aggressiveness of each first cuting element may be determined by simulation. For example, a model of a drill string including the earth-boring tool may be provided as input, which model may be, for example, a three-dimensional system model or a mathematical model of critical components and behaviors of the drill string. Characteristics of an earthen formation to be bored as part of a simulated earth-boring operation may also be input, selected from a database of known earthen characteristics, or estimated based on the known characteristics of nearby earthen formations. The characteristics may be, for example, a uniform material or may include strata of differing materials as part of a planned boring trajectory. An earth-boring operation may be simulated by estimating the forces on the various components of the drill string, including the earth-boring tool and its components, when in contact with the earthen formation under a simulated axial and torsional load, calculating resulting cuting action on the earthen formation, calculating a dynamic response of the drill string, rotating the drill string by a specified amount, and repeating this process until the earth-boring operation is complete. In some examples, a finite element analysis may be performed as part of, or to complete, the simulation. Additional example methods of simulating an earth-boring operation are disclosed in U.S. Patent No. 10,851,637, issued December 1, 2020, to Herbig et al., the disclosure of which is incorporated herein in its entirety’ by this reference.

[0060] The aggressiveness detected or calculated for defining the first slope may be the maximum aggressiveness, the minimum aggressiveness, or the average aggressiveness (e.g., the mean aggressiveness) exhibited by a given first cuting element at the specified velocity’. For example, the aggressiveness may be detected or calculated across a range of velocities and / or a range of depths of cut, and maximum aggressiveness at each velocity may be determined, utilized to define the first curve, and utilized to calculate the first slope. As another example, the aggressiveness may be detected or calculated across a range of velocities and / or a range of depths of cut, and an average aggressiveness at each velocity may be determined, utilized to define the first curve, and utilized to calculate the first slope.To provide a comparison, a similar process may be performed for each second cuting element of a second earth-boring tool. For example, a second slope of a second curve defined by ploting a change in aggressiveness of the second cuting element against a change in velocity of the second cuting element for a range of velocities of the second cuting element may be determined for each second cuting element of the second earth-boring tool, as shown at act 604. Each of these acts may be performed in at least substantially the same or a similar manner as described in connection with the first cutting elements of the first earth-boring tool discussed in connection with act 602. In some examples, the second slope may further be determined against change in velocity for a range of velocities and a range of depths of cut.

[0061] The second earth-boring tool may differ from the first earth-boring tool, the second cutting element may differ from the first cuting element, or the second earth-boring tool may differ from the first earth-boring tool and the second cuting element may differ from the first cutting element in at least one characteristic. For example, differences in design may include rake angle, shape of cuting surface, perimeter shape of cutting element, maximum diameter of cuting element, perimeter shape of cuting surface, cuting element size, chamfer presence, number of chamfers, chamfer angle(s), presence or absence of backup cuting elements, blade profile, cuting element layout, number of blades, blade spacing, presence of secondary blades, number of secondary blades, ratio of secondary' blades to primary blades, number of nozzles, placement of nozzles, orientation of nozzles, maximum diameter of earthboring tool. Introducing one or more differences may beter enable evaluators to determine whether a given change is likely to produce performance improvements. In some examples, the change may be isolated to a single difference in the overall earth-boring tool. In other examples, the change may be a single difference in one or more cuting elements (e.g.. each cutting element) supported by the earth-boring tool.

[0062] The second earth-boring tool may be selected for manufacture when a second average of the second slopes for each second cutting element is greater than a first average of the first slopes for each first cutting element, as indicated at act 606. For example, a general approach of designing earth-boring tools in accordance with this disclosure may be to select and deploy cutting elements exhibit increasing aggressiveness with increasing speed. In some examples, this approach may result in the deployment of cuting elements exhibiting greater aggressiveness being deployed within the gage region, shoulder region, and potentially nose region of the earth-boring tool, whereas cuting elements exhibit lesser aggressiveness maybe deployed within the cone region and potentially nose region of the earth-boring tool. More specifically, this approach may result in cutting elements exhibiting the least aggressiveness being deployed closest to the axis of rotation, cutting elements exhibiting the greatest aggressiveness being deployed farthest from the axis of rotation, and cutting elements intermediate these extremes therebetween, with aggressiveness generally increasing as distance from the axis of rotation increases. In other examples, absolute values for aggressiveness may not necessarily increase with increasing distance from the axis of rotation, although the slope of the curve of change in aggressiveness against a change in velocity7may increase. In still other examples, the second earth-boring tool may be selected for manufacture when the second slopes for each second cutting element at actual or anticipated operational velocity is greater than the first slopes for each first cutting element at the actual or anticipated operational velocity. Once selected, the second earth-boring tool may be made, as indicated at act 608.

