U.S. patent number 3,853,004 [Application Number 05/190,881] was granted by the patent office on 1974-12-10 for methods and systems for measuring, displaying and recording time-rate of penetration.
This patent grant is currently assigned to Eastman Oil Well Survey Company. Invention is credited to Steve Edward Cebuliak, Clifford Harvey Leach, John Wallace Snyder, John Henry Westlake.
United States Patent |
3,853,004 |
Westlake , et al. |
December 10, 1974 |
METHODS AND SYSTEMS FOR MEASURING, DISPLAYING AND RECORDING
TIME-RATE OF PENETRATION
Abstract
The provision of means to measure, display and record the rate
of a boring bit penetration during a drilling process by measuring
the movement of the bit supporting cable and interpreting said
measurement to include the time of the penetrating movement of the
bit and thereafter displaying and recording said time rate of
penetration of said bit.
Inventors: |
Westlake; John Henry (Calgary,
Alberta, CA), Snyder; John Wallace (Calgary, Alberta,
CA), Leach; Clifford Harvey (Calgary, Alberta,
CA), Cebuliak; Steve Edward (Calgary, Alberta,
CA) |
Assignee: |
Eastman Oil Well Survey Company
(Houston, TX)
|
Family
ID: |
22703195 |
Appl.
No.: |
05/190,881 |
Filed: |
October 20, 1971 |
Current U.S.
Class: |
73/152.45;
33/700 |
Current CPC
Class: |
G01P
3/484 (20130101); G01P 3/489 (20130101); G01P
3/50 (20130101); E21B 45/00 (20130101); G01P
1/122 (20130101); G01P 3/481 (20130101) |
Current International
Class: |
G01P
3/481 (20060101); G01P 1/12 (20060101); G01P
3/50 (20060101); G01P 3/489 (20060101); G01P
3/484 (20060101); G01P 3/42 (20060101); E21B
45/00 (20060101); G01P 1/00 (20060101); E21b
045/00 () |
Field of
Search: |
;73/151.5 ;33/125B
;340/345 ;250/231SE |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Myracle; Jerry W.
Claims
What is claimed is:
1. A method of determining the magnitude of the linear movement
into the earth of a selected element, such as a drill bit, on a
drill string which is supported by means vertically movable within
a derrick, wherein transient, random linear movement of the drill
string does not produce substantial error in the determination,
including the steps of:
transducing the linear movement of the drill string into rotary
motion;
transducing such rotary motion into a set of electrical signals
which cumulatively present binary coded words indicative of the
direction and angular displacement of the rotary motion,
the binary coded words being presented in a selected and repetitive
sequence so long as the rotary motion is caused by the downward
movement of the drill string;
monitoring continuously the binary coded words being presented;
producing a count of the binary coded words so long as such binary
coded words are presented in the repetitive, selected sequence and
not producing a count of the binary coded words when they are not
presented in the repetitive, selected sequence; and
once the binary coded words have ceased to be presented in the
repetitive, selected sequence, not producing a count of the binary
coded words, even when they are again presented in the repetitive,
selected sequence, until the last binary coded word previously
counted has again been presented.
2. A method of determining the magnitude of the linear movement of
an element, such as a drill bit, on a drill string which is
supported by means vertically movable within a derrick, wherein the
transient, random linear movement of the drill string does not
produce substantial error in the determination, according to claim
1, wherein the step of transducing the rotary motion into a set of
electrical signals cumulatively presenting binary coded words,
includes the steps of:
revolving about an axis a light-interrupting member having
light-transmitting portions therein;
illuminating one side of the light-interrupting member in a
selected pattern; and
sensing on the other side of the light-interrupting member in the
selected pattern the illumination which penetrates through the
light-transmitting portions of the light-interrupting member as
such member revolves.
3. A method for determining the rate of penetration into the earth
of a selected element, such as a drill bit, on a drill string
supported by means vertically movable within a derrick, wherein
transient, random linear movement of the drill string does not
produce substantial error in the determination, including the steps
of:
transducing the linear movement of the drill string into rotary
motion;
transducing such rotary motion into a set of electrical signals
which cumulatively present binary coded words indicative of the
direction and angular displacement of the rotary motion, the binary
coded words being presented in a selected and repetitive sequence
so long as the rotary motion is caused by the downward movement of
the drill string;
monitoring the binary coded words being presented;
producing a count of the binary coded words so long as such binary
coded words are presented in the repetitive, selected sequence and
not producing a count of the binary coded words when they are not
presented in the repetitive, selected sequence;
once the binary coded words have ceased to be presented in the
repetitive, selected sequence, not producing a count of the binary
coded words, even when they are again presented in the repetitive,
selected sequence, until the last binary coded word previously
counted has again been presented;
determining the binary coded words counted in a selected interval
of time; and
comparing the number of binary coded words counted in the selected
interval of time with the selected interval of time to determine
the rate of penetration of the element with respect to time.
