| 摘要 |
Seismic pulses, distributed irregularly in time (according to a random or pseudo-random code, for example) are transmitted into the ground, and the direct waves and those reflected by the discontinuities of the subterrain are picked up a receiver system (G). The frequency spectrum of the signals emitted and received is subdivided into several bands and the components of the signals in each of the bands are reduced to elementary signals giving their sign changes (sign bit) and recorded. A correlation of the elementary signals respectively associated with the signals emitted and received, to a summation of the correlation products associated with each sensor is then carried out for each sensor of the receiver system, and seismic sections are produced with the sums obtained, which are highly comparable to those which would be obtained by digitising the signals received in full precision, as in the conventional methods. Application to 2D or 3D prospecting around a well (borehole) (1) during drilling with a drilling tool (bit) (2, 4), for example. <IMAGE>
|
