Estimation of Interlayer Elastic Dispersion Attributes Based on a New Frequency- Dependent Elastic Impedance Inversion Method

Fluid identification using seismic data is critical for the characterization of hydrocarbon reservoirs. Poroelastic behaviors associated with wave-induced fluid flow allow for hydrocarbon detection using seismic attributes derived from frequency-dependent information. However, the conventional inversion methods usually estimate the frequency-dependent seismic reflectivity across subsurface interfaces, which may lead to ambiguities in the interpretation of the obtained results. A novel frequency-dependent elastic impedance (FD-EI) inversion approach is proposed in this study by extending the elastic impedance equation, as represented by the elastic modulus, to the form in the frequency domain. The proposed method has the advantage of calculating the interlayer dispersion properties, instead of the frequency-dependent interface reflectivity, for fluid identification. The estimated interlayer dispersion attributes show more apparent physical meanings than the traditional frequency-dependent interface properties. It can, thereby, provide intuitive interpretations for hydrocarbon identifications. Synthetic examples show that the interlayer dispersion attribute estimated by the proposed method can reliably indicate tight sandstone targets with less ambiguity than a traditional interface frequency-dependent attribute. Real data applications of tight sandstone reservoirs further validate the effectiveness of the proposed FD-EI inversion method here. For gas-bearing tight sandstones, the obtained interlayer dispersion attribute can be used as a fluid identification factor with the improved accuracy. By using appropriate elastic impedance representations, the proposed method provides a valuable tool for fluid detection in various hydrocarbon resources by extending the method for the estimation of other interlayer dispersion attributes.