4. A method for determining the rate of penetration into the earth
of a selected element, such as a drill bit, on a drill string which
is supported by means vertically movable within a derrick, wherein
transient, random linear movement of the drill string does not
produce substantial error in the determination, including the steps
of:
transducing the linear movement of the drill string into rotary
motion;
transducing such rotary motion into a set of electrical signals
which cumulatively present binary coded words indicative of the
direction and angular displacement of the rotary motion, the binary
coded words being presented in a selected and repetitive sequence
so long as the rotary motion is caused by the downward movement of
the drill string;
monitoring the binary coded words being presented;
producing a count of the binary coded words so long as such binary
coded words are presented in the repetitive, selected sequence and
not producing a count of the binary coded words when they are not
presented in the repetitive, selected sequence;
once the binary coded words have ceased to be presented in the
repetitive, selected sequence, not producing a count of the binary
coded words, even when they are again presented in the repetitive,
selected sequence, until the last binary coded word previously
counted has again been presented;
determining from the counted binary coded words when the element
has moved downward a selected distance;
determining the interval of time required for the drill string to
move such selected distance downward; and
comparing the selected downward distance moved by the element with
the time interval required for such movement to determine the rate
of penetration of the element with respect to time during its
downward movement through the selected distance.
5. In a system for inserting an element, such as a drill string or
the like, into an elongated receiving means, such as a hole being
drilled in the earth, the system including an apparatus for
grasping the element and moving it linearly into the receiving
means, a subsystem for determining the linear movement of the
element into the receiving means such that transient, random linear
movement of the element does not introduce substantial error into
the determination, wherein the improvement comprises:
means for translating the linear movement of the portion of the
system grasping the element into rotary motion; and
means for translating the direction and angular displacement of the
rotary motion into a set of electrical signals cumulatively
presenting binary coded words, the binary coded words being in a
selected and repetitive sequence of at least three different binary
coded words so long as the rotary motion is in a selected
direction;
means for monitoring the binary coded words and producing a count
of such binary coded words so long as such binary coded words are
presented in the repetitive, selected sequence and, once the binary
coded words cease to be presented in the repetitive, selected
sequence, not producing a count of the binary coded words, even
when they are again presented in the repetitive, selected sequence,
until the last binary coded word previously counted has again been
presented; and
logic means for determining from the counted binary coded words the
linear movement of the element into the receiving means.
6. In a system for inserting an element, such as a drill string or
the like, into an elongated receiving means, such as a hole being
drilled in the earth, the system including apparatus for grasping
the element and inserting it into the receiving means, a subsystem
for determining the rate of penetration of the element into the
receiving means such that transient random linear movement of the
element does not produce substantial error in the determination,
wherein the improvement comprises:
means for translating the linear movement of the portion of the
system grasping the element into rotary motion;
means for translating the direction and angular displacement of the
rotary motion into a set of electrical signals cumulatively
presenting binary coded words, the binary coded words being in a
selected and repetitive sequence of at least three different binary
coded words so long as the rotary motion is in a selected
direction;
means for monitoring the binary coded words and producing a count
of such binary coded words so long as such binary coded words are
presented in the repetitive, selected sequence, and, once the
binary coded words cease to be presented in the repetitive,
selected sequence, not producing a count of the binary coded words,
even when they are again presented in the repetitive, selected
sequence, until the last binary coded word previously counted has
been presented;
means for determining the number of binary coded words counted in a
selected interval of time; and
means for comparing the number of binary coded words counted in the
selected interval of time with the selected interval of time to
determine the rate of penetration of the element with respect to
time.
7. In a system for inserting an element, such as a drill string or
the like, into an elongated receiving means, such as a hole being
drilled in the earth, the system including apparatus for grasping
the element and inserting it into the receiving means, a subsystem
for determining the rate of penetration of the element into the
receiving means such that transient, random linear movement of the
element does not produce substantial error in the determination,
wherein the improvement comprises:
means for translating the linear movement of the portion of the
system grasping the element into rotary motion;
means for translating the direction and angular displacement of the
rotary motion into a set of electrical signals cumulatively
presenting binary coded words, the binary coded words being in a
selected and repetititve sequence of at least three different
binary coded words so long as the rotary motion is in a selected
direction;
means for monitoring the binary coded words and producing a count
of such binary coded words so long as such binary coded words are
presented in the repetitive, selected sequence and, once the binary
coded words cease to be presented in the repetitive, selected
sequence, not producing a count of the binary coded words, even
when they are again presented in the repetitive, selected sequence,
until the last binary coded word previously counted has again been
presented;
means for determining from the counted binary coded words when the
element has moved a selected distance in the receiving means;
means for determining the interval of time required for the element
to move through such selected distance; and
means for comparing the selected distance moved by the element with
the interval of time required for such movement to determine the
rate of penetration with respect to time during its movement
through such distance.
8. An apparatus for determining the rate of penetration into a well
hole or the like of an element, such as a drill bit, on a drill
string which is attached to a support means movable longitudinally
within a derrick, comprising:
a member associated with the derrick and mounted for rotation about
an axis;
means associated with the drill string or with the support means
for causing the member to rotate responsive to the linear movement
of the drill string, the direction of the rotation of the member
being responsive to the direction of the linear movement of the
drill string;
means associated with the rotating member for transducing the
direction and angular displacement of the member into a set of
electrical signals presenting binary coded words indicative
thereof, the binary coded words being presented in a selected and
repetitive sequence of at least three different binary coded words
so long as the rotary motion is responsive to downward movement of
the drill string;
means for monitoring the binary coded words and producing a count
of such binary coded words so long as such binary coded words are
presented in the repetitive, selected sequence and, once the binary
coded words cease to be presented in the repetitive, selected
sequence, not producing a count of the binary coded words, even
when they are again presented in the repetitive, selected sequence,
until the last binary coded word previously counted has again been
presented;
means for determining from the counted binary coded words when the
element has moved a selected distance in the receiving means,
means for determining the interval of time required for the element
to move through such selected distance; and
means for comparing the selected distance moved by the element with
the interval of time required for such movement to determine the
rate of penetration with respect to time during its movement
through such distance.
