US3126973A - Rotary drilling bit - Google Patents

Description

March 31, 1964 o. M. KlEL 3,126,913

ROTARY DRILLING BIT Filed June 23. 1961 Orhor M. Kiel INVENTOR.

ATTORNEY United States Patent 3,125,973 ROTARY DRILLDIG BIT Othar M. Kiel, Tulsa, Okla, assignor to .lersey Production Research Company, a corporation of Delaware Filed June 23, 1961, Ser. No. 11%,195 7 Claims. (til. 175378) This invention relates to a rotary drill bit. More particularly, the invention relates to a drill bit of the roller cone type for use with rotary well drilling tools.

A common type of drill bit presently used in the petroleum industry to drill deep wells into the earth is the multi-cone rotary bit. This bit typically comprises three rollers cones each having a plurality of circumferential rows of teeth. The cone type cutters are circumferentially spaced on the body of the bit in such a manner that rotation of the cones on the bottom of the hole will cut the underlying formation. During rotation, the drilling force exerted on the bit is concentrated on the ends of the wedge-shaped teeth which contact the earth formation to cause a chipping away of the earth and thereby form a hole or well. The chipped portions of the earth are carried away by the circulation of drilling fluid which is pumped from the surface through hollow drill pipe, to the top of the well where the portions are removed from the drilling fluid. The drilling fluid in addition to transporting the cuttings also cleans and cools the cutters.

The circumferential rows of teeth formed on the cutters are spaced apart and are often olfset relative to the rows on adjacent cutters so as not to interfere with the rotation of the cones, and to make substantially complete contact with the bottom of a Well.

An over-all object of this invention is to provide a drill bit for use inthe rotary drilling of wells which has increased efiiciency and bit life.

Another object of this invention is to provide a conetype drill bit for the rotary drilling of Wells wherein the cones are non-circular and capable of imparting a vibratory effect to the drill bit and thereby increase its penetration efiiciency.

Another specific object of this invention is to provide a rotating cone type drill bit wherein the outer row of teeth (i.e. the heel teeth) on a conical cutter element defines a non-circular periphery, and wherein the inner rows of teeth on each cone define a circular periphery. The outer row provides a vibrating effect on the drill bit as it is rotated against the earth while the inner rows serve to stabilize and maintain the drill bit on a straight drilling path.

These and other objects and a better understanding of this invention may be had by referring to the following description and claims taken in conjunction with the following illustrations, of which:

FIGURE 1 is a perspective view of a drilling bit having tri-cone cutting elements which is contemplated to be the best mode of practicing this invention.

FIGURE 2 is a bottom view of the tri-cone drilling bit of FIGURE 1 which shows the cutting face exposed to a formation being drilled.

FIGURE 3 is a plan view looking axially of a single cone to show the non-circular arrangement of the outer row of teeth as taught by this invention.

Referring now to the drawings and in particular to FIGURES 1 and 2, a typical rotary drill bit improved in accordance with this invention is indicated generally by the numeral Ill. The drill bit It) is normally supported by a threaded portion 12 to a drill stem (not shown) which extends to the surface of the earth where rotary motion is imparted to the drill bit Itl. Drill bit It) includes three equally spaced circumferential conical cutters 14, 14'

Patented Mar. 31, I964 and 14"each rotatably supported and journalled within the downwardly projecting body or legs 16.

Each of the conical cutters is integrally formed with circumferential rows of wedge-shaped teeth 17 designated as inner rows 18 and 19 and an outer row 20. In a typical rotary drill bit, the circumferential rows of teeth 18, 19 and 2% are formed so that a curve drawn through the outer tips of the teeth 17 of each row in a plane perpendicular to the axis around which the cones 14 rotate will define a circle. Assuming circular rows of teeth, the drill bit 10 rotates substantially evenly against the formation in which a hole is being formed with very little vibration or oscillatory motion. The multiplicity of teeth 17 in each row 18, I9 and 20 means that there are many teeth in continuous contact with the earth. Therefore, the drill bit Iii rotates relatively smoothly against the earth and depends primarily upon the weight established by the drill string above the bit to chip away the hard formations encountered in oil well drilling.

