EP0129953A2 - Verfahren und Anordnung zur Digitalisierung der Höchstamplitude und der Ankunftszeit eines akustischen Signals - Google Patents

Verfahren und Anordnung zur Digitalisierung der Höchstamplitude und der Ankunftszeit eines akustischen Signals Download PDF

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Publication number
EP0129953A2
EP0129953A2 EP84302033A EP84302033A EP0129953A2 EP 0129953 A2 EP0129953 A2 EP 0129953A2 EP 84302033 A EP84302033 A EP 84302033A EP 84302033 A EP84302033 A EP 84302033A EP 0129953 A2 EP0129953 A2 EP 0129953A2
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EP
European Patent Office
Prior art keywords
time
signal
sample value
value
analog
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Application number
EP84302033A
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English (en)
French (fr)
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EP0129953A3 (de
Inventor
Billy Gene Ballard
Charles Louis Dennis
Donald Michael Williams
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ExxonMobil Oil Corp
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Mobil Oil Corp
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Publication date
Application filed by Mobil Oil Corp filed Critical Mobil Oil Corp
Publication of EP0129953A2 publication Critical patent/EP0129953A2/de
Publication of EP0129953A3 publication Critical patent/EP0129953A3/de
Withdrawn legal-status Critical Current

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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/12—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling
    • E21B47/14—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling using acoustic waves

