METHOD AND DEVICE FOR SEISMIC PROSPECTING BY SIMULTANEOUS TRANSMISSION OF SEISMIC SIGNALS BASED ON RANDOM PSEUDO SEQUENCES

摘要

P - -Method and device for seismic prospecting by simultaneous emission by several vibrators of seismic signals obtained by phase modulating a periodic signal whose amplitude and time-related derivatives of the amplitude are canceled at the beginning and at the the end of each period, by pseudo-random sequences. Receivers coupled with the formation capture the seismic signals returned by the subsurface discontinuities in response to the periodic signals transmitted and record them in an acquisition system. and registration. The emitted seismic signals are formed either from elementary sequences of a duration at least equal to the product of the number of seismic sources simultaneously vibrating by the listening time, or from this increased elementary sequence, before and after, of parts of a duration at least equal to the listening time, the reception and recording of the signals returned by the discontinuities of the sub-ground in response to the signals transmitted, and the processing of the recorded signals. The respective contribution of each of the different seismic sources is isolated by correlating the signals received and recorded either by signals constructed from said elementary sequence, increased, before and after, of parts of a duration at least equal to the time of listening, obtained by circular permutation, either of the said elementary sequence.-Applications to seismic prospecting or seismic monitoring of deposits, for example. / P