Elastic Simultaneous Inversion for Young’s and Poisson Impedances

Abstract

Summary Elastic inversion works as an important tool in ealstic paramters estimation. The product of Young’s modulus and density (Young’s impedance, YI) and product of Poisson ratio and density (Poisson ratio impedance, PI) show great potential in lithology predicting and “sweet spot” such as brittleness evaluaiton or fluid discrimination of unconventional resouces. The high demanding quality requirements for pre-stack data in density inverion render the estimation of YI and PI arduous with conventional pre-stack inversion approach. In this study, a pragmatic elastic simultaneous inversion approach is proposed to invert YI, PI and density directly from P-wave seismic data to avoid the uncertainty brought by density. The linearized P-wave reflection equation in terms of YI, PI and density is initially derived. Parameter sensitivity analysis illustrates that YI and PI could be reasonably estimated from P-wave reflectivity if the decorrelation scheme is utilized in inversion algorithm. Furthermore, a pragmatic AVA inversion in Bayesian scheme is suggested to implement the direct inversion of YI and PI from pre-stack seismic data. Synthetic and field data examples demonstrate the feasibility of the proposed inversion approach in the estimation of YI and PI and show the potential of this approach in “sweet spots” discrimination.