US3363706A - Bit with extended jet nozzles - Google Patents

Description

Jan. 16, 1968 R. FEENSTRA BIT WITH EXTENDED JET NOZZLES Filed July 20, 1965 FIG. 2

FIG.

FIG. 6

INVENTOR ROBIJN FEENSTRA MW HIS ATTORNEY United States Patent ABSTRACT 0F THE DHSQLGFiURE Performance of a three-cone, rotary drill bit may be improved by extending the jet nozzles thereof below the bit body to a level slightly above the lowermost surface of the cutter cones. The extended nozzles are reinforced and protected from bending during drilling operations by protective jackets placed between the nozzle and the borehole wall.

The invention relates to a rotary drilling bit with rotary cutting elements suitable to disintegrate rock material of underground formations, and provided with jet nozzles which are suitable to direct high velocity jets of drilling fluid to the bottom of a hole being drilled, so as to erode the hole bottom, to remove the cuttings therefrom and at the same time to clean and cool the cutting elements. These nozzles are preferably made of a wearresisting material since the driling fluid flowing therethrough usually has abrasive properties. In particular, the present invention relates to a rotary drilling bit of the above construction, in Which the jet nozzles are of the so-called extended type. Whereas the jet nozzles of the normal type are mounted directly in the bit body, the extended type nozzles are carried at the lower end of tubular elements extending in a downward direction from the bit body and communicating with the interior thereof. Each tubular element protrudes between a 'pair of adjacent rotary cutting elements.

In view of the fact that the distance existing between the discharge opening of each jet nozzle and the bottom of the hole is smaller in the case of extended jet nozzles than the case of nozzles directly mounted in the bit body, the fluid velocity over the hole bottom of the jet streams issuing from the jet nozzles is remarkably greater when using extended nozzles than when using nozzles which are directly mounted in the bit body. The resulting greater fluid velocity along the hole bottom results, as has been found in tests carried out in the laboratory as well as in the field, in a higher penetration rate of the drilling bit during the drilling process carried out thereby.

Unfortunately, it has been found in the field tests with rotary drilling bits having extended jet nozzles, that the extended nozzles are very liable to damage, especially by engagement of foreign objects with the lower ends thereof. Such damage often causes displacement of the lower ends of the tubular elements carrying the nozzles, which is to be considered absolutely undesirable since as a result of the small distance existing between the outer Wall of each tubular element and the adjacent cutting elements, the damage of the tubular elements will even become greater when these elements are forced against the rotating cutting elements. Moreover such displace ment may even prevent the cutting elements from rotating, resulting in skidding of the cutting elements and premature wear of some of the teeth carried thereby.

Strengthening the lower ends of the tubular elements might be a solution for preventing excessive damage thereof. However, due to lack of space, such strengthening is not feasible in view of the limited areas available between each pair of adjacent rotary cutting elements,

through which areas the tubular elements have to pass.

Another solution would be to use extended jet nozzles of shorter length, which nozzles would have their lower ends at a level relative to the rotary cutting elements where a suiiicient space is available for allowing the use of the required reinforcements. This solution would, however, decrease the drilling penetration rate since the distance between the discharge of each nozzle and the borehole bottom would have been increased which would unfavorably affect the interaction of the bit teeth and the hole bottom.

The present invention now provides a solution for the existing problem, whereby damaging of the lower ends of the extended jet nozzles is prevented without influencing the drilling penetration rate.

A rotary drilling bit according to the invention comprises a bit body, legs extending from said body in a downward direction, bearing members on said legs, rotary cutting elements rotatably carried by the bearing members, tubular elements carried by the body, each tubular element communicating at one end thereof with the interior of the bit body and carrying at the other end thereof a nozzle, and protruding in a downward direction between a pair of adjacent cutting elements, each tubular element being provided, except at the lower end thereof, with a wear-resisting cover protecting at least that part of the tubular element facing the exterior of the drilling bit.

The tubular element may be a pipe or tube. In another embodiment, the tubular element may be a body through which a channel passes.

The wear-resisting cover may have a U-shaped horizontal cross-section and may, in one embodiment, be separate from the tubular element. In another embodiof the tubular element.

