US3181632A

US3181632A - Diamond drill bit

Info

Publication number: US3181632A
Application number: US159020A
Authority: US
Inventors: Raynal Jean
Original assignee: Societe Nationale des Petroles dAquitaine SA
Current assignee: Societe Nationale des Petroles dAquitaine SA
Priority date: 1960-12-16
Filing date: 1961-12-13
Publication date: 1965-05-04
Anticipated expiration: 1982-05-04
Also published as: FR1282700A

Description

May 4, 1965 J. RAYNAL DIAMOND DRILL BIT 3 Sheets-Sheet 1 Filed Dec. 13, 1961 F /'9. pmolz ART 2 PRIOR ART 1 PRIOR ART IN VEN TOE Jim/v R4 wvn 1. BY

A TTOR/VEYS 5 Sheets-Sheet 2 Filed Dec. 13, 1961 Fly-7 INVENTOE JEAN EA YN/IL BY 62 (4 TTOENE Y5 May 4, 1965 J. RAYNAL 3,131,632

DIAMOND DRILL BIT Filed Dec. 13, 1961 3 Sheets-Sheet 3 /N VEN rozz JEAN Rn V/VAL United States Patent 9 Claims. in. 17s-s29) This invention relates to rotary diamond drill bits of the type having abrasive areas in which diamonds are embedded, and having an outlet passage for drilling fluid.

In most known rotary drill bits of this general type the drilling fluid is passed axially into the bits and is then divided into a plurality of secondary jets in an end portion of the bit, so that the fluid assumes in each of such secondary jets a radial velocity component within the flow passage defined by the bit outlet and the bottom of the drill hole being excavated. This radial velocity interferes with the proper flow of fl-uid across the abrasive areas of the bit so that the diamonds are not kept in the clean, mud-free condition in which they will develop their optimum cutting action.

It is an object of this invention to provide an improved diamond drill bit in which the above and other defects of prior diamond drill bits associated with the flo'w of drilling fluid are obviated. An object is to provide a diamond drill bit in which the drilling eflectiveness is enhanced and maintenance problems reduced through a more eflective design and cooperation of the abrasive surfaces and the drilling fluid flow passages.

Other objects will appear.

Exemplary embodiments of the invention will be described wi-th reference to FIGS. 4-11 of the accompanying drawings given for purposes of illustration but not of limitation. In the drawings:

FIGS. 1-3 relate to a conventional form of diamond drill bit, FIG. 1 being a bottom plan view thereof, FIG. 2 a section on line II-II and FIG. 3 a section on line III-III;

FIG. 4 is an idealized perspective view of the vein of drilling fluid present within the cavities of an improved diamond drill bit according to a form of the invention;

FIG. 5 is a bottom plan view of an improved drill bit according to the form of the invention shown in FIG. 4;

FIGS. 6 and 7 are elevational views thereof on two mutually normal planes;

'FIG. 8 is a bottom plan view of drill bit according to another form of embodiment of the invention;

FIG. 9 is a similar view in yet another modified embodiment;

FIG. 10 is a side view of a ribbed or fluted drill bit according to a further modification, and

FIG. 11 is an idealized perspective view analogous to FIG. 4 showing the shape of the drilling fluid vein present in the cavities of another form of drill bit according to the invention.

Some of the shortcomings of conventional drill bits will first be briefly described with reference to FIGS. 1-3, which illustrates a typical diamond drill bit of a widely used type which need not be described in detail, beyond saying that the bit includes three generally helicoidal albrasive areas 5 which are studded with diamonds, and between which three helicoidal grooves 3 are defined, which constitute outlet channels for drilling liquid delivered into and through the bit by means not shown. FIG. 1 shows a vector diagram of the flow velocities of the fluid in an outlet groove 3. It will be noted that there is a radial velocity component V1 of the fluid with respect ,to the bottom of the hole being drilled. The vector V2 indicates the relative linear velocity of rotation of the ice drill-hole bottom with respect to the bit, and the vector V3 is the resultant velocity of the fluid with respect to the bit.

As shown in FIG. 2, the drilling fluid is delivered as indicated by arrow 1 into an axial passage of the drill bit. It is noted that FIG. 2 is only a half view, showing the borehole and drill bit on one side of the center axis 2. The arrows 4 indicate the flow velocity of the fluid through an outlet channel or groove. The sectional view of FIG. 3 serves merely to illustrate the flow passage for drilling fluid which is defined between the bottom of a groove 3 on one side, and the surface 6 of the well being drilled on the other.

