US3762486A

US3762486A - Big hole drilling bit

Info

Publication number: US3762486A
Application number: US00232159A
Authority: US
Inventors: W Grovenburg; R Gatliff
Original assignee: US Atomic Energy Commission (AEC)
Current assignee: US Atomic Energy Commission (AEC)
Priority date: 1972-03-06
Filing date: 1972-03-06
Publication date: 1973-10-02
Anticipated expiration: 1990-10-02
Also published as: AU5292373A; FR2175080B1; FR2175080A1; GB1390738A; AU463698B2; JPS4911704A; DE2311088A1

Abstract

A big hole drilling bit of the type utilizing a plurality of roller cutters mounted for cutting in a plane perpendicular to the axis of rotation of the bit. Regrinding of cuttings is reduced by providing baffles in association with individual roller cutters to prevent the normal pumping action of the cutters from depositing their own cuttings in front of them. Baffles may merely disrupt the pumping action of the roller cutters or they may be designed to utilize the pumping action to assist in transporting cuttings toward a pickup opening through which the transport of the cuttings to the earth''s surface is initiated.

Description

United States Patent Grovenburg et al. Oct. 2, 1973 BIG HOLE DRILLING BIT 2,654,578 10/1953 Pearce 175 313 1751 William Tulsa, $123123? #1323 Elflfifijiii "lei/ 51 3; -1 Robe" Gaul, Las Vegas, 3,674,314 7/1972 Scaravilli 175 313 x 3,583,503 6/l97l Cosk| 175/313 [73] Assignee: The United States of America as represented by the United States Primary Examiner-Dav1d H. Brown Atomic Energy Commission, Attorney-Roland A. Anderson Washington, DC. [221 Filed: Mar. 6, 1972 [57] ABSTRACT A big hole drilling bit of the type utilizing a plurality of [21} PP N05 232,159 roller cutters mounted for cutting in a plane perpendicular to the axis of rotation of the bit. Regrinding of cut- 52 U.S. c1 175/313, 175/353, 175/376 tings is reduced by Pmviding baffles association with. 51 Int. Cl E2lb 9/12 individual Prevent the normal Pumping 581 Field of Search 299/90; 175/313, action Cutters from depositing their Own Cuttings 175531, 336 350, 353 376 in front of them. Baffles may merely disrupt the pumping action of the roller cutters or they may be designed [56] References Cited to utilize the pumping action to assist in transporting UNITED STATES PATENTS cuttings toward a pickup opening through which the transport of the cuttings to the earths surface is initil,686,957 lO/l928 Bull 175/313 X ated l,39l,626 9/l92l Gilthorpe... 2,041,467 5/1936 Green 175/313 X 10 Claims, 4 Drawing Figures BIG HOLE DRILLING BIT BACKGROUND OF THE INVENTION The invention described herein was made in the course of, or under Contract AT(26-l )38 with the U. S. Atomic Energy Commission.

This invention relates to an improved rotary drill bit for boring holes in the earth. More particularly, it relates to a drill bit for drilling relatively large diameter holes of the type wherein a plurality of roller cutters are mounted for cutting generally in a plane perpendicular to the axis of rotation of the bit.

Recent years have seen a developing interest in the drilling of relatively large diameter holes up to 120- inches in diameter, and even larger. One type of drill bit that has been employed for drilling such holes by rotary drilling methods utilizes a number of roller cutters mounted on a bit plate in a manner so that, generally speaking, each cutter engages the formation in a plane perpendicular to the axis of rotation of the bit. Upon rotation of the bit, engagement of the teeth of the roller cutters with the formation at the bottom of the hole causes rotation of the roller cutters. Successive teeth of the roller cutters engage the formation as the roller cutters rotate. Some arrangement is provided for removing the cuttings produced by the action of the cutters on the formation from the bottom of the hole and transporting them to the surface of the earth.

One commonly used arrangement for removing cuttings is the sweep type pickup which employs an elongated radially extending pickup opening in the bit plate which is in fluid flow communication with one of the passages, either cylindrical or annular, connecting the bottom of the hole with the earth's surface. These passages are formed by the drill string, or between the drill string and the walls of the formation, or between two concentrically oriented drill strings if multiple strings are employed. A circulating fluid, gas or liquid, flows across the bit, entrains cuttings therein and flows up the passage to the surface carrying cuttings with it. Reduced pressure on the top of the passage, injection of high pressure air into the passage, or some other means may be used to provide the energy to lift the circulating fluid and cuttings out of the hole through the passage to the surface of the earth. The criteria governing the placement of the cutters on the bit plate have generally been concerned with providing full coverage of the cutting surfaces over the entire area of the hole bottom with some redundancy.

