Extended Elastic Impedance (EEI)

Calculate EEI for optimal fluid or lithology separation. EEI rotates the Vp-Vs plane to maximize sensitivity to target properties.

AVO Rock Physics Inversion

Input Parameters

Rock Properties

m/s
m/s
g/cc

EEI Angle (χ)

degrees
χ=0: P-impedance | χ=±90: S-impedance

Quick Angles

Presets

Results

Theory & References

Extended Elastic Impedance

Whitcombe et al. (2002) equation:

EEI(χ) = Vp(1+tan²χ) × Vs(-8K·sin χ) × ρ(1-4K·sin²χ)

Where K = (Vs/Vp)² (typically ≈ 0.25)

Special cases:

  • χ = 0°: EEI = Vp × ρ (P-impedance)
  • χ = ±90°: EEI = Vs × ρ (S-impedance)
  • χ ≈ 35°: Maximizes fluid sensitivity
  • χ ≈ -15°: Maximizes lithology sensitivity

Applications

  • Fluid Detection: χ ≈ 35° enhances fluid contrast
  • Lithology Mapping: χ ≈ -15° for sand/shale discrimination
  • AVO Analysis: EEI angles relate to AVO intercept/gradient
  • Direct Hydrocarbon Indication: Optimal angle for gas/brine separation
  • Seismic Inversion: Simultaneous inversion for multiple EEI angles

Elastic Parameters

Lamé parameters:

λ = ρ(Vp² - 2Vs²)

μ = ρVs²

LMR (Lambda-Mu-Rho):

λρ = λ × ρ

μρ = μ × ρ

Useful for lithology and fluid discrimination