Drill Bit Center Jet

Abstract

A drill bit construction including a center jet for preventing the accumulation of masses of earth formation between and above the cutters, the jet being provided by a nozzle which breaks up or diffuses the stream of pressurized drilling mud issuing therefrom to avoid abrasive concentration of the jet on portions of the teeth of the cutters. In addition, a jet nozzle construction and mounting arrangement permitting installation and replacement of nozzles downwardly through the drilling mud passage in the body of the bit, there being means provided for reducing turbulence where it is not desired, while at the same time providing controlled diffusion or breaking up of the stream and also means for protecting the bit body adjacent the nozzle against undue abrasive action.

Description

This invention relates to a drill bit construction, and more particularly to oil well and similar drill bits having body portions with rotary cutters thereon.

Historically, drill bits with rotary cutters have been provided with body portions having pressurized mud passages and outlet ports, with or without nozzles disposed about the outer undersides of the bit body between cutter carrying legs or journals. These ports are provided to carry or direct pressurized drilling mud into the hole being formed by the cutters as the bit body rotates and the cutters rotate on the body. The pressurized stream of drilling mud mixes with the cuttings from the formation, forming a slurry which is forced to the top of the hole around the drill string by the pressurized mud flowing down through the string and through the ports or jets. A center jet extending downwardly through the dome or central underside of the tool body has been provided heretofore but it has comprised an open port or a nozzle from which a solid stream of pressurized mud issues, the stream being directed to the teeth on the rotary cutters which are closest to each other in the longitudinal central and upper longitudinal portion of the bit unit beneath the dome. The highly pressurized substantially solid stream of drilling mud is quite abrasive and produces harmful wear on the cutter teeth.

It is an object of the present invention to provide a drilling tool having a close grouping of rotary cutters wherein there is provided a center jet from which issues a controlled flow of pressurized drilling mud in a broken up or diffused condition, both to more effectively prevent the accumulation of shale balls or earth formations between the downwardly facing dome of the tool body and the relatively closely spaced inwardly and upwardly directed portions of the rotary cutters, as well as to prevent objectionable wear on the cutter teeth which would otherwise occur if the stream from the center jet was maintained in a single highly abrasive column or stream.

More generally, it is an object of the invention to provide a controlled jet construction in the form of a nozzle which is directed more or less toward the teeth of one or more cutters of a drilling tool wherein the stream of pressurized mud is broken up or diffused to prevent wearing of the teeth from the abrasive action of the mud.

A further action of the invention is to provide a drilling tool with a center jet directed downwardly from the lower central portion of the tool at the dome thereof, wherein a nozzle is removably mounted in the jet port and is accessible for removal and replacement, as well as original insertion downwardly through the conventional drilling mud passage extending axially of the tool body and open at the top.

A further object is to provide a mounting sleeve for a jet nozzle which is anchored in the bit boon and extends outwardly or downwardly beyond the face of the dome of the body of the bit and secured to the dome by a weld amply filling the corner defined by the outer wall of the sleeve and the downwardly facing dome of the body in order to reduce abrasive destruction of the metal of the bit body around the sleeve due to eddying and agitation of the drilling mud and/or cuttings.

The above and other objects and advantages of the invention will more fully appear from the following description in connection with the accompanying drawings:

FIG. 1 is a side elevational view of a drilling bit showing it in relationship to a drilling string to which it is attached, the drilling string and the walls of a hole being drilled being shown in broken lines;

FIG. 2 is an enlarged detail partially in vertical section of the lower portion of a drill bit body with portions of rotary cutters shown in broken lines;

FIG. 3 is a sectional view taken approximately on the line 3--3 of FIG. 2;

FIG. 4 is an enlarged detail in vertical section of a form of diffuser nozzle or jet;

FIG. 5 is a sectional view taken approximately on the line 5--5 of FIG. 4;

FIG. 6 is a view similar to FIG. 4 but showing a modified form of nozzle construction;

FIG. 7 is a sectional view taken approximately on the line 7--7 of FIG. 6;

FIG. 8 is a view similar to FIGS. 4 and 6, showing another form of nozzle construction;

FIG. 9 is a bottom plan view of the drill bit of FIG. 1.

