| 摘要 |
<p>An acoustic telemetry arrangement in a borehole, enables sending of digital data from a down-hole location to the surface. Use s made of an acoustic channel 130 filled with e.g. water, through which an acoustic carrier is transmitted generated at the surface, for example by an oscillating piston 141. At a downhole location, a reflecting terminal 133, 134 is provided. The reflection characteristics of the terminal can be altered in accordance with a digital signal. The variation causes the reflected carrier wave to be modulated in phase and/or amplitude, the carrier wave being sensed at the surface by transducers 150 and the data being extracted by a phase or amplitude demodulator. The reflecting terminal comprises a Helmholtz resonator chamber 132, in communication with the acoustic channel 130 through a tube 162, which can be opened or closed by a valve 161 driven by control 163 connected to a measurement system 170. A receiving transducer 164 may allow communication in a downhole direction. The modulator is essentially low power and may receive power from the surface by converting acoustic waves into electrical power.</p> |