9. An apparatus according to claim 8 wherein:
the rotating member is opaque and has light-transmitting portions
therein at selected locations;
the means associated with the rotating member for transducing the
direction and angular rotation of the member into a set of
electrical signals providing binary coded words indicative thereof
includes:
means mounted on the one side of the rotating member for
illuminating such side of the member in a selected pattern, and
means mounted on the other side of the rotating member for sensing
in the selected pattern the illumination from the light means which
penetrates through the light-transmitting portions of the opaque
rotating member as such member revolves and for generating a set of
electrical signals responsive to the presence or absence of such
illumination.
Description
This invention relates to methods and systems for the
uni-directional measurement, display and recording, in a physical
operation, of the time rate of movement of a first element relative
to a second element in contact therewith, where a first of said
elements is progressively diminished at the contact interface by
penetration, erosion, drilling or other form of consumption by the
second of said elements.
More particularly, the present invention has general application in
industrial process work, and has a specific application in boring
bit penetration in a well drilling operation, which specific
application will hereinafter in this specification be described in
detail, it being understood that such illustrates merely by way of
example, a preferred form of the methods and systems for the
practise of the invention.
In the field of sub-surface petroleum exploration, a bore-hole may
be drilled into the earth by means of a mechanical drilling rig
that supports, and causes to rotate, a drilling stem having a
boring bit affixed to its lower end. As the bore-hole is drilled
deeper into the earth, the drill stem may be lengthened by the
addition of sections at the surface.
A typical rotary drilling rig includes a floor mounted disc having
a square hole at its centre. While drilling is in progress, this
disc is caused to rotate by the rig's main source of mechanical
power. The square hole in the disc loosely accommodates a steel
shaft colloquially known as a "kelly". The kelly, free to move
through the hole in the disc, and being of square cross section,
rotates with the disc.
The lower end of the kelly is connected to the circular cross
section drill stem, while its upper end is connected to a swivel
joint in the moveable bottom block of a block and tackle system.
The top block of the system is affixed to the rig superstructure
(the "crown" of the derrick). A steel cable, run-from a drum driven
by the rig's main source of mechanical power, is threaded through
the sheaves of the upper and lower blocks. The net effect is to
provide a means of raising and lowering the rotating drill
stem.
During the drilling operation, a fluid - colloquially known as
"mud" - is forced down the hollow drill stem, through the bit, and
back to the surface through the annulus between the stem and the
walls of the borehole. The purpose of the drilling fluid is to
carry the bit cuttings to the surface and to provide lubrication
and cooling of the bit.
The main factors that contribute to the efficiency of the drilling
operation are; the physical condition of the bit, the rate of bit
rotation, the weight placed upon the bit, the viscosity of the
drilling fluid, and the rate at which this fluid is circulated. Of
these, the only factor that cannot be determined directly, at the
surface, is the physical condition of the bit. One common drilling
method is to use a constant weight and rate of rotation, then
monitor the rate at which the borehole progresses. A decreasing
penetration rate may indicate deterioration of the bit, but the
stratified nature of the sub-surface may confuse the issue. For
example, if the bit progresses from one geological formation to
another, wherein the transition is to a more difficult material, it
may appear to the driller that the bit has deteriorated to the
point at which it must be replaced. Replacing the bit is an
expensive, time consuming operation because the entire drill stem
must be raised, with sections being stacked as they are pulled from
the earth, until the bit reaches the surface.
In an attempt to minimize this problem, "logs" describing the
sub-surface geology of adjacent completed wells are often
consulted. If the changes in earth structure can be predicted with
reasonable accuracy, the changes in penetration rate may be
justified, and a bit may not be changed until it is, in fact,
unserviceable.
Further, the influence of one variable upon another contributes to
the art of well drilling in that, for example, increasing the
weight on the bit and/or its rate of rotation may or may not
increase the rate of bit penetration.
From the foregoing, it is apparent that the rate at which the
borehole progresses is an extremely important parameter in the
drilling process.
In the present state of the art, drilling rate is measured as a
function of time (ie: the time it takes to drill, say, 1 foot).
These measurements are subsequently processed mentally,
mechanically or electronically, to establish the rate of
penetration in engineering units of velocity. From the standpoint
of the driller, a presentation of the time required to drill one
foot can be confusing in a dynamic operation. Further, to permit a
sub-surface Geologist to correlate the rate of penetration with
logs from adjacent wells, time consuming interpretation of time
based information is required. This is because the logs are not
functions of time but functions of depth of penetration.
It is an object of this invention to provide new and improved
methods of measuring, displaying and recording the time rate of
boring bit penetration in engineering units of velocity, wherein
the recording presents time rate of penetration versus depth of
penetration - rather than versus time.
