| 摘要 |
<p>1292993 Borehole logging MOBIL OIL CORP 21 Oct 1969 [24 Oct 1968] 51564/69 Heading H4D The three-dimensional configuration of a borehole wall is represented on a display and recording device as patterns in which intensity is a function of the distance of the borehole wall from an acoustic pulse-echo logging tool which scans the wall. In the Fig. 1 embodiment the wall is scanned helically by a rotating transmit/receive transducer 14, to detect any deformation of casing 11, as logging tool 13 is moved through the borehole. The horizontal deflection of cathode ray tube (CRT) 52 beam is synchronized with the transducer rotation by means of downhole potentiometer 30. The (slow) vertical deflection of the CRT beam is synchronized with logging tool depth by means of wheel 132, gear reducer 131 and potentiometer 130. The CRT beam intensity is modulated with a signal which increases as the acoustic echo-time decreases and vice versa; this signal is derived as follows. Downhole circuit 26, including a gate to attenuate transmitter breakthrough, sends signals comprising the envelopes of the attenuated transmission pulse and the borehole wall echo pulse to transistorized uphole circuits 53 (detailed in Fig. 7, not shown), where the transmission pulse is used as a sync. pulse, is delayed at 91, and gates amplifier 94 on to pass the echo pulse. The echo pulse gates amplifier 94 off again. Gate 92 is turned on by the sync. pulse and off by the gated echo pulse and controls ramp voltage generator 96. The peak voltage of the ramp generated while gate 92 is on is detected at 98 and is subtracted at 99 from a reference voltage to give a voltage which decreases as echo-time increases. The output of monostable multivibrator 102 is clamped to the latter voltage at 100, 101 to provide the beam intensity modulation signal for CRT 52. The CRT screen is photographed at 57. A magnetometer may be used instead of potentiometer 30 if the borehole is not cased, to provide a CRT horizontal deflection synchronized with rotation of transducer 14 past magnetic north.</p> |
