Radially stabilized drill bit

A stabilized drill bit has a cylindrical main body, a formation cutting face at the lower end of the body, and means by which the upper end of the bit can be connected into a drill string. A drilling fluid flow passageway extends axially through the main body and provides flow of drilling fluid to the drilling face. A plurality of hydraulic actuated stabilizing members are arranged circumferentially about the throat and within the main body. Stabilizing members have a borehole wall engaging face thereon which can be retracted flush with the outer surface of the main body, and extended away from the main body face and into contact with the borehole wall, thereby stabilizing the drill bit as the bit is rotated while making hole. Hydraulic means is connected to the stabilizing members by which the members are progressively extended toward the borehole wall as the members become worn, and which normally prevents retraction of the stabilizing members so long as drilling fluid pressure is effected within the passageway. The stabilizing members are retracted when the drilling fluid is reduced to a predetermined value.

BACKGROUND OF THE INVENTION 
The present invention pertains to an improved drill bit for forming 
boreholes as in drilling oil and gas wells. Moore particularly, the 
present invention pertains to drill bits which employ and contain 
polycrystalline diamond cutting elements, and are usually referred to as 
"PDC" drill bits. 
Many "PDC" drill bits of the prior art experience a destructive whipping 
action, or radial vibration of the drill bit which randomly occurs during 
rotary operation due to clearance between the outside of the drill bit and 
the wall of the borehole. This whipping tendency intensifies in proportion 
to the hardness or toughness of the formation being drilled and in 
proportion to the rotational speed of the drill bit, causing impact 
contact between the cutting elements of the drill bit and the formation 
material being drilled, which in turn results in fractured, chipped, or 
displaced cutting elements, thus drastically shortening the operating life 
of the drill bit and causing the operating life to be inconsistent and 
unpredictable. 
Another problem often found in prior art "PDC" drill bits is erosion which 
is caused by high velocity drilling fluid acting on the cutting mountings 
of the cutting elements, on the drill bit face, and on other components of 
the bit. This shortens the operating life of the drill bit. 
Another problem associated with prior art "PDC" drill bits is balling, 
plugging, or packing of cut material onto the face of the drill bit due to 
uneven or unbalanced fluid flow over the face of the drill bit which 
results in reduced penetration rates and inadequate and uneven cooling of 
the cutting elements and thereby unpredictably diminish the resultant 
drilling operation. 
Because of the above problems, "PDC" drill bits have heretofore been used 
economically only in drilling a very limited range of different rock and 
earth formations. U.S. Pat. Nos. 712,887 (Wyczynski); 2,857,141 
(Carpenter); and 3,062,303 (Schultz) each contain radially acting 
stabilizing means. However, as the respective specifications show, each of 
those are based on considerably different and less effective principles of 
operation than the present invention. 
SUMMARY OF THE INVENTION 
A stabilized drill bit having a main body of general cylindrical 
configuration and a pin end opposed to a lower drill face. The lower 
drilling face is of a particular novel configuration and includes cutters 
thereon for penetrating geological formations when the drill bit is 
rotated and making hole. A throat is formed longitudinally through the 
main body for passage of drilling fluid from a drilling string, through 
the bit, and through the drilling face. The drilling fluid exits the bit 
and flows across the face in a novel manner. 
A plurality of circumferentially arranged bores are formed from the outer 
surface of the bit into communication with the bit throat. Hydraulically 
actuated stabilizing members are reciprocatingly received within the 
bores. Each of the stabilizing members have an outer face which is 
retracted into alignment with the outer surface of the bit, and which can 
be extended outwardly from the surface of the bit and into engagement with 
the wall of a borehole. 
Hydraulic means are incorporated into the bit by which each of the 
stabilizing members are forced to move in a direction outwardly of the 
main body when the hydrostatic pressure within the throat is greater than 
the hydrostatic pressure measured at the face of the stabilizing members. 
The hydraulic means maintains the stabilizing members in the extended 
configuration, and as the face of the stabilizing member is worn, the 
member is further extended into engagement with the borehole wall. 