Definitions

  • the present invention relates to a method and apparatus for digitizing the maximum amplitude and time occurrence of an acoustic signal and, more particularly, of an acoustic signal produced in a borehole televiewing apparatus.
  • Borehole televiewing apparatus is commonly used to produce an image representing the physical characteristics of the inside surface of a borehole.
  • a borehole transducer positioned within a borehole tool transmits an acoustic pulse into the borehole in a scanning period.
  • the acoustic pulse is reflected by the borehole wall and received by a receiver/detector in the tool, which, in turn, transmits the envelope of the reflected signal to a recording and/or imaging apparatus located at a surface location.
  • Incremental rotative movement of the transducer about the borehole for each of a plurality of successive scanning periods produces reflection signals which can be used to produce a representative image of the borehole wall structure, which may be recorded and/or displayed on a cathode ray tube.
  • Representative borehole televiewer devices are described and illustrated in U. S. Patent Nos. 3,668,619 and 3,369,626.
  • an analog signal path is provided from the envelope detector in the borehole tool to the surface recording and/or image display devices.
  • Analog signal transmission presents problems in that the attenuation characteristics of the transmission lines limit the dynamic range of, and thus distort, the transmitted signal, making it difficult to obtain high quality raw data at the surface equipment.
  • One way of improving the fidelity of the transmitted signal is to digitize it at the borehole tool and transmit only digital data to the surface equipment.
  • the scanning frequency of the transmitter/receiving apparatus is typically quite high, e.g., 2,000 scanning periods per second, and a high sampling frequency is also required, e.g., 500 sampling pulses per scanning period, to faithfully reproduce a high quality image at the surface.
  • tne invention resides in one aspect in a method for determining the maximum amplitude and its time of occurrence of an analog signal comprising:
  • the invention resides in apparatus for determining the maximum amplitude and its time of occurrence of an analog signal comprising:
  • an acoustic pulse signal P (Fig. 1) is transmitted from a transducer 5 located in a borehole tool 1 (Fig. 4) by means of a pulse generator 3 at a time t 0 , which defines the beginning of a scanning period t 0 ...t 0+1 .
  • the transmitted signal P is reflected by the borehole peripheral surface back to the borehole tool as a reflected acoustic pulse signal R during the scanning period and is detected by transducer 5.
  • An additional echo signal R' generated from reflections beyond the borehole wall also typically occur during the scanning period and it too is detected by transducer 5.
  • Other reduced amplitude miscellaneous reflection signals and noise components R" may also be present in the signal received and detected by transducer 5.
  • the maximum amplitude and time of occurrence data are sequentially transmitted to surface equipment 10 over conventional well logging transmission lines 9 by means of a multiplexer 6 and data encoder 8, e.g., a manchester data encoder.
  • Apparatus at the surface receives the maximum amplitude and time of occurrence data and reconstructs an analog signal therefrom, which can be used in a conventional borehole televiewer display apparatus to construct an image of.:the borehole interior wall structure.
  • Fig. 2 illustrates in greater detail the digitizing apparatus 7 for digitizing the maximum amplitude and time of occurrence of the reflected acoustic pulse signal R.
  • the reflected acoustic pulse signal R detected by acoustic transducer 5, is applied to the analog input of a high speed sampling analog-to-digital converter 11.
  • a high frequency sampling input signal consisting of typically 100ns pulses, is applied to the sampling input of converter 11, while a window control signal is applied to an enabling input of converter 11 from a programmable decoder 33.
  • the window control signal enables converter 11 and establishes a time window W (from time t 1 to time t 2 in fig. 1), during which the apparatus of Fig.
  • the time window W is established where the reflected signal R is expected to occur.
  • the time of its beginning, as well as its duration, are empirically determined to ensure that it encompasses the reflected acoustic pulse signal R.
  • the window W may be as wide as a scanning period, i.e., t 0 ...t 0+1 , but as a practical matter, it is typically shorter, as shown in Fig. 1.
  • the window control signal is generated automatically a predetermined period of time after an acoustic pulse P is transmitted into the borehole by the borehole tool, i.e., a predetermined period of time after t 0 , for example, by a counter 31 counting a clock frequency f c and feeding the programmable decoder 33 which decodes the output of counter 31 and generates, at the appropriate time, the window control signal.
  • the timing cycle for operation of counter 31 and decoder 33 is the scanning period t 0 ...t 0+1 . Accordingly, counter 31 is reset at the beginning of each scanning period by a signal to generated thereat by the pulse generator 3.
  • the programmable decoder 33 may be, for example, a Harris HM-7616 PROM, or a programmable logic array. Decoder 33 produces the window control signal and other output signals described below at predetermined times, in accordance with program selection inputs thereto and the monitored output of counter 31. To change the timing of the'window control signal and the other output signals, the program selection inputs are changed. For convenience, the program selection inputs to decoder 33 are controlled by the surface equipment 10 which interconnects with decoder 33 by transmission lines 9 (Fig. 4) of a well logging cable.
  • the timing signals generated by decoder 33 include the window control signal, as well as latch control and reset control signals discussed in greater detail below.
