Fluid discrimination incorporating viscoelasticity and frequency-dependent amplitude variation with offsets inversion

Fluid identification by nonlinear frequency‐dependent amplitude variation with offset inversion based on scattering theory

“…As shown in Appendix D, assuming 𝑄 S ≫ 𝑄 P , and Equation (5) can be approximated as (Zong et al, 2021)…”

“…The imaginary part (𝑖∕𝑄 p ) appears in Equation ( 6), and for the convenience of practical application, it is assumed that the medium has weak viscoelasticity (Zong et al, 2021), so the imaginary parts can be discarded (when the medium is weak viscoelastic, the imaginary part is much smaller than the real part). And then substituting Equation ( 6) into (4), the quadratic scattering coefficient equation is obtained as…”

“…When fluid is present in rock, the irregular movement of the molecules in the fluid dissipates the energy of the transverse wave, causing a significant attenuation of energy in the S-wave but a relatively small attenuation of the P-wave in liquid. Therefore, when seismic waves propagate in reservoirs containing fluids, the attenuation of S-waves is much greater than that of P-waves Zong et al, 2021). Therefore, in this study, it is assumed that 𝑄 s is greater than 𝑄 p , and then Equation (D-4) can be approximated as…”

“…have been widely used in the inversion process. However, the inhomogeneity and viscoelasticity of the medium can induce the dispersion of seismic waves and cause the seismic waveform to change during propagation (Lan & Zong, 2022; Li & Liu, 2019; Li et al., 2019; Samec & Blangy, 1992; Zhang & Wang, 2021; Zong et al., 2021). Therefore, in the prediction of complex reservoir fluid, the viscosity of the medium needs to be further considered.…”

“…The constant Q theory, as proposed by Liner (2014), provides a framework for connecting the dispersion and attenuation of seismic waves. When accounting for the viscosity of the medium, the widely adopted method is to incorporate the nearly constant Q theory (Futterman, 1962) into the elastic medium parameters, effectively transforming the elastic medium into a viscoelastic medium (Lan & Zong, 2022; Li & Liu, 2019; Li et al., 2019; Zhang & Wang, 2021; Zong et al., 2021). By considering the viscoelasticity of the medium, the fluid prediction error caused by the conventional elastic medium assumption can be eliminated, and the reservoir fluid can be more accurately identified.…”