The Effects of Seismic Data Conditioning on Pre-Stack Simultaneous Impedance Inversion

The demands that reservoir characterization place on seismic data far outweigh those of traditional structural interpretation. Because of this, gather conditioning is seen by many as a prerequisite to pre-stack inversion. This paper discusses three conditioning processes – signal/noise (S/N) improvement, stretch removal, and reflector alignment. It then seeks to document the improvements that these processes achieve in the gathers and in the inversion. Specifically, the gathers were measured for AVO fit using a 2-term Shuey equation and found to be improved by 20%. A comparison of wavelets extracted from the angle stacks found amplitude and phase spectra to be much more stabilized, even out to the far angle stack. The far angle stack seismic/synthetic inversion residuals showed a 40% drop in amplitude and completely different frequency and reflector character. Finally, the AI/SI cross-plot showed a much more compact signature that allowed lithology and pay discrimination. Conversely, the raw data cross-plot contained noisy data that entered into the area of the polygon where the pay signature lay. Geobodies captured from improperly conditioned data are thus (1) inflated in size, and (2) have lower impedances. These errors, in turn, lead to incorrect rock property and reserve estimations.