Application of frequency split structurally oriented filtering to seismic whitening and seismic inversion workflows

Abstract

This paper describes a new seismic processing method that uses dip-steered filtering to improve the performance of subsequent seismic whitening and relative impedance inversion. Given favourable acquisition and processing parameters, the availability of high frequency signals is ultimately limited by poor Signal/Noise ratio (S/N) at high frequencies. Managing this noise is key to accessing the high frequency information. We show that although spatial filters applied to broadband seismic data mainly affect the central pass-band, a frequency splitting approach can specifically benefit the targeted high frequency parts of the spectrum. The dip-steered filters trade spatial resolution for increased S/N, but only in the frequency bands that are boosted during the whitening process. The S/N of the low frequencies can be improved using a similar process prior to acoustic impedance inversion. In a relative impedance inversion workflow, de-noising the low frequencies allows accurate inversion of thicker beds. Applying the technique prior to full-bandwidth inversion allows the use of lower seismic frequencies, and reduces reliance on a pre-existing background model. We can apply frequency split dip-steered filtering to pre-stack common offset volumes or partial stacks in a similar fashion. This delivers frequency balanced partial stacks with lower noise and increased resolution, ultimately leading to a reduction of offset dependent tuning and higher resolution elastic inversion products. Logs are not required for the process but independent well ties demonstrate the validity of the technique and are used to QC the products. The value of increased resolution in the seismic data volumes is illustrated with several case histories from different surveys and reservoirs.