The type of drilling fluid flow thus provided in conventional diamond drill bits of which the one illustrated in FIGS. l3 is a typical example has several serious drawbacks. Thus, the flow section of the passages usually diverges, so that the flow velocity decreases. Moreover, the fluid flowpath includes a portion in which the flow velocity is parallel to the bottom of the well, as will be particularly clear from FIG. 2. Moreover throughout the flo-vwpath the fluid is channeled in the outlet grooves, so that it is prevented from streaming across the diamondstudded cutting areas 5 of the drill bit; such streaming however would be extremely desirable in that it would provide a much more eflicient washing action preventing the accumulation of mud which otherwise plugs the diamonds and limits their cutting action. Objects or" this invention are to eliminate these difliculties.

According to an aspect oi the invention, a drill bit comprises at least two component parts provided with diamond-studded abrasive areas, said parts being separated by an intermediate cavity of relatively narrow width dimension and of generally flat rectangular (or slot-like) shape, the midplane of which coincides with a diametric or radial plane of symmetry of the drill bit, and means are provided for injecting the drilling fluid from an axial inlet passage into said cavity. It will be appreciated that with such an arrangement the drilling fluid, rather than being subdivided into a plurality of comparatively ineffective minor streams retains its full dynamic impetus or jet eflect throughout its flowpath through the tool and the total variation of momentum to which the fluid stream is subjected is made to occur over a considerably smaller area of ground, than is the case in conventional drill bits, so that its cleaning or flushing action gains considerably in effectiveness. Moreover as will presently appear a streaming of the fluid across the abrasive surfaces of the bit is produced thereby improving the sustained cutting ability of the diamonds imbedded in said surfaces.

The above features will be more clearly apparent from a consideration of FIG. 4 which intends to illustrate the form of the liquid vein present within the internal cavities of an improved drill bit, the actual solid portions of which are not shown. Thus the portion 7 of the fluid vein is that flowing through the axial delivery or inlet passage of the drill bit. As the fluid issues from this inlet passage it is pinched or laminated within the fiat cavity defined between the two parts of the bit as earlier stated, thereby constituting a narrow, high-velocity sheet of fluid having increased eflectiveness, in contrast with the several jets into which the fluid vein divides in conventional drill bits of the kind first described.

It may here be noted that in certain types of diamond drill bits of the prior art the drill bit has been provided with a narrow slot-like cavity along a diametrically ex tending plane thereof, into which the drilling fluid was injected. However in prior drill bits of that type the cavity separating the abrasive elements of the drill included flared outer portions towards the side edges of the end of the drill bit, thereby greatly reducing the jet effect developed by the fluid vein. Moreover the bit was so forces set up by the rotation of the drill.

face while portion 21 is smooth.

shaped that the fluid flowpath included a sectiondire'cted outward and upward of the drill bit, so that the tangential velocity effect of the jet was all but completely suppressed.

pressure differentials across each abrasive H area, thereby H improving the effectiveness of the washing or flushing action.

Thus, returning direction up to the point of impact of the fluid against the bottom of the hole. True this purely axial flow con- In contrast, the fiat separating cavity of the drill bitofto FIG. 4, it willbe notedthat the flow velocity of the drilling fluid is axially directed, i.e. is par allel to the axis of,the drill hole, and retains such axial dition tends to be disturbed by the action of centrifugal 7 However, this adverse effect can and preferably is disposed with, according to the invention, as by providing rectifier bafile means, e.g. as shown at 9 and 10 within the cavity (FIGS.

-5, 6 and 7), which will act to restore the axialiflow of the fluid.

Thus, referring again to FIG. '4, it will be noted that the flow velocity of the drilling fluid is, all along the outer edge of the slot 17, directed perpendicularly to the wall of However the main part of the flow must "be V ingfluid discharged in afast solid jet oi a'flat sheet-like the hole. 7 V axially directed; i.e., parallel to the. axis of the drill hole and this condition tends to be disturbed by the action of centrifugal forces set up by the rotation of the drill. Such an adverse effect can be, and is preferably controlled, ac-

cording to the invention, by providing'rectifier baflie means; e.g.', as shown at 9 and 10 within the cavity,

which will act to restore the axial flow of the fluid.

