Geophysical Insights hosting the 2018 Oil & Gas Machine Learning Symposium in Houston on September 27, 2018
Introduction to Machine Learning for Multi–Attribute Interpretation and AASPI attributes - A 1-day, DGS Continuing Education course in Denver, CO on September 18th
Dr. Tom Smith presenting on Machine Learning at the 3D Seismic Symposium on March 6th in Denver
What is the "holy grail" of Machine Learning in seismic interpretation? by Dr. Tom Smith, GSH Luncheon 2018
Using Attributes to Interpret the Environment of Deposition - A Video Course. Taught by Kurt Marfurt, Rocky Roden, and ChingWen Chen

Attenuation

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

Recommended Colorbar: 

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 - 1.png

Example:

 Vertical Seismic Section using Attenuation

Vertical Seismic Section using Attenuation

 Time slice of Attenuation

Time slice of Attenuation

  Frequency Spectrum for Attenuation


Frequency Spectrum for Attenuation

Computation: 

Attenuation is computed by dividing the first derivative of envelope by smoothed frequency:

Attenuation - 5.png

The smoothed frequency is used due to the presence of spikes in normal instantaneous frequency.

References:

  • 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.