U.S. patent number 3,853,184 [Application Number 05/266,502] was granted by the patent office on 1974-12-10 for means for detecting wear on well drill bits.
Invention is credited to Doyle W. McCullough.
United States Patent |
3,853,184 |
McCullough |
December 10, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
MEANS FOR DETECTING WEAR ON WELL DRILL BITS
Abstract
The specification discloses sensor means in a rotary drilling
bit for detecting the extent of wear on critical wear points in the
bit during the drilling operation and means for signaling to the
driller at a remote location from the bit the extent of such
wear.
Inventors: |
McCullough; Doyle W.
(Westfield, TX) |
Family
ID: |
26750191 |
Appl.
No.: |
05/266,502 |
Filed: |
June 26, 1972 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
69549 |
Sep 4, 1970 |
|
|
|
|
Current U.S.
Class: |
175/39;
175/40 |
Current CPC
Class: |
E21B
12/02 (20130101) |
Current International
Class: |
E21B
12/02 (20060101); E21B 12/00 (20060101); E21b
013/00 () |
Field of
Search: |
;175/39 ;73/151.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Murtagh; John E.
Assistant Examiner: Favreau; Richard E.
Attorney, Agent or Firm: Pravel & Wilson
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. Pat.
application, Ser. No. 69,549, filed Sept. 4, 1970, now abandoned.
Claims
What is claimed is:
1. Wear detecting means for detecting wear in drill bits used with
drilling fluid in rotary well drilling operations comprising:
a. wear means in said bit adjacent bit parts normally worn during
drilling operations;
b. a closed fluid pressure system isolated from the drilling fluid
pressure in the bit with conduit means in said bit for
communicating fluid pressure in said closed system to said wear
means;
c. fluid pressure means operably connected to said fluid conduit
means for supplying fluid pressure to said wear means;
d. pressure responsive means operably connected to said fluid
conduit means;
e. means with said pressure responsive means for restricting flow
of the drilling fluid flowing through said bit to increase the line
pressure of such drilling fluids;
f. means for sensing changes in line pressure of such drilling
fluid;
g. means operably connected with said sensing means for signaling
changes in said drilling fluid line pressure.
2. The invention of claim 1, wherein said wear detecting means
includes a plug adjacent to the outer circumference of said
drilling bit to detect a reduction in the gauge of such bit due to
wear in drilling operations.
3. The invention of claim 1 wherein said drilling bit includes
bearings for supporting roller cones thereon and said wear means
are positioned adjacent said bearings to detect wear thereof.
4. The invention of claim 1 wherein said pressure responsive means
includes a hydraulic cylinder having a piston therein that is
adapted to be moved longitudinally with respect to such cylinder in
response to pressure conducted through said fluid conduit
means.
5. The invention of claim 1 wherein said means with said pressure
responsive means for restricting flow of the drilling fluid used
with said bit includes butterfly valve means operably connected to
said pressure responsive means wherein said butterfly means
includes an orifice therein for restricting flow of such drilling
fluid.
6. The invention of claim 1 wherein said wear means includes a
plurality of wear means at critical wear points in said bit and
said means with said pressure responsive means includes butterfly
valves each having an orifice therein of a different size to
restrict the flow of drilling fluid to a different amount to
thereby identify the particular critical wear point which is worn
on the bit.
7. The invention of claim 1 wherein said drilling bit includes
cutting teeth and said wear means are located adjacent to tips of
said teeth of the said drilling bit.
8. The invention of claim 7 wherein said wear means adjacent to
tips of such drill bit teeth include pin means to open said fluid
conduit means when the wear means adjacent the bit tip has been
worn away.
9. The invention of claim 1 including:
a. drill bit containing a plurality of roller cones carried on
spindles;
b. passages in said spindles;
c. a rotatable member surrounding said spindle and closing the
outer end of the passage in said spindle;
d. said rotatable member including an opening therethrough;
e. means with said wear means for rotating said rotatable member on
said spindle while aligning said opening with said passage to
release the pressure therein.
10. The invention of claim 9 wherein said rotatable member is
formed with a plurality of ratchet teeth on the outer surface
thereof and said means for rotating said rotatable member includes
a pin having one end adapted to engage said ratchet means and the
other end adjacent said wear means with means for urging said pin
into engagement with said ratchet means and a restraining means on
the end of the pin adjacent said wear means which is adapted to be
worn away when said wear means is removed to release said pin for
moving into engagement with said ratchet means.