Reference will now be-made to FIGS. 5-7 which illustrate the actual construction of oneform of drill bit according to the invention. Thedrill bit comprises a bit Stock 11 formed with an axial 'bore 12 through it for the delivery of the drilling fluid, and provided at its top with a tapered threaded section 1.3 for connection with'a drill shank. The bit further includes a generally semi-oval drill head 14'which is divided by a generally diame'tric' cut or slot 17 into two spaced

elements

15 and 16. It will be appreciated that it is the slot 17 inthe drill bit shown in FIGS. 5-7 which provides the flat vein of fluid referred to previously and designated 8 in FIG. 4. 'The ends of the spaced elements 15 and'16are tapered inwardly in'the manner shown in clotted lines 17a in 6 and 7 to provide a relatively flat conical concavity 17b in the end of the drill bit. V V

According to an advantageous feature'in thisform of 7 .side of the slot.

A pair of diametrically

opposed stabilizer projections

23 and 24 are provided on the upper end of' the bit stock 1 1 for centering'and guiding the bitin its rotation, the

V projections

23 and 24 being adapted to engage the sides of the drill hole and consequently being diamond-studded.

Preferably moreover a pair :of opposite

tapered projections

25 and 26 are provided on the inwardly directed facing surfaces of the two

elements

15 and 16, so as to reduce the size of the core that tends to form inside thev gap or slot 17. Any small corethatdoes form is quickly broken up by the jet of drilling fluid discharged through said slot.

' As shown in .FIG. 5, the drill bit is adapted'in operation "to be rotated in the direction indicated by arrow 27.

Hence, referring ;to this direction of rotation, it will be observed that the abrasive area 18 of element 15 is disposed on the trailing side from the slot 17 and the upwardly oifset smooth area 21 of the other element 16 is disposed on the leading side from slot 17 Similarly abrasive area 20 is on'thetrailing side of. the slot while the upwardly displaced smooth area 19is on the leading I V Tlie's mooth,

area

19, 21 of each element of the bit should be upwardlyoffset a minimum amount so as not substantially to engage the bottom of the drill hole (since it is not fitted with diamonds) while still being capable of limiting or preventing'theleakage of drilling fluid inthe forward direction of rotation of the bit In. the operation of the drill hit just described, the drillconfigurationthrough slot 17' strikes the bottom of the V3, which drives 1t under andacross the tra l ng abrasive the invention, each of the

bit elements

15 and 16 is "pro vided with an abrasive. area on only one-half of its cutting edges. The element 15 has adiamond-Studdedabrasive area only in the half-portion 18 :of its edge surface where-as the half-portion 19 has none; similarly element 16 ha an abrasive area on the portion-20 ofits edge sur- The

smooth portions

19 and 21 of the respective bit elements 15 and .1 6 are displaced or offset upwardly froin the related abrasive portions18 and 20, as willbeclear from FIG. 7.

that the ,cutting areas are shaped stepwise. Considering It will also be notedfrom FIGSJ'6 and 7;,

for instance cutting area 18 ,of'element 15, there. is a-- -lowermostcontour line 22 (also-see FIG. 5 fromeither side of .which 'the adjacent con-tour linesare positioned at higher elevations over the surface of area 18, the three steps spaced radially inwardlyofcontour22 thus defining a. segmentof an axial cavity in the bottom surface ofithe bit. The other segments thereof are provided by the corvresponding steps on abrasive portion 20. andiby the 'respective. adjacent indentation 'on those extremities; of

drill hole with maximum force. As' earlier noted and as indicated by the vector diagram -in :FIG. 7, the radial velocity component ofthe fluid is substantially zero, while it is flowing through the bit. The flui'd flow velocity has this characteristic becausethe narrow slot width prevents the fluid from attaining any substantial velocity perpendicular to the midplane of the slot'while the tendency of the fiuid to flow in a' radial direction parallel to said jmidplane is counteracted by the inwardly directed radial velocity components induced by baflies 9 and 10. On

