Elastic Impedance Inversion

AVO modeling and inversion from angle band cubes

Elastic impedance inversion (EI) is a generalization of acoustic impedance for variable incidence angles. It provides a consistent and absolute framework to calibrate and invert nonzero-offset seismic data. EI allows the well data to be tied directly to the high-angle seismic data, which can then be calibrated and inverted without reference to the near offsets. EI is performed in an interactive, Windows-based framework with direct access to all the required seismic, well, and rock physics modeling data. It allows the user to construct as high an angle stack as is stable and then to calibrate or invert using the equivalent EI log.

Elastic impedance inversion is performed in three parts:

1. Well data analysis of elastic rock properties and generation of EI logs

2. Wavelet extraction, using the EI logs and the input angle stacks

3. AVO and AVA inversion of seismic cubes, using the classic two-term Shuey approximation or a full implementation of the Aki-Richards AVO equations 

The well data analysis and modeling uses the EI functionality in the Rock Physics Calculator to estimate K and K error over a defined interval and calculate EI from the well logs (after Well Data Conditioning). This provides input to the wavelet estimation and to the seismic cube inversion steps. Comparisons are made with elastic constants also calculated using the Rock Physics Calculator. Reflectivity series are calculated at required angles. Wavelet extraction is performed using the EI logs and the input angle stacks. The final step involves AVO analysis and processing using the classic two-term Shuey approximation or a full implementation of the Aki-Richards AVO equations.

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