CA1295321C - Large compact cutter rotary drill bit utilizing directed hydraulics for eachcutter - Google Patents

Abstract

LARGE COMPACT CUTTER ROTARY DRILL BIT UTILIZING
DIRECTED HYDRAULICS FOR EACH CUTTER

Abstract of the Disclosure An improved rotating drag bit for cutting plastic, sticky, water reactive and shale formations is devised by providing a plurality of large diamond cutters having a circular cutting face in excess of three-quarter inch in diameter.
Each large cutter is provided with at least one hydraulic nozzle which in turn provides a directed hydraulic flow at the corresponding cutter face. The directed hydraulic flow is positioned to apply a force to the chip which tends to peel the chip away from the cutter face. In addition, the hydraulic flow is positioned with respect to the chip so as to apply an off-center torque to the chip which is used to peel the chip away from the cutter face and toward the gage of the bit. In particular, the nozzle defines a jet which is characterized by a direction and velocity of hydraulic fluid determined by the jet characteristics. The core is generally symmetric about its longitudinal axis and has a length along the longitudinal axis and width perpendicular thereto. The point of the jet most distant from the nozzle defines an impact point of the jet against the chip and cutter face. The longitudinal axis of the jet is chosen so that at least a portion of the jet lies between the cutter face and the chip as it is being peeled from the cutter.
Hydraulic removal of the chips is further facilitated by a plurality of junk slots having a contoured compound surface.
The junk slot is characterized by having at least two distinct cross-sectional profiles, namely an asymmetric profile at its lower portion nearest the bit face and a symmetric profile along its upper portion. The asymmetric and symmetric profiles are connected by a surface providing a smooth hydrodynamic transition.

Description

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2 LARGE COMPACT CUTTER ROTARY DRILL BI~ UTILIZING
3D~CR~SCT~D HYDRAU~IC!S FOF~ EACH CU~T~R

5Back~round of the Invention 7 Field of the Invention 8 The invention is related to the field of earth boring 9 tools, and in particular rotating drag bits having large 10 polycrystalline diamond compact cutters or other large 11 composite-type cutters of similar materials for use in 12 drilling in shale, clay and other sticky formations, 13 sometimes referred to as "gumbo".

15 Description of the Prior Art 16 one of the most significant problems encountered when 17 drilling in shale, clay or other water reactive, sticky 18 formations is the tendency of the bits to ball or become 19 clogged during drilling. ~he typical appro~ch o~ the prior 20 art in dealing wit:h such soft and sticky formations has been 21 o provide large cutters with strong hydraulics in the 22 roximity of the cutters and to attempt to remove the 23 uttings from the cutter faces with a high volume, high 24 elocity hydraulic jet flow. See, for example, Feenstra, 25 'Rotary Bit with Ridges", U.S. Patent 4,116,289 (1978).

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1 Typically, such prior art cutters include impregnated 3 diamond blade cutters, sintered diamond compact cutters, 4 such as manufactured by General Electric Co. under the 5 trademark "Compax", are limited in size, typically being 6 equal to or less than 13.3 mm in diameter. Therefore, in order to obtain the cutter sizes required or desirable for 8 sticky drilling, impregnated diamond elements are used such 9 as sho~m by Short, "Blade-Type Drill Bit", U.S. Patent 10 3,153,458 (1964), and Feenstra, supra.
Recently, however, large size diamond compact discs 11 have become commercially available measuring between three 12 quarters of an inch and two inches in diameter. However, 3 these large diamond discs have been employed essentially as 14 their smaller predecessors, such as diamond stud cutters sold under the trademark "Stratapax" by General Electric 16 Company. As a result, the large diamond dlscs have been 18 subject to the same drawbacks and detriments with respect to 19 cutting sticky or plastic or water reactive formations as prior art blade bits.

21 Therefore, what is needed is some means whe.reby the large diamond cutter may be employed to cUt into clay, shale 22 or plastic formations in such a manner that bit balling and 23 other drawbacXs of the prior art are substantially avoided.

. ~95321 1 Brief Summary of the Invention 3 The invention is an improvement in a rotating bit for 4 cutting a plastic formation comprising a plurality of 5 polycrystalline diamond cutters. At least one cutter has a 6 arge diamond cutting surface which is at least as large as 7 a three quarter inch diameter circle. The nozzle defines a 8 directed hydraulic flow to the large cutter. The flow 9 directed by the nozzle is arranged and configured to apply a 10 force to the chip which is cut by the large cutter. The 11 orce tends to peel the chip from the face of the cutter.

12 As a result, the plastic formation is cut with little 13 tendency of the bit to ball.

14 The bit comprises a plurality of the large cutters and 15 a corresponding plurality of the nozzles. At least one 16 nozzle is provided for each large cutter and provides the 17 directed hydraulic flow to each cutter face.

18 The nozzle clirects the hydraulic flow to the cutter 19 face of the larg~ cutter into the proximity of the center of 20 gravity of the chip.

21 The nozzle directs the hydraulic flow into the 22 proximity of the center of gravity of the chip and radially 23 nward of the center of gravity of the chip. A torque is 24 thus applied to the chip tending to peel the chip off the 25 -utting face of the large cutter toward the gage of the bit.