[0063] In some examples, the second earth-boring tool may be selected for manufacture only when the second slope for each second cutting element is greater than zero. For example, each second cutting element on the second earth-boring tool may exhibit increasing aggressiveness with increasing velocity. In some such examples, those cutting elements exhibiting the greatest aggressiveness at each velocity7may be deployed farthest from the axis of rotation while those cutting elements exhibiting the least aggressiveness at each velocity may be deployed closest to the axis. In other such examples, those cutting elements demonstrating the greatest increase or the least decrease in aggressiveness with increasing velocity may be deployed farthest from the axis of rotation while those cutting elements experiencing the least increase or greatest decrease in aggressiveness at each velocity may be deployed closest to the axis.

[0064] In some examples, the second earth-boring tool may be selected for manufacture only when each of the second slopes for each second cutting element is greater than each corresponding first slope of the first slopes for each corresponding first cutting element. For example, the second earth-boring tool may be selected for manufacture only when each of its second cutting elements represents an expected performance improvement over each corresponding first cutting element of the first earth-boring tool. More specifically, the second earth-boring tool may be selected for manufacture only when each of its second cutting elements exhibits a greater increase or lesser decrease in aggressiveness with increasing velocity when compared to the corresponding increase or decrease inaggressiveness with increasing velocity of each corresponding first cutting element of the first earth-boring tool.

[0065] In some examples, the process may be iterated. For example, repeated instances of determining slope and selecting greater average slope, changing at least one characteristic of a design of the first earth-boring tool, the first cutting elements, or the first earth-boring tool and the first cutting elements before each iteration may be performed. Repeated instances may better enable designers to evaluate multiple options and further improve expected performance. In some examples, the change made to the at least one characteristic of the design of the first earth-boring tool, the first cutting elements, or the first earth-boring tool and the first cutting elements comprises replacing a first cutting element resulting in a lowest first slope with a replacement first cutting element.

[0066] In some examples, the different first cutting element may differ from the first cutting element resulting in the lowest first slope in shape, size, rake angle, side rake angle, surface finish, number of chamfers, tip size and angle, or shape, size, rake angle, side rake angle, surface finish, number of chamfers, and tip size and angle. For example, the different first cutting element may differ from the first cutting element resulting in the lowest first slope in shape, and the difference in shape may include a difference in surface area of a cutting surface, in a presence of a chamfer, in an angle of the chamfer, in a peripheral shape of the cutting surface, or in any combination of these. As another example, changing the at least one characteristic of the design of the first earth-boring tool, the first cutting elements, or the first earth-boring tool and the first cutting elements may involve changing a blade profile or a cutting element layout of the first earth-boring tool.

[0067] Values of the resulting performance evaluation criterion for examples where the average diameter of the earth-boring tool is unspecified, calculated by determining the derivative of the aggressiveness with respect to the local cutting velocity may be, for example, within a range extending from about -0.48 s / m to about -0.11 s / m in the cone region, within a range extending from about -0.16 s / m to about -0.09 s / m in the nose region, and within a range extending from about -0.13 s / m to about -0.06 s / m in the shoulder region. In examples where the average diameter of the earth-boring tool is about 6.75 inch (about 17 cm), the performance evaluation criterion may be in a range extending from about -0.17 s / m to about -0.11 s / m in the cone region, within a range extending from about -0.14 s / m to about -0.11 s / m in the nose region, and within a range extending from about -0.11 s / m to about -0.06 s / m in the shoulder region. In examples where the average diameter of the earth-boringtool is about 8.75 inch (about 22 cm), the performance evaluation criterion may be in a range extending from about -0.41 s / m to about -0.14 s / m in the cone region, in a range extending from about -0.16 s / m to about -0.10 s / m in the nose region, and in a range extending from about -0.12 s / m to about -0.06 s / m in the shoulder region. In examples where the average diameter of the earth-boring tool is about 12.25 inch (about 31 cm), the performance criterion may be in a range extending from about -0.48 s / m to about -0.12 s / m in the cone region, in a range extending from about -0.12 s / m to about -0.09 s / m in the nose region, and in a range extending from about -0.13 s / m to about -0.06 s / m in the shoulder region.

[0068] FIG. 7 is a graph 700 showing illustrative values for aggressiveness of various first cutting elements in corresponding positions on an earth-boring tool against velocity. In this particular example, rotational velocity (e.g., as measured in rotations per unit of time) is used. In other examples, instantaneous velocity (e.g., as measured in unit of distance per unit of time) may be used.

[0069] Graph 700 depicts the measured or calculated aggressiveness of two different sets of cutting elements, a first set of first cutting elements 702 and a second set of second cutting elements 704, at different velocities. Going from left to right, the graph 700 may show the measured or calculated aggressiveness for first cutting elements 702 and second cutting elements 704 in radial positions having increasing distance from the axis of rotation of the earth-boring tool. In each comparison, the second slope of the second curve for the second cutting element 704 is greater than (e.g., less negative than) the first slope of the corresponding first curve for the first cutting element 702. In such a situation, the second cutting element 704 would be preferred over the first cutting element 702.

