Seismic impedance inversion is a commonly used procedure in practical geophysics. Many commercial packages are aimed at translating seismic traces that react to the contrast of the elastic properties into absolute impedance volumes. The goal of this operation is obvious: because the absolute rather than relative values of the elastic properties can be related to porosity, mineralogy, texture, and fluid via rock physics transforms, such transforms can, in principle, be applied to the seismically derived impedance volume to ascertain the rock properties in the subsurface. For a detailed review of methods and practices, we refer the reader to an encompassing treatise on impedance inversion by Latimer (2011) where a multitude of authors and their publications are listed.

Here we present a case study by Dvorkin and Alkhater (2004) based on simple rock-physics-based logic to delineate porosity and fluid in an impedance section. The reservoir under examination consists of relatively soft sands. As a result, the acoustic impedance of the gas-saturated sand is much smaller than that of the oil- and water-saturated sand. This large impedance difference allows us to identify the pore fluid only from the P-wave data, without using offset information. As a result, we map both pore fluid and porosity by using impedance inversion applied to stacked seismic data.