11. The invention of claim 1 wherein said fluid pressure means
includes means for imposing a positive pressure on said wear means
and means for actuating said pressure responsive means when said
positive pressure is released to cause said pressure responsive
means to restrict the flow of drilling fluid through said bit.
12. The invention of claim 11 including a negative pressure circuit
with said positive pressure and switching means for switching said
pressure responsive means from a positive pressure to a negative
pressure to remove said restriction from the flow of drilling fluid
through said bit.
13. The invention of claim 1, including:
a drill bit containing a roller cone mounted for rotation on a
spindle;
a passage in said spindle adapted to receive fluid under pressure
from said fluid pressure means;
a pressure plug means mounted in said passage to prevent the escape
of pressurized fluid from said passage in said spindle; and
plug breaking means mounted with said roller cone for breaking said
pressure plug means in response to wear of said roller cone whereby
fluid escapes outwardly of said passage.
14. The invention of claim 13, wherein said plug breaking means
includes:
a releasable pin releasably mounted in said roller cone for
movement to a released position in which rotation of said roller
cone causes said release pin to engage and break said pressure
plug; and
wear release means for moving said releasable pin to said released
position in response to wear of said roller cone.
15. A wear detecting sensor for detecting wear in a rotating part,
comprising:
a rotating part mounted on a non-rotating part for rotation with
respect thereto;
a releasable pin releasably mounted in said rotating part for
movement to a released position;
wear release means mounted with said releasable pin to move said
pin to a released position in response to wear of said rotating
part;
said non-rotating part having a passage therein to receive
pressurized fluid; and
pressure plug means mounted in said passage for plugging said
passage, said plug means including a breakable portion whereby
rotation of said rotating part with said releasable pin in said
released position causes said releasable pin to engage and break
said breakable plug portion to allow pressurized fluid in said
passage to escape.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a device for sensing the extent
of wear on various parts of a drill bit such as the external
diameter or gauge of the bit, the bearings on which the moving bit
parts rotate and the condition of the cutting or drilling edges of
such bit together with means in the drill string for signaling to
the surface when the wear on any of such portion of the bit reaches
a predetermined amount.
2. Description of the Prior Art
In the drilling of well bores with well drilling bits it is very
important to detect a predetermined degree of wear of the drill bit
as soon as such wear occurs, although such wear occurs when the bit
is several thousand feet below the surface of the earth. In the
rotary method of drilling wells where a drill bit is advanced into
the earth by rotation of the drill pipe and pressure applied
downward on the bit and a drilling fluid is pumped in and out of
the well bore, drill bits have been provided which will drill
several hundred feet without being replaced, but wear occurs on the
drill bit in three different parts, namely the gauge or hole size
cutting edges, the bearings (in the case of a roller type drilling
bit), and the bottom cutting or drilling edges.
When the bit gets out of gauge, it drills a tapered hole or what is
known as a tight hole. When a new bit is run back in the hole,
there is danger of pinching the bit and locking the cones or
rollers so that they will not turn and drill. This requires another
trip out of the hole and back to bottom again to replace the jammed
bit with another new bit. If there is much tight hole, as such is
usually the case, this second new bit will be damaged reaming the
hole down to the bottom to which the hole was originally drilled,
in which case the second bit will have to be pulled out of the hole
and another new bit will have to be run to get back on bottom.
A large number of "green" or partially used or worn bits are pulled
out of the hole because the driller has no way of knowing when the
cutting or drilling edges of the drill bit are worn out. In the
case of roller or cone bits, some times the space between the
cutting teeth on the rollers or cones get filled and packed tight
(commonly called break-up) with the formation through which it is
drilling causing the drill bit to appear to be dull. When the
drilling time slows down, the driller pulls the bit without really
knowing what condition the bit is in. As a result, a green bit,
which could make another 100 feet or more of hole, is pulled from
the hole.
In those formations where the bit can be turned fast, the bearings
(in the roller or cone type bit) will usually wear out before the
bit teeth. When the bearings wear small enough, the rollers or
cones drop off the bit, and require a costly fishing or retrieving
job to remove them from the well hole. Sometimes it is impossible
to continue drilling a well and it has to be abandoned because not
all fishing jobs are successful in getting the junk iron out of the
hole.
