Patent GB-1490997-A (GB)
Title: Methods and apparatus for recording well logging data
IPC: G01V3/34
Filed: 1974-07-12
Abstract: 1490997 Well-logging data-recording SCHLUMBERGER Ltd 12 July 1974 [12 July 1973] 30897/74 Heading G1G and G1N [Also in Division H4] Well-logging data of two types are recorded by sweeping an energy beam repetitively across an axis of a recording medium in response to synchronizing signals, arranging for the first type of data to modulate at least the beam intensity to produce first indicia on the medium, arranging for the second type of data to modulate both the intensity and location of the beam to produce second indicia, and moving the axis relative to the medium so that the indicia recorded in successive sweeps are representative of the data at different depths in the well. In the Fig. 6 embodiment a depth pulse is generated at 136 each time the logging tool 134 moves through a given depth increment in a borehole. A depth pulse initiates counting at 144 of clockpulses from clock 140. The count is converted at 145 to an analogue staircase-waveform which provides the horizontal (X) sweep drive signal of CRT 149. Processing circuit 163 produces an output signal whose amplitude represents acoustic wave traveltime #t as measured by downhole tool 134. When the X drive signal amplitude equals the #t signal a short bright-up pulse is fed via circuit 159 to the CRT and results in a spot 173 whose X co-ordinate thus indicates #t. After a given number of clockpulses have been counted at 144, decoder 150  switches over circuit 159 to pass signals to the CRT from processing circuit 162 instead of from 163. Decoder 150 also triggers acoustic pulse transmission by generator 152 at this time, and causes connection of counter 144 to switch to a higherrate clock source 142 so that the CRT sweep rate increases. The received acoustic waveform is then fed via circuits 162, 159 to both the brightness and vertical (Y) deflection controls of the CRT to form trace 169. CRT 149 may be a storage tube, or a  photographic recording medium 178 may be used. On completion of an X sweep the CRT beam, or the medium, is incrementally shifted in the Y direction. Sweep completion is detected by decoder 150 which also switches over clocks 140, 142 again and resets circuit 159 at this time. The beam sweep may be synchronized by an oscillator 183 instead of directly by the depth pulses. Resistivity or induction logging data, or recorded rather than "live" data, may be displayed on the CRT. Instead of different data being displayed in co-linear portions 169, 170 of the CRT sweep, these portions may be displaced vertically by beam-switching, Fig. 12, (not shown). The Fig. 14 circuitry is for displaying the magnitude and direction of tilt of a borehole or of earth formations around it. Tilt magnitude and direction are represented, Fig. 28, by the X-co-ordinate and orientation, respectively, of "arrows" 251. The data to be displayed are provided in digital form by downhole tool 206 and processing circuit 209, and vary with depth of the tool. A depth pulse signal initiates counting at 219 of clockpulses from 216. As before, the D/A-converted count provides the X drive signal. When the count reaches a value corresponding to the tilt magnitude, as sensed by comparator 223, the count is stopped and an "arrow" display is initiated provided that either (a) there has been a significant variation in the data, or (b) a given number of depth pulses have been generated at 212. Counter 235 then starts counting pulses from clock 228, the pulses representing successive 15 degrees wide azimuthal sectors. Each time the count has a value corresponding to the tilt direction, comparator 243 triggers one-shot 244 to give a CRT bright-up pulse. A sine-wave of frequency 1/24 the clock 228 frequency is formed by divider 229 and filter 230, and its amplitude is incremented each twenty-fourth pulse from clock 228 by means of D/A converter 233 and modulator 236. Phasequadrature versions of this modulated sine-wave control the CRT beam deflections to give a spiral sweep which, with the bright-up pulses from 244, produces an "arrow" display. Comparator 234 adds a bright-up pulse on the nth turn of the spiral to produce the arrow head 250. The value of n may be made dependent on the reliability of the tilt data. Other embodiments are described in which (a) the arrow-type display is combined with a display of the Fig. 6 type, Fig. 27, (not shown), or (b) the logging tool is an acoustic pulse-echo type scanning the borehole in azimuth and echo signals cause both brightness and Y-deflection modulation of a CRT trace, the X-deflection of which is synchronized with the azimuthal scanning, Fig. 4, (not shown).