Methods and systems that determine a velocity wavefield from a measured pressure wavefield

摘要

Methods and systems that compute an approximate velocity wavefield based on a measured 2201 pressure wavefield and knowledge of the free-surface shape when the pressure wavefield was measured are described. The measured pressure wavefield is used to compute 2202 an approximate frozen free-surface profile of the free surface. The reflectivity and normal derivative of the reflectivity are computed 2203. A normal derivative of the pressure wavefield is computed 2204 based on the reflectivity and the normal derivative of the reflectivity. The approximate frozen free-surface profile and the measured pressure wavefield are then used to compute 2205 an approximate vertical-velocity wavefield that does not include low-frequency streamer vibrational noise. The approximate vertical-velocity wavefield and measured pressure wavefield may be used to separate the pressure wavefield into up-going and down-going pressure wavefields.