Institut Francais Du Pe'trole

Van Bui-Tran

Christian Grouffal

G&eacute;rard Thierry

Thi Thu Nguyen

Method and device intended for synchronized acquisition of seismic signals by one or more acquisition units suited for seismic signal digitizing, allowing to obtain, for each signal, a series y&lsqb;n&rsqb; of samples of these signals readjusted from a reference time on, from a first series x&lsqb;n&rsqb; of digitized samples of this seismic signal produced from any initial time prior to the reference time. The method essentially comprises detecting a synchronization signal indicative of this reference time (T,), measuring the effective time difference (D) between the reference time and the initial time, determining coefficients of a digital filter (F) suited to compensate for the fractional part (d) of the measured effective time difference, and applying this compensation digital filter to the first series of samples, which allows to obtain a series of digitized samples readjusted from the reference time. In order to accelerate determination of the filter coefficients depending on the difference D observed, the coefficients of a certain number of intermediate filters corresponding to determined fractions of the sampling interval are preferably precalculated. The method can be applied for seismic prospecting or monitoring, earthquake detection, etc.

Synchronized seismic signal acquisition method and device

The invention relates to a two-phase method of transmitting, to a central station (CS), seismic signals received by seismic receivers (R) and picked up by collecting units (A) disposed in the field. In the first phase, a compression is applied to each seismic trace, the ratio of which is adapted to the duration of a transmission window placed in the time intervals between successive seismic transmission-reception cycles, as well as to the rate of the transmission route used. The compressed trace as a whole is thus transmitted, allowing an operator at central station (CS) to check qualitatively that recording took place correctly in each collecting unit (A) even though he does not have the exact trace available. In the second phase, at the end of the current seismic session for example, the seismic traces are reconstituted in the central station with the necessary accuracy, either by complete transmission of the data preferably after prior compression, or, in certain cases, by transmission of residues eliminated in the first phase for the requirements of the first transmission.

Growing community of inventors

Coachères, France

Van Bui-Tran