The Myth of Low Frequency Shadows

Low frequency shadows have long been hailed as direct hydrocarbon indicators on the order of bright spots and flat spots (Balch, 1971; Sheriff, 1975; Taner et al, 1979). Time has not diminished their appeal. Indeed, recent years have seen renewed interest, in connection with methods of spectral decomposition (Castagna et al., 2003; Welsh et al., 2008; Nebrija et al., 2009). In spite of this, few examples of shadows have ever been published, and few of those are convincing as hydrocarbon indicators, discounting those caused by shallow gas. This contrasts with bright spots, flat spots, and AVO, for which published examples are numerous and credible.