In FIG. 1 broken lines 12 show the sides of a hole being drilled in the ground. Extending into the hole are sections 14 and 16 of drill string, the section 16 comprising a sub, to the lower end of which is secured in a conventional manner, a drill bit body 18. As shown in FIG. 2 the bit body has a lower portion 22 and downwardly from the portion 22, extend legs 24. These legs are preferably three in number and downwardly and inwardly from each leg, there extends a journal 26 upon which is rotatably mounted a rotary cutter 28 having teeth 30. As shown in FIG. 9 these cutters have their teeth 30 rather closely positioned and as viewed in FIG. 2, there is a pocket formed between the inner and upwardly disposed portions of the cutters and the underside 32 of the bit body which is conventionally known as a dome.

In FIG. 2 there is shown a lubricating unit 34 of conventional type, the details of which are not set forth herein. Extending from the lubricating unit 34 are passages 36 which lead to different portions of the structure to lubricate bearings for the rotary cutters 28.

The bit body 22 has an upwardly open and downwardly extending pressurized drilling mud flow passage 37. This passage has its lower end reduced, as at 38, and is provided with a final reduction 40 which defines a shoulder 42 between it and the reduced portion 38.

Mounted in the bottom portion 38, 40 of the drilling mud flow passage is a sleeve 44 whose lower end 44A extends downwardly below the face of the dome 32 and the sleeve is secured to the dome by a weld 46 which preferably fills the angle between the projecting portion 44A of the sleeve and the surrounding adjacent face portion of the dome 32. The sleeve 44 is provided with longitudinally intermediate internal threads 48 to threadedly receive an inner sleeve 50. This sleeve is provided with a tapered upper portion 52 which is castellated as at 54 to receive a suitable wrench or other tool for inserting and removing the inner sleeve 50 relative to the outer sleeve 44. Beneath the end of the inner sleeve 50 an O-ring 53 is positioned against a shoulder 54 which faces upwardly in the sleeve 44.

The inner sleeve 50 has a downwardly directed shoulder 56 which bears against the upper end of a nozzle element 58 which extends downwardly through an opening 60 in the sleeve 44. The nozzle 58 has a downwardly extending shoulder 62 which bears against the upwardly facing shoulder 54 of the sleeve 44. When the nozzle 58 is clamped between the shoulder 56 and 54, the O-ring 53 is placed under compression to a sufficient degree to provide a seal between the shoulder 54, the bottom end of sleeve 50 and the adjacent circumferential portion of the nozzle 58.

The upper inner end portion of the sleeve 44 is tapered as at 64. The taper 64 of the sleeve 44 is provided to permit relatively smooth flow of pressurized drilling mud downwardly through the passage 37, its reduced diameter 38 and into the sleeve and nozzle structure just described.

The nozzle 58 may be provided with an enlarged inlet portion 66. This is to provide a relatively smooth inlet flow into the upper end of the nozzle. From the upper portion the nozzle may be cylindrical as indicated at 68. The lower end of the nozzle 58 is provided with vertical slots 70 and these slots lie between legs 72 which are shown to be three in number in the specific embodiment. The ends of the legs 72 are turned downwardly and inwardly toward each other to provide a downwardly disposed central outlet portion 74 and outlets through the spaces 70 between the legs 72. Thus the stream of pressurized drilling mud issuing from the nozzle 58 is not confined to a single more or less solid stream but is broken up by the inwardly turned ends of the legs 72 and diffused flow of drilling mud is permitted downwardly through the bottom opening 74 and laterally outwardly through the openings 70 between the legs 72. This diffusion of the flow renders the drilling mud highly efficient at this point in preventing the accumulation of shale cuttings into hard lumps or balls and also eliminates the destructive abrasive action which is found when a single high pressure stream of drilling mud is directed downwardly against the more inwardly disposed teeth 30 of the rotary cutters 28. The arrows 76 indicate generally the manner in which the drilling mud is diffused as it flows from the nozzle. The nozzle of FIG. 2 and FIG. 4 is also illustrated in FIG. 3. The latter figure shows the central position of the nozzle relative to the drill bit body 22. FIG. 3 illustrates the manner in which some drill bit bodies are formed in three sections 22A, 22B and 22C. These sections are shown with abutting portions connected by a weld 78. This weld surrounds the central jet area, as shown in FIG. 3, and may also lie about a circumferential jet 81 of a more conventional type and location. In forming the ports in which the nozzles are mounted, the three-piece drill bit body is welded together by the welds 78 and then the ports are bored in their proper locations, the sleeves 44 are welded in place and the jet nozzles are installed downwardly through the pressurized mud passage 37.