Experience with drill bits of the type just described has not been entirely satisfactory. Very low penetration rates have proved to be the rule rather than the exception. Bit balling, bottom balling and regrinding of cuttings have been evident. Some minor improvements have been realized by introducing the circulating fluid to the bottom of the hole by means of jets and increasing the rate of flow across the bottom of the hole, and discarding the sweep type pickup in favor of a center pickup. However, there are practical limits on the rate of flow of circulating fluid that can be achieved and analysis of the total energy expended versus the drilling penetration rate indicated that a very low efficiency was being obtained.

We have discovered a big hole drilling bit design with markedly improved performance over those used heretofore. The big hole bit according to our invention much more efficiently utilizes the total energy expended in the drilling operation and makes it possible to obtain significantly increased penetration rates over previous practice.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a big hole drilling bit that is more efficient and achieves increased penetration rates over those used heretofore. Briefly summarized, our drill bit takes into account the fact that individual roller cutters actually act as pumps as they rotate in conjunction with rotation of the drill bit. This pumping action of an individual roller cutter causes its own cuttings to be continuously deposited in front of it thereby resulting in a continual regrinding of cuttings. In addition to being inefficient in itself, this contributes to bit balling and bottom balling and detracts from the desired circulation of the cuttings toward the pickup opening. Accordingly, our drill bit incorporates means in association with individual roller cutters which prevent the cuttings produced by a cutter from being deposited in front of it by the pumping action of the cutter. While merely blocking the flow of cuttings over the top of the cutters provides a bit with significantly improved performance, we have found that designing baffle arrangements which direct the pumping action of individual cutters radially inwardly, generally toward the pickup opening, provides even more effective utilization of the total energy expended. This latter arrangement accommodates the necessary radially inward flow of cuttings toward the pickup opening with the forced circulation of a much smaller rate of flow of circulating fluid across the bottom of the hole.

An exceedingly effective utilization of the pumping action of the individual roller cutters is accomplished by arranging the roller cutters in a number of series wherein each successive cutter of the series is positioned radially inward and circumferentially forward with respect to the direction of rotation of the bit, and the baffle means for each cutter excepting of course the most radially inward of the series is designed to discharge its cuttings immediately behind the successive cutter, i.e., at the suction side of that roller cutter pump. The baffle means of the most radially inward cutters discharge toward the central pickup opening. Series of roller cutters utilizing cutters having baffles that merely block the flow of cuttings over the cutter in addition to cutters having baffles which discharge radially inwardly have also proven to be very effective under some circumstances.

A 96-inch diameter rotary drilling bit which incorporated baffle means to control the pumping action of the roller cutters in accordance with the foregoing accomplished penetration rates which were over several times as great as those of a bit where such control was not provided. The cuttings produced by the bit using baffles contained a much smaller proportion of fine particles, indicating less regrinding of cuttings, and when the bit was extracted from the hole there was no evidence that bottom balling or hit balling had occurred.

While the foregoing briefly summarizes an object of the invention and means by which it is accomplished, additional objects and details of the invention and its numerous significant advantages will be more apparent after consideration of the following description of preferred embodiments thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective, partially broken away view of a drilling bit according to the invention.

FIG. 2 is a plan view of the bottom of the drill bit of FIG. 1.

FIG. 3 is a partial plan view of a drill bit incorporating another embodiment of th invention.

FIG. 4 is an enlarged perspective view of a roller cutter of the bit of FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIGS. 1 and 2, large diameter drill bit includes a bit body, or support structure, 12 having a bit plate 14 and a plurality of roller cutters mounted thereon. The roller cutters include

gage cutters

16, 18 and 20,

interior cutters

22, 24, 26, 28, and 32 and center cone cutter 34. The cutters are mounted in a conventional manner for rotation about their longitudinal axes on saddles such as 36 and 38 in the case of gage and interior cutters and on cantilever mount 40 in the case of center cutter 34. Conventional means are provided on the upper surface of bit body 12, not shown, for connecting bit 10 to a drill string by which the bit is lowered into the hole and rotated to make hole.

Baffle arrangements

46, 48, 50, 52, 54, 56, 58, and 62 are provided, one in association with each of the gage and interior cutters. Each baffle is positioned circumferentially forward, i.e., with respect to the direction of rotation of the bit, of the roller cutter with which it is associated. As best shown in FIG. 1 with respect to typical baffle arrangement 54, each baffle arrangement includes an end wall 64, a side wall 66, and a bottom baffle plate 68. Side wall 66 is formed from an angle to facilitate fastening baffle plate 68 by suitable means such as bolts 70 to the horizontally extending leg. The height of side wall 66 increases with distance toward the center to give a downward slope to baffle plate 68. Gusset 72 adds structural rigidity to the baffle arrangement.

