Seismic AVA inversion of elastic and attenuative parameters in viscoelastic media using the Zoeppritz equations

Abstract

When seismic wave passes through oil-gas bearing reservoir, it will cause relatively large attenuation effect due to energy dissipation. Two constants characterizing attenuation strength, P- and S-wave inverse quality factors, are widely used in seismic prediction. Although various attenuation-related petrophysical models have been introduced into the approximate reflection coefficient equations to describe a viscoelastic medium, the low accuracy of the approximation in the range of moderate to large incident angle limits the approximation-based amplitude variation with angle (AVA) inversion methods in estimation of attenuation factors. To avoid the impact caused by the uncertainty of the linear factors in the attenuation model, we propose an AVA inversion based on Zoeppritz equations to directly estimate elastic properties (P- and S-wave velocity, and density) and attenuation factors (P- and S-wave inverse quality factors). First, we introduce the complex velocity model into the Zoeppritz equations to decouple the viscoelastic velocity into elastic velocity and inverse quality factors. Under the generalized linear inversion framework, we then derive the Jacobian matrices and establish a joint PP- and PS-wave inversion to improve the stability and accuracy. Tests on both synthetic and real multi-component seismic data sets verify the elastic properties and attenuation factors can be reasonably and stably predicted. It can be concluded that the established approach is an effective tool in attenuation factors estimation, and the predicted attenuation factors appear as an additional proof for the identification of gas-bearing reservoirs.