vstriking the bottom of the well thefluid is "deflected tangentially as indicated by vector, V2 and assumes the resultant velocity relative tothe bit indicated by vector surface on eachaside of the bit; It will be appreicated that for a given discharge rate V1 of the fluid the effectiveness of the flushing action of the fluid on 'theabrasive surfaces will be the greater as the-velocity ratio V2/V1 'is greater, and hence as the angular rate ofbitrotation is fi I The velocity diagram indicated achieves a dual beneficial efiect. In the first place the fluid, on striking the ibOttOITl Of the well, is .subjected'to a variation in its momentum which is very high (l t eifect) and thus exerts a maximum flushing eifectjagainst the iwell bottom. {Thereafter the fluid on being deflectedtangentially exerts I resistance ofjthe bit surfaces inwhich the diamonds are imbeddedt Flow -velocities' in a range of 60 met'ers per second aregenerally foundisuitable. It is'important to :note that since, according to the invention, the drilling fluid 'is' released from the bit an extremely short distance from theibottom of the well, the flow-velocitiesused may :if desiredxbe selected atsubstantially lower values than inconventidrial. bitsi. The distanceat which the jet is releasedffrom the bit i s only a millimeters fromthe bottom of the well, i.e. a distance c orresponding to the projecting length. of the diamonds. Y It will be understood thatthecontours'of the bit shown in FIGS. 5 to 8 may be varied considerably without departing from the teachings of the invention. The contours selected by way of example are typical of those widely used at present.

In the modified embodiment shown in FIG. 8, the general construction is the same as described for the first embodiment, the only difference being the fact that the two

elements

28 and 29 of the bit, separated by the gap or slot 30 according to the invention, include

abrasive cutting areas

31 and 32 which are of generally triangular form, tapering toward the end of the bit.

In the further modification of FIG. 9, the arrangement differs from those heretofore shown in that both

elements

33 and 34 of the bit, separated by the gap 35, are fitted with diamonds throughout their end surfaces, there being no ofiset smooth areas as in the first embodiment disclosed. Such a bit may prove advantageous in that the drilling fluid discharged through slot 35 will have less tendency to escape by leakage past the end surface of the bit element positioned in front of the gap in the direction of rotation. The flushing effect is thereby further improved. However, a drill bit of the type shown in FIG. 9 is obviously more expensive both to construct, owing to the greater amount of diamond material required, and to operate, since more hydraulic power must be applied to offset the increase in the total pressure loss sustained by the drilling fluid across the end surfaces of the bit.

As already noted, the effectiveness of the flushing action increases as the rate of bit rotation is increased. However, in case of an excessively high rotational velocity, the centrifugal force acting on the body of the drilling fluid contained in the central slot of the bit tends to throw the fluid outwards and the washing effectiveness in the central parts of the cutting areas may then be decreased. As earlier indicated, this may be remedied by the provision of rectifier blades 9 and (FIGS. 5 and 6) within the slot. Alternatively, the cross sectional shape of the slot in a plane normal to the drilling axis may be modified as by increasing its width dimension to-ward the center of the bit.

In the modification shown in FIG. 10, the general construction of the drill bit is similar to that shown in FIGS. 5-7. It additionally includes a pair of longitudinal flanges or

ribs

36 and 37 projecting normally from the elements and 16. These flanges 0r ribs serve to oppose equalization of the pressures obtaining on opposite sides of the oppositely disposed elements of the bit. That is, it may be observed that the drill bit of the invention can be compared to a revolving vane in which an excess pressure tends to build up ahead of the end of each element of the drill bit in the direction of drill rotation and a corresponding pressure drop to the rear thereof. The resulting pressure differentials tend to increase the rate of flow of the drilling fluid past the abrasive areas and hence the effectiveness of the diamond-flushing action. Normally however these pressure difierentials may be cancelled by the establishment of a flow of fluid across each outerface of the bit. This undesirable pressure-equalizing effect is opposed by the provision of the flanges or

ribs

36 and 37 in that the same subdivide the area defined on the outer side of each

element

15, 16 thereby opposing the equalization of pressure on said side of each element and correspondingly enhancing the pressure differentials noted.

In all of the embodiments of the invention heretofore described, the drill bit was provided with a single diametrically extending slot or gap between two parallel spaced bit elements. However, the number of bit elements is not necessarily limited to two. Thus there may be provided three bit elements separated from one another by three circumferentially equispaced slots or gaps through which the drilling fluid is discharged. FIG. 11 illustrates the appearance of the fluid vein present in the cavities of a drill bit thus constructed. It is believed that in the light of the explanations already given, the construction of a drill bit according to the invention wherein the cavity configuration will be substantially that shown in FIG. 11 can readily be inferred by those familiar with the art so that further detailed description of such embodiment would be superfluous.

