EEI

Description Computes Extended Elastic Impedance (EEI) volumes from a set of angle stacks.
Module(s) QI
Requirements Seismic Volumes (multiple angle stacks)
Related  
Works with Stacks

The EEI process computes EEI volumes by deriving Intercept (I) and Gradient (G) from the input angle stacks via per-sample linear regression of amplitude against sin²(θ) (Shuey two-term approximation: A(θ) = I + G·sin²(θ)). I and G are then rotated by a specified phase angle, and for each chi angle in the configured scan range, EEI(χ) = I·cos(χ) + G·sin(χ) is computed.

Create an EEI process

  1. In the Control Panel, open the Process tab.
  2. At the tab header, click the Add icon and select New Process.
  3. Search for or scroll down, and select EEI > Add.
  4. Type a name for the process and click OK and Close.

Configure EEI

  1. Angle stacks: Select two or more seismic angle stacks with known incidence angles (degrees). Near, mid, far, and ultra-far stacks are typical. All stacks must be from the same survey.
  2. Phase angle: Phase rotation applied to the derived Intercept and Gradient before computing EEI.
  3. Chi scan start / end / increment: The range of chi angles (degrees) over which the EEI chi scan gather is computed. End must be greater than start, and the increment must be at least 1°.

Output

Output volumes:

  • EEI I: Phase-rotated intercept volume.
  • EEI G: Phase-rotated gradient volume.
  • EEI chi scan: A gather volume with one trace per chi angle across the configured chi scan range.

As a result of this process, the output volumes will be added in the Volume tab. To quickly open an output volume, right-click the process item in the Process tab and click Open the output volume. Vice versa, the process can be opened from the Volume tab directly — right-click the volume (indicated in italics) and click Open the Process.