Borehole Wave Propagation In Isotropic And Anisotropic Media III: Anisotropic Formation
In this paper we extend the 3-D finite difference method to simulate wave propagations in an anisotropic medium. The scheme is tested in the homogeneous medium. The finite difference results agree excellently with the analytic solutions of a point force source in the transversely isotropic medium...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Technical Report |
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Massachusetts Institute of Technology. Earth Resources Laboratory
2012
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| Online Access: | http://hdl.handle.net/1721.1/75227 |
| _version_ | 1811094841334956032 |
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| author | Cheng, Ningya Cheng, C. H. Toksoz, M. N. |
| author2 | Massachusetts Institute of Technology. Earth Resources Laboratory |
| author_facet | Massachusetts Institute of Technology. Earth Resources Laboratory Cheng, Ningya Cheng, C. H. Toksoz, M. N. |
| author_sort | Cheng, Ningya |
| collection | MIT |
| description | In this paper we extend the 3-D finite difference method to simulate wave propagations in
an anisotropic medium. The scheme is tested in the homogeneous medium. The finite
difference results agree excellently with the analytic solutions of a point force source
in the transversely isotropic medium. The finite difference synthetics are compared
with ultrasonic lab measurements in a scaled borehole drilled along the X axis in an
orthorhombic phenolite solid. Both monopole and dipole logs agree well.
The 3-D time domain finite difference method is applied to the fluid-filled borehole
wave propagation problems in the anisotropic formation. The following results are
obtained:
1. In a borehole drilled along the Z axis in a phenolite formation, the monopole log
shows the P wave travelling with velocity v[subscript zz]. There are no shear-pseudo-Rayleigh wave arrivals. The dipole log is dominated by the single slow flexural mode.
2. In a borehole drilled along the Y axis in a phenolite formation, the monopole log
shows the P wave travelling with velocity v[subscript yy]. There are shear-pseudo-Rayleigh wave arrivals shown on the monopole seismograms between the P and Stoneley
waves due to the shear wave anisotropy. The anisotropy also causes the shear
wave splitting in the dipole log. The two shear wave arrivals correspond to the
fast and the slow flexural modes.
3. The disagreement between the shear wave velocity from the Stoneley wave inversion
and the direct shear wave log velocity from field data is beyond the errors in
the measurements. It is shown that the formation permeability is not the cause
of the discrepancy. From the estimated "shear/pseudo-Rayleigh" phase velocities
in the array full waveform log and the 3-D finite difference synthetics in the
anisotropic formation, the discrepancy can be explained as shear wave anisotropy. |
| first_indexed | 2024-09-23T16:06:22Z |
| format | Technical Report |
| id | mit-1721.1/75227 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T16:06:22Z |
| publishDate | 2012 |
| publisher | Massachusetts Institute of Technology. Earth Resources Laboratory |
| record_format | dspace |
| spelling | mit-1721.1/752272019-04-10T18:05:21Z Borehole Wave Propagation In Isotropic And Anisotropic Media III: Anisotropic Formation Cheng, Ningya Cheng, C. H. Toksoz, M. N. Massachusetts Institute of Technology. Earth Resources Laboratory Cheng, Ningya Cheng, C. H. Toksoz, M. N. In this paper we extend the 3-D finite difference method to simulate wave propagations in an anisotropic medium. The scheme is tested in the homogeneous medium. The finite difference results agree excellently with the analytic solutions of a point force source in the transversely isotropic medium. The finite difference synthetics are compared with ultrasonic lab measurements in a scaled borehole drilled along the X axis in an orthorhombic phenolite solid. Both monopole and dipole logs agree well. The 3-D time domain finite difference method is applied to the fluid-filled borehole wave propagation problems in the anisotropic formation. The following results are obtained: 1. In a borehole drilled along the Z axis in a phenolite formation, the monopole log shows the P wave travelling with velocity v[subscript zz]. There are no shear-pseudo-Rayleigh wave arrivals. The dipole log is dominated by the single slow flexural mode. 2. In a borehole drilled along the Y axis in a phenolite formation, the monopole log shows the P wave travelling with velocity v[subscript yy]. There are shear-pseudo-Rayleigh wave arrivals shown on the monopole seismograms between the P and Stoneley waves due to the shear wave anisotropy. The anisotropy also causes the shear wave splitting in the dipole log. The two shear wave arrivals correspond to the fast and the slow flexural modes. 3. The disagreement between the shear wave velocity from the Stoneley wave inversion and the direct shear wave log velocity from field data is beyond the errors in the measurements. It is shown that the formation permeability is not the cause of the discrepancy. From the estimated "shear/pseudo-Rayleigh" phase velocities in the array full waveform log and the 3-D finite difference synthetics in the anisotropic formation, the discrepancy can be explained as shear wave anisotropy. Massachusetts Institute of Technology. Borehole Acoustics and Logging Consortium ERL/nCUBE Geophysical Center for Parallel Processing 2012-12-05T18:06:11Z 2012-12-05T18:06:11Z 1994 Technical Report http://hdl.handle.net/1721.1/75227 Earth Resources Laboratory Industry Consortia Annual Report;1994-04 application/pdf Massachusetts Institute of Technology. Earth Resources Laboratory |
| spellingShingle | Cheng, Ningya Cheng, C. H. Toksoz, M. N. Borehole Wave Propagation In Isotropic And Anisotropic Media III: Anisotropic Formation |
| title | Borehole Wave Propagation In Isotropic And Anisotropic Media III: Anisotropic Formation |
| title_full | Borehole Wave Propagation In Isotropic And Anisotropic Media III: Anisotropic Formation |
| title_fullStr | Borehole Wave Propagation In Isotropic And Anisotropic Media III: Anisotropic Formation |
| title_full_unstemmed | Borehole Wave Propagation In Isotropic And Anisotropic Media III: Anisotropic Formation |
| title_short | Borehole Wave Propagation In Isotropic And Anisotropic Media III: Anisotropic Formation |
| title_sort | borehole wave propagation in isotropic and anisotropic media iii anisotropic formation |
| url | http://hdl.handle.net/1721.1/75227 |
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