Numerical Simulation of Acoustic Fields Excited by Cross-Dipole Source in Deviated Wells in Transversely Isotropic Formation

详细信息   

• 责任者：Yan Shouguo (College of Physics ; Jilin University ; Changchun 130012 ; China) ; Song Ruolong
• 刊名：Chinese Journal of Geophysics
• 出版年：2011
• 卷期：54(9)
• 关键词：声波测井 ; acoustical logging ; 横向各向同性 ; transverse isotropy
• 页码：p.2412-2418
• 图表：illus., 2 tables, 16 refs.
• 分类号：1600
• issnNo：ISSN0001-5733
• isbnNo：CN11-2074/P

摘要

The acoustic fields excited by cross-dipole acoustic source in borehole surrounded by transversely isotropic （TI） formation, whose symmetry axis is oblique, are numerically simulated by 3D stress velocity finite difference （SV-FD） method. Several key problems are resolved to improve the computational accuracy, such as derivation of modulus matrix related to oblique angle, establishment of SV FD equations under cylindrical coordinates, and treatment of singular points on borehole axis. The method is validated by comparing numerical result with that obtained by real axis integration method, when the symmetry axis of TI formation is parallel with borehole axis. The flexural waveforms of xx and yy components of borehole acoustic fields with various dip angles are simulated, and the dispersion curves of flexural waves are obtained by weighted spectral semblance method. The results show obvious splitting of flexural wave with different polarization in TI formation. The dispersion curves of xx and yy split at low-frequency,and overlap at high-frequency. The velocities at low-frequency cut-off frequencies agree with those calculated by theoretical formula.