[0070] FIG. 8 is a graph 800 showing illustrative aggressiveness of an individual cutting element 802 for a variety' of velocities. As shown in FIG. 8, the cutting element 802 may be at least substantially cylindrical in shape, and may have chamfer extending around a lateral periphery' of the cutting element 802 proximate to a rotationally leading end thereof. As reflected in the graph 800, such a cutting element 802 may exhibit high aggressiveness at low velocities and a rapid decline in aggressiveness with increasing velocity. In some implementations, such a cutting element 802 may be suited for deployment within a shoulder and / or a nose region, where velocities w ill be low' to moderate and the resulting slope of the aggressiveness-velocity' curve may be highest.

[0071] FIG. 9 is a graph 900 showing illustrative aggressiveness of another example of an individual cutting element for a variety’ of velocities. As shown in FIG. 9, the cutting element902 may be at least substantially cylindrical in shape, and may have a chamfer extending around a lateral periphery of the cutting element 902 proximate to a rotationally leading end thereof. As reflected in the graph 900, such a cutting element 902 may exhibit low aggressiveness at low velocities and gradually increasing aggressiveness with increasing velocity. In some implementations, such a cutting element 902 may be suited for deployment within a shoulder region and / or a nose region, where velocities will be highest (or at least higher relative to the cone region) and the resulting slope of the aggressiveness-velocity curve may be highest (or at least higher than it would be at lower velocities).

[0072] FIG. 10 is a graph 1000 showing illustrative aggressiveness of another example of an individual cutting element 1002 for a variety of velocities. As shown in FIG. 10, the cutting element 1002 may be at least substantially cylindrical in shape, and may have chamfer extending around a lateral periphery of the cutting element 1002 proximate to a rotationally leading end thereof. As reflected in the graph 1000, such a cutting element 1002 may exhibit moderate, relatively steady aggressiveness across all measured velocities. In some implementations, such a cutting element 802 may be suited for deployment within a nose region, where velocities will be moderate and the resulting slope of the aggressivenessvelocity curve may be moderate, or may be suitable for deployment across all regions for its steady aggressiveness response.

[0073] FIG. 11 is a graph 1100 showing illustrative aggressiveness of another example of an individual cutting element 1102 for a variety of velocities. As shown in FIG. 11. the cutting element 1102 may be at least substantially cylindrical in shape, may have a small chamfer extending around a lateral periphery of the cutting element 1102 proximate to a rotationally leading end thereof, and may have a divot, depression, or recess (which may generally be shaped as a rounded square or a four-leaf clover) in the cutting surface at the leading end. As reflected in the graph 1100, such a cutting element 1102 may exhibit moderate to high aggressiveness at low velocities and decreasing aggressiveness with increasing velocity. In some implementations, such a cutting element 1102 may be suited for deployment within a shoulder region, where velocities will be highest and the resulting slope of the aggressiveness-velocity curve may be highest, and may further be suitable for deployment in the nose region for its only moderate decline in aggressiveness response.

[0074] FIG. 12 is a flowchart illustrating another method 1200 of making an earth-boring tool. The method 1200 may involve, for a first earth-boring tool, determining a first slope of a first curve defined by plotting a change in aggressiveness of the first earth-boring toolagainst a change in rotational velocity of the first earth-boring tool for a range of rotational velocities of the first earth-boring tool, as indicated at act 1202. In some examples, the first slope may further be determined against change in rotational velocity for a range of rotational velocities and a range of depths of cut.

[0075] The aggressiveness of the first earth-boring tool may be calculated by dividing a torque acting on the first earth-boring tool (e.g., the sum of all moments on the tangential forces acting on the first earth-boring tool) by a weight applied to achieve that rate of penetration (e.g., axial force, weight-on-bit (WOB)). The tangential and axial forces, including WOB, acting on the first earth-boring tool may be determined by direct measurement utilizing sensors (e g., stress sensors, strain sensors) deployed on or in the earth-boring tool, a hanger of a drilling rig, a top drive of a drilling rig, or elsewhere in the drill string for sensing forces during an actual earth-boring operation. Alternatively, the aggressiveness of the first earth-boring tool may be determined by simulation, which may be performed at least substantially as described previously herein.

[0076] The aggressiveness detected or calculated for defining the first slope may be the maximum aggressiveness, the minimum aggressiveness, or the average aggressiveness (e.g., the mean aggressiveness) exhibited by the first earth-boring tool at the specified rotational velocity7. For example, the aggressiveness may be detected or calculated across a range of rotational velocities and / or a range of depths of cut, and maximum aggressiveness at each rotational velocity may be determined, utilized to define the first curve, and utilized to calculate the first slope. As another example, the aggressiveness may be detected or calculated across a range of rotational velocities and / or a range of depths of cut, and an average aggressiveness at each rotational velocity may be determined, utilized to define the first curve, and utilized to calculate the first slope.