~ 5321 1 The directed flow of the nozzle is characterized by a 2 jet. One feature of the jet is an inner core with a length 3 of four to seven times the outer diameter of the orifice of 4 the nozzle. In the core, the center line velocity remains 5 virtually equal to the exit velocity. Another feature of 6 the jet is the'width of the jet and pressure cone associated 7 with it which is approximately two times the outer diameter 8 of the nozzle when the core is at full length. See 9 generally, "Preliminary Analysis of a Free Jet From a 10 Circular Nozzle," M. B. Friedman, DTC Hydraulics Consultant, 11 Technical Note No.l,'September 21, 1984.
12 The jet is defined by flow of hydraulic fluid from the 13¦ nozzle in a direction and velocity primarily determined by 14 the orientation of the nozzle. The core is substantially 15 symmetric about a longitudinal axis. The ~et has a width _ 16 perpendicular to the longitudinal axis and a length along 17 the longitudinal axis. That point on the longitudinal axis 18 of the jet most distant from the nozzle is defined as an 19 impact point of the jet. The impact point of the jet is 20 directed toward a location proximate to attachment of the 21 chip to the rock formation.
22 If the maximum energy of the core is to be realized the 23 impact point of the jet is at least within 0.4 to 0.7 inch 24 of the center of gravity of the corresponding chip for the 25 illustrated design. This should not be construed as a 26 limiting factor however. The essence of this approach is to 1 ~ ~gressively o~ pointedly attack the ~hip ~ith the drilling 2 fluid. It is entirely within the scope and spirit of the 3 invention that jet characteristics and relationship to the 4 cutter and chip may be entirely outside the optimal ranges 5 set forth above. In fact, the cutters may be nearly as 6 effective with a nonoptimal jet as with an optimal jet, although 7 it is expected that optimal jets and jet relationships to the 8 cutters will produce better results.
9 The longitudinal axis of the jet can be disposed at 10 least at one point ~etween the chip and cutting face of the 11 corresponding cutter if so desired.
12 ~he invention is also a method for removing chips cut 13 from a formation by a bit having a center and gage 14 comprising the steps of cutting a chip by a cutter, 15 directing a defined hydraulic flow toward the chip, and 16 applying a force from the hydraulic flow to the chip in a 17 direction away from the cutter which is cutting the chip to 18 thereby peel the chip off the cutter. As a result, the 19 formation is drilled without substantial risk of balling the 20 bit.
21 In the step of applying the force, the force is applied 22 at a point into the proximity of the center of gravity of 23 the chip to thereby generate a torque on the chip.
2~ In the step of applying the torque to the chip, the 25 torque is applied to the chip and peels the chip from the 26 cutter toward the gage.

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1 ¦ In the step of cutting the formation, the chip is cut 2 ¦by a cutter having a cutting surface with an area at least 3 ¦as great as a circle 0.75 inch in diameter.
4 ¦ The invention is also an improvement in a rotating bit 5 ¦having a bit face and gage comprising at least one junk slot 6 defined in the yage of the bit. The junk slot has a 7 compound profile along its longitudinal length opposite the 8 gage. The compound profile includes at least two distinct 9 cross-sectional configurations perpendicular to the 10 longitudinal axis of the junk slot, and a smooth 11 hydrodynamic transition being provided between the at least 12 two distinct profiles. As a result hydraulic flow within 13 the junk slot is substantially improved.
14 The two profiles of the junk slot comprise a symmetric 15 profile and asymmetric profile.
16 The symmetric profile is longitudinally defined within 17 the junk slot farther from the bit face than the asymmetric 18 rofile.
19 At least one portion of the asymmetric profile is 20 identical to the symmetric profile.
21 The invention is more graphically depicted in the 22 ollowing drawings where like elements are referenced by 23 ike elements.

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1 Brief Description of the Drawinqs 3 Figure 1 is a top plan view of an inside of a mold from which a matrix bit incorporating the invention is 5 f abricated.
6 Figure 2 is a diagrammatic cross-sectional view of a 7 bit manufactured from the mold plan shown in Figure 1.
8 Figure 3 is a diagrammatic depiction of the direction 9 of hydraulic flow with respect to the cutter face and chip 10 of a single cutter as depicted in Figures 1 and 2.
11 Figure 4 is a diagrammatic side sectional view of the 12 depiction of Figure 3.
13 Figure 5 is a perspective view of a single cutter as 1~ shown in Figures 1-4.
The invention and its various embodiments may be better 16 understood by now turning to the following detailed 17 description.
18 . .
19 petailed Description of the Preferred Embodim~

21 An improved rotating drag bit for cutting plastic, 22 sticky, water reactive clays and shales is devised by 23 providing a plurality of large diamond cutters having a 24 circular cutting face equal to or in excess of 0-75 inch in 25 diameter. In the preferred embodiment, the cutters are 26 approximately one inch in diameter or larger. Each large 2a 129532~

1 cutter is provided with at least one hydraulic nozzle which 2 in turn provides a directed hydraulic flow at the 3 corresponding cutter face. The directed hydraulic flow is 4 positioned to apply a force to the chip which tends to ~ hydraulically separate the chip away from the cutter face.
6 In addition, the hydraulic flow is positioned with respect 7 to the chip so as to apply an off-center torque to the chip 81 which is used to peel the chip away from the cutter face and 9 toward the gage of the bit. In particular, the nozzle 10 defines a jet which is characterized by a direction and 11 velocity of hydraulic fluid determined by the jet 12 characteristics. The core is generally symmetric about its 13¦ longitudinal axis and has a length along the longitudinal 14¦ axis and width perpendicular thereto. The point of the jet 15 most distant from the nozzle defines an impact point of the 16 jet against the formation, the chip and/or cutter face. The 17 longitudinal axis of the jet is chosen so that at least a 18 portion of the jet can lie between the cutter face and the 19 chip as it is being peeled from the cutter. Hydraulic 20 removal of the chips is further facilitated by a plurality 21 of junk slots having a contoured compound surface.

