Inversion for reservoir parameters using first- and second-order derivatives of elastic impedance
Huaizhen Chen, Kristopher A. Innanen
Estimation of reservoir porosity, shale content and fluid type is the key and difficult problem of geophysical exploration. We relate seismic reflection coefficient and elastic impedance (EI) to reservoir porosity, shale content and fluid. Using the nonlinear reflection coefficient and EI, we present a two-step inversion method, which involves: 1) the linear inversion of partially incidence-angle-stacked data to predict EI; and 2) the nonlinear inversion of EI to estimate shale content, porosity, fluid modulus and density. We use the first- and second-order derivatives of EI with unknown parameters to improve the accuracy of the inversion for reservoir parameters. The robustness and reliability of the proposed inversion method are verified using noisy synthetic seismic data and a real data set.