Baffle plate 68 is preferably fabricated from a resilient material such as rubber. Its width is selected so that there is actually a negative clearance between forward edge 71 and the teeth of the cutter. Accordingly, successive rows of teeth of the cutter strike baffle plate 68 as the cutter rotates and force the forward portion downwardly until edge 71 slips by the row of teeth and springs upwardly toward its normal planar relationship. This imparts a vibrating or shaking action to the plate which facilitates the flow of cuttings out of the baffle arrangement. Since the diameter of the cutter will decrease as the teeth of the cutter wear down through use, the baffle plate can be made wider than is initially necessary so that the desired negative, or at least zero, clearance is maintained through a longer period of bit use.

As best shown in FIG. 1 in connection with baffle arrangement 48, the baffle arrangements are open on their radially inwardly side. Accordingly, as roller 18 rotates clockwise as viewed in FIG. 1 by engagement of its teeth with the formation at the bottom of the hole and rotation of bit 10 in a counter-clockwise direction as viewed in FIG. 2, cuttings and circulating fluid are pumped by the rotation of cutter 18 through the space 74 between the top of the cutter and horizontal portion 76 of saddle 36. The pumping action is directed by baffle arrangement 48 through its open end 80 in a radially inward direction generally toward pickup opening 82 at the center of plate 14. Means not shown place pickup opening 82 into fluid flow commu- 5 nication with the surface of the earth through one of the passages formed by the drill string or between the drill string and the formation, or between multiple drill strings if such are used, in any conventional manner known in the art.

As will be best seen through consideration of FIG. 2, the discharge out of the open, radially inward end 80 of baffle arrangement 48 will bring the cuttings produced by cutter 18 to the rear of cutter 28. Since this is the suction side of the pumping action created by the rotation of cutter 28, cuttings produced by cutter 18, as well as the cuttings produced by cutter 28 itself, will be pumped over the top of cutter 28 and discharged out of open, radially inward end 86 of baffle arrangement 58. Those cuttings will in turn be pumped over the top of cutter 26 and discharged out of open end 88 of baffle arrangement 56 towards pickup opening 82. It can be seen then, that the radially inward movement of cuttings is facilitated by arranging

roller cutters

18, 28 and 26 in a series, the relative positional relationship being such that cuttings from each radially outward cutter are assisted in their journey towards the center pickup by the pumping action of the next radially inward cutter. It will be noted that in the drill bit depicted in FIGS. 1 and 2 the three gage and six interior cutters are arranged in three such series of cutters. The six interior cutters are positioned on three radii in a manner which provides redundancy of cutting surfaces over the bottom of the hole.

In the preferred embodiment of FIGS. 1 and 2 three jets, 92, 94, and 96, are positioned for discharge just behind the three gage cutters and three jets, 98, and 102, are positioned for discharge generally in the area of the discharge from the outlets of

innermost baffle arrangements

52, 56 and 60. That particular arrangement is considered to be quite satisfactory in combination with the use of a dual string with an air lift arrangement in the inner string for providing the energy for transporting cuttings to the earths surface. However, it is to be understood that the invention is not dependent upon the use of such jets. Any arrangement which provides for movement of circulating fluid across the bit toward the pickup should be satisfactory.

While, generally speaking, utilization of the normal pumping action of the roller cutters to assist in the transport of cuttings toward the pickup opening by use of baffle arrangements such as those just discussed in relation to FIGS. 1 and 2 is considered to be preferred, benefits can be realized by baffle arrangements which merely block the pumping action of the cutter. This will be better appreciated after consideration of FIGS. 3 and 4 which illustrate the manner in which modification of an existing big hole bit can be accomplished to gain the benefits of the invention. As shown in FIG. 3 each of the

gage cutters

112, 114, 116 and 118 and

interior cutters

120, 122 and 126 has in association therewith a baffle arrangement of the type just described in connection with FIGS. 1 and 2. As will be apparent from examination of FIG. 3, the existing positions of

cutters

128 and 130 do not permit use of that previously described baffle arrangement. However, the blocking type baffle arrangement of FIG. 4 can be used with

cutters

128 and 130.

As shown in FIG. 4, baffle plate 132 is positioned in the space between the top of roller cutter 130 and horizontal portion 134 of saddle 136. Baffle plate 132 blocks the flow of fluid and cuttings over the top of roller cutter 130 thereby preventing the cuttings of cutter 130 from being deposited in front of it for regrinding. The pumping action of cutter 130 will cause the cutting to strike baffle plate 32 resulting in turbulence behind cutter 130 which will assist in holding the cuttings in suspension. The normal movement of the circulating fluid toward central pickup opening 138 will carry the suspended cuttings in that direction.