22 A rotating drill bit is provided with a large diamond 23 compact slug, typically of one to two inches in diameter or 24 greater, each of which is provided with at least one 25 hydraulic nozzle. Hydraulic fluid is directed under 26 pressure from the nozzle to a predetermined point with . . ~2~532~

1 respect to the corresponding large diamond cutter and its 2 corresponding chip. In particular, the fluid flow frcm the 3 no2zle is ~ocusse~ or h~s a point of maximum impulsive 4 impact at a predetermined point positioned with respect to 5 the rock chip cut by the corresponding cutter so that a 6 force is applied to the chip to separate it from the diamond 7 cutter by hydraulic differential unloading and/or applying 8 an unbalanced torque to the chip. In essence, the focal 9 point of the stream of hydraulic fluid from the nozzle is 10 directed at a point at or near the base and to the inside of 11 attachment or adhesion of the rock chip to the face of the 12 diamond cutter. The manner in which this can be implemented 13 can best be understood by first turning to the interior top 14 plan view of a mold shown in Figure 1 by which a bit 15 incorporating the invention is molded according to 16 conventional matrix infiltration processes.
17 ¦ ~hat is shown in Figure 1 is a plan view of the 18¦ settings of the large diamond compact cutters on the face of 19¦ a bit as seen looking into a mold in which such a diamond 20¦ bit would be made by matrix infiltration. Thus the bit, 21 generally denoted by reference numeral 10, is characterized 22 by an exterior cylindrical surface or gage 12 terminated on 23 its lowermost portion by a bit face, generally denoted by 2~ reference numeral 14. Defined within gage 12 i5 a plurality 25 of junk slots 16 and 18. Junk slots 16 are distinguishable 2G from junk slots 18 in that junk slots 16 have a uniform 2a ~2~53Z~

1 contour as opposed to a contoured or compound surface within 2 jun~ slots 18 as will be described below.
3 In the embodiment illustrated in Figure 1, a 12 1/4 4 inch diameter bit is illustrated in which nine large cutters 5 21-29 will be formed. For the sake of clarity of 6 illustration each cutter is shown in midline cross-sectional 7 view with the diamond cutter in place. In actuality the 8 diamond slugs may be fixed or brazed into the bit in a later 9 step, and would not be seen in place in the mold as depicted 10 in Figure 1. See generally, Rhode et. al., "Diamo~d 11 Drilling Bit for Soft and Medium Hard Formations," US Patent 12 ~,098,363 (1978) for background information concerning the 13 casting of the bit body, cutter shapes and materials, and 14 various methods of attachment of the cutters. However for 15 ease of conceptualization, Figure 1 illustrates the diamond 16 cutters in place as would be seen loo~ing downward through 17 the diamond bit toward the rock formation. In reality in a 18 top plan view of a mold, only the pockets into which the 19 diamond slugs were later brazed would be seen.
Corresponding to each cutter is a nozzle 31-39 which 21 provides a directed ~low as also described more completely 22 below. Nozzle 31 thus provides directed flow for cutter 21, 23 nozzle 32 for cutter 22 and so forth through nozzle 39 and 2~ cutter 29. In addition to cutters 21-29, a plurality of 25 gage cutters 40 are defined within the shoulder and gage of 27 bit 10 as better depicted and described below in connection 1 ~29~321 1 ¦with Figure 2, but which are also illustrated in Figure 1 in 2 la sometimes overlying relationship. The depiction in Figure 3 ¦1 of gage cutters 40 appears to be overlying since the 41 cutters, which may be vertically separated, are superimposed 51 in the diagrammatic view of Figure 1.
6 In addition to ~unk slots 16 and 18, a plurality of 7 collectors 42 are similarly provided within gage 12. ~hese 8 are provided to enhance the cleaning and cooling of gage 9 cutters 40. Gage defining cutters 40 are comprised of 10 conventionally fabricated Stratapax or Compax cutters and 11 can, by virtue of their relative scale to cutters 21-29, 12 provide a relative feel for the sizes of cutters 21-29. In 13 the prior art, gage defining cutters 40 usually represented 14 the largest integral diamond compacts then available for 15 cutting in shale or plastic formations. In the present 16 application, what was previously the primary cutters in 17 prior art polycrystalline diamond compact drill bits, now 18 serve only a secondary cutting function as gage defining 19 cutters.
Before considering further details o~ the relationship 21 bet~een the directed hydraulic flow from nozzles 31-39 and 22 their corresponding cutters 21-29, turn first to the 23 perspective depiction of Figure 5 wherein a single one of 2~ the cutters is illustrated. Cutter 24 is chosen for the 25 purposes o~ example. Cutter 24 comprises a tungsten carbide 27 slug 44 1.50 inches in diameter and approximately 0.3 inch , . .