It is another object of this invention to provide a means whereby
drilling rate information may be electronically telemetered to a
distant location, such information being in a Binary Coded Decimal
format.
In accordance with one feature of this invention, the average time
rate of bit penetration, over each sequential thirty second time
interval, is presented to drilling personnel in the form of an
illuminated digital in-line read-out in feet per hour (or other
velocity units such as meters/hour, inches/second, cm/second,
etc.).
In accordance with another feature of this invention, an analog
record is produced wherein the abscissa is depth of penetration in
feet, and the ordinate is rate of penetration in feet per hour (or
other velocity units if required).
In accordance with another feature of this invention, no moving
cable link is required between the moving block or swivel joint and
the facilities on the floor of the drilling rig.
In accordance with another feature of this invention, the measuring
system automatically shuts down when the stem is raised, so that
the return trip to the bottom of the hole is not presented as
indicative of drilling rate. This feature also applies to the up
and down motion of the stem supporting mechanism attendant upon the
addition of lengths of drill stem.
In accordance with another feature of this invention, mechanical
vibration and/or random vertical motion of the drill stem will not
be accepted as valid "rate of penetration" data. This also applies
to the drill stem supporting mechanism in cases where the two are
disconnected.
In accordance with another feature of this invention, drilling rate
data are made available in both parallel and serial digital forms
for subsequent processing and/or telemetering.
In accordance with another feature of this invention, extremely
small increments (EG: tenths of an inch) of depth of penetration
can be determined over fixed time intervals.
In accordance with another feature of this invention, the
electronics circuitry is exclusively solid state to provide the
rugged, dependable operation required in the drilling rig
environment.
In accordance with another feature of this invention, the system is
self-calibrating in that, on start up, the position of its input
transducer is of no significance.
AN OVERVIEW OF THE METHOD AND A TYPICAL SYSTEM
The system comprises a remote system input "head," an electronics
"main frame," a remote electronics digital read-out unit, and a
remote analog strip chart recorder having depth of penetration on
its abscissa and time rate of penetration on its ordinate.
The remote input head comprises a rotatable wheel and electronics
circuitry that, by means of an optically coupled shaft position
encoder, is capable of transmitting Binary Coded Decimal
information down the derrick to the electronics main frame located
in the driller's cabin (colloquially known as the "dog-house"). The
input head is installed, by means of a springloaded bracket, such
that its rotatable wheel is placed in intimate contact with either
the draw works cable as it passes over one of the upper block
sheaves, or with a sheave itself. Which of the cable/sheave
contacts is used will dictate the circumference of the rotatable
wheel. For example, the cable over the slow sheave moves at twice
the drilling rate. Assuming that the present system's driving wheel
is caused to rotate by the cable over the slow sheave or by the
slow sheave itself, to present the contained shaft position encoder
with a 1 foot of penetration per revolution input, the driving
wheel must be 2 feet in circumference.
Parallel BCD data are transmitted via a multi pair cable down the
derrick to the instrument main frame. This main frame contains
power supplies and solid state electronics logic circuitry. Power
is supplied to all sub-system assemblies by the main frame, and its
logic circuitry processes data representative of amount of
penetration into data representative of time rate of
penetration.
Two read-out units are provided. One of these is an illuminated
digital in-line read-out and the other is an analog strip chart
display. The digital read-out unit may be placed at a reasonable
distance from the main frame in a location convenient to the
driller, and it presents the actual drilling rate in, say, feet per
hour, updated every (for example) 30 seconds. The analog strip
chart recorder has a chart paper drive mechanism that incrementally
steps the chart in response to depth of penetration, while its pen
traces the rate of penetration in velocity units. By means of a
switch on the main frame, the user may select any of a number of
full-scale deflections applicable to the strip chart record. For
example, if drilling is slow, he may choose a full-scale recorder
deflection of 25 or 50 feet per hour; if drilling is relatively
fast, he may select a full-scale deflection of 200 feet per hour.
Another switch on the system main frame permits the user to select
an "integrating" time constant for the strip chart recorder that
effectively "smoothes out" the analog record. If he wants maximum
detail in the analog record, he selects the lowest integrating
switch position. If he prefers to sacrifice detail for over-all
clarity with respect to correlation of logs from adjacent wells, he
selects a higher integrating time constant that removes the peaks
of the record and averages the readings. Still another switch on
the main frame permits the user to select any of a number of
abscissa weightings for the strip chart record. He can select, for
example, any of 5, 10, 20, 40, or 80 inches of chart paper per 100
feet of penetration.
The digital display unit, in presenting drilling rate in feet per
hour updated every 30 seconds, is telling the driller how many
tenths of an inch he drilled during the immediately preceding 30
second time interval. An optional printer/totalizer may be
connected to the digital read-out unit that will provide a
print-out and new total every 30 seconds. For example, sequential
readings of 31, 36, 27 and 24 feet per hour (total 118) means that
11.8 inches of drilling was accomplished during this particular 2
minute time interval.
