Patent ID: 6807489
Filing Date: 2004-10-19
Classification: G01V

Abstract:
A seismic processing method for recovering, within a VSP type seismic prospecting method, of absolute amplitude ratios between, seismic signals corresponding to upgoing waves emitted by a seismic source coupled with a geologic formation and reflected from subsoil discontinuities, the seismic signals being received by separated seismic receivers coupled with a wall of a well through the geologic formation, in a depth zone of the well, and seismic signals corresponding to downgoing waves received by the seismic receivers coming directly from the seismic source, comprising:normalizing downgoing waves at the seismic receivers of a zero-phase amplitude pulse in a frequency band determined by a signal-to-noise ratio observed in the frequency band, which is carried out after deconvolution of a signature of a total field of the downgoing and upgoing waves by the downgoing waves, which compensates for the upgoing wave attenuation in a downgoing wave path between-the source and the receiver; separating the upgoing and downgoing waves with multitrace velocity filters including parameters adjusted to observed waves; compensating differences between amplitudes received by each seismic receiver, due to spherical divergence between a path of the upgoing waves and a path of the downgoing waves coming directly from the seismic source, and wherein the normalizing downgoing waves at seismic receivers in a form of zero-phase amplitude pulse is between a level of each seismic receiver and a level of each reflecting discontinuity, to normalize an amplitude of reflectors at a value measured by receivers located immediately above the reflectors.