Note: Descriptions are shown in the official language in which they were submitted.
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1335988
~ DRI~T BIT WITH INTEGRA~LY ~ORGED STABI~IZER
BACgGROUND OF IHE l~v~lloN
4 l. FlelC o~ the ~nvention
This invention relate6 to drill bits for drilling through
6 rock and other hard formations ln drilling oll wells, and more
7 psrticularly to rotary bits having depending legs with cutters
8 rotatably ~ounted on ~ournals extending lnwardly and downwardly
9 from the inner sides of the legs.
11 2. Description of t~e Prior Art
~2 Drilling bits of this type are con~entionally suspended from
~3 drill pipe extending downwardly from the drilling rig located at
9 the surface. Generally, the string of drill pipe is rotated by
~5 the drllling rig and this rotation is transmitted to the bit at
l6 the bottom of the hole. In 60me cases, rotation of the bit is
7 accomplished through the use of a fluid motor mounted on the bot-
18 tom of the drill string just above the bit. In either case, the
19 drill string, being of less diameter than the hole being drilled,
20 ls sub~ect to lateral whipping or other movement which creates a
21 certain amount of angularity to the string which is imparted, to
22 a certain degree, to the bit itself. This results ln a tilting
23 o~ the bit which causes ;xcesslve pressure of the lower leg por-
24 tion6 of the blt against the formation as the bit is rotated.
25 This phenomenon is even more critical in directionPl drill~ng
26 where the bit is oriented at extreme angles from the vertical.
27 Because of physical constraint6 within the bore hole, bits were
28 originally constructed with relatively thin leg constructions.
29 AB a result, the rotating bit operated with an undue lateral
30 swinging or rocking motion which greatly reduced the operating
31
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~ life of the blt since the lower portion of the legs r~pidly wore
2 aw_y, le_ding to a se_l ~nd/or be_r~ng f ilure.
3 Stabilizers for the drill string have been utilized hereto-
4 fore but they were located _bove the drill bit ~ome dlstance away
5 from it, 60 that the bit 6till had an opportunity to move or tilt
6 laterally.
7 ,
8 U.S. Patent No. 3,628,616 obviated some of these problems by
g providing 6tabilizing means directly on the drill bit, thereby
~0 eliminating the need for additional subs and greatly reducing the
11 rocking motion of the bit. This 6tabilization me_ns consisted of
12 hard metal pads welded directly onto the upper portion of the bit
body. These pads were of sufficient thickness to greatly
g lengthen the l~fe of the bit while still keeping the upper bit
5 body dia~eter within the limits provided by the diametrical cut-
16 ting path or bore described by the rotary cutters.
~7 In addition, this type of welded pad structure of necessity
18 had sharp corners which created stress risers on the leg. This,
~9 of course, i6 undesirable, since it greatly shortens the fatigue
20 life due to the ~chAn~cal notch created by welding in the
~ weaXe6t part of the leg.
22
23 Moreover, it was found that high flow rates of drilling flu-
24 id during operation can erode the weld-on "plate" type pad right
25 ff'
26 Another shortcoming with the structure found in the '616
27 patent was that the lower portion of the lug with its straight
28 surface, formed a dam for hindering the upward flow of the dril-
29 ling fluid through the borehole annulus. This in turn created
30 undue pressures and increased erosion on the lower leg portions
31 of the bit.
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I The type of bit described ln U.S. Patent No. 3,628,616 also
2 included a plurallty of tungsten carbide in6erts mounted on the
3 wear pad. However, these inserts have a t~ ncy to crack and
4 unduly wear during operation.
5 SUMMARY OF ~HE INv~l~ON `~
~ The present invention obv$ates the abo~e mentioned shortcom-
8 ings, by providing stabilizing means lntegrally forged on the
g drill blt body. This construction i8 achieved by having the
10 st~bilizing lugs pre-formed on the leg forgings. The lower sec-
tion of each stabili2ing pad is rounded toward lts outer sldes
~2 and functions to cooperate with a recesseA portlon of the drill
13 bit body located beneath the lug- to create a flow channel away
from the lower extremities of the blt body.
A primary advantage of this construction is that a metallur-
16 gically solid bit body is formed that will resist breakage. In
addition, being a forged part, the forged lugs galn a substanial
~8 increase in toughness and reliability through improvement of
19 grain 6tructure in the metal. With this design, the fibrous met-
20 al grain is lined up parallel to the most severe stresses and
21 shoc~ loads that will be imposed on the leg. By taking advantage
22 of metal flow during the forging process, r~Y~u~ ~e^h~lcal
23 properties are obtained at the critically stressed sectlons.
24
Such a construction can also be conformed optimally to offer
26 good stabilization w~ile enhancing fluid flow and cutting remov~l
27 created by the flow channel construction.
28 Another advantage of the present invent$on is that the
29 forged cons'ruction provides a readily machinable boss that can
30 be turned to any diameter and reguire less operations than weld-
31 on legs.
