METHOD AND DEVICE FOR DETERMINING A VERTICAL SEISMIC PROFILE BY MEASURING VIBRATIONS FROM A WELL

摘要

Seismic measurements are carried out during drilling operations by a set of seismometers 24 placed on the ground surface 25 around the axis 21 of a drilling train 20 comprising a conventional drill bit 16 as well as strain gauges 52, 54 , 56, 58, 62, 64, 74, 76 and accelerometers 42, 44, 46, 48, 50, 80, 82, 84 arranged to measure axial and torsional vibrations of the drill string 20. The relative signals to the vibrations induced by the drill bit 16, or by another source, and transmitted by the drill string 20 are compared with signals received by the set of seismometers 24, so as to determine the characteristics of the earth formation 10 on the basis of measuring the acoustic speed from acoustic vibrations transmitted directly or reflected by said formation 10.