The hydraulic means further enables retraction of the stabilizing members 
respective to the borehole wall surface when the pressure drop across the 
face of the bit has been equalized. 
One object of the present invention is to provide a "PDC" drill bit having 
a substantially increased operating life with equal or greater drilling 
penetration rate than prior art "PDC" drill bits and having the capability 
of drilling more predictably and economically through an extremely wide 
range of different rock and earth formations. 
Another object of this invention is to provide a drill bit having reduced 
tendency to whip, or radially vibrate, during rotary operation. 
Another object of the present invention is to provide an improved drill bit 
having reduced tendency to ball or plug. 
Another and further object of this invention is to provide a "PDC" drill 
bit that is economical to manufacture. 
An additional object of the invention is the provision of a rotary drill 
bit having retractable stabilizer members arranged about the circumference 
thereof which can be extended into engagement with the borehole wall while 
making hole. 
Other objects and advantages of the present invention will be apparent upon 
consideration of the following specification, with reference to the 
accompanying drawings forming part thereof, and in which like numerals 
correspond to like parts throughout the several views of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the figures of the drawings, and in particular FIG. 1, the 
present invention comprises an improved drilling bit, generally indicated 
by the numeral 110. The bit has a main body 21 made of a suitable material 
such as steel. The main body 21 is generally cylindrical in shape and the 
upper end thereof is threaded in a conventional manner, or is otherwise 
provided with a known means for attachment to the end of a drill pipe or 
"drill string". The main body 21 has a central fluid passage or throat 22 
extending from the top threaded end, along the central axis towards the 
lower end or face 23. The lower marginal end of the bit can be an integral 
part of the bit, as seen in FIG. 1, or it can be a separate member 
suitably attached to the main body 21. 
Near the face 23, the throat 22 branches into the illustrated two flow 
ports 24 which extend from the throat 22 and through the face 23. Flow 
restrictors 25 are installed in each of the ports 24 and are retained in 
place by snap rings 26 or other suitable retaining means. Opposed flow 
slots 27 are machined into the face 23 and into the sides of the main body 
21 as more clearly seen in FIGS. 2 and 5. The slots 27 communicate with 
the two port 24, and as seen in FIGS. 1 and 2, each slot commences at the 
respective ports 24 and then spirals outward in a direction opposite to 
the normal rotational direction of the bit. The slots continue along 
opposite sides of the face 23, then extend up the opposite sides of the 
main body 21. 
In FIGS. 1-2, the bit has mounted thereon a plurality of commercially 
available polycrystalline diamond cutters such as the illustrated cutting 
elements 1 through 18. The cutting elements 1-18 preferably are the 
STRATAPAX (TM) manufactured by The General Electric Company. The cutters 
are installed in a conventional manner, such as by mounting the cutters on 
a stud, and pressing the stud into mounting holes formed in the face 23. 
The cutting elements 1-18 preferably are arranged in two opposite spiral 
patterns directly behind the flow slots 27, such as illustrated in FIG. 2. 
In FIG. 1, the cutters 1-18 are spuriously drawn side by side to show the 
cutting profile. In actual practice, the cutters 1-18 are each 
advantageously positioned to cut distinct but overlapping circular paths 
during the drilling operation, so that a continuous and complete cutting 
operation is achieved on the bottom of a borehole. 
FIGS. 6 and 14 show extra cutters 52 which are added to the periphery of 
the bit to enhance the ability of the bit to maintain accuracy of the 
diameter of the borehole. Any number of peripheral or "gauge" cutters 52 
may be added as needed. Each of the cutters 1-18 and the gauge cutters 52 
are oriented with respect to the main body 21 to engage the formation at 
the most optimum cutting angle and thereby provide optimum penetration 
rate of the bit. 
The present invention includes a plurality of novel radial stabilizing 
pistons 29 installed in complementary radial bores 30 formed through the 
sides and into the main body 21 of the bit 110 to intersect the throat 22. 