  • the digitizing apparatus also includes a digital comparator 15 which continually compares a current amplitude sample value S from converter 11 (the A input to comparator 15) with a previously stored amplitude value S n-x (the 8 input to comparator 15) stored in a latch 17. Wnenever the current sample value S n exceeds the previously stored value S n-x (input A I input 6), the comparator applies an enabling signal to latches 17 and 19 which causes latcn 17 to store the current sample value S n as the stored sample value, which is then used for comparison with subsequent current sample values S occurring during the time window W.
  • latch 17 will, at the end of time window W, contain an amplitude value representative of the peak amplitude of reflected signal R.
  • the time of occurrence of the peak amplitude is determined by counter 21 which counts the output pulses from an oscillator 23.
  • Counter 21 is reset at the beginning of a scanning period by means of the signal t 0 , so that the counter 21 contains a value representing the instantaneous time (or running time) following the time t 0 .
  • the output of counter 21 is applied to latch 19 and, whenever comparator 15 determines that a present amplitude value sample S n is to be stored in latch 17, it causes latch 19 to store the time of occurrence of that sample value in latch 19. Accordingly, at the end of time window W, latch 19 contains time of occurrence information for the maximum amplitude sample value then stored in latch 17.
  • the window control signal from decoder 33 is removed from the enable input to converter 11, which effectively stops operation of the Fig. 2 circuit as no new sample values can be generated.
  • the data stored in latches 17 and 19 is stored for transmission to surface equipment 10 after the end of time window W by a latch control signal applied to latches 25, 27 which respectively receive and store for transmission the contents of latches 17 and 19.
  • the latch control signal is generated by decoder . 33 after the transmission of time window W.
  • Fig. 2 illustrates an apparatus in which a single time window W is employed
  • the illustrated apparatus can also be used with a plurality of time windows W 1 ...W n of, for example, the same duration within a scanning period t 0 ...t 0+1 , as shown in Fig. 3.
  • a different programming of decoder 33 is selected by the programming inputs thereto so that suitable time window control, latch control and reset control signals are generated for each timing window.
  • Counter 21 need not be reset for each time window, but is reset once for each scanning period t 0 ...t 0+1 , at time t 0 , as described earlier.
  • Fig. 5 illustrates the apparatus employed in surface equipment 10 for reconstructing an analog signal having an amplitude and time of occurrence corresponding to the digital amplitude and time of occurrence data produced by the Fig. 2 apparatus.
  • the surface apparatus includes a decoder 41, e.g., a manchester decoder which receives the encoded data from the apparatus and which produces a conventional "valid word" output whenever it recognizes that a valid encoded data word (either amplitude or time of occurrence data) has been received.
  • the "valid word” output of decoder 41 enables a flag detector 43, which examines a flag bit in the decoded word, to determine whether it contains amplitude or time of occurrence information.
  • the flag detector 43 loads the decooed data word into a down counter 45 by enabling the counter 45 if the data word represents time of occurrence data, and loads the data word into a latch 47 by enabling latch 47 if the data word represents amplitude data.
  • down counter 45 When loaded with a new data word, down counter 45 immediately begins deincrementing tne loaoed count value by means of a clocking signal input thereto until a predetermined count value, e.g., zero, is reached, at which time a one-shot multivibrator 49 is enabled.
  • the output of one-shot multivibrator 49 is used to enable a digital-to-analog converter 51, which converts the digital amplitude data stored in latch 47 into an analog signal value on output line 53.
  • the reconstructed analog signal is shown in Fig. 6.
  • the analog signal generated on output line 53 has an amplitude value corresponding to the maximum analog signal amplitude value digitized in the borehole tool, with time of occurrence from a predetermined start time, e.g., t o' corresponding to the time of occurrence of the maximum analog signal amplitude digitized in the borehole tool.
  • a characteristic of the Fig. 5 reconstruction apparatus is that it is not necessary separately to transmit or receive information representing the start time of a scanning period, e.g., t 0 , as this information is implicitly contained in the time of occurrence data.
  • the analog output on line 51 may be used oy a conventional borehole televiewing apparatus to record and reconstruct an image representing the physical characteristics of the inside surface of a borehole.
  • the reconstruction apparatus illustrated in Fig. 5 is intended to operate with one'time window in a scanning period t 0 ...t 0+1 , and cannot easily be adapted for use with a plurality of time windows.
  • An alternative reconstruction apparatus for use with one, two or four time windows during a scanning period is shown in Fig. 10.
  • the Fig. 10 apparatus is used in conjunction with the data transmission format shown in Fig. 8, which will be described first.
  • the signal transmitted from the borehole tool-to-surface receiving equipment 10 for use with the one, two or four window reconstruction of Fig. 10 has the data format illustrated in Fig. 8.
  • Each scanning period t 0 ...t 0+1 of, e.g., 500us is divided into a frame of the same time period, e.g., 500us, containing four equal duration data block D 1 ...D 4 .
  • Each data block contains paired maximum amplitude (A) data and corresponding time of occurrence (T) data.
  • each data block D 1 ...D 4 contains pair amplitude and time values corresponding to respective windows, e.g., A 1 , T l ; A 2 , T 2 ; A 3 , T 3 ; A 41 T 4 .
  • the data frames illustrated in Fig. 8 are formed by the apparatus illustrated in Fig. 9, which is a modification of the Fig. 4 borehole tool apparatus 1.
  • the data frame is formed in a parallel to serial frame register 63.
  • Sequential paired amplitude and time data from encoder 8 are loaded into the various stages of register 63 by way of loading gates 61.
