Two-parameters Approximation and Stable Elastic Impedance Inversion for λρ

Lame petrophysical parameters λρ is the central parameter for lithology discrimination in oil exploration. We often obtain it by indirectly calculating of compressibility, shear and density information via three parameters inversion. The density term always can’t be inverted stably, it will provide the λρ volume. And three parameters inversion methods are often plagued by numerical instability. In order to avoid estimating the density and enhance the stability of inversion, we reduce the dimension of model space by simplifying the three parameters Gray approximation based on λ, μ and ρ to the two parameter approximation based on λρ and μρ. Tests on synthetic data and real data application show that our λρ extraction method by two term elastic impedance inversion is effective for lithology discrimination.