Experimental And Finite Difference Modelling Of Borehole Mach Waves
A series of model experiments are done in the ultrasonic laboratory to study the radiation of downhole sources in a variety of formations. Three models are used in the experiments. They are a lucite model, a lucite model with free glass pipe in the center, and a glass cased soil model. In addition...
| 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/1721.1/75193 |
| _version_ | 1826205792918831104 |
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| author | Cheng, N. Y. Zhu, Zhenya Cheng, C. H. Toksoz, M. N. |
| author2 | Massachusetts Institute of Technology. Earth Resources Laboratory |
| author_facet | Massachusetts Institute of Technology. Earth Resources Laboratory Cheng, N. Y. Zhu, Zhenya Cheng, C. H. Toksoz, M. N. |
| author_sort | Cheng, N. Y. |
| collection | MIT |
| description | A series of model experiments are done in the ultrasonic laboratory to study the radiation of downhole sources in a variety of formations. Three models are used in the
experiments. They are a lucite model, a lucite model with free glass pipe in the center,
and a glass cased soil model. In addition, the finite difference modelling technique is
used to simulate the wave propagation in these models and the results of the laboratory
and numerical experiments are compared. In the lucite borehole model the waveforms
recorded in the experiment agree very well with the finite difference synthetics. The
snapshots of the wavefield from finite difference simulation show the radiation pattern
of the P and S wave in the lucite formation. These patterns are consistent with the
theoretical calculations. In the lucite model with the free glass pipe, the finite difference synthetics are also in good agreement with the experimental observations, especially for the conical P-wave arrival. The angle between the wavefront of the conical P wave and the borehole axis observed from the snapshot agrees with the theory. In the cased soil model the arrival time of the finite difference synthetics is in good agreement with the lab measurements. The relative amplitudes of the P wave and Mach wave are not correctly modelled because of no intrinsic attenuation in the finite difference calculation. The Mach cone angle from the snapshot agrees with the theoretical prediction. Finally the finite difference method is used to simulate the Mach wave propagation in the formation with two horizontal layers. In the two slow formation layers case, Mach wave generated in the first layer reflected back from and transmitted through the boundary and another Mach wave is generated at the second layer when the Stoneley wave travels into the second layer. In the one slow and the one fast formation layer case, the Mach wave generated in the slow formation is reflected back at the boundary and leaked into the fast formation layer. There is no Mach wave in the fast formation layer. |
| first_indexed | 2024-09-23T13:19:12Z |
| format | Technical Report |
| id | mit-1721.1/75193 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T13:19:12Z |
| publishDate | 2012 |
| publisher | Massachusetts Institute of Technology. Earth Resources Laboratory |
| record_format | dspace |
| spelling | mit-1721.1/751932019-04-12T20:31:20Z Experimental And Finite Difference Modelling Of Borehole Mach Waves Cheng, N. Y. Zhu, Zhenya Cheng, C. H. Toksoz, M. N. Massachusetts Institute of Technology. Earth Resources Laboratory Cheng, N. Y. Zhu, Zhenya Cheng, C. H. Toksoz, M. N. A series of model experiments are done in the ultrasonic laboratory to study the radiation of downhole sources in a variety of formations. Three models are used in the experiments. They are a lucite model, a lucite model with free glass pipe in the center, and a glass cased soil model. In addition, the finite difference modelling technique is used to simulate the wave propagation in these models and the results of the laboratory and numerical experiments are compared. In the lucite borehole model the waveforms recorded in the experiment agree very well with the finite difference synthetics. The snapshots of the wavefield from finite difference simulation show the radiation pattern of the P and S wave in the lucite formation. These patterns are consistent with the theoretical calculations. In the lucite model with the free glass pipe, the finite difference synthetics are also in good agreement with the experimental observations, especially for the conical P-wave arrival. The angle between the wavefront of the conical P wave and the borehole axis observed from the snapshot agrees with the theory. In the cased soil model the arrival time of the finite difference synthetics is in good agreement with the lab measurements. The relative amplitudes of the P wave and Mach wave are not correctly modelled because of no intrinsic attenuation in the finite difference calculation. The Mach cone angle from the snapshot agrees with the theoretical prediction. Finally the finite difference method is used to simulate the Mach wave propagation in the formation with two horizontal layers. In the two slow formation layers case, Mach wave generated in the first layer reflected back from and transmitted through the boundary and another Mach wave is generated at the second layer when the Stoneley wave travels into the second layer. In the one slow and the one fast formation layer case, the Mach wave generated in the slow formation is reflected back at the boundary and leaked into the fast formation layer. There is no Mach wave in the fast formation layer. Massachusetts Institute of Technology. Borehole Acoustics and Logging Consortium 2012-12-04T15:20:22Z 2012-12-04T15:20:22Z 1992 Technical Report http://hdl.handle.net/1721.1/75193 Earth Resources Laboratory Industry Consortia Annual Report;1992-10 application/pdf Massachusetts Institute of Technology. Earth Resources Laboratory |
| spellingShingle | Cheng, N. Y. Zhu, Zhenya Cheng, C. H. Toksoz, M. N. Experimental And Finite Difference Modelling Of Borehole Mach Waves |
| title | Experimental And Finite Difference Modelling Of Borehole Mach Waves |
| title_full | Experimental And Finite Difference Modelling Of Borehole Mach Waves |
| title_fullStr | Experimental And Finite Difference Modelling Of Borehole Mach Waves |
| title_full_unstemmed | Experimental And Finite Difference Modelling Of Borehole Mach Waves |
| title_short | Experimental And Finite Difference Modelling Of Borehole Mach Waves |
| title_sort | experimental and finite difference modelling of borehole mach waves |
| url | http://hdl.handle.net/1721.1/75193 |
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