The radius of the outer wall of each cover is at most equal to the radius of the outermost parts of the cutting elements, and preferably the difference between these radii is at most 4; inch.

The radius of the outer wall of each cover is preferably at least inch greater than the radius of the outermost parts of the lower ends of the tubular elements.

The invention will be further described with reference to the drawings in which:

FIGURE 1 shows by way of example a perspective view of a rotary drilling bit according to the invention with a sector cut away so as to show one of the extended nozzles in longitudinal section;

FIGURE 2 shows (on a scale smaller than FIGURE 1) schematically a cross-section taken over line 22 in FIG. 1, indicating at which part of the drilling bit the sector has been cut away, as well as the direction (arrow I) in which the view shown in FIG. 1 has been taken; and

FIGURES 3-6 are cross-sections of conduit tubes provided with protection covers of four diiferent constructions, all according to the invention.

The rotary drilling bit as shown in the drawing comprises a bit body 1 which is provided at the upper side thereof wtih a hollow shank 2, in the outer wall of which is formed a screw thread 3. The interior 4 of the bit body l communicates with a conduit 5 formed within the shank 2.

Three legs 6 (only two of which appear in FIG. 1) form part of the bit body 1 and extend in a downward direction. In a manner known per se (and not shown in the drawing) each leg 6 is provided with hearing means for rotatably supporting a conical cutting element 7, which element is provided with teeth or other cutting 3,3 3 members. The central axis of each element intersects (or passes at a close distance to) the central axis of the rotary drilling bit. Only two of the three rotary cutting elements 7 have been shown in FIG. 1.

Between each pair of adjacent cutting elements 7, i.e., eccentrically to the central vertical axis of the bit, there protrudes an extended nozzle 8, of which only one appears in FIG. 1. Each nozzle 8 consists of a tubular element or conduit 9 connected to the bit body 1 and having its interior in communication with the interior 4 of the body 1. If desired, the tubular elements 9 may form a single entity with the body 1 or, if the body is composed of three identical parts each including a leg 6, each part may form a single entity with a tubular element 9. In the design shown, however, each tubular element 9 is formed by a curved conduit or tube which at the upper end thereof passes through a bore formed in the bit body 1 along a downwardly diverging axis, and is connected thereto in a suitable manner, e.g., by welding. The lower end of each tubular element 9 is substantially vertical and carries a jet-forming nozzle 10 which is preferably made of a Wear-resisting material and may be connected to the element 9 in a manner known per se, e.g., by means of a snap-ring or brazing, using a suitable seal, e.g., rings or plastic sealants (not shown).

A protective cover 11 is placed over the greater part of the tubular member 9, with the exception of the lower end thereof. In the example shown in FIG. 1, the cover 11 and the tubular element 9 consist of separate parts. The cover 11 which consists of wear-resisting material, has a U-shaped horizontal cross-section and is connected to the bit body 1 in a suitable manner, e.g., by welds, such as 13. If desired, the cover 11 and the tube or conduit 9 may be connected by welds (such as 14), which are arranged where the cover 11 forms an angle to the tube 9.

The cover does not need to consist of wear-resisting material for the total volume thereof. Thus, if desired, the cover lllla may be formed by a body 15 (FIG. 3) provided at the exterior surface thereof with a wear-resisting layer 16, such as a hard facing of large sized grains of tungsten carbide, hard metal and/or diamonds, which is applied to the outside of the bit. The open channel 17 of this cover is directed toward the central axis of the bit.

In another embodiment the wear-resisting protective cover according to the invention is not formed separately from the tubular member, but is formed by applying and bonding a Wear-resisting layer 18 (FIG. 4) to the outer surface of the tubular member 9a. This layer 18 may be a hard facing of large sized grains of tungsten carbide, hard metal or diamonds.

The wear-resisting protective cover according to the invention does not need to show a continuous surface. If desired, the cover may be formed of separate inserts 19 (FIG. of wear-resistant material, which inserts are fixed to a cover body 20, preferably U-shaped, at close distances from each other, e.g., by suitable locking means, welding or brazing.

The inserts 19 may be of various cross-section, for example, they may be elongated in the direction of the axis of the drilling bit, or consist of pins having their axes substantially normal to the outer surface of the cover body 20.