[0077] For a second earth-boring tool, a second slope of a second curve defined by plotting a change in aggressiveness of the second earth-boring tool against a change in rotational velocity7of the second earth-boring tool for a range of velocities of the second earth-boring tool may be determined, as indicated at act 1204. Each of these acts may be performed in at least substantially the same or a similar manner as described in connection with the first earth-boring tool discussed in connection with act 1202. In some examples, the second slope may further be determined against change in rotational velocity7for a range of rotational velocities and a range of depths of cut.The second earth-boring tool, including its component parts, may differ from the first earth-boring tool, including its component parts, in at least one characteristic. For example, differences in design may include rake angle of one or more cutting elements, shape of cutting surface of one or more cutting elements, perimeter shape of one or more cutting elements, maximum diameter of one or more cutting elements, perimeter shape of cutting surface of one or more cutting elements, chamfer presence on one or more cutting elements, number of chamfers on one or more cutting elements, chamfer angle(s) of chamfer(s) on one or more cutting elements, cutting element size, presence or absence of backup cutting elements, blade profile, cutting element layout, number of blades, blade spacing, presence of secondary blades, number of secondary blades, ratio of secondary' blades to primary blades, number of nozzles, placement of nozzles, orientation of nozzles, maximum diameter of earthboring tool. Introducing one or more differences may better enable evaluators to determine whether a given change is likely to produce performance improvements. In some examples, the change may be isolated to a single difference in the overall first and / or second earthboring tool. In other examples, the change may be a single difference in one or more cutting elements (e.g., each cutting element) supported by the first and / or second earth-boring tool.

[0078] The second earth-boring tool may be selected for manufacture when the second slope for the second earth-boring tool is greater than the first slope for the first earth-boring tool, as indicated at act 1206. For example, a general approach of designing earth-boring tools in accordance with this disclosure may be to select and deploy’ earth-boring tools exhibiting increasing aggressiveness with increasing rotational velocity. In some examples, the second earth-boring tool may be selected for manufacture when the second slope for the second earth-boring tool at actual or anticipated operational velocity' is greater than the first slope for the first earth-boring tool at the actual or anticipated operational velocity. Once selected, the second earth-boring tool may be made, as indicated at act 1208.

[0079] In some examples, the process may be iterated. For example, repeated instances of determining slope and selecting greater average slope, changing at least one characteristic of a design of the first earth-boring tool and / or the second earth-boring tool, including their component parts, before each iteration may be performed. Repeated instances may better enable designers to evaluate multiple options and further improve expected performance. In some examples, the change made to the at least one characteristic of the design of the first earth-boring tool and / or the second earth-boring tool, including their component parts, may include replacing a first cutting element and / or a second cutting element resulting in a lowestfirst slope and / or a lowest second slope with a replacement first cutting element and / or a replacement second cutting element.

[0080] Values of the resulting performance evaluation criterion for examples where the average diameter of the earth-boring tool is unspecified, calculated by determining the derivative of the aggressiveness with respect to the rotational velocity7of the bit may be, for example, within a range extending from about -0.00051 min / rev to about -0.00042 min / rev. In examples where the average diameter of the earth-boring tool is about 6.75 inch (about 17 cm), the performance evaluation criterion may be in a range extending from about -0.00046 min / rev to about -0.00045 min / rev. In examples where the average diameter of the earthboring tool is about 8.75 inch (about 22 cm), the performance evaluation criterion may be in a range extending from about -0.000512 min / rev to about -0.00046 min / rev. In examples where the average diameter of the earth-boring tool is about 12.25 inch (about 31 cm), the performance criterion may be in a range extending from about -0.00044 min / rev to about -0.00042 min / rev.

[0081] FIG. 13 is a flowchart illustrating another method 1300 of making an earth-boring tool. The method 1300 may involve, for a first earth-boring tool, determining a first slope of a first curve defined by plotting a change in torque acting on the first earth-boring tool against a rotational velocity of the first cutting earth-boring tool for a range of rotational velocities of the first earth-boring tool, as indicated at act 1302. In some examples, the first slope may further be determined against change in rotational velocity for a range of rotational velocities and a range of depths of cut.

[0082] The torque acting of the first earth-boring tool may be calculated by multiplying a rotational force acting on the first earth-boring tool by an average radius of the first earthboring tool. The rotational force acting on the first earth-boring tool may be determined by direct measurement utilizing sensors (e.g., stress sensors, strain sensors) deployed on or in the earth-boring tool, a hanger of a drilling rig, a top drive of a drilling rig, or elsewhere in the drill string for sensing forces during an actual earth-boring operation. Alternatively, the torque acting on the first earth-boring tool may be determined by simulation, which may be performed at least substantially as described previously herein.

[0083] The torque detected or calculated for defining the first slope may be the maximum torque, the minimum torque, or the average torque acting on the first earth-boring tool at the specified rotational velocity. For example, the torque may be detected or calculated across a range of rotational velocities and / or a range of depths of cut, and maximum aggressivenessat each rotational velocity may be determined, utilized to define the first curve, and utilized to calculate the first slope. As another example, the aggressiveness may be detected or calculated across a range of rotational velocities and / or a range of depths of cut, and an average aggressiveness at each rotational velocity may be determined, utilized to define the first curve, and utilized to calculate the first slope.

