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Synthetic waveforms of axial motion in a borehole with drill string
Biancamaria Farina1, Flavio Poletto1, José M Carcione1
1Istituto Nazionale di Oceanografia e di Geofisica Sperimentale-OGS, Borgo Grotta Gigante 42/c, 34010 Sgonico, Trieste, Italy.
The Journal of the Acoustical Society of America
|March 4, 2017
Summary
This study simulates wave motion in boreholes using advanced numerical methods. Rigid boundary conditions provide accurate results for wave propagation in various geological formations.
Area of Science:
- Geophysics
- Acoustics
- Computational Seismology
Background:
- Wave propagation in boreholes is crucial for understanding subsurface geology.
- Existing multi-modal analyses have limitations in handling complex borehole environments.
Purpose of the Study:
- To develop and validate a general numerical simulation method for wave motion in fluid-filled boreholes.
- To analyze wave propagation characteristics influenced by drill strings and geological formations.
Main Methods:
- Three-dimensional, axis-symmetric, full-wave numerical simulation in cylindrical coordinates.
- Utilized a small radius to avoid singularity at the origin and tested rigid vs. free-surface boundary conditions.
- Simulated wave propagation in both hard and soft geological formations.
Main Results:
- Rigid boundary conditions were found to be a better approximation than free-surface conditions.
- Generated synthetic waveforms, amplitude distributions, and motion diagrams.
- Analyzed dispersion, amplitude, and orbital polarization of excited modes, comparing results with literature.
Conclusions:
- The proposed numerical approach is more general than multi-modal analysis.
- It accurately simulates wave motion in complex borehole environments with arbitrary property variations.
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