An important feature of the present invention is its immunity to
erroneous drilling information caused by mechanical vibrations and
the occasional raising of the lower block (EG: to add lengths of
drill stem). If the driller raises the kelly for any reason, the
present system automatically shuts down and illuminates a red lamp
on the digital read-out unit. When the driller resumes drilling, he
presses a RESET button on the digital read-out unit, and the system
re-commences operation. Without this feature, the system would
interpret mechanical vibratory motion, and the lowering of a new
section of drill stem, as indicative of downward motion of the bit.
Incidentally, a green lamp on the digital read-out unit informs the
driller that the system is operational.
Another important feature of the present invention lies in its
automatic self-calibrating capability. On start-up, the angular
position of the rotatable wheel, and its affixed transducer, is of
no consequence to the system.
An optional feature in the present invention is electronics
circuitry that serializes and identifies drilling rate data for
presentation to a digital telemetry link. This provides the user
with a means of transmitting accumulated data over telephone lines
and/or wireless links.
DETAILED SYSTEM DESCRIPTION
For a better understanding of the present invention, together with
other and further objects and features thereof, reference is made
to the following description taken in conjunction with the drawings
in which:
FIG. 1 illustrates the various assemblies comprising the present
invention,
FIG. 2 illustrates the components comprising the READ-HEAD,
FIG. 3 is a block diagram illustrating one arrangement of circuitry
in the present invention,
FIG. 4 illustrates the logic diagrams of COUNTER number 1 and the
COMPARATOR,
FIG. 5 illustrates the COUNTER PRE-SET and AUTOMATIC SHUT-DOWN
logic,
FIG. 6 illustrates the RESET PUSH-BUTTON and RED LAMP circuits,
FIG. 7 illustrates, in block form, the COUNTER INCREMENTER
circuit,
FIG. 8 illustrates, in block form, the READ -IN COMMAND and COUNTER
CLEAR circuit,
FIG. 9 illustrates, in block form, the analog recorder PAPER
ADVANCE circuit.
Referring to FIG. 1: In a typical drilling rig arrangement, the
cable (1) from the draw-works is threaded through a number of
sheaves in a pair of blocks, the lower of which supports a swivel
joint, a kelly, and the drill stem. The movement of the cable over
the "slow" sheave (2) occurs at twice the rate of actual bit
penetration.
The present invention provides a READ-HEAD (3) whose input drum is
intended to make physical contact with the existing cable over the
slow sheave, or with the slow sheave itself, and hence rotate in
sympathy with an axial movement of this cable.
A multi pair electrical cable (4) is affixed at its upper end to
the Read-Head by means of an adequate male/female electrical
connector, and at its lower end, via a similar electrical
connecting means, to the system MAIN FRAME (5), usually located in
a convenient place in the rig's operating area. The electrical
cable is run from the read-head (at the derrick crown) down a leg
of the derrick (affixed thereto by means of spaced cable clamps) to
the main frame.
The main frame contains the means whereby the data provided by the
read-head are electronically processed for subsequent presentation
to the DIGITAL READ-OUT UNIT (6) and the ANALOG STRIP CHART
RECORDER (7). The main frame also contains panel switches to permit
the user to select integrating time constants, abscissa weightings,
and full-scale deflection factors for the analog strip chart
recorder.
Referring to FIG. 2: The READ-HEAD comprises a cylindrical housing
(8) in which there is axially mounted a rotatable assembly
consisting of a reading drum (9) intended to make contact with the
draw-works cable over the slow sheave or the slow sheave itself,
said drum being rigidly affixed to a shaft (10), which is supported
at the ends of the housing by means of bearings (11). Rigidly
affixed to the said shaft is an optical shaft position encoder (12)
having two Binary Coded Decimal sequences, each representing
decimal 1 to 60. The shaft position encoder is shown in more detail
in FIG. 2(B). Rigidly affixed to the said housing is a group of six
Gallium Arsenide light emitting diodes (or incandescent lamps)
(13), arranged so that each is aligned with one of the six binary
levels contained in the shaft position encoder. On the other side
of said shaft position encoder, there is a "stack" of six light
sensitive photo transistors (14), each aligned with its
corresponding light source through the applicable levels of the BCD
shaft position encoder. Each of the said photo transistors is
mounted on a DECODER circuit card (15) that also includes
amplifying and pulse shaping electronics circuitry. One circuit to
accomplish the desired decoding, amplifying and shaping is shown in
FIG. 2(C). Here, the photo transistor (16), under the influence of
random light or light directed by the shaft position encoder
(.lambda.) produces an output detectable by the differential
amplifier (17), that is biased to reject "noise" caused by random
light, and amplify "signals" caused by light directed by clear
spaces in the shaft position encoder. Signals are squared by the
Schmitt trigger circuit (18), amplified by the buffer amplifier
(19), and presented as an output U (in the case of the photo
transistor/electronics card in the least significant bit position
of the shaft position encoder). The output signal U is also
inverted by means of a unity gain logic inverter (20) to present a
second output U. With six identical cards, the pairs of data
outputs U,U; V,V; W,W; X,X; Y,Y; and Z,Z are available to indicate
the presence and absence of signals seen in each data word by the
particular alignment of the shaft position encoder.
The overall effect of the read-head assembly, then, is to detect
axial motion of the rig's draw works cable, and, by means of an
optically coupled shaft position encoder, present adequately shaped
and amplified digital data words to the system main frame.