SUMMARY OF THE INVENTION
The present invention directs itself to a means for indicating to
the driller that the drilling bit has worn away the maximum amount
of wear either at the gauge or the well bore sizing portions of the
drill bit, the cutting or drilling edges of the drill bit, and the
bearings in the roller or cone type of drilling bits. In this
manner the driller will be definitely advised that the maximum
degree of wear has occurred and he can immediately take steps
necessary to stop drilling and replace the bit.
It is, therefore, one of the objects of the invention to provide a
drill bit with the gauge cutting portion of the bit with a core or
drill hole that will act upon a control signal to indicate when the
maximum wear has occurred on the gauge portion of the bit.
Another object of the invention is to provide a new and improved
drill bit with means for indicating when teeth on the bit are worn
to a predetermined degree. It is also an object to provide a new
and improved drill bit having a device with the cutting teeth on
the cones that will trip and act upon a ratchet spool to uncover a
cored or drilled hole in the bearing spindle and actuate a control
signal to indicate when the maximum wear has occurred on the teeth
of the drill bit.
Another object of the invention is to provide a drill bit with the
bearing spindles with a core or drilled hole that will act upon a
control signal to indicate when the maximum wear has occurred on
the bearings of the drill bit.
Another object of the invention is to provide a new and improved
means of indication for each one of the drill bit cutting cones in
the case of a bit having a plurality of cutting cones.
Another object of the invention is to convert the control signal to
a discernible signal at the surface of the ground by the instrument
drill sub by turning pre-sized orifices into the mud or air (in the
case of using air for the drilling fluid medium) stream. By turning
different pre-sized orifices into the drilling fluid stream, the
pressures will vary from the normal, and these changes in pressure
(one each for the gauge of the bit, the bearings that the cutting
cones roll on, and the cutting teeth of the bit) can be detected at
the surface of the ground in the pipe line from the mud pump by a
pressure to current transducer and this signal amplified and sent
to an audible horn and a strip chart recorder for a premanent
record of the different events that gives a visible indication of
what part of the bit has worn.
Another object of the invention is to provide the information
immediately at the surface of the ground and to distinguish as to
which part or parts have reached their maximum wear.
Still another object of the invention is to provide the information
with enough time lag sufficient to let the driller continue to
drill another foot or so if conditions would warrant doing so.
A construction designed to carry out the invention will be
hereinafter described, and other and further objects of the
invention will be shown when the following description is
considered in connection with the accompanying drawings, and
wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic view of a well bore showing therein a
drilling apparatus constructed in accordance with this
invention;
FIG. 2 is an enlarged, longitudinal view, partly in elevation and
partly in section, showing the drill bit and details of wear
sensors;
FIG. 3 is an enlarged cross-sectional view taken on line 3--3 of
FIG. 2 showing the arrangement of the cone teeth wear indicating
mechanism;
FIG. 3A is an enlarged cross-sectional view taken along line 3--3
of FIG. 2 illustrating an alternate embodiment for an arrangement
for a wear sensor in the rotating cone;
FIGS. 4A and 4B are enlarged, longitudinal, sectional views of the
upper and lower portions, respectively, of the instrument drill bit
sub;
FIG. 5 is a cross-sectional view, taken on line 5--5 of FIG.
4-A;
FIG. 6 is an enlarged longitudinal view of the air cylinder and
crank mechanism that moves the different size orifices in the mud
or air stream;
FIG. 7 is a schematic of the above ground signal circuit and
indicating instrument components;
FIG. 8 shows an example of a typical strip recording chart that
shows how the different events are recorded; and
FIG. 9 is a schematic of the pneumatic control circuit of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Briefly, the drilling sensor apparatus of the present invention is
designated generally A in FIG. 1 of the drawings wherein 9
designated a well bore drilled by rotary drilling equipment
including a drill stem or pipe 8 extending downwardly through the
well bore and supporting drill collars and the instrument sub 10
thereon. The drilling bit 11 is mounted at the lower end of the
instrument sub. As will be described in detail hereinafter, the
drill bit 11, as well as the instrument sub 10, include means for
signaling to the surface when wear on various critical parts of the
drill bit exceed a predetermined amount and thereby enable the
driller at the surface to maximize the use or life of each drill
bit and also minimize the risk of drilling either a tapered hole or
having the bit fail in operation.
