ABSTRACT. This study presents an analysis of the linear inversion scheme for estimating anisotropy in the neighborhood of a receiver placed in a well using the vertical components of the slowness and polarization vectors of P-waves measured in multi-azimuth walkaway vertical seismic profile (VSP) surveys. Independently of the medium above the geophone (homogeneous or heterogeneous) and the shape of the well (directional or curved, vertical or sloped), an inversion is performed from a first-order approximation around a reference isotropic medium. The analysis of the inversion scheme considers factors such as the noise level of the data, the type of P-wave, the degree of the anisotropy of the medium, the choice of parameters in the reference isotropic medium and the degree of heterogeneity of the medium.Keywords: anisotropy estimation, multi-azimuth walkaway VSP data, weak anisotropy.
RESUMO.Neste trabalhoé apresentada uma análise do esquema de inversão linear para a estimativa de anisotropia na vizinhança de um receptor situado em um poço a partir da componente vertical do vetor de vagarosidade e do vetor de polarização das ondas P medidos em experimentos de VSP walkaway multiazimutal. Independente do meio acima do geofone (homogêneo ou heterogêneo) e da geometria do poço (inclinado, reto ou curvo), a inversãoé feita a partir de uma aproximação de primeira ordem em torno de um meio isotrópico de referência. O esquema de inversãoé analisado considerando diferente fatores, tais como: nível de ruído nos dados, tipo de onda P, grau de anisotropia do meio, escolha dos parâmetros no meio isotrópico de referência e grau de heterogeneidade do meio.Palavras-chave: estimativa de anisotropia local, dados de VSP walkaway multiazimutal, fraca anisotropia.
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