~2~5321 1 thick. Mounted in the face of the slug 44 is an integral 2 diamond compact table 4~. Diamond table 46 and slug 44 are 3 manufactured and ~onded together within a diamond press and 4 are sold as such a unit by De Beers of South Africa. See 5 generally, Peschel, "Cutter Head, Drill Bit and Similar 6 Drilling Tools,~' US Patent 4,200,159 (1980) for background 7 relating to brazing of slug cutters into an infiltration 8 bit, and in particular refer to Figure 7 and the associated 9 text of Peschel. Diamond table 46 has a diameter 10 substantially equal to that of slug 44. Substrate or 11¦ carrier 45 is brazed into pocket 48. Slug 44 is then brazed 121 into pocket 48 in front of substrate 45. Pocket 48 is 13¦ formed in an island 50 which is a grooved projection of the 14¦ basic body 14. At the present time, De Beers supplies slug 151 44 and table 46 as an integral unit. This unit has a 16¦ longitudinal thickness of approximately 8 mm (0.315 inch) 17 and lacks sufficient thickness for adeguate shock protection 18 and load resistance. Hence, carrier 45 , which is made of 19 tungsten carbide and is approximately 14 mm thick is bonded 20 or brazed thereto. Generally, cutter~ 21-29 of the 21 embodiment of Figure 1 have a predetermined rake angle of 22 diamond table 46 as determined by a milled-in rake angle of 23 island 50. In the illustration of Figure 1, however, each 2~ cutter 21-29 has been shown only in a midline section for he sake of clarity. Therefore it must be kept in mind that 26 ortions of the face of diamond table 46 actually extend 28~ 12 , . . .

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1 both in front of and behind the midsection line shown in 2 Figure 1 for each cutter 21-29 by an amount depending on the ~ ra~e angle of each cutter.

4 The preferred embodiment is a diamond compact disc 5 brazed into a pocket with a support or carrier. The cutter 6 can have different shapes, e.g. triangular, hexagonal, 7 square, or octagonal. The cutter can be composed of 8 thermally stable diamond or some other material such as 9 silicon carbide, tungsten carbide, or boron carbide. During 10 manufacture of the bit, the cutter can be furnaced with the 11 bit body in order to attach it to the bit. What is 12 disclosed here is a large cutter with at least one directed 13 nozzle providing cleaning and cooling of the cutter.

14 Consider now the relationship between the direction of 15 hydraulic flow from each nozzle 31-39 and its corresponding 16 cutter 21-29. In particular, consider cutter 24 and nozzle 17 34 depicted in Figure 1. Listed below in Table 1 is a 18 summary of cutter locations.

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3 No . ~ _Rad . _ SR _BR
4 21 0.78 0 3 15 22 1.89 135 5 13 61 23 2.90 245 5 10 71 24 3.75 28 5 10 81 25 4.39 150 5 11 91 26 4.98 270 5 13 101 27 5.44 70 5 15 28 5.4~ 190' 5 15 121 29 5.44 310 5 15 14 The locations listed above are the locations which are 15 machined in the graphite mold from which the bit is made.
16 After furnacing, these locations are reduced a small amount 17 due to shrinkage upon cooling. Cutter 24 has the center of 18 its midline section of diamond table 46 at a radial distance 19 of 3. 75 inch from the center of bit 10 prior to shrinkage.
20 T2king the center of cutter 21 as an arbitrary reference 21 point of 0 degrees, the azimuthal position of the center of 22 cutter 24 appears at an angular position of 28 degrees.
23 Face 46 o~ cutter 2~ is not parallel to a radius, but has a 2~ side rake of 5 degrees. In other words, as viewed in Figure 25 1, cutter 24 has been rotated so that face 46 is not aligned 26 ith the radius but is rotated or canted counterclockwise ~y ~295321 1 5 degrees in a plane parallel to the bit profile.
2 Similarly, the back rake of cutter 24 is 10 degrees, 3 although not shown in the figures. In other words, if the 4 diamond face 46 of cutter 24 were shown in three dimensions, 5 a rotation perpendicular to the bit profile as shown in 6 Figure 1 of 10 degrees would be observed.
7 Turn now to the nozzle placement, in particular for 8 nozzle 34, as summarized in Table 2 below.
9 . ,.

13 No. Rad. _ Offset 14 31 0.77 248 20 172 32 1.60 103 20 69 16 33 2.30 225 35 67 17 34 3.20 14 35 61 18 35 3.89 138 35 57 19 36 4.55 259 35 50 37 4.79 59 40 48 21 38 4.79 179 40 48 22 39 4.79 299 40 48 24 Nozzle 34 has its center at a radial displacement of 3.20 25 inch from the center of bit 10. Arrow 68 diagrammatically 27 represents the direction of hydraulic flow of nozzle 34.

. . ~ z5~5321 1 The azimuthal position of the center of nozzle 34 is at an 2 azimuthal angle of 14 degrees, as denoted by angle alpha in 3 Table 2, again from a reference line of the face of cutter 4 1. The angular offset of the direction of hydraulic flow 5 denoted by arrow 68 is then 61 degrees offset from the 6 reference direction. Furthermore, nozzle 34 is tilted from 7 the vertical axis, the longitudinal axis of bit 10, by 35 8 degrees in a direction which is perpendicular ~o the plane 9 of the drawing of ~igure 1 . These two angular orientations 10 combined with the 61 degree offset therefore specify that 11 the point, denoted by reference numeral 66, at which arrow 12 68 impacts the formation. Point 66 is at the base of and in 13 front of diamond surface 46 of cutter 24. The physical 14 significance of arrow 68 and its corresponding point 66 is 15 understood as follows.
16 The directed hydraulic nozzle flow with respect to 17 diamond face 46 may better be understood by turning now to 18 the diagrammatic depictions of Figure 3 and 4. Figure 3 is 19 a plan diagrammatic view of a cutter, such as cutter 24.
20 Substrate 44 behind and bonded to diamond table 46 is shown 21 n diagrammatic top plan view and immediately behind a chip 22 6 being cut from the rock formation. As better seen in 23 ide diagrammatic view in Figure 4, chip 56 is s~he red from 24 he rock formation, generally denoted by reference numeral 25 58. Since formation 58 is sticky or plastic, chip 56 26 remains su~stantially intact and will generally move upward ~2~32~L

