Methods and systems for computing notional source signatures from near-field measurements and modeled notional signatures

摘要

Methods and systems for computing notional source signatures from modeled notional signatures and measured near-field signatures are described. Modeled near-field signatures are calculated from the modeled notional signatures. Low weights are assigned to parts of a source pressure wavefield spectrum where signatures are less reliable and higher weights are assigned to parts of the source pressure wavefield spectrum where signatures are more reliable. The part of the spectrum where both sets of signatures are reliable can be used for quality control and for comparing the measured near-field signatures to modeled near field signatures. When there are uncertainties in the input parameters to the modeling, the input parameters can be scaled to minimize the differences between measured and modeled near-field signatures. Resultant near-field signatures are computed by a weighted summation of the modeled and measured near-field signatures, and notional source signatures are calculated from the resultant near-field signatures. 1- Method for computing notional source signatures For each seismic source elements 601 Input modeled notional source 603 signatures Input recorded near-field 602 signatures CalcUate modeled near-field sgnatures from the notional 604 [ signatures Transform from time domain to ~605 frequency domain ansform from time domain to 606 frequency domain Compare recorded and modeled 7 signatures in frequency domain alibrato 60 uncertain 4 q ~s'Scale recorded near-field s nature to modeled near-fi d No signature Compute frequency dependent weight functions for modeled and - 610 recorded signatures Cmue eghted summation - 611 Transform from frequency domain 61 to time domain 1 Yes More Source5 61 elements No~o 614 Compute notional source signatures from near-fieldFG 6 signatures FG