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1 The present lnvention also utillzes polycrystalline ~a~nd
2 compacts pressed into the stabilizer lugs to r-Y~ze wea~ The
3 insert configuration can either be flat or rounded and be flush
4 with the lug surface or extend beyond it. The advantage of the
5 rounded inserts extending beyond the luq is that the annular
6 space available for cuttings to ~low by i5 increased. This con-
_ struction also provides secondary gage cutting to help maintain
8 bore hole diameter. Moreover, less torgue is generated due to
.
g the reduction of surface area in contact wlth the hole wall.
BRIEF DESCRIPTION OF THE DRAWINGS
I
~2 Figure l is a perspective view of the drill bit in accor-
dance with the present invention;
~4 Figure 2 is an enlarged ~ectional view on one of the legs of
~5 the drill bit taken along lines 3-3 of Figure l;
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Figure 3 is a sectional view of the forging utilized to form,
28 the leg;
~9 Figure 4 is an enlarged side view of the leg;
21 Figure 5 i6 an enlarged fragmentary view of the stabilizer
22 lug in accordance with the present invention; and
23 Figure 6 is an enlarg?ed fragmentary vlew of a second embodi-
24 ment of the stabilizer lug of the present invention.
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26 DETAILED DESCRIPTION OF TXE
27 PR~k~ EMBODIMENT
28 Figure l illustrates a drill bit lO having a body 12 and a
29 threaded pin portion 14 which is adapted to be threadably con-
. .
30 nected to the lower end of a drili string. Extending downwardly
3~ from the bit body 12 are legs 16. As shown in Figure 2, each leg
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1 16 has an inwardly and downwardly directed journal 18 which is
2 adapted to rotatably support a cutter illustrated at 20 in Figure
3 2 by broken lines. The cutters 20 are oriented to describe a
4 circular path, the outer diameter of which forms the gage diameter
of the bit.
6 The base of the journal 18 is defined by a surface of revol-
7 ution 22 lying in a plane normal to the longitudinal axis of the
8 journal 18. The surface of revolution 22 and the lower end of the
9 leg 16 define a relatively thin tapering bottom leg portion
commonly known as a shirttail 24. The radial extremity of the
11 shirttail 24 does not extend out to the outer diameter of the bit
12 10 but has a clearance with the sidewalls of the bore hole.
13 Stabilizer lugs 30 are formed on the upper portion of each leg
14 16 extending radially outwardly to substantially the gage diameter
of the bit 10. Figure 3 illustrates a forging 40 of one of the
16 legs 16. The forging 40 comprises a dome section 41, a journal
17 section 42, a shirttail section 43 and a stabilizer section 44.
18 The journal section 42 is machined to form the journal 18 and
19 the surface of revolution 22 as shown in Figure 2. The shirttail
section 43 is also machined to remove some parent metal, shown in
21 broken lines, of the forging 40 to form the shirttail 24. This is
22 more clearly shown in Figure 4.
23 The forging 40 is also turned to machine away a portion of the
24 stabilizer section 44, shown in broken lines, to form the stabi-
lizer pad 30. Three such leg forgings are welded together to form
26 the rock bit.
27 As shown in Figure 1, the lower portion of each stabilizer pad
28 30 forms a rounded portion 51 which curves upwardly to join with
29 the sides 53 of the lug 30. This rounded portion 51 cooperates
with a recessed portion 55 formed on the leg 16 to form a
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1 flow ch~nnQ~ to enhance the flow of drilling fluld from around
2 the shlrttall 24 upwardly around the stabilizer lug30.
3 Drilling fluid (not ~llustrAted) enters the bore hole via a
4 plurality of nozzles 60 extending through the bit body 12.
6 Referring again to Figures 1 and 2, a lubricating system i8
_ al~o illustrated having a reservoir 61 having a pressure
8 equalizer 62 located therein. The one side of the egualizer com-
g munic~tes with the outside of the bit through ports 63 formed in
~0 a cap 65. The other side of the egualizer 62 co~m~nlcates with
1~ the interior of the bearing chamber through pas6ages 66 and 6~.
12 Lubricant (not illustrated) completely fills the reservoir 61,
l3 passages 66 and 67 and the bearing cavity.
4 Figure 4 more clearly illustrates a plurality of bores 45
~5 for receiving a plurality of inserts 46. Each insert 46 is
l6 preferably made of polycrystalline diamond and can have its outer
1~ surface 47 substantially flat in order to be flush with the outer
18 surface of the stabilizer lug 30. (See ~igure 5).
19
Alternatively, each insert 46 can also have rounded outer
21 pro~ections 48 extending beyond the outer surface of the
22 stabilizAr lug 30. (See Figure 6).
23 In addition, each ipsert 46 may be comprised entirely of
24 polycrystalline diamond, or else it may comprise of a wafer
25 brazed to a root portion made of tungsten carbide.
26
27 In operation, it has been found that integrally for2ed
28 stabilizer lug~ 30 have obviated many of the shortcomings found
29 in the prior art constructions. In addition, tpe diamond inserts
30 46 have greatly reduced wear on the stabilizer lug, thereby great-
31 ly increasing the useful life of the drill bit.
32
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1 It should be understood that changes can be made in the ex-
2 act form, details and proportions of the construction without
3 departing from the spirit of the invention.
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