[0084] For a second earth-boring tool, a second slope of a second curve defined by plotting a change in torque acting on the second earth-boring tool against a change in rotational velocity of the second earth-boring tool for a range of velocities of the second earth-boring tool may be determined, as indicated at act 1304. Each of these acts may be performed in at least substantially the same or a similar manner as described in connection with the first earth-boring tool discussed in connection with act 1302. In some examples, the second slope may further be determined against change in rotational velocity for a range of rotational velocities and a range of depths of cut.

[0085] The second earth-boring tool, including its component parts, may differ from the first earth-boring tool, including its component parts, in at least one characteristic. For example, differences in design may include rake angle of one or more cutting elements, shape of cutting surface of one or more cutting elements, perimeter shape of one or more cutting elements, maximum diameter of one or more cutting elements, perimeter shape of cutting surface of one or more cutting elements, chamfer presence on one or more cutting elements, number of chamfers on one or more cutting elements, chamfer angle(s) of chamfer(s) on one or more cutting elements, cutting element size, presence or absence of backup cutting elements, blade profile, cutting element layout, number of blades, blade spacing, presence of secondary7blades, number of secondary blades, ratio of secondary' blades to primary blades, number of nozzles, placement of nozzles, orientation of nozzles, maximum diameter of first and / or second earth-boring tool. Introducing one or more differences may better enable evaluators to determine whether a given change is likely to produce performance improvements. In some examples, the change may be isolated to a single difference in the overall first and / or second earth-boring tool. In other examples, the change may be a single difference in one or more cutting elements (e.g.. each cutting element) supported by the first and / or second earth-boring tool.

[0086] The second earth-boring tool may be selected for manufacture when the second slope for the second earth-boring tool is greater than the first slope for the first earth-boring tool, as shown at act 1306. For example, a general approach of designing earth-boring tools inaccordance with this disclosure may be to select and deploy earth-boring tools inducing increasing torque with increasing rotational velocity. In some examples, the second earthboring tool may be selected for manufacture when the second slope for the second earthboring tool at actual or anticipated operational velocity is greater than the first slope for the first earth-boring tool at the actual or anticipated operational velocity. Once selected, the second earth-boring tool may be made, as indicated at act 1308.

[0087] In some examples, the process may be iterated. For example, repeated instances of determining slope and selecting greater average slope, changing at least one characteristic of a design of the first earth-boring tool and / or the second earth-boring tool, including their component parts, before each iteration may be performed. Repeated instances may better enable designers to evaluate multiple options and further improve expected performance. In some examples, the change made to the at least one characteristic of the design of the first earth-boring tool and / or the second earth-boring tool, including their component parts, may include replacing a first cutting element and / or a second cutting element resulting in a lowest first slope and / or a lowest second slope with a replacement first cutting element and / or a replacement second cutting element.

[0088] Values of the resulting performance evaluation criterion for examples where the average diameter of the earth-boring tool is unspecified, calculated by the derivative of the torque with respect to the rotational velocity of the bit may be, for example, within a range extending from about -4.49 ft-lb.min / rev to about -1.47 ft-lb.min / rev. In examples where the average diameter of the earth-boring tool is about 6.75 inch (about 17 cm), the performance evaluation criterion may be in a range extending from about -1.47 ft-lb.min / rev to about -1.14 ft-lb.min / rev. In examples where the average diameter of the earth-boring tool is about 8.75 inch (about 22 cm), the performance evaluation criterion may be in a range extending from about -3.6 ft-lb.min / rev to about -3.3 ft-lb.min / rev. In examples where the average diameter of the earth-boring tool is about 12.25 inch (about 31 cm), the performance criterion may be in a range extending from about -4.49 ft-lb.min / rev to about -1.47 ft-lb.min / rev.

[0089] FIG. 14 is a graph 1400 showing illustrative first and second torque-rotational velocity curves 1402 and 1404 for first and second earth-boring tools. The values and graph of FIG. 14 may have been generated by simulating the performance of the first and second earth-boring tools, though a similar curve may be generated by collecting actual data from an earth-boring operation. It is expected that the second earth-boring tool will exhibit greater stability when compared to the stability of the first earth-boring tool, and particularlytorsional stability. The first slope of the first torque-rotational velocity curve 1402 is less than (e.g., more negative than) the second slope of the second torque-rotational velocity curve 1404. In other words, the second earth-boring tool may induce greater torque (or at least induce a lesser decrease in torque) with increasing rotational velocities when compared to the first earth-boring tool. Thus, the second earth-boring tool may be preferred for manufacturing and deployment because of its expected greater stability during earth-boring operations.

[0090] FIG. 15 is a graph 1500 showing illustrative curves for torque against revolutions per minute (RPM) for an earth-boring tool for a variety of applied weights on the earth-boring tool. The values and graph of FIG. 14 may have been generated by collecting actual data from an earth-boring operation, though a similar curve may be generated by simulating the performance of the earth-boring tool. Applied weight may affect the depth of cut of the earthboring tool (and the average depth of cut of individual cutting elements supported by the earth-boring tool). As shown in FIG. 15, the torque applied at a given rotational velocity may change responsive to the applied weight and depth of cut. Thus, varying the applied weight and depth of cut, or at least ensunng comparison is made between earth-boring tools and cutting elements under similar conditions of applied weights and / or depths of cut, may provide more accurate evaluations of comparative performance in accordance with the criteria disclosed herein.

