Deterministic spectral balancing for high-fidelity AVO

A common problem for Amplitude Versus Offset (AVO) analysis is that the frequency spectra of near and far-offset data are different; near-offset sections contain more high-frequency energy than far-offset sections do. This variation in frequency content can significantly alter the AVO response, since the interference patterns between adjacent reflection events (for instance the top and bottom of a reservoir layer) will be different on the near and far-offset data. Difference in interference (tuning) can create false AVO anomalies or make valid AVO anomalies disappear. Because of their different frequency spectra, correlating reflection events between near and far-offset sections is sometimes difficult or ambiguous. We present here a method that addresses this problem and produces data appropriately compensated for high-fidelity AVO analysis. The method consists of two main steps that deterministically correct for the effects of NMO stretch and absorption (Q). It is critical that both steps are applied. While NMO stretch compensation plays the key role in balancing near and far-offset spectra, it will reduce the far-offset amplitudes and suppress AVO anomalies if frequency-dependent absorption losses are not accounted for.