The low-frequency gas shadow on seismic sections

About six years ago, Greg Partyka and his colleagues at Amoco Research showed how an old technique (the Fourier transform) could be used effectively for seismic interpretation and visualization. This idea has come to be known as spectral decomposition. In recent years, many spectral decomposition techniques have been developed and utilized for stratigraphic analysis and direct hydrocarbon detection. With the refined spectral decomposition techniques now available, the low-frequency shadow beneath gas reservoirs is another old idea that has renewed importance and interest in the exploration community. Almost a decade ago, Dan Ebrom studied a variety of possible mechanisms for the low-frequency shadow and why it might be associated with hydrocarbons. He presented his analysis at the 1996 SEG Summer Research Workshop.