Seismic scattering inversion for fracture weakness in heterogeneous HTI media
Pan Xinpeng1, Zhang Guangzhi1,2, Yin Xingyao1,2
1. School of Geosciences, China University of Petroleum(East China), Qingdao, Shandong 266580, China; 2. Laboratory for Marine Mineral Resources, National Laboratory for Marine Science and Technology, Qingdao, Shandong 266071, China
Abstract:A single set of vertically aligned fractures embedded in a purely isotropic background medium may be considered to be a long-wavelength effective transversely isotropic medium with a horizontal symmetry axis (HTI).The estimation of fracture weakness is of vital importance to characterize the anisotropy in heterogeneous anisotropic media.The elastic inverse scattering theory is one of the effective ways to be used for the inversion for the elastic and anisotropic parameters in the heterogeneous media.Based on the elastic inverse scattering theory,we first derive a linearized PP-wave reflection coefficient containing fracture weakness in heterogeneous HTI media.Then we propose a novel parameterization method of azimuthal elastic impedance (AEI) in anisotropic HTI media with the parameter combination of fracture weakness.To improve the inversion stability and the lateral continuity,we develop the anisotropic AEI inversion method in Bayesian framework using the regularization of both Cauchy-sparse constraint and smoothing model constraint.Finally the nonlinear iteratively reweighted least squares (IRLS) strategy is used to estimate the fracture weaknesses.Tests on synthetic and real data show that the estimated results agree well with the well logging data and it further validate that the proposed approach can stably and reliably estimate the fracture weakness.
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