[0091] Evaluating performance of earth-boring tools and / or cutting elements on the basis of aggressiveness at operating velocity, including rotational velocity’, or on the basis of applied torque at operating velocity, may provide a better evaluation of operational performance, especially in terms of operational stability. Specifically, evaluating performance by comparing the slope of an aggressiveness-velocity curve, or a torque-velocity curve, for a range of velocities, may enable improved design, manufacture, and deployment of earthboring tools and cutting elements. In particular, it is expected that doing so may increase stability, and particularly torsional stability, which may increase the useful life of the earthboring tool and associated cutting elements, and improve ability to remain on a target trajectory. It is further expected that doing so may reduce unstable earth-boring behaviors, and particularly torsional instability (e g., slip-stick vibrations), reduce impact damage and abrasive w ear on the earth-boring tool and its components, reduce time spent outside of an intended trajectory, and reduce detours and re-boring when compared to designs resulting from other approaches known to the inventors.Additional, nonlimiting examples within the scope of this disclosure include:

[0092] Example 1: A method of making an earth-boring tool, comprising: for each first cutting element of a first earth-boring tool, determining a first slope of a first curve defined by plotting a change in aggressiveness of the first cutting element against a change in velocity of the first cutting element for a range of velocities of the first cutting element; for each second cutting element of a second earth-boring tool, determining a second slope of a second curve defined by plotting a change in aggressiveness of the second cutting element against a change in velocity of the second cutting element for a range of velocities of the second cutting element; selecting the second earth-boring tool for manufacture when a second average of the second slopes for each second cutting element is greater than a first average of the first slopes for each first cutting element; and making the second earth-boring tool.

[0093] Example 2: The method of Example 1, further comprising iterating a process of determining slope and selecting greater average slope, changing at least one characteristic of a design of the first earth-boring tool, the first cutting elements, or the first earth-boring tool and the first cutting elements before each iteration.

[0094] Example 3: The method of Example 2, wherein changing the at least one characteristic of the design of the first earth-boring tool, the first cutting elements, or the first earth-boring tool and the first cutting elements comprises replacing a first cutting element resulting in a lowest first slope with a replacement first cutting element.

[0095] Example 4: The method of Example 3. wherein the different first cutting element differs from the first cutting element resulting in the lowest first slope in shape, rake angle, side rake angle, surface finish, number of chamfers, tip size and angle, or shape, rake angle, side rake angle, surface finish, number of chamfers, and tip size and angle.

[0096] Example 5: The method of Example 4. wherein the different first cutting element differs from the first cutting element resulting in the lowest first slope in shape and wherein a difference in shape comprises a difference in surface area of a cutting surface, in a presence of a chamfer, in an angle of the chamfer, in a peripheral shape of the cutting surface, or in any combination of these.

[0097] Example 6: The method of Example 2, wherein changing the at least one characteristic of the design of the first earth-boring tool, the first cutting elements, or the first earth-boring tool and the first cutting elements comprises changing a blade profile, a number of blades, a position of one or more cutting elements on one or more blades, or blade profile,number of blades, and position of one or more cutting elements on one or more blades of the first earth-boring tool.

[0098] Example 7 : The method of any one of Examples 1 through 6, wherein determining comprises measuring while performing an earth-boring operation or calculating while simulating an earth-boring operation.

[0099] Example 8: The method of any one of Examples 1 through 7, wherein selecting the second earth-boring tool for manufacture comprises selecting the second earth-boring tool for manufacture when the second slope for each second cutting element is greater than zero.

[0100] Example 9: The method of any one of Examples 1 through 8, further comprising selecting the second earth-boring tool for manufacture when each of the second slopes for each second cutting element is greater than each corresponding first slope of the first slopes for each corresponding first cutting element.

[0101] Example 10: A method of making an earth-boring tool, comprising: for a first earthboring tool, determining a first slope of a first curve defined by plotting a change in aggressiveness of the first earth-boring tool against a change in rotational velocity of the first earth-boring tool for a range of rotational velocities of the first earth-boring tool; for a second earth-boring tool, determining a second slope of a second curve defined by plotting a change in aggressiveness of the second earth-boring tool against a change in rotational velocity of the second earth-boring tool for a range of rotational velocities of the second earth-boring tool; selecting the second earth-boring tool for manufacture when the second slope for the second earth-boring tool is greater than the first slope for the first earth-boring tool; and making the second earth-boring tool.

[0102] Example 11: The method of Example 10, wherein determining comprises measuring while performing an earth-boring operation or calculating while simulating an earth-boring operation.

[0103] Example 12: The method of Example 11 or Example 10, further comprising iterating a process of determining slope and selecting greater slope, and changing at least one characteristic of a design of the first earth-boring tool or the second earth-boring tool before each iteration.

