| Title | An improved multiscale and leaky P-wave removal analysis for shear-wave anisotropy inversion with crossed-dipole logs |
| Publication Type | Journal Article |
| Year of Publication | 2016 |
| Authors | Li, M, Tao, G, Wang, H, Zhang, K, Vega, S |
| Journal | Petrophysics |
| Volume | 57 |
| Issue | 3 |
| Pagination | 270293 |
| Abstract | Most of the shear-wave anisotropy inversion methods are based on the waveform similarity of split fast and slow shear waves, employing an optimization algorithm to solve the derived nonlinear objective function. Although current methods can decrease the ambiguity in determining the fast shear-wave azimuth, the assumption of waveform similarity can hardly be satisfied in field cases, leading to inaccurate anisotropy estimations. In addition, due to the influence of borehole conditions and formation properties, the crossed-dipole data gathered from the field are often mixed with leaky P-wave in slow formations. These factors may severely degrade the reliability of the anisotropy inversion. In this paper, we propose an algorithm based on a shift-invariant multiscale analysis tool, dual-tree complex wavelet transform and slowness-time correlograms (STC) to suppress the leaky P-wave that could not be removed by the band-pass filter. Subsequently, the main characteristics of the flexural wave can be more clearly extracted to enhance the waveform similarity in multiple time-frequency domains. Finally, a multi-objective inversion function is introduced to further reduce the ambiguity in shear-wave anisotropy inversion. The applications of this algorithm to synthetic data and field data indicate more stable and accurate inversion results compared with current methods, especially in formations with weak anisotropy. |
| URL | https://www.onepetro.org/journal-paper/SPWLA-2016-v57n3a4 |
