Attribute analysis

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Attribute analysis is the process of inferring geological information from seismic attributes.

The idea is to relate the seismic to reservoir properties you care about. This means proving that the property is related to the seismic in as quantitative way as possible. A nice way to do this is to crossplot the property with the seismic attribute — that way you also know the error of the estimate. A map showing wiggly channels is interesting, but nowhere near enough.

Workflow

  1. Establish the temporal and spatial bandwidth of the seismic. You will need to know the acquisition parameters. Temporal bandwidth can be measured from the data.
  2. Tie some wells, if available. Use the modelled traces to determine what you might be able to see in the seismic data: thickness, impedance contrast, etc.
  3. Make some forward models of the expected channel response. You can use tools like Hampson-Russell, Geographix LogM, or Agile's modelr.io.
  4. Using what you've learned, make some maps from the seismic data, such as amplitude maps from horizons or over intervals. If you have quantitative goals, you can try inverting these attributes for reservoir properties you care about (porosity, thickness, etc).

Windowing attributes

Let the expected geology and basic geophysics and statistics guide all of your decisions. Use a window that captures the interval of interest (look at the wells!) without too much non-interesting stratigraphy. But use a big enough window that you don't see a lot of artifacts from large amplitude values coming in and out of the window (this also depends on the quality of the horizons and smoothness of the geology).

Windows don't have to be symmetrical about a horizon. It depends where the features you're interested in are. In my experience, stratigraphic windows are often useful — from one horizon to the next. If you're interested in the horizon itself, consider just using its amplitude directly. If it's too noisy, try improving the pick or smoothing the amplitude map, before confusing things by throwing more geology in there.

Smoothing

It may sometimes be useful to smooth horizons or attributes to pull out features of interest. It's usually better to use unsmoothed seismic data (ask your processor) to do the extraction, then smooth the results — this way you have dynamic control over the degree of smoothing, the filter choice, etc.

References

External links

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Attribute analysis
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