FIGS. 6 and 7 show a nozzle 80 having three downwardly extending legs 82, the lower ends of which have rounded inwardly directed portions 84 which create a turbulence in the same manner as the inwardly turned ends of the legs 72 shown in FIG. 4. In FIG. 8 there is shown a modification wherein there is a sleeve 86 secured in the drill bit body 22 by a weld as shown. The sleeve 86 is provided with a downwardly facing shoulder 88 to engage a complementary shoulder formed in the body 22. The inside of the sleeve 86 has a threaded portion 92 which is engaged by threads on an inner sleeve 90 with a downwardly facing shoulder 94. Located in the inner sleeve 90 is a nozzle 96 having an upwardly disposed shoulder 98 engaging the downwardly directed shoulder 94 of the inner sleeve 90.

The nozzle 96 rests upon an upwardly disposed shoulder 100 in the outer sleeve 86 and is clamped between it and the shoulder 94 of the inner sleeve 90. Between the lower end of the inner sleeve 90 and the shoulder 100 is an O-ring 102 which forms a seal between the outer and inner sleeves and the nozzle.

It should be noted that the inner bore 104 of the nozzle 96 is cylindrical in shape. Ordinarily this would provide a rather smooth flow through the nozzle but in this instance, it is provided with an inner wall which is rough in texture. This causes the mud stream which comes in contact with the wall of the nozzle to be slowed, slowing the entire stream to some extent but at the same time, producing a turbulence of the stream in the nozzle so that it will not flow out in a solid more or less cylindrical stream. In other words, it will tend to break up and not concentrate itself in a single stream on any part of the rotary cutter or cutters.

I have shown seal means in the form of O-rings in the nozzle assembly itself. It is highly desirable that there be a seal between the outer sleeve and the wall of the port formed through the drill bit body 22. If there is any leakage between the outside of the outer sleeve and the wall of the bore of the body in the drill bit there will eventually be sufficient abrasive action to erode the bit body and the outer portion of the sleeve and destroy or displace the nozzle assembly. The weld between the downwardly projecting lower end of the outer sleeve below the surface of the dome 32 not only secures this sleeve in the bit body but also provides a complete seal between the bit body and the sleeve which is anchored therein. Thus, there is no possibility of leakage and erosion between the bit body and said sleeve.

From the foregoing it will be seen that I have provided a drill bit construction particularly adapted for use with rotary cutters wherein means is provided for breaking up the stream issuing from a drilling mud nozzle so that it will not erode away or wear the teeth on the cutter. Furthermore, where a grouping of cutters is utilized as in conventional types of rotary cone drilling bits, a central controlled jet through one of the nozzles will prevent the formation of earth formation or shale packing below the dome of the bit body and between the cutters, which conventionally are three in number where rotary cones are used. Not only does the stream from the center jet or nozzle prevent the formation of shale balls and earth formation but in so doing, the stream of drilling mud is broken up or diffused so that there is not any concentrated abrasive action on any portion or portions of the rotary cutters. While I have illustrated several types of jet nozzles for creating diffusion of the stream, it is of course understood that many various types and shapes of nozzles can be devised and utilized with the result of breaking up or diffusing the mud stream for the purposes above described.

The construction and arrangement of the nozzles and their anchoring sleeves provide for original insertion of the anchored outer sleeve, the removable inner sleeve and nozzle downwardly through the usual drilling mud passage which extends axially through the bit body and is open at the top. In addition to the original installation my arrangement permits the removal and replacement of nozzles without requiring major repairs to the tool.

It should of course be understood that various changes can be made in the form, details, arrangement and proportions of the various parts without departing from the spirit of the invention.

Claims

I claim:

1. A center jet drill bit construction including a rotary bit body having cutter journals downwardly and inwardly directed from spaced outer portions of the body and having closely positioned rotary cutters thereon, the body having a downwardly directed dome face between and inwardly from the journals, the dome face and inwardly and upwardly disposed cutter sectors defining a pocket in which shale formation particles collect and adhere to each other in massed ball-like obstructions to drilling mud circulation, the drill body having an upwardly open internal longitudinal drilling mud passage including a mud outlet port directed downwardly through the dome surface, said port comprising a diffusion element to direct a diffused stream of pressurized drilling mud into said pocket and prevent the formation of shale balls, said diffusion element comprising mud flow control means for preventing the stream of drilling mud from impinging in an injuriously high pressure abrasive stream concentration on the inwardly and upwardly disposed sectors of the rotary cutters.