The bores 30 are symetrically arranged about the longitudinal axis of the 
bit. The pistons 29 are arranged to be positioned as near the face 23 as 
possible after allowing sufficient space for the other illustrated 
components therebetween. The preferred embodiment of FIGS. 1-4 show eight 
such pistons 29, however any suitable number may be employed. The pistons 
29 are reciprocated by differential pressure thereacross, with each piston 
29 having a small diameter at the inner end thereof and a large diameter 
at the outer end thereof. The radial bores 30 have corresponding diameters 
respective to the small end of the pistons 29 facing radially inward 
towards the center axis of the main body 21 and with the large ends of the 
pistons 29 facing radially outward. The pistons 29 may be installed 
directly in the main body 21 as shown, or alternatively may be installed 
in a separate body (not shown) which is removably attachable to the main 
body 21. The pistons 29 are slidably sealed to the sides of the radial 
bores 30 by o-rings 31, or similar means, so that a sealed variable volume 
chamber 32 is formed between the smaller and larger ends of each piston 
29. The chambers 32 increase in volume as the pistons 29 move radially 
outward and decrease in volume as the pistons 29 move radially inward. The 
inward travel of the pistons 29 is limited by the larger diameter portion 
of the pistons 29 abutting against the shoulder formed at the bottom of 
the larger diameter portion of the bore 30. The outward travel of the 
pistons 29 is limited by the illustrated shoulder 33'. The pistons 29 are 
prevented from rotating in the bore 30 by a detent formed by punch 
impressions 33, or other suitable means, which slidably engage grooves 28 
formed along the side of the pistons 29. The grooves 28 extends from the 
rim of the outer ends of the pistons 29, inwardly along the side of the 
pistons 29, to a position just short of the outer o-ring seals 31, thus 
allowing adequate outward travel of the pistons 29, without disrupting any 
of the seals 31. Each piston 29 may contain one or more grooves 28 as 
needed. 
The outer face of the pistons 29 are provided with wear resistant tungsten 
carbide buttons 36 pressed into complementary axial holes formed in the 
face of the pistons 29, so that the wear resistant button 36 is flush or 
aligned with the outer face of the piston 29, thereby making the outer 
ends of the pistons 29 wear resistant. The pistons 29 may alternatively be 
made entirely of a wear resistant material such as ceramic, or may be made 
wear resistant by other known expedients. 
In the cross-sectional illustration of FIG. 4, a check valve 34 is seen to 
be provided with a corresponding fluid passage 35 for each chamber 32 to 
allow an incompressible hydraulic fluid, such as viscous oil, to enter but 
not leave the variable chamber 32. In the embodiment of FIGS. 1-4, a 
common cylindrical fluid reservoir 51 is provided to pairs of chambers 32 
and to respective pairs of check valves 34, with the fluid inlet ends of 
the check valves 34 being positioned within the reservoir 51. The 
reservoir 51 is arranged radially respective to the longitudinal central 
axis of the main body 21. The reservoir 51 is illustrated as being located 
between pairs of chambers 32 and check valves 34. A small, concentric 
radial hole 46 extends radially inward into communication with the throat 
22, and into communication with the respective passages 35, and provides a 
means by which a blocking valve assembly 45 can be actuated. 
Each radial hole 46 is fitted with one blocking valve 45, which includes a 
valve element and a mating valve seat formed at one end of a sleeve 50. 
The blocking valve assembly 45 is arranged to selectively block or freely 
allow fluid flow into or out of the reservoir 51. The inner end of each 
blocking valve 45 is reciprocatingly sealed respective to the 
corresponding radial bore 46 by an o-ring 49, or similar seal means, and 
is arranged to function as a piston, with the o-ring 49 positioned inward 
relative to the corresponding pair of passages 35. The outer end of each 
blocking valve 45 is reduced in diameter respective to the holes 46, to 
allow fluid to pass from the passage 35 into the hole 46 and vice versa, 
and includes an end portion which is shaped to be received in sealed 
relationship against the illustrated valve seat of the sleeve 50. The 
inward travel of each valve 45 is limited by the illustrated shoulder; 
however, a snap ring or similar retainer positioned within the inner 
extremity of each hole 46 can serve as an alternative. The outward travel 
of each valve 45 is limited by the outer end thereof seating and sealing 
against the valve seat of the sleeve 50. Each sleeve 50 is fastened and 
sealed in the illustrated fixed position within each corresponding hole 
46, and is positioned to provide the desired contact with respect to the 
corresponding valve 45. The length and inner bore of the sleeves 50 are 
sized to accommodate shanks 44 of isolating caps 43 so that the shanks 44 
can reciprocate freely in a guided manner within the bore of the sleeves 
50. 