[0104] Example 13: The method of Example 12, wherein changing the at least one characteristic of the design of the first earth-boring tool comprises changing a blade profile of the first earth-boring tool, changing a cutting element layout of the first earth-boring tool, changing a shape of a first cutting element of the first earth-boring tool, changing a size ofthe first cutting element of the first earth-boring tool, changing a rake angle of the first cutting element of the first earth-boring tool, or changing a combination or subcombination of the blade profile of the first earth-boring tool, the cutting element layout of the first earth-boring tool, the shape of the first cutting element of the first earth-boring tool, the size of the first cutting element of the first earth-boring tool, and the rake angle of the first cutting element of the first earth-boring tool.

[0105] Example 14: The method of Example 13. wherein changing the at least one characteristic of the design of the first earth-boring tool comprises changing the shape of the first cutting element of the first earth-boring tool wherein a difference in shape comprises a difference in surface area of a cutting surface, in a presence of a chamfer, in an angle of the chamfer, in a peripheral shape of the cutting surface, or in any combination of these.

[0106] Example 15: A method of making an earth-boring tool, comprising: for a first earthboring tool, determining a first slope of a first curve defined by plotting a change in torque acting on the first earth-boring tool against a rotational velocity of the first cutting earthboring tool for a range of rotational velocities of the first earth-boring tool; for a second earth-boring tool, determining a second slope of a second curve defined by plotting a change in torque acting on the second earth-boring tool against a change in rotational velocity of the second earth-boring tool for a range of rotational velocities of the second earth-boring tool; selecting the second earth-boring tool for manufacture when the second slope for the second earth-boring tool is greater than the first slope for the first earth-boring tool; and making the second earth-boring tool.

[0107] Example 16: The method of Example 15, wherein determining comprises measuring while performing an earth-boring operation or calculating while simulating an earth-boring operation.

[0108] Example 17: The method of Example 15 or Example 16, further comprising iterating a process of determining slope and selecting greater slope, and changing at least one characteristic of a design of the first earth-boring tool or the second earth-boring tool before each iteration.

[0109] Example 18: The method of Example 17. wherein changing the at least one characteristic of the design of the first earth-boring tool comprises changing a blade profile of the first earth-boring tool, changing a cutting element layout of the first earth-boring tool, changing a shape of a first cutting element of the first earth-boring tool, changing a size of the first cutting element of the first earth-boring tool, changing a rake angle of the first cuttingelement of the first earth-boring tool, or changing a combination or subcombination of the blade profile of the first earth-boring tool, the cutting element layout of the first earth-boring tool, the shape of the first cutting element of the first earth-boring tool, the size of the first cutting element of the first earth-boring tool, and the rake angle of the first cutting element of the first earth-boring tool.

[0110] Example 19: The method of Example 18, wherein changing the at least one characteristic of the design of the first earth-boring tool comprises changing the shape of the first cutting element of the first earth-boring tool wherein a difference in shape comprises a difference in surface area of a cutting surface, in a presence of a chamfer, in an angle of the chamfer, in a peripheral shape of the cutting surface, or in any combination of these.

[0111] Example 20: The method of any one of Examples 15 through 19, wherein selecting the second earth-boring tool for manufacture when the second slope for the second earthboring tool is greater than the first slope for the first earth-boring tool comprises selecting the second earth-boring tool for manufacture when the second slope for the second earthboring tool is within a range extending from about -4.49 ft-lb.min / rev to about -1.47 ft-Ib.min / rev.

[0112] While certain illustrative examples have been described in connection with the figures, those of ordinary skill in the art will recognize and appreciate that the scope of this disclosure is not limited to those examples explicitly show n and described in this disclosure. Rather, many additions, deletions, and modifications to the examples described in this disclosure may be made to produce additional examples within the scope of this disclosure, such as those specifically claimed, including legal equivalents. In addition, features from one disclosed example may be combined with features of another disclosed example while still being within the scope of this disclosure.

Claims

CLAIMSWhat is claimed is:

1. A method of making an earth-boring tool, comprising:for each first cutting element of a first earth-boring tool, determining a first slope of a first curve defined by plotting a change in aggressiveness of the first cutting element against a change in velocity of the first cutting element for a range of velocities of the first cutting element;for each second cutting element of a second earth-boring tool, determining a second slope of a second curve defined by plotting a change in aggressiveness of the second cutting element against a change in velocity of the second cutting element for a range of velocities of the second cutting element;selecting the second earth-boring tool for manufacture when a second average of the second slopes for each second cutting element is greater than a first average of the first slopes for each first cutting element; andmaking the second earth-boring tool.

2. The method of claim 1, further comprising iterating a process of determining slope and selecting greater average slope, changing at least one characteristic of a design of the first earth-boring tool, the first cutting elements, or the first earth-boring tool and the first cutting elements before each iteration.

3. The method of claim 2, wherein changing the at least one characteristic of the design of the first earth-boring tool, the first cutting elements, or the first earth-boring tool and the first cutting elements comprises replacing a first cutting element having a lowest first slope w ith a replacement first cutting element.

4. The method of claim 3, wherein a different first cutting element differs from the first cutting element resulting in the lowest first slope in shape, rake angle, side rake angle, surface finish, number of chamfers, tip size and angle, or shape, rake angle, side rake angle, surface finish, number of chamfers, and tip size and angle.