2. The structure in claim 1, and the mud flow control means comprising a nozzle portion having an internal flow passage, the flow surface of which has a different coefficient of friction than that of the drilling mud passage in the bit body.

3. The structure in claim 1, and the mud flow control means comprising a mud stream agitator nozzle in the outlet port.

4. The structure in claim 3, and said agitator nozzle having a mud flow passage defined by wall portions tapering in shape from cylinders of revolution about the longitudinal axis of the mud flow passage.

5. The structure in claim 1, and there being a plurality of said journals and cutters located about the rotational axis of the bit body, and said mud flow control means having means for breaking up the drilling mud stream and directing its flow downwardly and outwardly multidirectionally from the mud outlet port.

6. The structure in claim 5, and the mud flow control means comprising a venturi throat.

7. The structure in claim 2, and the mud flow control means comprising a nozzle unit having a portion extending below the dome face, the extending portion having downwardly and laterally directed outlets and having mud stream interceptors adjacent the outlets to break up the unidirectional characteristics of the mud stream, a plurality of said journals and cutters being located about the rotational axis of the bit body, said mud flow control means having means for breaking up the drilling mud stream and directing its flow downwardly and outwardly multidirectionally from the mud outlet port, and the mud flow control means comprising a nozzle unit having a portion extending below the dome face, the extending portion having downwardly and laterally directed outlets and having mud stream interceptors adjacent the outlets to break up the unidirectional characteristics of the mud stream.

8. The structure in claim 7, and the mud flow control means comprising a nozzle portion having an internal flow passage, the flow surface of which has a different coefficient of friction than that of the drilling mud passage in the bit body, the flow surface of the nozzle flow passage being roughened to dampen the pressure flow of drilling mud therethrough.

9. A center jet drill bit construction including a rotary bit body having cutter journals downwardly and inwardly directed from spaced outer portions of the body and having closely positioned rotary cutters thereon, the body having a downwardly directed dome face between and inwardly from the journals, the dome face and inwardly and upwardly disposed sectors defining a pocket in which shale formation particles collect and adhere to each other in massed ball-like obstructions to drilling mud circulation, the drill body having an upwardly open internal longitudinal drilling mud passage including a mud outlet port directed downwardly through the dome surface to direct a stream of pressurized drilling mud into said pocket and prevent formation of shale balls, said port having a fixed sleeve therein extending outwardly through the port beyond the dome face of the bit body, the outwardly extending outer wall portion of said sleeve defining a bight with the adjacent portion of the dome face, a metal weld in said bight to anchor the sleeve and provide a fluid tight seal between the sleeve and the outer end of the port, the sleeve having an upper end portion comprising an upwardly open nozzle receiver of a width less than that of said upwardly open longitudinal drilling mud passage, a mud flow controlling unit of a size capable of being insertible downwardly through said drilling mud passage and positioned in and closely fitting the nozzle receiver of said sleeve, and the nozzle unit including means accessible through said drilling mud passage and securing the nozzle in the sleeve.

10. The structure in claim 9, and said nozzle unit securing means comprising an upwardly removable sleeve of less width than that of said drilling mud passage and threaded into the upper end of the fixed sleeve and engaging and securing the nozzle unit in the fixed sleeve.

11. The structure in claim 10, and said nozzle unit having an upper portion spaced from the adjacent upper and inner wall of the fixed sleeve, and said retaining means being threaded into the upper end of the fixed sleeve between the latter and the spaced upper portion of the nozzle unit.

12. The structure in claim 10, and the upper inner wall of the fixed sleeve being threaded, the upwardly removable retaining sleeve having external threads and an internal downwardly facing abutment, the fixed sleeve having, below its threaded portion, and internal upwardly facing abutment, the removable sleeve being threaded into the fixed sleeve, and the nozzle unit being secured in the fixed sleeve between the two abutments.

13. The structure in claim 12, and a seal in the fixed sleeve between the upwardly facing fixed sleeve abutment and the lower end of the removable retaining sleeve and also about the lower end of the nozzle unit.