As shown in FIG. 2, the drill bit 11 may be of the type provided
with a plurality of cutter cones 20 mounted upon spindles 18
carried on suitable antifriction bearings 19. The cutters are
provided with cutting teeth 23 and have their heel portions
projecting outwardly beyond the body 16 of the drill bit to insure
the drilling of a full gauge hole through which the body of the bit
and the related drilling equipment will pass as the drilling of the
well progresses downwardly.
It is important that the operator of the drilling equipment known
when the cutting diameter of the drilling bit has been reduced by
wearing away of the heel portion of the cutter cones 20 to keep
from drilling an undersized portion of the well bore, when the
antifriction bearings 19 fail or become excessively worn and permit
the cutter cones to slip off of the spindles 18 an be lost in the
well bore, necessitating a cleaning or fishing operation in the
well bore, and also when the cutting teeth 23 of the drill bit
cutters 20 have become worn to the point at which they no longer
cut efficiently.
In the present invention, the sensors for detecting wear in the
drill bit include a plurality of pressurized fluid conduits 13, 14
and 15 having wear means adjacent to the critical wear points in
the bit 11 which, when worn sufficiently, will open the pressurized
conduits to allow a pressure drop therein and actuate signaling
devices to indicate to the driller the fact that such wear has
occurred. As best seen in FIGS. 4-A and 4-B of the drawings, a
plurality of butterfly valves 33, 37 and 43 are positioned in the
drilling mud conduit 29 of the instrument sub 10-A. As shown, each
butterfly valve is provided with a different sized orifice and each
such valve is connected to a fluid pressure cylinder which, in
response to a drop in fluid pressure in one of the fluid pressure
lines 13, 14 or 15 to which it is connected, rotates the butterfly
valve and thereby causes a temporary restriction in the fluid
passage 29 which in turn provides an audible as well as a visual
signal to the driller at the surface in a manner to be described in
detail hereinafter.
Considering now the apparatus of the present invention in more
detail, as shown in FIG. 2 of the drawing, each of the fluid
passages 13, 14 and 15 is provided with a circumferentially
extending groove 13-A, 14-A and 15-A, respectively, formed in the
upper shoulder 11-A of the drill bit 11. Corresponding fluid
passages 13-B, 14-B and 15-B, respectively, are provided in the
instrument housing 10-A for communicating fluid pressure from the
sensors in the bit 11 to the actuator pistons 32, 36 and 41 as
shown. A passage or orifice 31 is provided in the cylinder 32 for
connecting a fluid pressure line thereto and similarly, orifices or
passages 35 and 40 are provided in each of the piston cylinders 36
and 41, respectively, for connecting the fluid pressure lines 14
and 15 thereto.
As best seen in FIG. 6 of the drawings, a piston 32-A is provided
in the cylinder 32 and is connected by means of a rod 32-B to a
crank arm 42 which in turn is connected to a shaft 42-A on which is
mounted the particular butterfly valve 33, 37 or 43 as the case may
be. As shown, the shaft 42-A is mounted and suitable bearings 42-B
to facilitate rotation of the shaft 42-A and the butterfly valve
associated therewith.
As best seen in FIG. 2 of the drawings, the preferred embodiment of
the present invention includes a bit 11 having a shank 16 thereon
which is provided with a fluid passage 15 having a plug 17
positioned at the outer surface of such shank 16 in the terminal
end of the fluid passage 15. When the heel portion of the cutting
teeth 23 has worn and the drilled hole is undersized, the shank 16
of the bit 11 will wear away. When the shank 16 and the plug 17
wear away sufficiently, the fluid passage 15 will be opened to
release fluid pressure therein and actuate the piston in the fluid
cylinder 36 to rotate the butterfly valve 37 and restrict flow
through the passage 29. As will be described in detail hereinafter,
this will operate an audible as well as a visual signal at the
surface to indicate to the driller that the shank portion 16 of the
bit has worn sufficiently to wear away the plug 17 which will
indicate to him that the bit has worn to the point that it is
making an undersized or tapered hole and that therefore it is
necessary that the bit be withdrawn from the bore hole and replaced
with a new bit.
Similarly, the fluid passage 14 has a plug 21 at its terminal end,
which, when the bearings 19 are worn and reduced in circumference,
will be worn by the surface 23-A of the cone 23. When such plug 21
is worn away, it will release the fluid pressure in the passage 14
to actuate the piston and the cylinder 41 and in turn butterfly
valve 43 so as to provide a restriction in the fluid passage 29
which will signal the driller at the surface in a manner to be
described in detail hereinafter.