1 across diamond face 46 of cutter 24 and normally tends to 2 adhere to face 46. Nozzle 34, corresponding to cutter 24, 3 provides a directed flow of hydraulic fluid to form a jet 60 4 shown in ~igure 4. Jet 60 is characterized by a region of 5 hydraulic flow which has a direction and velocity 6 principally determined by nozzle 34. Generally, core 61 has 7 a length denoted by dimension 62 in Figure 4 of four to 8 seven times the outer diameter of the orifice of nozzle 34 9 and a pressure cone associated with the jet with a width, 10 denoted by reference numeral 64 approximately two times the 11 outer diameter of the orifice of nozzle 34. Like the flame 12 tip of a torch, core 61 has a tip 66 which defines an impact 13 point of ~et 60. Furthermore, core 61 is generally 14 symmetric about a longitudinal axis 68 from the center of 15 nozzle 34 to impact point 66. Impact point 66 can be 16 characterized as the point of primary or maximized force 17 furtherest away from the orifice of the corresponding 18 nozzle. As best depicted in Figure 3, axis 68 of jet 60 is 19 directed to the base of chip 56 so that the impact point 20 will lie near the base of chip 56, typically within the 21 lower half of diamond face 46 and offset from the center of 22 hip 56 or face 46. Ideally, impact point 66 will lie at a 23 istance of 0.4 to 0.7 inches away from the center of 24 gravity 70 of chip 56, as depicted in Figure 4. This 25 imparts or tends to impart a force which pries off chip 56 2~ from diamond face 46 as za 17 ~Z~53Z~

1 depicted in Figures 3 and 4. Otherwise, chip 56 would 2 generally be tightly adhered to diamond face 46.
3 In addit~on, a torque al5~ tends to be applied to chip 4 56 by virtue of the moment arm between impact point 66 and 5 center of gravity 70. Therefore, chip 56 also tends to ~e 6 twisted off or peeled off face 46. In the preferred 7 embodiment, torque applied to each c~ip 56 on each cutter 8 and chip is directed to peel chips 56 toward gage 12 of bit 9 10.
This feature is better illustrated in Figure 2. Turn 11 to Figure 2 which is a diagrammatic cross-sectional 12 depiction of half of the profile of bit 10 showing each of 13 the circular diamond faces 46 of cutters 21-29 superimposed 14 on the profile as would be obtained after a full revolution 15 of bit 1~. Firstly, it is immediately apparent that cutters 16 21-29 provide overlapping coverage from center line 72 of 17 bit 10 to gage 12. In fact, the outermost cutters 27-29 18 provide triple redundancy at gage 12 where cutting rates and 19 impact shocks are generally highest. Further, the density 20 of cutter overlap can be seen to increase toward gage 12.
21 In other words, a greater fraction of the cutting face of 22 cutter 26 overlaps with the cutting faces of cutters 27-29 23 than does the degree of overlap between the cutting faces of 2~ cutters 21 and 22.
Figure 2 also illustrates the vertical dispersion of 26 gage protection cutters 40. Each of the full cutters 40 is 2~
2a ~ la . ~Z9~3Zl 1 provided with triple redundancy on bit 10 with the exception 2 of fractional cutters 40a, which have been cut by laser 3 cutting or FDM to comprise a portion of the full disc with a 4 flat edge 74 directed outwardly to define gage 12. A
5 sixfold redundancy of cutters 40a is provided on bit 10.
6 Cutters 40 and 40a do not actively cut the formation. ~hey 7 insure the hole si~e is maintained. They do not cut the 8 bottomhole, and do not require direct cleaning.
9 Consider no~ the relationship between the directed flow 10 of nozzles 31-34 in collnection with the cutting faces of 11 cutters 21-29 as depicted in Figure 2. Again consider for 12 e~ample cutter 24. Cutter 24, as is each cutter, is 13 associated with an imaginary line 76 along which the center 14 of gravity of chip 56 will be positioned. The exact point 15 of the center of gravity of chip 56 along line 76 will 16 depend upon the depth of cut as well as upon the amount of 17 cutter remaining after wear. ~hus line 76 represents the 18 locus of the center of gravity of chip 56 over time.
19 Similarly, the projection of axis 68 of hydraulic jet 60 20 onto the cuttiny face o~ cutter 24 de~ines an imaginary line 21 78. As shown in Figure 2, line 78, which is indicative of 22 the center of effort of jet 60, lies inboard of line 76 23 representing the position on t~le center of gravity of chip 24 56. Thus, a peeling torque is provided for cutter 24 25 regardless of the amount of wear or the degree of embedment 2~ of cutter 2~ into formation 58.