  • the program selection inputs to decoder 33, which select the number-of timing windows in the Fig. 2 digitizing apparatus are used to operate loading gates 61 so that one of the data formats illustrated in Fig. 8a, 8b or 8c is created in frame register 63, corresponding to a surface selection of one, two or four timing windows.
  • the serial output of frame register 63 is applied to transmission lines 9 for transmission to the surface apparatus illustrated in Fig. 10.
  • the Fig. 10 apparatus is designed to receive any one of the selected data formats shown in Figs. 8a, 8b or 8c and reconstruct therefrom, the maximum amplitude and time of occurrence data for each of the time windows used in the system.
  • Incoming encoded data is decoded by decoder 83 and then loaded frame-by-frame serially into a frame receiver register 67.
  • decoder 83 To simplify further discussion, it will oe assumed, for the moment, that four windows have been selected by the programming inputs to decoder 33 and loading gates 61.
  • the parallel outputs of register 67 are applied to a data select circuit 69 having ganged switches 71a and 71b.
  • Switch 71a sequentially connects each of the amplitude values A 1 ...A 4 to an output line 0 1
  • switch 71b sequentially connects each of the timing values T 1 ...T 4 to an output line 0 2 . Consequently, as switches 71a, 71b sequentially move, paired amplitude A and timing T data are applied to output lines 0 1 and 0 2 of data select circuit 69.
  • Switches 71a and 71b move in unison in response to a command signal from sequencer 73, which is generated with a period of to/4, that is, four times in a scanning period t 0 ...t 0+1 . Assuming a scanning period of 500us, the command signals occur every 125 ⁇ s. Thus, during the frame time of 0-500 ⁇ s data is available at the output lines 0 1' 0 2 of selector'69 as follows:
  • the command signals begin when sequencer 73 is informed by the output of frame detector 81 that a frame of data is present in register 67.
  • a comparator 71, time base counter 73, oscillator 85, coincidence gate 75 and digital-to-analog converter 77 are employed.
  • Time oase counter 73 is reset by a signal t 6 at the beginning of a scanning period of the signal reconstruction apparatus. This scanning period is equal in duration to that used in the borehole tool, i.e., t 0 ...t 0+1 , but its initiation need not coincide with that of the scanning period' in the borehole tool.
  • time base counter 73 begins counting the output of oscillator 85.
  • Comparator 71 receives the count value from counter 73 and compares it witn a timing value then present at the 0 2 output line of data select circuit 69. Whenever comparator 71 detects a coincidence between a timing value and the output of counter 73, it supplies an enable signal to gate 75 which allows a maximum digital amplitude value A corresponding to the timing value to pass to digital-to-analog converter 77, where the maximum amplitude value is reconstructed at a proper time with respect to the beginning t 6 of a scanning frame in the reconstruction apparatus.
  • T 4 will be sequentially connected to the data selector 69 outputs by the command signal and the maximum amplitude values A 1 ...A 4 will be reconstructed, in properly timed sequence in a scanning period by the timing values T 1 ...T 4 .
  • the Fig. 10 apparatus can also be used with a one or two window system as well.
  • each of the four data blocks loaded into register 67 will have the same data A 1 , T 1 , as shown in Fig. 8a.
  • comparator 71 will still only provide one output signal when it determines coincidence between T 1 and the output of counter 73, no matter which data block D 1 ...D 4 switch 71 is then examining, so that a maximum amplitude output properly timed with respect to the beginning t 6 of a reconstruction scanning frame is produced by digital-to-analog converter 77.
  • comparator 71 will recognize only two timing values T 1 and T 2 and will appropriately enable gate 75 so that corresponding maximum amplitude values A 1 and A 2 will be applied at the proper time to converter 77 and reconstructed.
  • counter 21 in the digitizing apparatus is reset only at the beginning of a new scanning period, i.e., at t 0 , so that each timing value T in a scanning period t 0 ...t 0+1 has a different value.
  • the Fig. 10 reconstruction apparatus is capaole of use in a system employing one, two or four timing windows during a scanning period t 0 ...t 0+1 . It should be apparent that other reconstruction apparatus could be easily devised for other numbers of timing windows.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Mining & Mineral Resources (AREA)
  • Geology (AREA)
  • Remote Sensing (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • Geophysics (AREA)
  • Acoustics & Sound (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geophysics And Detection Of Objects (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
  • Electrophonic Musical Instruments (AREA)
EP84302033A 1983-06-24 1984-03-27 Verfahren und Anordnung zur Digitalisierung der Höchstamplitude und der Ankunftszeit eines akustischen Signals Withdrawn EP0129953A3 (de)

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US50736983A 1983-06-24 1983-06-24
US507369 1983-06-24

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EP0129953A2 true EP0129953A2 (de) 1985-01-02
EP0129953A3 EP0129953A3 (de) 1986-06-25

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4199729A (en) * 1975-03-20 1980-04-22 Compagnie Industrielle des Telecommunications Cit-Aicatel Variable peak detector
GB2094473A (en) * 1981-03-10 1982-09-15 Standard Oil Co Method and apparatus for logging boreholes
US4382290A (en) * 1977-07-11 1983-05-03 Schlumberger Technology Corporation Apparatus for acoustically investigating a borehole

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4199729A (en) * 1975-03-20 1980-04-22 Compagnie Industrielle des Telecommunications Cit-Aicatel Variable peak detector
US4382290A (en) * 1977-07-11 1983-05-03 Schlumberger Technology Corporation Apparatus for acoustically investigating a borehole
GB2094473A (en) * 1981-03-10 1982-09-15 Standard Oil Co Method and apparatus for logging boreholes

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CA1251866A (en) 1989-03-28
NO841650L (no) 1984-12-27
EP0129953A3 (de) 1986-06-25

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