Incidentally, the cable used to transmit the data words to the main
frame also carries the power to the read-head.
It should be noted that the circuit shown in FIG. 2(C) is but one
approach to he data reporting technique. An alternative circuit can
be used in which the differential amplifier and the Schmitt trigger
are replaced by a single operational amplifier.
Referring to FIG. 3: When the system is energized, pulses from the
clock (17) are fed to COUNTER number 1 (18) via the COUNTER PRE-SET
AND AUTOMATIC SHUT-DOWN (19) and COUNTER INCREMENTER (20) circuits.
Meanwhile, the random angular position of the binary coded shaft
position encoder presents an arbitrary data word to the photo
transistor decoders (14 & 15 FIG. 2), which is then transmitted
to the COMPARATOR (21) in parallel digital format. As COUNTER
number 1 accepts and counts clock pulses, sooner or later the
contents of this counter will coincide with the input data word,
and the coincidence is detected by the COMPARATOR. The resulting
output from the comparator disables the clock feed to counter
number 1, and illuminates the green lamp on the REMOTE DIGITAL
READ-OUT UNIT (22) to signify that the system is "synchronized" in
preparation for drilling rate input data. This primary coincidence
also feed a pulse to counter number 1 that increases the contents
of this counter by 1. At this point, counter number 1 contains a
number one larger than the current data word from the photo
transistors. If the shaft position encoder is now rotated clockwise
(the direction indicative of bit penetration), the next data word
seen by the comparator will coincide with the data word held in
counter number 1, causing another output pulse to be generated by
the comparator. This output pulse updates counter number 1 by 1,
and also enters COUNTER number 2 (23) as a valid count. This
sequence of events is repeated for each data word/counter number 1
coincidence. Counter number 1 is compatible with the input data
words, since it is designed to count from 1 to 60 inclusive, then
re-set to 1 and repeat its counting cycle.
If the shaft position encoder rotates counter-clockwise, due to
vibration and/or an upward motion of the stem supporting mechanism,
the next word presented to the comparator by the photo transistors
will be two less than that stored in counter number 1; no
coincidence will exist, no pulse will be fed to counter number 2,
and no increase in counter number 1 occurs. If the reverse rotation
continues beyond the design limit for vibratory motion (EG: if the
drilling block is raised to add a length of drill stem), the system
will recognize, as will be shown later, that following 59, the
counting sequence reaches 31 before it reaches 30, and shut-down
occurs. The shut-down event extinguishes the green lamp on the
digital read-out panel, and energizes the adjacent red lamp,
informing the operator that he must press the re-set button to
obtain further readings. The start-up procedure described above is
activated by the re-set button.
Because of the arbitrary angular position of the shaft position
encoder when an excessive reverse motion occurs, and recognizing
that there are two "1 to 60" counting sequences per foot of cable
movement, and since the reading must pass 59 before shut-down
occurs on 31, it follows that the design limit for reverse travel
is not less than 3 inches and not more than 6 inches.
In accordance with the earlier description of properly sequenced
"forward" readings, counter number 2 accumulates a count of the
number of times coincidence occurs in the comparator. The contents
of counter number 2, over fixed time intervals, is a measure of the
rate of clockwise shaft position encoder rotation, and hence
represents the velocity of boring bit penetration during the well
drilling operation.
To preserve the continuity of readings, the system includes
"transfer and store" circuitry in association with counter number
2. Here, at the end of each 30 second time interval, parallel (or
"jam") transfer is effected from counter number 2 to a BUFFER
REGISTER (24) consisting of electronic latching switches. This
frees the counter to accumulate the next reading while the current
reading is presented as a digital read-out that persists for 30
seconds. At the end of this 30 second time interval, the new
counter number 2 reading is transferred to the buffer register -
displacing the previous reading, the digital read-out is
momentarily extinguished - then presented with the new contents of
the buffer register. Counter number 2 is then cleared and
immediately begins counting coincidences in the next 30 second time
interval. This provides continuous readings, updated every 30
seconds, of the drilling velocity in feet per hour.
Counter number 2 consists of 12 Flip Flops connected to provide a
three decade counter. Each decade contains four flip flops and
standard "count of ten" feedback circuitry. The contents of this
counter, then, is recognizeable as "hundreds," "tens," and "units,"
available in simultaneous or "parallel" output.
The 30 second time intervals are derived from the built in clock.
This clock is an oscillator designed to produce 8.54 pulses per
second. These pulses are fed to the DIVIDE BY 256 COUNTER (25),
which consists of eight series connected flip flops. When this
counter resets to zero (when 256 pulses have been received from the
clock), an output pulse is generated by the flip flop in the "Most
Significant Bit" position. With 8.54 pulses per second divided by
256, the output from this counter is 1 pulse per 30 seconds. Every
30 seconds, then, a rectangular pulse is fed to the READ-IN COMMAND
AND COUNTER CLEAR circuit (26). In this circuit, the leading edge
of the pulse is differentiated, amplified and then used to transfer
the contents of counter number 2 to the buffer register. The
trailing edge of the pulse is also differentiated and amplified to
provide a pulse that clears counter number 2. This means that every
30 seconds the contents of counter number 2 are jam transferred to
the buffer register for holding and simultaneous digital read-out,
and the counter is cleared in preparation for the next count.