Also, the fluid passage 13 is connected to a passage 27 which, as
best seen in FIG. 3 of the drawings, is positioned in the end of
the spindle 18 on which the cutter cone 20 is mounted. A ratchet
wheel or spool 26 is rotatably mounted about the end of the spindle
18 and is provided with a passage 27-A therein, which, when aligned
with passage 27 will release the fluid pressure in the line 13 to
actuate the piston in cylinder 32 and rotate the butterfly valve 33
to signal the operator at the surface that the tips 23 of the cone
20 have worn. Wear plugs 23' are provided in the ends of the
passages 23-B in the cone 20. Such passages are arranged so as to
communicate an internal passage 23-C which surrounds the end of
spindle 18 and provides a housing in which the ratchet wheel 26 is
free to turn. As shown, such wear plugs 23' are positioned in the
cutting tips 23 so that as such tips wear, they necessarily wear
the wear plugs 21'. As shown, the wear plugs 21' are mounted at the
end of a shaft 25 which extends through a lock member 24 and
through an inner pin guide 23-F. Such pin projects into the passage
23-C and, when moved longitudinally of the passage 23-B, will
engage the teeth 26-A on the ratchet wheel 26 to rotate the ratchet
counterclockwise as the roller cone is rotated in the normal
drilling operations when the bit 11 is turned to the right. When
the inner end of the pin 25 engages such teeth 26-A, it will rotate
the ratchet counterclockwise and when the opening 27-A is aligned
with passage 27 fluid pressure in the line 13 will thus be released
to actuate the butterfly valve 33 in the instrument housing
10-A.
In the preferred form of this invention, pin 25 is urged inwardly
toward the ratchet 26 by means of a compression coil spring 25-A
that surrounds such pin the passage 23-B. The outer end of the pin
extends through a suitable opening 24-A in the lock 24 and has a
head 25-C thereon for holding the pin against longitudinal movement
inwardly of the passage 23-B. After the wear plug 21 has worn
sufficiently, the head 25-C will be worn off the pin 25 by
continued rotation of the roller cone 20 and when such head is worn
off, the compressed spring 25-A will be released and will move the
pin 25 inwardly to engage the teeth of the ratchet 26, turn the
ratchet and thereby release the pressure to signal that the teeth
23 have been worn to a predetermined amount.
It will be understood that as the bit 11 is rotated to the right,
the roller cones 20 will rotate in a counterclockwise direction as
viewed in FIG. 3 of the drawings and that the pin 25 will rotate
the ratchet in a counterclockwise direction to align the passage
27-A with the passage 27.
An alternate embodiment for indicating wear of the teeth of the
roller cone 24 is illustrated in FIG. 3A. In FIG. 3A, the spindle
18 again has passage 13 extending substantially axially
therethrough in fluid communication with the radially extending
passage 27 which terminates at the outer surface of the spindle 18
which is part of the internal passage 23-C between the end of the
spindle 18 and the roller cone 23. A plugging element 126 is
mounted by any suitable means such as sweat soldering into the
passage 27 in order to allow the passages 27 and 13 to hold or
contain fluid pressure. The plugging element 126 has a bore 126d
therein that extends internally the length of the plugging element.
The wall forming the plug bore 126d is weakened by circumferencial
indentations at 126a to provide a weakened joint which allows the
tip 126c of the plug to be broken off under the force of the pin
25, when such pin has been moved by spring 25a to its release
position. Thus, after the head 25-C of the head 21 has been
sufficiently worn off, the spring 25a moves the pin 25 to a release
position in the internal passage 23-C. Thereafter, as the roller
cone continues to rotate counterclockwise, the end of the released
pin 25 engages the breakable tip 126c and, due to the weakened
joint 126a, breaks the tip 126c off of the plug 126, thereby
allowing the pressurized fluid in the passages 13 and 27 to escape
so that such pressure loss may be used to indicate or provide a
signal as discussed in greater detail hereinafter.