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1 It may be verified with each of the cutters that line 2 78 representative of the center force of jet 60 lies inboard 3 of its corresponding line 76.
4 Returning to Figure 1, it can now be illustrated that 5 the point of impact 66 does not in each case lie at the same 6 distance away from cutter face 46 of its corresponding 7 CDtter. This is largely an artifact of manufacture arising 8 from the limited space within bit 10 in which nozzles 31-39 9 may be angled. Such displacements can in any case be 10 manipulated as a design feature of the present invention.
11 In the illustrated embodiment nozzles 31-39 are 12 replaceable from the exterior of bit face 14. Therefore, 13 sufficient space must be provided between each nozzle 31-39 14 and it corresponding cutter 21-29 to allow insertion and 15 removal of the nozzle and to allow the use of appropriate 16 tools. In the case where the nozzles are permanently fixed 17 or are removable from the interior of bit 10, it may be 18 possible that the variation of the distance between impact 19 oint 66 and corresponding cutter faces 46 as shown in 20 Figure 1 woulcl not occur. The fluid can actually impact 21 cutter face 4~; between the cutter and chip 56 if so desired.
22 The junk slot is characterized by having at least two 23 distinct cross-sectional profiles, namely a symmetric 2~ profile at its upper portion farthest from the bit face and 2~ an asymmetric profile along its lower portion. The 1 3L2~53Z~L

1 asymmetric and symmetric profiles are connected by a surface 2 providing a smooth hydrodynamic transition.
3 Co~sid~r sp~oi~ioa~ly t~ ao~toured jun~ u 4 depicted in Figure 1. Junk slot 18 is a longitudinal cavity 5 defined within gage 12 to facilitate removal of cut 6 material. In the lower portion of junk slot 18, nearest bit 7 face 14, junk slot 18 is characterized by a first asymmetric 8 profile shown in dotted outline in Figure 1 as portion 80.
9 The upper portion of junk slot 18, furthest away from the 10 face 14, has a distinct second profile ~2 as depicted in 11 solid outline in Figure 1. Thus, the lower section of junk 12 slot 18 has a nonuniform asymmetric profile 80 while the 13 upper section has a substantially uniform symmetric profile 14 82. The transition between profiles 80 and 82 within the 15 middle region of junk slot 18 is smoothed so that cross 16 sections (not shown~ would reflect a smooth hydrodynamic 17 transition between the dramatically different profiles 80 18 and 82.
19 In the illustrated embodiment the first profile 80 has 20 been shown with a wedge ~haped leadin~ portion, which 21 transitions to a full depth, following portion which is 22 equivalent to second profile 82. It is entirely within the 23 scope of the invention that profile 80 may be reversed, `
2~ namely having a full depth leading profile transitioning to 2S a wedged-shaped following portion. Furthermore, any junk 26 slot profile known in the art, in addition to profiles 80 . ~29~i32~

1 and 82 illustrated in Figure 1, may be used or variously 2 combined with each other as may be desired. Similarly, the S longl~udinal relationshlp of the portions may be reversed if 4 desired. For example, asymmetric profile 80 may 5 characterize the upper section of junk slot 18, while full 6 portion 82 would characterize the lower section nearest bit 7 face 14.
8 It has been observed that reverse flow, turbulent or 9 unstable flows and eddies which have been observed in 10 conventional junk slots, which have a single profile 11 throughout their longitudinal length, can be avoided or at 12 least substantially diminished when the compound surface 13 represented by profiles 80 and 82 of junk slot 18 are used 14 according to the invention.
Many alterations and modifications may be made by those 16 having skill in the art without departing from the spirit 17 and scope of the invention. Therefore the illustrated 18 embodiment must be understood merely as an example set forth 19 for the purposes of illustration and not by way of 20 limitation of the invention as defined in the following 21 claims.

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Claims (45)

1. An improvement in a rotating bit for cutting chips from a plastic formation comprising:
a plurality of cutters, wherein at least one cutter has a large diamond cutting surface at least as large as a three quarter inch diameter circle, each cutter adapted to cut a chip from said formation; and at least one nozzle means for directing a defined hydraulic flow only to said large cutter, said flow directed by said nozzle means applying a torque to said chip cut by said large cutter, said torque tending to twist said chip from said face of said cutter, said nozzle means associated with said cutter having a center placed in nonsymmetrical relationship to said lateral dimension of said associated cutter, wherein said nozzle directs said hydraulic flow to said cutter face of said large cutter at a position in the proximity of the center of gravity of said chip, whereby said chips of said plastic formation are cut by the minimum tendency of said bit to ball.

2. The improvement of claim 1 wherein said nozzle directs said hydraulic flow into the proximity of the center of gravity of said chip and radially inward of said center of gravity of said chip with respect to the center of said bit, a torque thus being applied to said chip tending to peel said chip off said cutting face of said large cutter toward said gage of said bit.

3. The improvement of claim 1 wherein said directed flow of said nozzle is characterized by a jet, said jet defined by flow of hydraulic fluid from said nozzle in a direction and velocity primarily determined by said nozzle, said jet having a pressure core being substantially symmetric about a longitudinal axis, said jet having a width perpendicular to said longitudinal axis and a length along said longitudinal axis, that point on said longitudinal axis of said jet most distant from said nozzle being defined as an impact point of said jet, said impact point of said jet being directed toward a location proximate to attachment of said chip to said rock formation.

4. The improvement of claim 3 wherein said impact point of said jet is within 0.4 to 0.7 inch of the center of gravity of said corresponding chip.

5. The improvement of claim 3 wherein said width of said pressure cone is approximately two times the outer diameter of said orifice of said nozzle.

6. The improvement of claim 3 wherein said longitudinal axis of said jet is disposed at least at one point between said chip and cutting face of said corresponding cutter.

