AN EXPERIMENTAL COMPARISON OF 3 DIRECT-METHODS OF MARINE SOURCE SIGNATURE ESTIMATION

Three methods for estimation of the pressure wavefield generated by a marine airgun array are tested experimentally and compared. In the tri al a variety of radiation angles and array configurations were used an d some large synchronization errors were deliberately introduced. The source was equipped with near-field hydrophones and a subsource minist reamer. A tethered far-field hydrophone was used so that the three est imated far-field signatures could be compared with an independent meas urement. The knowledge of the source signature is important for on-boa rd source array QC, deconvolution, multiple attenuation, stratigraphic trap prediction, modelling and inversion, AVO analysis and reservoir monitoring. The methods perform very well and give estimates whose fre quency-domain spectra match the measured spectra to within a few dB an d within a few tens of degrees of phase over the tested bandwidth of 3 .5-110 Ha. The time-domain error-energy is typically only a few per ce nt of the signal energy for radiation angles within about 30 degrees o f the vertical. The third method proved to be sensitive to an experime nt;al shortcoming leading to overloading of the ministreamer and meani ngful comparison was not possible for some test configurations.