Considering now the control circuit of the present invention as
shown in the schematic view of FIG. 9, a fluid pressure tank 54
provides fluid, such as compressed air, under of approximately
1,000 to 5,000 psi. A vacuum tank 51 is also provided with the
control circuit for providing a negative pressure for use in
operating control circuit as will be described in detail
hereinafter. Also, as will be described in detail hereinafter, the
tanks 54 and 51 as well as the valves shown in the schematic in
FIG. 9 of the drawing are housed in the instrument control housing
10-A and are shown in more detail in FIG. 5 of the drawings. The
valves 56 and 56-A which control the tanks 54 and 51, respectively,
as well as valves 59 are accessible from the exterior of the
housing 10-A.
With the tank 54 charged under suitable operating pressure, the
valve 57 which had theretofore been closed, is opened and the
valves 59, which are operably connected with each of the fluid
sensor circuits 13, 14 and 15, respectively, are also opened to
precharge such lines 13, 14 and 15 under positive pressure. With
the valve 59 opened, the pilot pistons in the pneumatic valves 60,
67 and 73 which are each associated with the fluid pressure lines
15, 14 and 13, respectively, are also charged to move the pistons
and such pilot valves to the right as shown in FIG. 9 of the
drawings and thereby connect the vacuum line or conduit 78-A with
each of the relay valves 62 in the lines 78-B. Each of the pilot
valves 60, 67 and 73 is provided with a spring 61, 68 and 74,
respectively, which is compressed by the pressure from the tank 54.
After the pilot valves have been charged, the valves 59 are closed.
Similarly, return pilot valves 69, 69-A and 75 are connected to the
conduit 78-B via the conduits 78-C and 78-D which, as shown,
connect opposite sides of valves.
When one of the wear sensors, such as the sensor 17, is worn away
as mentioned above while the well is being drilled, this releases
fluid pressure in the line 15 into the well bore 9 reducing the
pressure in the pilot valve 60 and permitting the spring 61 to move
the valve from a connection to lines 78-A to connect the positive
pressure lines 57-A which will then be connected to the conduit
78-B. The positive pressure in 78-B will be communicated through
the lines 78-B to lines 78-C and D. The pressure through 78-D will
move the pilot valve 69 to the left to switch the line 78-C into
operable connection with the line 78-E which passes positive
pressure through the line 31 into the piston chamber 32 to rotate
the butterfly valve 33 and restrict fluid flow through the passage
29. Also, positive pressure is introduced from the lines 78-E into
the lines 78-F to actuate the valves 62-A and 62-B to close
temporarily the fluid passage through the lines 88 and 98 to render
the sensor apparatus, which actuates the other two butterfly valves
43 and 37, temporarily inoperative so as to give a clear indication
to the driller at the surface that the wear plug 17 has been
released and thereby avoid any confusion as to which critical
portion of the bit is worn out.
As shown, a choke 64 is provided in the line 78-H that connects the
opposite sides of the piston and the return valve 69. Also, an
accumulator tank 65 is provided with the choke 64. After the volume
tank 65 has filled sufficiently, the pressure will then equalize in
the valve 69 on opposite sides of the piston therein, and the
spring 69-B will switch the valve 63 back to a connection with the
vacuum line 78-K that is connected to the vacuum tank 51. AS the
vacuum reduces the pressure in the line 78-C and 78-E and line 31,
the piston in the chamber 32 is moved back to its starting position
to open the butterfly valve 33 and permit normal circulation of
drilling fluid through the passage 29 in the manner which it
occurred prior to signaling to the surface of the wear on the bit
11.
Thus, it will be appreciated that a temporary restriction in the
mud circulation line will occur when a particular part of the bit
has been worn and due to the differences in size of the orifice or
openings 34, 38 and 44, pressure buildup in the mud line will vary
according to the particular portion of the bit which has worn.
Also, the chokes 64, 70 and 76 are of variable sizes so that the
time required to return the particular butterfly valve with which
they are associated to the original position, will vary so that not
only will the signal at the surface vary according to the pressure
buildup in the line, but also according to the length of time that
such pressure buildup remains. In other words, in order to give a
clear indication to the driller at the surface of which portion of
the bit has worn, and to prevent more than one event or one worn
portion of the bit to be signaled at a time, the different surges
and duration of such surges avoids any confusion.
As shown in FIG. 7 of the drawings, the increase in pressure occurs
in the mud flow line 79 and is sensed by the pressure-current
transducer 80 and amplified by an amplifier 81 with the signal
being sent to the relay 82. Such relay 82 is connected to an
audible horn 83 to provide an audible signal of wear on the bit
having occurred, and also a strip recorder 84 prints a record of
the event on a chart 85. An enlarged view of the chart 85 is shown
in FIG. 8 of the drawings to illustrate the different pen marks
that are made as a result of different parts of the bit having
become worn. For example, the pen traces a continuous line 86 to
indicate minor variations in mud pressure in the mud line 79.