7. An improvement in a rotating bit for cutting a chip from a plastic formation comprising:
a plurality of polycrystalline diamond cutters, wherein at least one cutter has a large diamond cutting surface at least as large as a three quarter inch diameter circle, each cutter cutting a chip from said formation; and at least one nozzle means for defining a directed hydraulic flow only to said large cutter, said flow directed by said nozzle means applying a torque to said chip cut by said large cutter, said torque tending to twist said chip from said face of said large cutter, wherein said nozzle means directs said hydraulic flow to said cutter face of said large cutter at a position into the proximity of the center of gravity of said chip as determined by chip shape, said chip shape in turn determined by shape of said large cutter, said nozzle means being positioned at a radially different distance from the center of said bit than the middle of the cutting face of said large cutter, wherein said bit has a center and a gage, and wherein said nozzle means directs said hydraulic flow into the proximity of the center of gravity of said chip and radially inward of said center of gravity of said chip with respect to the center of said bit, a torque thus being applied to said chip tending to peel said chip off said cutting face of said large cutter toward said gage of said bit, whereby said chip of said plastic formation is cut by the minimum tendency of said bit to ball.

8. An improvement in a rotating bit for cutting a plastic rock formation comprising:
a plurality of polycrystalline diamond cutters, wherein at least one cutter has a large diamond cutting surface at least as large as a three quarter inch diameter circle, each cutter cutting a chip from said formation; and at least one nozzle means for defining a directed hydraulic flow only to said large cutter, said flow directed by said nozzle means for applying a torque to said chip cut by said large cutter, said torque tending to twist said chip from said face of said cutter, wherein said directed flow of said nozzle means is characterized by a jet, said jet defined by flow of hydraulic fluid from said nozzle means in a direction and velocity primarily determined by said nozzle means, said jet having a core being substantially symmetric about a longitudinal axis, said jet having a pressure cone having a width perpendicular to said longitudinal axis and a length along said longitudinal axis, that point on said longitudinal axis of said jet most distant from said nozzle means being defined as an impact point of said jet, said impact point of said jet being directed at a point between said chip and said cutting surface of said cutter to wedge said chip away from said cutting face of said cutter, said nozzle means associated with said cutter being oriented with respect thereto so as to direct said hydraulic jet to impinge proximate the location at which said cutting face extends farthest from said bit and nonsymmetrically with respect to said lateral extent of said cutting face, whereby said chip of said plastic formation is cut by the minimum tendency of said bit to ball.

9. A method for removing chips cut from a formation by a bit having a center and gage comprising the steps of:
cutting a chip by a cutter, said chip having a center of gravity as determined by the shape of said chip, the shape of said chip in turn being determined by said cutter which cuts said chip from said formation;
directing a defined hydraulic flow including a pressure core toward said chip to apply a torque to said chip by said pressure core, to thereby twist said chip off said cutter, said hydraulic flow being directed by a nozzle means associated with said cutter cutting said chip said nozzle means for defining a directed hydraulic flow substantially only to said cutter, said nozzle means having a center placed in nonsymmetrical relationship to said lateral dimension of said cutter, whereby said formation is drilled without substantial risk of balling said bit.

10. The method of claim 9 where in said step of applying said torque, said torque is applied at a point into the proximity of the center of gravity of said chip as determined from the shape of said chip as cut by said cutter to thereby generate a maximal torque on said chip.

11. The method of claim 9 where in said step of applying said torque to said chip, said torque is applied to said chip and peels said chip from said cutter toward said gage.

12. The method of claim 9 where in said step of cutting said formation, said chip is cut by a cutter having a cutting surface with an area at least as great as a circle approximately three quarters of an inch in diameter.

13. A rotating bit for cutting a plastic formation comprising:
a bit body;
at least one cutter defining a lateral dimension and mounted on said bit body; and a nozzle associated with said cutter and adapted to define a directed hydraulic flow substantially only to said cutter, said nozzle having a center placed in nonsymmetrical relationship to said lateral dimension of said cutter, wherein said nozzle center is placed radially inward of the midpoint of said lateral dimension of said cutter.

14. The bit of claim 13, wherein said at least one cutter comprises a plurality of cutters.

15. A drill bit for cutting a plastic formation, comprising:
a substantially round bit body;

a plurality of cutters mounted on said bit body, each of said cutters defining a substantially radially-extending cutting face; and a fluid-directed nozzle associated with each of said plurality of cutters, each of said nozzles being positioned at a radially different distance from the center of said bit than the middle of the cutting face of said cutter with which said nozzle is associated, wherein each of said nozzles is positioned radially inward of the middle of the cutting face of its associated cutter.

16. A cutter and nozzle arrangement for use in a rotary bit for earth boring, comprising:
a cutter defining a laterally-extending cutting face and mounted on the face of a bit defining a gage portion; and a fluid-directing nozzle associated with said cutter and oriented with respect thereto so as to direct an hydraulic jet to impinge proximate the location at which said cutting face extends farthest from said bit and nonsymmetrically with respect to said lateral extent of said cutting face.

17. The cutter and nozzle arrangement of claim 16, wherein said nozzle is oriented with respect to said cutter so as to direct said hydraulic jet to a location between the point on said cutting face farthest from said bit gage and the midpoint of the lateral extent of said cutting face.

18. An improvement in a rotating drag bit for drilling in a plastic subterranean formation, comprising:
a plurality of substantially planar cutters comprised of a super hard material, at least one of said cutters having a cutting surface defining a lateral dimension;
at least one nozzle means associated with said at least one cutter and having a center placed in nonsymmetrical relationship to said lateral dimension thereof, said nozzle means being oriented to define a directed hydraulic flow toward said at least one cutter to impact in proximity to the point at which said at least one cutter engages said formation in cutting a chip therefrom.