What I claim is:

1. A rotary drill bit comprising stock means adapted to be attached to the lower end of a drill pipe and provided with a generally axial passage for the delivery of the drilling fluid and a head means secured to said stock means, said head means being constituted by at least two portions extending longitudinally of the axis of said drill pipe, each of said portions having at least one abrasive area on an outer surface of said head means and at least one surface defining a respective wall of a slot, extending at least from said axis, to the outer surface of said head, said walls being symmetrically disposed on opposed sides of a plane passing through said axis and being shaped so that, along at least a portion of said axis, the width of said slot, at any point in a plane perpendicular to said axial plane, is not greater than its width at said axis.

2. A bit as recited in claim 1 wherein only two of said portions are employed, each defining substantially onehalf of said head means, and wherein said slot extends entirely across a diameter of said head.

3. A bit as recited in claim 1, wherein along at least a portion of the axial extent of said head, said surfaces defining respective walls of said slot are flat over the entire radial extent of said head.

4. A bit as recited in claim 1 wherein said surfaces defining respective walls of said slot converge in a radial direction from said axis to the periphery of said head along at least a portion of the axial extent of said head.

5. A bit as recited in claim 1 wherein each of said portions also has a smooth area displaced axially away from the bottom of said bit with respect to said abrasive area.

6. A bit as recited in claim 1 wherein each of said portions extending longitudinally of said drill pipe includes a tapered projection extending into said slot from said surface defining a respective Wall of said slot.

7. A drill bit as recited in claim 1 further comprising baflle means mounted in said slot for deflecting said drilling fluid towards said axis in a direction parallel to said axial plane.

8. A drill bit as recited in claim 1 wherein each of said portions comprises, on an outer surface thereof, at least one longitudinal rib for engagement with the sides of a drillhole to oppose equalization of the differential pressures set up across the surfaces of said portions during drill rotation.

9. A drill bit as recited in claim 1 further comprising: at least two stabilizer projections on said stock means for engagement with side walls of the drill hole; and abrasive means mounted on the engaging end surfaces of said projections.

References Cited by the Examiner UNITED STATES PATENTS 646,752 4/00 Niel et al -403 X 1,600,073 9/26 Smith 175-408 X 2,050,988 8/36 Zublin 175-96 2,264,440 12/41 Havliek 175-329 2,325,745 8/43 Crum 175-335 2,497,144 2/50 Stone 175-329 X 2,740,651 4/56 Ortloff 175-329 X 3,095,053 6/63 Pistole et a1. 175-329 FOREIGN PATENTS 1,228,941 3/60 France.

CHARLES E. OCONNELL, Primary Examiner.

Claims

1. A ROTARY DRILL BIT COMPRISING STOCK MEANS ADAPTED TO BE ATTACHED TO THE LOWER END OF DRILL PIPE AND PROVIDED WITH A GENERALLY AXIAL PASSAGE FOR THE DELIVERY OF THE DRILLING FLUID AND A HEAD MEANS SECURED TO SAID STOCK MEANS, SAID HEAD MEANS BEING CONSTITUTED BY AT LEAST TWO PORTIONS EXTENDING LONGITUDINALLY OF THE AXIS OF SAID DRILL PIPE, EACH OF SAID PORTIONS HAVING AT LEAST ONE ABRASIVE AREA ON AN OUTER SURFACE OF SAID HEAD MEANS AND AT LEAST ONE SURFACE DEFINING A RESPECTIVE WALL OF A SLOT, EXTENDING AT LEAST FROM SAID AXIS, TO THE OUTER SURFACE OF SAID HEAD, SAID WALLS BEING SYMMETRICALLY DISPOSED ON OPPOSED SIDES OF A PLANE PASSING THROUGH SAID AXIS AND BEING SHAPED SO THAT ALONG AT LEAST A PORTION OF SAID AXIS, THE WIDTH OF SAID SLOT, AT ANY POINT IN A PLANE PERPENDICULAR TO SAID AXIAL PLANE, IS NOT GREATER THAN ITS WIDTH AS SAID AXIS.