When the butterfly valve 33 having the largest diameter of orifice
34 restricts flow in the conduit 29, pressure in the mud line 79
and the choke 64 prevents the return of such butterfly valve 33 to
its normal position for a time that is indicated by the length of
the line 87 or which indicates the duration of the increased pump
pressure while the valve 33 is restricting flow into line 29.
Similarly, when the butterfly valve 37 having the intermediate
sized orifice 38 therein restricts flow into line 29, the pump
pressure is increased so that the line 89 is further to the right
than the normal line 86 or the line 87 and, similarly, the length
of the line 89 which indicates the duration of such elevated pump
pressure is longer than line 87 because the choke 70 is sized so as
to prevent the return of the butterfly valve 37 to its normal
position a longer time than would be the case with the choke
64.
By the same token, when the butterfly valve 43, having the smallest
diameter orifice 44 therein, is turned so as to restrict flow
through the line 29, the readout on the strip chart 85 produces the
line 91 which is the furtherest to the right on chart 85 indicating
the highest pressure in the line 79 corresponding to the greatest
restriction in the flow line. The length of the line 91 is
determined by the choke 76 which holds the valve 43 in the closed
position for a longer period of time than would be the case with
the other chokes 70 or 64. Thus, it would be appreciated that the
different trace lines 87, 89 and 91 indicate to a driller at the
surface which portion of the drill bit as reached a critical wear
point. Also, with the present invention, a date and time record may
be put on the strip chart by means of a date-time stamp which will
be actuated by movement of the tracing head some fixed distance
beyond the normal mud pump pressure indicated by line 86. When the
mud pump is shut down, the recording pen returns to a position
indicated by the line 93.
As best seen in FIG. 5 of the drawing, the instrument housing 10-A
includes a longitudinally extending cylindrical body 55 having a
relieved portion 55-A for receiving the pressure tank 54. A
longitudinally extending cap 52 is secured by a plurality of bolts
52-A to the housing 55. Such cap 52 has an arcuate outer surface
corresponding to the outer surface of the housing 55 so that when
the cap is positioned on the housing a longitudinally extending
cylinder 10-A is formed. The longitudinally extending passage 29 is
formed in the housing 55 and receives the butterfly valves 33, 37
and 43. Such housing 55 also includes an opening or relieved
portion 55-B in which is positioned the actuating cylinders 32, 36
and 41 for rotating the butterfly valves 33, 37 and 43,
respectively.
In operation, the apparatus of the present invention is connected
to the lower end of a string of drill collars with the bit 11
secured at the lower end of such instrument housing 10-A. When the
bit is in operation, the pressure in the fluid systems maintains a
positive pressure on each of the wear plugs on sensors 17 and 21
and also maintains a positive pressure in the passage 27 in the
spindle of the bit 11.
In the event sufficient wear occurs on the bit to wear away any of
the wear plugs, pressure in the hydraulic system is released to
signal to the surface the fact of a change in the mud pump pressure
in the drill string. As described herein above, when pressure in
the hydraulic system is released, the hydraulic cylinder connected
to the wear plug which is released is caused to rotate to turn the
butterfly valve attached thereto so as to restrict fluid flow to
the passage 29. After a timed interval, depending upon the
particular choke 64, 70 or 76, the fluid pressure in the hydraulic
system causes such butterfly valve to be returned to a position
extending longitudinally of the flow passage 29 to thereby relieve
the restriction in the mud line and terminate the signal of the
apparatus of this invention indicating that the bit is worn in a
particular place.
After a signal of the worn condition of the bit hs been received at
the surface, the drilling operations may be interrupted to pull the
worn bit from the well bore and replace it with anew bit and
continue drilling of the well bore. With the apparatus of this
invention the maximum use from a particular bit may be obtained
without running the bit beyond its maximum wear point so as to
cause either a tapered hole or to loose a part of the bit in the
well bore.
The foregoing disclosure and description of the invention are
illustrative and explanatory thereof, and various changes in the
size, shape and materials as well as in the details of the
illustrated construction may be made without departing from the
spirit of the invention.
* * * * *