The isolating caps 43 are received within the bore of the reservoir 51, and 
are movably sealed in a reciprocating manner therein by o-rings 48, so 
that hydraulic fluid contained therewithin is isolated from contaminants 
from without. The caps 43 have the before mentioned rigidly attached 
shanks 44 which are radially oriented into the sleeves 50 to stabilize the 
caps 43. The shanks 44 are grooved or flattened to allow fluid to pass 
through the sleeve 50 into and out of the reservoir 51. The caps 43, with 
their shanks 44, are arranged to freely move in a stabilized manner as 
fluid enters or leaves the reservoir 51 to thereby accommodate any change 
in volume. The radial travel of the caps 43 is sufficient to provide 
adequate fluid displacement for the corresponding chambers 32. The outward 
travel of the caps 43 is limited by punch impressions 47 formed on the rim 
of the reservoirs 51, or by other suitable stop means. 
During assembly of the apparatus of the present invention, the chambers 32, 
check valves 34, passages 35, holes 46, and the reservoir 51 are all 
filled with a suitable hydraulic fluid, and all gas bubbles are evacuated 
therefrom so that an incompressible fluid is contained therein. Hydraulic 
fluid can be filled through resealable drilled holes located in the caps 
43, or in the body 21, or the filling could be completed before the caps 
43 are installed, or various other filling methods might be utilized in 
order to achieve this desired result. 
As best seen illustrated in FIGS. 1 and 5, each of a plurality of 
additional wear resistant buttons 36 are pressed flush into each of a 
plurality of radial holes arranged symmetrically around the outer 
periphery of the lower marginal end of the main body 21 at a location 
immediately above the face 23. Any other suitable means may be employed to 
protect the periphery of the main body 21 from undue abrasion and wear. 
In FIG. 1, the flow restrictors 25 are each arranged to provide optimum 
fluid flow restriction therethrough while also providing relatively low 
fluid output velocity therefrom into the flow slots 27 and onto the face 
23. In the present embodiment, each of the flow restrictors 25 comprise a 
plurality of commercially available wear resistant nozzles 37 having an 
o.d. corresponding to the size of the ports 24 so that each port 24 
contains a first or uppermost nozzle, one or more intermediate nozzles, 
and an outlet or lowermost nozzle. In the present embodiment, the first 
nozzle in each port 24 is inverted or otherwise shaped to provide diffused 
fluid flow and has its orifice 41 sized to provide optimum fluid flow 
restriction. The intermediate nozzles located in each port 24 are also 
inverted or otherwise shaped to provide diffused fluid flow, but have 
their orifices sized to provide relatively low fluid flow restriction. The 
outlet nozzle in each port 24 is non-inverted or otherwise shaped to 
provide straightened fluid flow, and its orifice 42 is sized to provide 
relatively low fluid output velocity. All the nozzles 37 are sealed to the 
walls of the ports 24 by o-rings 38. Different quantities, shapes, and 
sizes of nozzles 37 may be installed in the ports 24 depending upon the 
kind and degree of fluid control desired. Also, the restrictors 25 may be 
of one piece, multistage construction rather than of a plurality of series 
connected individual nozzles. The restrictors 25 are thus arranged to 
provide both a means for developing a desired fluid pressure drop and a 
means for reducing the resultant fluid escape velocity. 
