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.

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.

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.