FIGURE 2 shows a bottom end view arrangement of a tri-cone drilling bit. Openings 24 provide means whereby drilling mud which is pumped down through the drill stem escapes from within the drill bit 10 to wash away and carry to the surface cuttings which are chipped loose by the pressure of teeth 17 as they are rotated against the earth.

Up to this point, the description of the bit shown in the drawing has been that of a conventional bit. That is, the conical cutters 14, I4 and 14 are somewhat typical of many cutter structures in their arrangement and relationship of teeth which are mounted on projecting leg spindles by means of ball bearings. This invention, then resides in a particular arrangement and relationship of the cutting teeth on each conical cutter.

The present invention takes advantage of the observation that the rotary drilling of wells can be greatly enhanced through the application of vibratory or percussion energy to a rotating bit. Past charts to exploit this observation have entailed the attachment of expensive and complicated devices to the drill stem above the bit. The present invention, however, does so in a very simple and inexpensive manner. In particular, the novel principle of this invention lies in the provision of a non-circular row of teeth on each conical cutter such that a vibratory or oscillatory action is imparted to the drill bit 10 so as to increase its penetration effectiveness and over-all drilling efficiency.

The preferred arrangement of the teeth according to this invention is best shown in the plan view of FIGURE 3. In this embodiment the inner rows of teeth 18 and 1% are circular as heretofore described. That is, curves drawn through the tips of teeth 17 in rows 18 and 19, and in planes perpendicular to the axis about which cone I i rotates, describe two separate circles.

The outer row 30 comprises teeth 32 and teeth 34. This outer row 3%, however, does not describe a circular configuration. That is, a curve drawn through the tips of teeth 32 and 34 in a plane perpendicular to the axis about which the cone rotates is non-circular. Although this non-circular arrangement may be of a multitude of geometrical configurations, it is considered the optimum embodiment to provide an elliptical arrangement where teeth 34 are of slightly less diameter (minor axis of the ellipse) than the diameter of teeth 32 (major axis). This is emphasized by dotted line 36 which would be the curve formed by the teeth 32 in the outer row if all of the teeth 32 and 34 were of equal diameter. It should be noted that the minor and major axes, or more generally the axes of the non-circular shape, whatever it may be, shall preferably intersect at a point which coincides with the conical cutter axis.

The embodiment illustrated in FIGURE 3 represents a typical conical cutter constructed in accordance with this invention for use in a conical multi-cutter drill bit.

In operation, the non-circular arrangement of the outer row of heel teeth on each conical cutter causes a vibratory or reciprocating motion of a drill bit as it is rotated during the drilling of a hole. To illustrate this feature of the present bit, it is first noted that as a conventional bit rotates on the bottom of a hole, the bottom remains esscentially fiat. With the new hit, however, elliptical cutters tend to produce a sinusoidal or wavy configuration on the bottom of a hole. As drilling continues, high portions of the elliptical cutters come into contact with high portions of the sinusoidal configuration on the bottom of the hole. This results in a sharp upthrust or vibration to the drill string. Teeth on adjacent cutters are lifted from the bottom of the hole and thereby leave the rock close to the point of impact less supported. Conversely, as low points of the elliptical cutters encounter low portions of the sinusoidal configuration, the adjacent circular cutters are dropped on the bottom of the hole. Since the portions of the hole adjacent to the resulting impacts (on the low portions of the elliptical cutter paths) are unconfined, larger than normal chips are produced with less expenditure of energy.

The vibratory motion engendered by the invention markedly increases the effectiveness of a bit to chip away hard formations which are encountered in drilling. The greatest volume of rock which must be chipped loose in any given borehole lies adjacent the circumference of the hole, and it is this particular are which is contacted by the outer row of teeth 30. The non-circular arrangement of this row of teeth permits the bit weight to be especially concentrated where the most difiicult drilling occurs.

In one test of the invention, the outer rows of worn cutting teeth on an 8% inch diameter tri-cone rotary drill bit were rebuilt to form the configuration of FIGURE 3, i.e., having an over-all elliptical shape. In this experiment, the difference between the major and minor axes of the outer row of teeth on each cone was about of an inch. The inner rows of teeth were maintained circular to allow the bit to turn freely and impart a directional effect to the drilling operation.

