Attribute Description: Attenuation attempts to represent the rate of absorption of the seismic energy as it goes through the earth. The absorption, transmission and reflection of sound directly relate to rock type and its impedance value as reflected by P and S wave velocity and density. These are effected by conditions such as porosity, saturation and pore pressure so it can be useful in reservoir characterization.
Interpretation Use: This attribute may provide value by
- Localizing Lithology types
- Providing an indication of pore pressure, fluid saturation and porosity
In this example, we are using “Average Energy”, a spectral based colorbar. This attribute puts out all positive values, in this example from 0 to 462. The brighter colors represent the higher rates of attenuation while the darker blues and greens represent the lower rates of attenuation. As seen in the example below, the deeper rocks attenuate the sound less, which makes sense as they are more compacted, and have a higher velocity than the shallower rocks. The spectrum reflects the large number of “0” values
Attenuation is computed by dividing the first derivative of envelope by smoothed frequency:
The smoothed frequency is used due to the presence of spikes in normal instantaneous frequency.
- Chopra, S. and K. J. Marfurt, 2007, Seismic attributes for prospect identification and reservoir characterization: Society of Exploration Geophysicists, Geophysical Developments #11.
- Taner, M. T., 2001, Seismic attributes: Canadian Society of Exploration Geophysicists Recorder, 26, no 7.