19. The improvement of claim 18, wherein said nozzle is oriented so that said directed hydraulic flow impacts in proximity to the center of gravity of said chip.

20. The improvement of claim 19, wherein said nozzle is oriented so that said directed hydraulic flow impacts radially inwardly, as measured from the center of the bit, of the center of gravity of said chips.

21. The improvement of claim 18, wherein said nozzle is oriented so that said directed hydraulic flow impacts in proximity to the center of gravity of said chip.

22. The improvement of claim 18, wherein said nozzle is oriented 60 that said hydraulic flow impacts between the point on said cutting surface farthest from said bit gage and the midpoint of said lateral dimension of said cutting surface.

23. A system for drilling a plastic subterranean earth formation, comprising:
a drill bit disposed at an end of a tubular drill string providing a supply of pressurized fluid thereto;

at least one cutter mounted on said bit and defining a cutting surface adapted to cut a chip from said formation upon engagement therewith and having a lateral dimension;
a jet of fluid emanating from said bit and projected to impact on a region on said chip proximate the center of gravity thereof at a point in proximity to that at which said cutting surface engages said formation.

24. The system of claim 23, wherein said jet is projected toward said region to impact on said chip radially inwardly, as measured substantially from the center of the bit, of said center of gravity.

25. The system of claim 24, wherein said jet is projected to impact substantially between said cutting surface and said chip.

26. The system of claim 23, wherein said jet comprises a flow of hydraulic fluid defined by a nozzle mounted to said bit, said jet having a longitudinal axis terminating at an impact point, said impact point being in proximity to said point of engagement between said cutting surface and said formation.

27. The system of claim 23, wherein said jet is projected to a point between the radially innermost extent of said cutting surface and the lateral midpoint thereof.

28. A cutting system for use on a drill bit for cutting a plastic subterranean formation, comprising:
a substantially round bit body;
a cutter defining a lateral dimension and mounted on said bit body;

a nozzle associated only with said cutter and located nonsymmetrically on said bit body with respect to said lateral dimension of said cutter for directing a jet of fluid from said bit body to the general location at which said cutter extends farthest from said bit body and at an oblique angle to said lateral dimension.

29. The system of claim 28, wherein the center of said nozzle is disposed radially inwardly of the midpoint of said lateral dimension of said cutter.

30. The system of claim 29, wherein said location is further defined as extending from the radially innermost extent of said cutter and the lateral midpoint thereof.

31. A method for drilling a plastic subterranean formation, comprising:
providing a rotating drag bit having at least one cutter defining a lateral dimension mounted thereon;
cutting said formation with said at least one cutter by rotating said drag bit, whereby a chip of said formation is cut from said formation while still remaining partially attached thereto and substantially adhered to said cutter; and removing said chip from said cutter and detaching said chip from said formation by impacting said chip with a fluid jet proximate the point of attachment to said formation, said jet originating at a point radially inward from the lateral midpoint of said cutter.

32. The method of claim 31, wherein said fluid jet impacts said chip at an oblique angle to the instantaneous path of said cutter as said bit is rotated.

33. The method of claim 31, wherein said fluid jet impacts said chip substantially between said chip and said cutter.

34. An improvement in a rotating bit having a bit face and gage including at least one junk slot defined in said gage of said bit, said junk slot extending substantially longitudinally along said gage and having a compound profile along said longitudinal extent, said compound profile including at least two distinct substantially longitudinally superimposed regions of different cross-sectional configuration connected by a hydrodynamically smooth transition region.

35. The improvement of claim 34, wherein said at least two profiles of said junk slot comprise a symmetric profile and asymmetric profile.

36. The improvement of claim 35, wherein said asymmetric profile is longitudinally defined within said junk slot nearer said bit face than said symmetric profile.

37. The improvement of claim 36, wherein at least one portion of said asymmetric profile is identical to said symmetric profile.

38. A drill bit, comprising:
a body member adapted for rotation about a longitudinal axis and having a bit face and a gage; and at least one junk slot formed longitudinally in said gage, said junk slot having at least two different substantially longitudinally superimposed cross-sectional configurations spaced apart along said longitudinal axis, and hydrodynamic transition region extending between said two different cross-sectional configurations.

39. The drill bit of claim 38, wherein one of said two different cross-sectional configurations is symmetrical, and the other of said two different cross-sectional configurations is asymmetrical.

40. The drill bit of claim 39, wherein said asymmetrical cross-sectional configuration of said junk slot is formed longitudinally nearer said bit face than said symmetrical cross-sectional configuration.

41. The drill bit of claim 39, wherein at least one portion of said asymmetrical cross-sectional configuration is substantially identical to a portion of said symmetrical cross-sectional configuration.

42. A method for improving hydraulic flow within a junk slot defined in the gage of a drill bit, comprising the steps of:
forming a first portion of said junk slot in the gage of said drill bit, said first portion having a first distinct cross-sectional configuration;
forming a second portion of said junk slot in the gage of said drill bit, longitudinally spaced from but substantially longitudinally superimposed over said first portion, said second portion having a second distinct cross-sectional configuration; and forming a smooth transition portion of said junk slot in the gage of said drill bit between said first and second portions.

43. The method of claim 42, wherein said first distinct cross-sectional configuration is asymmetrical.

44. The method of claim 43, wherein said second distinct cross-sectional configuration is generally symmetrical.

45. The method of claim 44, wherein a portion of said asymmetrical configuration is substantially identical to a portion of said symmetrical configuration.