The blocking type baffle arrangement of FIG. 4 can also be used to advantage with cutter 124 even though there is sufficient room for the use of the other type of baffle arrangement. The recoil of the cuttings off of a blocking type baffle associated with cutter 124 would put them in closer proximity to the center of the pickup than a directed type of baffle previously discussed in connection with FIGS. 1 and 2. The use of a blocking type baffle with cutter 128 would also provide some advantages although some of the cuttings of cutter 128 will be deposited in front of cutter 130 and be reground thereby. This is considered to be preferable to having cutter 128 regrind its own cuttings since movement toward the center pickup is initiated. In this connection, it will be realized that advantages of the invention would be gained even if only blocking type baffles were utilized.

While a blocking type baffle of a particular configuration is illustrated in FIG. 4, other satisfactory arrangements will come readily to mind. Any arrangement that blocks the flow of circulating fluid and cuttings over the top of the roller cutter will provide the desired function.

While the fundamental novel features of the invention have been shown and described and pointed out as applied to embodiments particularly described and further variations have been suggested and indicated by way of example, it will be readily appreciated by those skilled in the art that various omissions and substitutions and changes may be made within the principle and scope of the invention as expressed in the appended claims.

What we claim is:

l. A large diameter bit for producing holes in the earth by rotary drilling comprising a cutter support structure, a plurality of roller cutters including gage cutters and a plurality of interior cutters radially inward thereof individually mounted on the bottom of said support in a manner to engage the bottom of a hole upon rotation of said bit therein, means mounted in association with at least one of said roller cutters for preventing cuttings produced thereby from being deposited in front of said cutter by the pumping action thereof, a pickup opening in said support radially inward of said at least one cutter and said means mounted in association therewith and means for directing cuttings produced by said at least one cutter toward said pickup opening.

2. The drill bit of claim 1 wherein said means mounted in association with said at least one roller cutter direct the flow of cuttings radially inwardly.

3. The drill bit of claim 1 wherein said means mounted in association with said at least one roller cutter block the flow of cuttings over the top of said cutter.

4. The drill bit of claim 1 wherein said means mounted in association with said at least one roller cutter are baffle arrangements provided in association with a plurality of individual roller cutters.

5. The drill bit of claim 4 including a series of cutters with each successive cutter being positioned radially inward and circumferentially forward with respect to the direction of rotation of said bit, said associated baffle means of at least one roller of said series discharging cuttings therefrom into the region immediately behind a successive roller of said series.

6. The drill bit of claim 5 wherein at least one cutter of said series has associated baffle means which block the flow of fluid over the top of said cutter.

7. The drill bit of claim 6 wherein all of the roller cutters thereof except a center cutter are arranged into a plurality of said series.

8. The drill bit of claim 5 wherein each preceding roller of said series has associated baffle means which discharges into the region immediately behind its next successive roller of said series.

9. The drill bit of claim 8 wherein all of the roller cutters thereof except a center cutter are arranged into a plurality of said series and said baffle means of the innermost cutter of each series discharge toward a pickup means adapted for connection to means for transporting cuttings out of the hole.

10. The drill bit of claim 9 wherein said pickup means is at the center of said bit.

I "3762486 I f bct eber 2-, 197 3 Patent No I fivent o fls) William Grovenburg and Robert R. Gasliff v It is cert-ifiedflthat error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

The middle initial "R" of lnvntof G tliff" s name should read --L-- v v Y I Signed- ,and sealed this 8th giay of Oejsp-ber 1974.

(SEA

Attest: v

N c MARSHALL DANN McCOY M. GIBSQN JR. 7

Commissioner of Patents 'Att'esting Officer uscoMM-oc e037 s-pss FORM PO-1050 (10-69) I V I 4 A U.S. GOVERNMENT PRINTING OFFICE: I959 0-366-334

Claims

1. A large diameter bit for producing holes in the earth by rotary drilling comprising a cutter support structure, a plurality of roller cutters including gage cutters and a plurality of interior cutters radially inward thereof individually mounted on the bottom of said support in a manner to engage the bottom of a hole upon rotation of said bit therein, means mounted in association with at least one of said roller cutters for preventing cuttings produced thereby from being deposited in front of said cutter by the pumping action thereof, a pickup opening in said support radially inward of said at least one cutter and said means mounted in association therewith and means for directing cuttings produced by said at least one cutter toward said pickup opening.