Each comparator sequential coincidence represents 1/120 shaft
encoder revolution. Since one revolution of the shaft encoder
represents 1 foot of bit penetration (consistent with the diameter
of the driving wheel), and remembering that there are 120-30 second
time intervals per hour, it follows that the number of coincidences
detected in each 30 second time interval is a measure of the rate
of bit penetration in feet per hour, and also a measure of the
number of tenths of an inch drilled in the 30 second interval. The
contents of counter number 2, then, requires no mathematical
treatment prior to read- out.
The DIGITAL TO ANALOG CONVERTER (27) accepts 12 inputs from the
buffer register and presents a single analog voltage representative
of the drilling rate in feet per hour. This is accomplished through
the use of standard electronics circuitry (12 buffer amplifiers,
twelve electronic switches, 12 precision resistors in a BCD ladder,
and a single operational amplifier). The output from the digital to
analog converter is presented to the RECORDER PEN DRIVE circuit
(28) through an INTEGRATOR (29) and a FULL SCALE DEFLECTION
SELECTOR (30).
The analog recorder, as previously mentioned, accommodates depth of
penetration on the abscissa and time rate of penetration on the
ordinate. The integrating circuit provides a means of selecting the
ordinate time constant such that the rate of penetration readings
can be averaged, over selectable time intervals, prior to
presentation to the recorder pen-drive mechanism. The scale
selecting circuit provides a number of choices in the value of
drilling rate information representative of full-scale deflection
of the recorder pen.
The chart paper abscissa advancing mechanism (31), in the analog
recorder, is a relay/escapement device responsive to depth of
penetration pulses obtained from counter number 1. In effect, as
the depth of the borehole progresses, the strip chart papaer is
incrementally advanced while its pen traces the rate of bit
penetration on the ordinate.
A BCD SERIALIZER (32) is available as an optional feature. This
circuit consists of a 12 bit shift register into which the contents
of the buffer register are periodically dumped. Separately derived
clock pulses then shift the contents of the register, sequentially,
into a MODEM system with control and identification bits being
added as required.
There follows a more detailed description of selected electronics
circuitry comprising the system.
Referring to FIG. 4: The (A) sketch is a simplified block diagram
of counter number 1. Here it is seen that this counter contains six
series connected flip flop circuits labelled A to F inclusive.
Standard feed-back circuitry (not shown) provides a counting scale
from decimal 1 to decimal 60, such that the 61st input pulse clears
the counter and sets the A flip flop to its 1 state. The net
operation, then, provides a 1 to 60 counter that continually
repeats this cycle as pulses are received at its input. Each flip
flop in counter number 1 has two outputs (labelled A,A; B,B; etc.)
to give a positive indication of whether the flip flop is in its 0
or 1 state. The A flip flop represents the least significant bit in
the counting sequence.
Again in FIG. 4, the (B) sketch shows the logic arrangement of the
comparator. This circuit consists of 12 2-input positive NAND
gates, six 2-input negative NOR gates, and one 6-input positive
NAND gate. A to F inputs are provided by counter number 1, while
the photo transistor decode units (FIG. 2(C)) provide inputs U to
Z. The function of the logic is to produce an output if, and only
if, the six bit word from the photo transistors is identical to the
six bit word held in counter number 1. If, for example, the two
words differ only in their least significant digits, there will
exist AU and AU at the inputs to the LSD NAND gates, and neither of
these gates will be enabled. The NOR function will not be
satisfied, so no input appears at the applicable six input NAND
gate position, and no comparator output is generated.
Referring to FIG. 5: On start-up, the operator presses the RESET
button on the remote digital read-out unit, and clock pulses will
appear in the output of this circuit. This is because Reset/Set
Flip/Flop number 1 enables NAND gate number 1, and R/S F/F number 2
is "high" (switched by the push-button), enabling NAND number 2.
Counter number 1, then, receives and counts pulses (through a
COUNTER INCREMENTER circuit) for as long as NAND number 1 is
enabled and R/S F/F number 2 is in the high condition. When counter
number 1 reaches coincidence with the random number seen by the
photo transistors, an output is generated by the comparator in the
form of a negative going pulse. This pulse enters the BUFFER
AMPLIFIER & INTEGRATOR, which feeds LOGIC INVERTER number 1
with a trapezoidal positive going pulse. The output of logic
inverter number 1 is a somewhat lengthened version of the
comparator output pulse, and has a slight time overlap. This pulse
switches R/S F/F number 1, disabling NAND number 1, and clock
pulses are blocked from the output. Logic inverter number 1 also
feeds a MONOSTABLE MULTIVIBRATOR that stretches and inverts the
pulse. The SHAPER is a trailing edge differentiator that produces a
short negative going pulse that is significantly delayed with
respect to the output of the comparator. An output is produced,
then, whenever a coincidence is detected by the comparator,
providing R/S F/F number 2 is in the high condition. The clock feed
through NAND number 1 is disabled for as long as R/S F/F number 1's
output is low.