5. The method of claim 4, wherein the different first cutting element differs from the first cutting element resulting in the lowest first slope in shape and wherein a difference in shape comprises a difference in surface area of a cutting surface, in a presence of a chamfer, in an angle of the chamfer, in a peripheral shape of the cutting surface, or in any combination of these.

6. The method of claim 2, wherein changing the at least one characteristic of the design of the first earth-boring tool, the first cutting elements, or the first earth-boring tool and the first cutting elements comprises changing a blade profile, a number of blades, a position of one or more cutting elements on one or more blades, or blade profile, number of blades, and position of one or more cutting elements on one or more blades of the first earth-boring tool.

7. The method of claim 1, wherein determining comprises measuring while performing an earth-boring operation or calculating while simulating an earth-boring operation.

8. The method of claim 1, wherein selecting the second earth-boring tool for manufacture comprises selecting the second earth-boring tool for manufacture when the second slope for each second cutting element is greater than zero.

9. The method of claim 1, further comprising selecting the second earth-boring tool for manufacture when each of the second slopes for each second cutting element is greater than each corresponding first slope of the first slopes for each corresponding first cutting element.

10. The method of claim 1 , wherein determining the first slope and the second slope comprises calculating, for each of the first cutting elements and each of the second cutting elements, aggressiveness values at a plurality of depths of cut for each of a plurality of velocities, and defining each of the first and second curves using a maximum aggressiveness value at each velocity.

11. The method of claim 1, further comprising arranging the second cutting elements on the second earth-boring tool such that the second cutting elements located closer to a rotational axis of the second earth-boring tool exhibit lesser rate of change of aggressiveness than the second cutting elements located farther from the rotational axis for at least an operational range of velocities of the earth-boring tool.

12. The method of claim 1, wherein selecting the second earth-boring tool for manufacture further comprises requiring that, for the second cutting elements of the second earth-boring tool, a derivative of aggressiveness with respect to local cutting velocity falls within:• a range from about -0.48 s / m to about -0.11 s / m in a cone region of the second earth-boring tool,• a range from about -0.16 s / m to about -0.09 s / m in a nose region of the second earth-boring tool, and• a range from about -0.13 s / m to about -0.06 s / m in a shoulder region of the second earth-boring tool.

13. An earth-boring tool produced by a process, comprising:for each first cutting element of a first earth-boring tool, determining a first slope of a first curve defined by plotting a change in aggressiveness of the first cutting element against a change in velocity of the first cutting element for a range of velocities of the first cutting element;for each second cutting element of a second earth-boring tool, determining a second slope of a second curve defined by plotting a change in aggressiveness of the second cutting element against a change in velocity of the second cutting element for a range of velocities of the second cutting element;selecting the second earth-boring tool for manufacture when a second average of the second slopes for each second cutting element is greater than a first average of the first slopes for each first cutting element; andmaking the second earth-boring tool.

14. The earth-boring tool of claim 13, further comprising iterating a process of determining slope and selecting greater average slope, changing at least one characteristic of a design of the first earth-boring tool, the first cutting elements, or the first earth-boring tool and the first cutting elements before each iteration.

15. The earth-boring tool of claim 14, wherein changing the at least one characteristic of the design of the first earth-boring tool, the first cutting elements, or the first earth-boring tool and the first cutting elements comprises replacing a first cutting element having a lowest first slope w ith a replacement first cutting element.

16. The earth-boring tool of claim 15, wherein a different first cutting element differs from the first cutting element resulting in the lowest first slope in shape, rake angle, side rake angle, surface finish, number of chamfers, tip size and angle, or shape, rake angle, side rake angle, surface finish, number of chamfers, and tip size and angle.

17. The earth-boring tool of claim 13, wherein selecting the second earth-boring tool for manufacture comprises selecting the second earth-boring tool for manufacture when the second slope for each second cutting element is greater than zero.

18. The earth-boring tool of claim 13, further comprising selecting the second earth-boring tool for manufacture when each of the second slopes for each second cutting element is greater than each corresponding first slope of the first slopes for each corresponding first cutting element.

19. The earth-boring tool of claim 13, further comprising arranging the second cutting elements on the second earth-boring tool such that the second cutting elements located closer to a rotational axis of the second earth-boring tool exhibit lesser rate of change of aggressiveness than the second cutting elements located farther from the rotational axis for at least an operational range of velocities of the earth-boring tool.

20. The earth-boring tool of claim 13, wherein selecting the second earth-boring tool for manufacture further comprises requiring that, for the second cutting elements of the second earth-boring tool, a derivative of aggressiveness with respect to local cutting velocity falls within:• a range from about -0.48 s / m to about -0.11 s / m in a cone region of the second earth-boring tool,• a range from about -0.16 s / m to about -0.09 s / m in a nose region of the second earth-boring tool, and• a range from about -0.13 s / m to about -0.06 s / m in a shoulder region of the second earth-boring tool.

Images