The above bit drilled two hundred and forty feet (240') of hole in approximately three and one-half hours. Records indicate that other wells drilled in the same area through the same formation using identical-type bits (but lacking the non-circular profile) required approximately seven and one-half hours to attain the same depth of drilled hole. Examination of the chips of earth returned to the surface by the drilling mud indicated that the elliptical arrangement of the outer row of teeth of the test bit produced chips of earth formation approximately ten times the size of the rock chips removed when a conventional drill bit was used. It was also observed that the drill stem appeared to be moving up and down approximately of an inch.

The arrangement of a conical cutter as shown in FIG- URE 3 wherein the inner rows of teeth 18 and 19 are maintained circular and the outer row of teeth 3% is noncircular or elliptical, is considered the preferred embodiment of the invention. This embodiment is not to be taken, however, as a limitation of the invention, but is merely exemplary of the application of the principles of the invenion. An additional embodiment which suggests itself is that of providing non-circular teeth on one or more of the inner circumferential rows 18 or 19 and retaining the outer row 30 circular to impart directiveness. Other embodiments include various geometrical non-circular ara Larangements other than elliptical of the outer row of teeth 30. One such arrangement includes an outer row configuration whereby there are four peripheral lengths of longler teeth interspaced with peripheral lengths of shorter teet Although this invention has been described with a certain degree of particularity, it is manifest that many changs may be made in the details of construction and the arran ement of components without departing from the spirit and scope of the appended claims.

What is claimed is:

1. A drill bit for the rotary drilling of wells comprising a body; a multiplicity of conical cutters rotatably supported by said body, a plurality of rows of teeth integral with each said cutter, at least one of said rows having teeth of unequal length with teeth of equal length disposed about apart to impart percussion motion to said bit during said drilling.

2. A drill bit for the rotary drilling of wells including a body, a multiplicity of conical cutters rotatably supported on said body, a plurality of rows of teeth integral with each cutter, the improvement comprising at least one of said rows having teeth of unequal length, said row being divided into four portions, the teeth in each separate portion being of equal length, the teeth in adjacent portions being of unequal length whereby to impart percussive motion to said hit upon rotation thereof during drilling.

3. A drill bit for the rotary drilling of a well in an earth formation comprising a body attachable at its upper end to a rotary drilling string; a multiplicity of conical cutters, each such cutter having an axis that is rotatably supported by said body at the lower end thereof to contact said formation; a plurality of rows of teeth circumferentially formed on each said cutter, said rows including an outer row of heel teeth on each cutter; the heel teeth on one peripheral portion of the outer row of each cutter having a radius from the axis of said cutter which is less than the radius of the heel teeth on another peripheral portion of the same outer row.

4. A drill bit of the type defined in claim 3, wherein the heel teeth on each said cutter define an elliptical circumferential shape with each axis of the ellipse intersecting the axis of its respective cutter.

5. A drill bit for the rotary drilling of wells comprising a body, a plurality of conical cutters rotatably supported and journalled within said body, a plurality of rows of teeth circumferentially and integrally formed on each said cutter, the outer row of teeth on each said cutter comprising heel teeth varying in length around said cutter to define a noncircular periphery, at least one inner row of teeth on each said cutter having teeth of equal length around said cutter to define a circular periphery.

6. A drill bit as defined in claim 5 in which the heel teeth in the outer row on each cutter vary in length so as to define an elliptical periphery.

7. A drill as defined in claim 5 in which the outer row of teeth on each cutter has four peripheral intervals of longer teeth interspaced with peripheral intervals of shorter teeth.

References Cited in the file of this patent UNITED STATES PATENTS 1,796,602 Hull Mar. 17, 1931 1,840,390 Failing Jan. 12, 1932 2,061,650 Catland Nov. 24, 1936 2,533,259 Woods et al Dec. 12, 1950

Claims (1)

1. A DRILL BIT FOR THE ROTARY DRILLING OF WELLS COMPRISING A BODY; A MULTIPLICITY OF CONICAL CUTTERS ROTATABLE SUPPORTED BY SAID BODY, A PLURALITY OF ROWS OF TEETH INTEGRAL WITH EACH SAID CUTTER, AT LEAST ONE OF SAID ROWS HAVING TEETH OF UNEQUAL LENGTH WITH TEETH OF EQUAL LENGTH DISPOSED ABOUT 180* APART TO IMPART PERCUSSION MOTION TO SAID BIT DURING SAID DRILLING.

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