In FIGS. 2 and 6-14, a fluid flow isolating ridge 39 extends from one side 
of the face 23 along the trailing edge of the cutters 1-18 on the first 
side of the face 23, across the center of the face 23, then along the 
trailing edge of the cutters 1-18 on the second side to the opposite side 
of the face 23. The ridge 39 is affixed or made integrally respective to 
the face 23 and is the minimum thickness for achieving the necessary 
required strength. The height of the flow isolating ridge 39 beyond the 
face 23 is equal to the height of the cutters 1-18 so that the ridge 39 
contacts the bottom of the borehole during the drilling operation. 
In FIGS. 2, 6-8, and 14, a plurality of fluid flow isolating ribs 40 extend 
concentrically along the face 23 from the trailing side of the ridge 39 
along paths concentric with the main body 21 to the leading edges of the 
corresponding slots 27. The ribs 40 are solidly attached to the ridge 39 
and to the face 23 and are the minimum thickness considered necessary for 
the required strength. The height of the ribs 40 beyond the face 23 is 
equal to the height of the cutters 1-18 and to the height of the ridge 39 
so that the ribs 40 similarly contact the bottom of the borehole during 
the drilling operation. The ribs 40 are symmetrically located on the face 
23 spaced radially from the center of the face 23 the maximum distance 
that provides adequate fluid flow isolation. The ridge 39 and the ribs 40 
are of a material, such a steel, that can be worn away readily by rubbing 
against the bottom of a borehole while making hole. 
As seen in FIGS. 1 and 3, parallel wrench flats 53 are machined onto 
opposite sides of the neck portion of the main body 21 in the conventional 
fashion to accommodate conventional tools for attaching or detaching the 
bit 110 to a drill pipe 62. 
In FIG. 15, a borehole 60 has a drill string 62 and drill collar 64 therein 
with the bit 110 attached to the lower end thereof. A drilling rig 70 
manipulates the drill string 62. Drilling fluid flows at 72 into the 
string and is returned through a rotating blowout preventor 74 in the 
usual manner. 
In operation, the upper threaded end of the main body 21 is attached in the 
conventional manner to the lower end of a drill pipe, or drill string 62 
and is then inserted in a borehole 60 and rotated in the conventional 
manner. The bit is forced downward against the bottom of the borehole by 
weight applied to the drill string in the conventional manner. As the 
invention is continuously rotated with weight applied, the ridge 39, the 
ribs 40, and the cutters 1-18 are all rubbed against the bottom of the 
borehole. The ridge 39 and the ribs 40 are reduced in height due to wear 
against the bottom of the borehole; however, the edges of the cutters 1-18 
wear only slightly due to their material of construction. Thus, the 
cutters 1-18 penetrate the bottom of the borehole and remove material 
therefrom as the bit is rotated with weight applied. The action of the 
cutters 1-18, moves the cuttings from in front of the cutters 1-18 into 
the slots 27. The gauge cutters 52 remove material from the wall of the 
borehole and there by achieve the desired diameter of the bore hole. 
Conventional drilling fluid, supplied in the conventional manner from a 
suitable pump, is continuously pumped downward at 72, through the drill 
string 62, through the throat 22 of the present invention, through the 
flow restrictors 25, through the flow slots 27, then back up the bore hole 
annulus located outside of the drill string. The cut material is carried 
along by the flowing drilling fluid and is thus removed at 74 from the 
borehole. 
Since the pressure drop across an orifice varies approximately as the 
square of the change in flow rate of a fluid flowing through the orifice, 
then the resultant fluid volume flowing through both orifices 41 (i.e. 
both restrictors 25) of the present invention will remain practically 
equal or balanced when appropriate total fluid volume and pressure is 
maintained. The orifices 41 can be sized to provide a predetermined or 
desired pressure drop for any given fluid flow rate. At any given fluid 
flow rate, the greater the pressure drop the more firmly equalized or 
balanced the flow through the restrictors 25 becomes. Also, each 
corresponding port 24, flow restrictor 25, and flow slot 27 forms and 
provides an isolated fluid path because the ridge 39 and the ribs 40 all 
contact the bottom of the borehole and thus prevent drilling fluid flowing 
in one slot 27 from escaping that slot except at the upper end of that 
slot. The flow of drilling fluid through either of the slots 27 will not 
become overbalanced or diverted and will therefore continue to flow 
adequately through each slot 27 and thereby force out the cut material 
even if packing or clogging tends to occur. Accordingly, balling or 
plugging is effectively avoided on the face 23 of the present bit. 