In another embodiment, only two wear-resistance parts or inserts 21 of elongated shape are used (FIG. 6), which are fixed to the cover body 22 in such a way that they are substantially parallel to the axis of the drilling bit.

Whereas the layers 16, 18 or the insert members 19 and 21 are of wear-resisting material, the bodies (FIG. 3), 9a (FIG. 4-), (FIG. 5) and 22 (FIG. 6), respectively, on which they are mounted, are preferably of a ductile material.

If desired, wear-resisting parts similar to inserts 19 (FIG. 5) and 21 (FIG. 6) may be directly mounted on the tubular element 9a, shown in FIG. 4, in place of layer 18.

For economic reasons the application of the wear-resisting cover or layer is restricted to those parts of the tubular elements 9, which do not face the interior of the drilling bit. In a suitable arrangement, the cover 11 has a U-shaped cross-section, and is situated around the tube or conduit 9 (FIG. 1). This arrangement is preferred when adapting rotary drilling bits designed for jet nozzles arranged in openings of the bit body for the application of extended jet nozzles and protective covers according to the invention. If a rotary drilling bit, according to the invention, is provided with tubular elements formed by bodies having a channel passing therethrough (e.g., FIG. 4) rather than simple tubes, the protective cover is preferably formed by a hard facing arranged at the outer side of each tubular element. These bodies may be welded to the bit body or form an integral part thereof.

The radius of the outer wall of the covers, measured with respect to the central axis of the drilling bit, is at least A inch greater than the radius of the outermost parts of the lower end of the tubular elements 9.

The radius of the outer wall of the covers is at most equal but preferably smaller than the outer radius of the outermost parts of the cutting elements 7. The difference between these two radii depends on the extent to which play in the bearing members of the cutting elements, as a result of wear, is considered acceptable before replacing the bit with a new one. Preferably this difference is in the order of inch and not greater than 4; inch.

Although a cover may extend over the lower part of a tubular element 9, it has been found from field tests with a drilling bit having covers protecting only the upper part of the elements 9, that this is sufiicient for preventing damage to the lower ends thereof. Moreover, such extension of the covers in a downward direction is often not feasible in view of the limited space available between the cutting elements 7, or, if done, is at the cost of the cross-section of the conduit 9, which then will wear out rapidly due to the abrasivity of the drilling fluid passing therethrough at high velocity.

In the field tests it has been found that the lower part of the nozzles 8, which used to become damaged in the drilling process if no covers were applied, remained undamaged after the addition of covers, even though these covers did not extend to these lower parts.

When the covers are U-shaped, it is necessary that the area remaining between the outer walls of the legs of the U-shaped covers and the side walls of the legs 6 be large enough to allow the passage of drilling fluid, laden with cuttings, in an upward direction. When the area is too small for this purpose, channels (not shown) may be provided through the legs 6, which commun cate with the space between the bit body and the cutting elements '7 at one end thereof, and at the other end, with the space above the legs 6.

The invention is especially applicable to drilling bits having an outer diameter which is 6 inches or larger. When using bits larger than 8 inches, in particular when larger than 10 inches, balling-up of the cutting elements during the drilling process often occurs. Preferably, an extra nozzle, centrally arranged with respect to the bit body, is provided for combating this phenomenon which consists of the sticking of rock flour to the cutting elements thereby reducing the cutting action of the bit on the bottom of the hole being drilled.

To prevent damage to the lower ends of the nozzles 8 as a result of contact with the bottom part of the hole, these lower ends have to be above the ridges which are left on the bottom as a result of the action of the outer row of teeth of the cutting elements 7. Since the highest ridges on the path over which the ends of the nozzles 8 are to pass are formed at the so-called gauge side of the heel teeth of the cutting elements, it is sufiicient if the level of the lowest parts of the nozzles 8 are just above the level of the root of the heel teeth at the gauge side. Further, the lowest parts of the nozzles 8 should not be more than 1 inch above the level of the root of the heel teeth at the gauge side so as not to weaken unduly the effect of the jets on the bottom of the hole being drilled. The lowest part of the nozzles 8 may either be formed by the lowest part of the tubular members or by the lowest part of the nozzles 10, provided that these nozzles 10 extend beyond the tubular elements.

