Abstract: Fractures and wellside unequal in-situ stress may lead to the S-wave anisotropy of formations.The analysis of the characteristics of S-wave anisotropy for wellside formation can indicate the fractures and unequal in-situ stress.Starting from S-wave splitting in the anisotropic formation,based on waveform inversion theory,we used the orthogonal dipole array acoustic data to analyze and evaluate the features of fractures and the S-wave anisotropy of low-porosity & low-permeability reservoir.Then,the calculated anisotropic parameters were used to evaluate the development and azimuth of fractures and the distribution of in-situ stress in low-porosity & low-permeability formation.Meanwhile,the relation between S-wave anisotropy of monopole and waveform dispersion curve of fast and slow bending wave was utilized to analyze the cause for S-wave anisotropy.Finally,combined with conventional logging data,core and FMI imaging data,the analysis result was verified and contrasted,and the result shows the two matches well.Application indicates that S-wave anisotropy parameters can effectively evaluate the development,trend and feasibility of fractures,exactly identify the distribution of in-situ stress and the azimuth of maximum horizontal stress.