In the AUTO SHUT-DOWN portion of the circuit, R/S F/F number 2 will
be switched to the low condition if, after enabling of the DETECT
SHAFT ENCODER number 59 NAND gate, DETECT SHAFT ENCODER number 31
is enabled prior to DETECT number 30 COUNTER number 1. This is
because the detection of number 59 on the shaft encoder causes R/S
F/F number 3 to present a high condition to NAND number 3, and if
number 31 on the shaft encoder is detected prior to number 30, both
inputs to NAND number 3 will be high, enabling this gate. This
switches R/S F/F number 2, disabling NAND number 2, blocking the
output. If, on the other hand, DETECT number 30 COUNTER number 1
NAND is enabled prior to the detection of shaft encoder number 31,
NAND number 3 cannot enable due to the low input presented by R/S
F/F number 3, and the R/S F/F number 2 output remains high. This
permits output NAND number 2 to enable whenever a pulse is received
from the comparator. In short, if the shaft encoder presents
readings in the proper sequence, the auto shut-down circuit does
not interfere with the presentation of coincidence pulses to
counter number 2. If reverse direction of shaft encoder rotation
occurs, the auto shut-down circuit permits travel beyond the next
number 59 until it sees number 31 before it sees number 30, and
shut-down results. Actuating the remote reset push-button switches
R/S F/F's number 1 and number 2, such that each will present a high
output, and the start-up cycle is repeated.
Referring to FIG. 6: The push-button circuit switches R/S F/F's
number 1 and number 2 (FIG. 5), enabling clock pulses and output
respectively. This activates the start-up sequence described
earlier. The RED LAMP is energized if either of these two flip
flops are in their "shut-down" state.
The GREEN LAMP circuit (shown in FIG. 5) contains a monostable
multivibrator that is triggered by the comparator output. This in
turn (after amplification) energizes the remote green lamp such
that it "flashes" at a rate consistent with the drilling velocity.
Alternatively, the green lamp may be energized by R/S F/F number
2's high output to NAND number 2.
Referring to FIG. 7: The COUNTER INCREMENTER circuit has two
functions. First, it re-conditions the output from the previous
circuit to improve the shape and timing of the pulses fed to the
counters, and, secondly, it provides a safeguard against noise
during the time that the system is in the "shut-down" state. To
re-shape the signal pulses, a differentiator is followed by a
monostable multivibrator. A positive pulse from the MS MV, plus a
high output from R/S F/F number 2 (FIG. 5) enables the positive
NAND gate, permitting the pulses to reach counters number 1 and
number 2.
Referring to FIG. 8: The output from the "divide by 256" circuit is
amplified and fed simultaneously to two differentiators in the READ
IN COMMAND AND COUNTER CLEAR circuit. The leading edge
differentiator produces a positive going pulse directly from the
input signal, while the trailing edge differentiator includes a PNP
transistor to detect the negatively going trailing edge of the
input signal. After amplification, two negatively going pulses are
produced - one slightly later than the other. The first of these
two pulses subsequently transfers the contents of counter number 2
to the buffer register latches, and the second clears counter
number 2. Considering the output of the divide by 256 circuit, this
sequence of events occurs once every 30 seconds.
Referring to FIG. 9: The ANALOG RECORDER PAPER ADVANCE circuit
accepts a pulse from counter number 1 every time this counter
clears from decimal 60 to decimal 1. Two pulses per foot of
penetration are available from this source. These pulses are used
to advance the strip chart in the analog recorder by actuating a
relay driven escapement. Circuitry is provided that permits the
user to select, by means of a multi position switch on the main
frame, the weighting of the chart abscissa.
The usual strip chart has 10 graticule divisions per inch, so
(remembering that the pulses from counter number 1 occur every six
inches of boring bit penetration) the arrangement shown permits the
selection of any one of 5, 10, 20, 40, or 80 feet of penetration
per inch of strip chart. The output is such that one pulse moves
the strip chart one graticule division - with due regard for
inertia and coasting of the chart drive mechanism. To accommodate
other abscissa weightings, the monostable multivibrator period is
adjustable through the use of a potentiometer in the RC relaxation
circuit. Further, the flip-flop string may be increased to
accommodate requirements for more compressed abscissa weightings.
In short, the system can be supplied with the specific abscissa
weighting scales required in the user's application, or he may
select various scales by means of a multi position switch. An
amplifier, in the output circuit, provides an adequate electrical
signal to actuate the paper advancing relay.
The remainder of the system circuitry (the Digital to Analog
Converter, the integrator, the full-scale deflection selector, the
remote digital read-out, the printer, the BCD serializer, the
buffer register, the clock, the analog recorder pen drive
mechanism, and the actual counting/dividing circuits) requires no
further elaboration because they are well known sub-system
components in the electronics art. For example, we make no claim to
the Eccles Jordan FLIP FLOP circuit that is readily available on
the electronics market. To discuss this circuit in detail would not
contribute significantly to the system description, because one
versed in the art of electronics logic circuitry would recognize
that the flip flop circuit, in its many configurations, is one of
the basic tools of the logic designer. The same holds true for such
devices as NAND and NOR gates, electronic latches in a buffer
register, oscillators, and so on.
While there has been described what at present is considered to be
a preferred embodiment of this invention, it will be obvious to
those skilled in the art that various changes and modifications may
be made therein without departing from the inventive concept
disclosed. It is therefore desired that only such limitations be
imposed on the appended claims as are stated therein.
* * * * *