The invention is also applicable to bits provided with jet nozzles having discharge openings, the axes of which are not normal to the hole bottom as indicated in FIG. 1. Thus, the axis of a tubular member and/or of a nozzle 10 and the central axis of the drilling bit do not need to be in a common plane. Such slanted arrangement of the nozzles 8 will combat bit balling of the cutting elements 7.

It will be understood that the present invention is not limited to the particular examples which have been described with reference to the drawings, since many modifications therein may be made. It is, therefore, contemplated to cover by the appended claims any such modifications as fall within the true spirit and scope of the invention.

I claim as my invention:

1. A rotary drilling bit for drilling wells of the type employed in petroleum explorat'on and production which comprises:

(a) a bit body having a fluid cavity therein;

(b) a plurality of leg members porjecting downwardly from the bit body and spaced around a central axis of said bit body;

(0) a bearing member mounted on each of the leg members and having the axis thereof directed downwardly toward the central axis of the bit body;

(d) a conical element rotatably carried by each of the bearing members whereby the bases of said conical elements cooperatively determine the gage of the well bore, each of said conical elements having a conical root surface from which a plurality of earth engaging elements project;

(e) conduit means carried by the bit body in communication with the fluid cavity and extending downwardly substantially between the bases of adjacent conical elements below said bit body to a level of substantially one inch above the lowermost level of said root surface;

(f) nozzles attached to the conduit means at the lower ends thereof (and positioned between adjacent cutting elements); and

(g) substantially hard-facing wear-resisting protective cover means disposed on at least a portion of the outer surfaces of the nozzles exterior of the central axis of the bit body forming a protective cover for each said conduit means.

2. A three-cone rotary drilling bit for drilling Wells of the type employed in petroleum exploration and production which comprises:

(a) a bit body having a fluid cavity therein;

(b) three leg members projecting downwardly from the bit body and spaced around a central axis of said bit body at uniform intervals;

(c) a bearing member mounted on each of the leg members and having the axis thereof directed downwardly toward the central axis of the bit body;

(d) a conical element rotatably carried by each of the bearing members whereby the bases of said conical elements cooperatively determine the gage of the well bore, each of said conical elements having a conical root surface from which a plurality of earth engaging elements project;

(e) conduit means carried by the bit body in communication with the fluid cavity and extending downwardly substantially between the bases of each two adjacent conical elements below said bit body to a level of substantially one inch above the lowermost level of said root surface;

(f) nozzles attached to the conduit means at the lower ends thereof (and positioned between each two adj acent cutting elements) and (g) substantially hardfacing wear-resisting protective cover means disposed on at least a portion of the outer surfaces of the nozzles exterior of the central axis of the bit body forming a protective cover for each of said conduit means.

3. A drilling bit as defined by claim 2 wherein said conduit means and protective cover means are separate elements.

4. A drilling bit as defined by claim 3 wherein said conduit means are tubes.

5. A drilling bit as defined by claim 4 wherein said protective cover means are elements having a U-shaped cross-section which partially encircles the upper portions of the tubes, the open portions of the cover elements being toward the central axis of the bit.

6. A drilling bit as defined by claim 4 wherein said protective cover means comprises:

(a) U-shaped elements which partially encircle the upper portions of the tubes, the open portions of the Ushaped elements being toward the central axis of the bit; and

(b) wear-resistant material bonded to the outer surfaces of said U-shaped elements.

7. A drilling bit as defined by claim 2 wherein said conduit means and protective cover means comprise:

(a) body members having flu d channels therethrough,

and wear-resistant material bonded to the outer surfaces of said body members which face the conical elements.

8. Apparatus as described by claim 2 wherein the outer radial extremity of said protective cover with respect to the bit axis is substantially within and A; inch less than the gage radius of said well bore.

References Cited UNITED STATES PATENTS 1,922,436 8/ 1933 Herrington 175-340 X 1,945,258 1/1934 Collins l-340 2,634,101 4/1953 Sloan 340 X 3,115,200 12/1963 Mandrell 175-340 3,207,241 9/1965 Neilson 175-340 CHARLES E. OCONNELL, Primary Examiner. NILE C. BYERS, 1a., Examiner.

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