Acoustic multi-mode wide-band logging device

摘要

A multi-mode receiver sonde having individual receiver stations. The receiver stations have transducers which have a flat frequency response over a selected bandwidth so that there is an approximately constant ratio in amplitude and substantially little phase difference between the response signal and an input acoustic signal from a liquid containing borehole. The wide-band output response signals are combined to form composite signals which represent selected borehole propagation modes. Accurate comparisons can then be made between the composite signals obtained by separate receiver stations so that changes in phase and amplitude over distance and time can be determined. In one highly preferred embodiment, the receiver sonde has a semi-rigid receiver array. The semi-rigid receiver array is adapted to decouple noise (tool-mode noise and/or road-noise) in one location within the array from other locations within the array by using compliant spacers between the receiver stations to absorb and scatter the noise.