Due to the configuration and arrangement of the flow restrictors 25, the 
velocity of the flowing drilling fluid as it leaves the restrictors 25 and 
enters the slots 27 is kept low enough so that no appreciable fluid 
erosion occurs on any part of the present bit even when a relatively high 
fluid flow rate and resultant pressure drop is maintained. 
Drilling fluid flowing through the present bit is at a relatively elevated 
pressure within the throat 22 because of the pressure drop measured across 
the restrictors 25. Therefore, an outward force is exerted on the smaller 
end of the pistons 29, forcing the outer ends of the pistons 29 to move 
outward to any one of a range of extended positions and into relatively 
light contact with the wall of the borehole. Also, the blocking valves 45 
are forced outward so that the outer ends of the valves 45 are seated in 
sealed relationship against the valve seat end of the sleeves 50, blocking 
any fluid flow therethrough. As the pistons 29 move outward, the chambers 
32 expand in volume, causing a pressure differential which forces the 
hydraulic fluid from the reservoir 51, through the check valves 34, 
through the passages 35 and into the chambers 32. The caps 43 move inward 
to accommodate the reduced volume within the reservoirs 51. The check 
valves 34 prevent any reverse flow of hydraulic fluid and thus provides a 
hydraulic barrier within the chambers 32 so that the pistons 29 cannot 
move inward from any extended position, even when an extreme opposite 
force is exerted inwardly on the pistons 29 from the wall of the borehole. 
In like manner, as the outer ends of the pistons 29 slowly wear due to 
friction against the wall of the borehole, the pistons 29 continually move 
slowly outward and more hydraulic fluid is drawn into and retained within 
the chambers 32. Thus, means are provided by which the pistons 29 are 
continually compensated for wear and remain in constant contact with the 
wall of the borehole. Accordingly, the present invention provides means by 
which a drill bit is prevented from whipping or radially vibrating. During 
this time, the cutters 1-18 and the gauge cutters 52 are positioned where 
they are protected from impact damage and from the premature failure which 
may otherwise result therefrom. 
Reduced circulation of drilling fluid reduces the pressure drop across the 
restrictors 25, and the fluid pressure within the throat 22 is therefore 
reduced until it becomes equalized with respect to the fluid pressure on 
the outside of the main body 21. Thus, in this condition, no outward force 
is exerted against the pistons 29 or the blocking valves 45. Hence, the 
outer ends of the blocking valves 45 are no longer sealed against the 
valve seat ends of the sleeves 50 and fluid is therefore allowed to flow 
therethrough. Thus, in this condition, when an inward force is exerted on 
the outer ends of the pistons 29, hydraulic fluid flows freely out of the 
chambers 32, through the passages 35, against the outer ends of the 
blocking valves 45, forcing the blocking valves inward away from the valve 
seat of the sleeves 50, so the fluid flows through the sleeves 50 past the 
shanks 44, and into the reservoirs 51. At this time, the caps 43 can move 
outward to accommodate the added fluid volume within the reservoirs 51. 
Therefore, the pistons 29 can be selectively allowed to retract inward by 
removing fluid pressure within the throat 22. 
The main body 21 and the holes and passages therein, the pistons 29, 
blocking valves 45, sleeves 50, and the caps 43 with shanks 44 all can be 
readily fabricated by convenional methods, such as machining or molding. 
The cutters 1-18, o-rings 31, wear resistant buttons 36, nozzles 37, 
o-rings 38, and the gauge cutters 52 are all readily available commercial 
products which can be installed in the bit of the present invention. 
Various different check valves 34 of conventional design may be either 
built into the present bit or purchased separately and assembled 
thereinto. Thus, the present invention can be readily and economically 
manufactured. 
Having thus described the invention, it is to be understood that certain 
modifications in the construction and arrangement of the parts thereof may 
be made, as deemed necessary, without departing from the scope of the 
appended claims.