Numerical simulation and development of data inversion in borehole ultrasonic imaging

The major function of underground nuclear waste disposal is to avoid the migration of radionucleides towards the biosphere during their active period. This function can be deteriorated by the EDZ (excavated damaged zone) around the excavation. The EDZ analysis is therefore crucial in the performance...

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Bibliographic Details
Published in:Journal of applied geophysics 2011-04, Vol.73 (4), p.357-367
Main Authors: Renaud, V., Balland, C., Verdel, T.
Format: Article
Language:English
Subjects:
Algorithms
Applied geophysics
Borehole
Boreholes
Computer simulation
Earth Sciences
Earth, ocean, space
EDZ
Environmental Sciences
Exact sciences and technology
Imaging
Internal geophysics
Mathematical analysis
Mathematical models
Modeling
Ray tracing
Sciences of the Universe
Tomography
Ultrasonic testing
Velocity
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Summary:The major function of underground nuclear waste disposal is to avoid the migration of radionucleides towards the biosphere during their active period. This function can be deteriorated by the EDZ (excavated damaged zone) around the excavation. The EDZ analysis is therefore crucial in the performance assessment of the storage. The paper deals with the determination of the EDZ around a nuclear waste storage cavity using borehole ultrasonic imaging (azimuthal tomography). Indeed, before processing experimental data obtained with this tool, it is necessary to establish that data can be satisfactorily inverted. This analysis is based on a method that is able to sound and image the rock mass velocity field. The velocity field is numerically simulated (3D geomechanical modeling) based on an assumption on the relationship between stress and velocity fields. In order to evaluate a radial velocity profile starting from inter-sensor distance and their corresponding traveltimes, different ray tracing algorithms are tested using synthetic data. These tests led to a simple and fast approach (implemented in a Mathematica package) to process a large quantity of data. ► EDZ of a nuclear waste storage cavity is examined using borehole ultrasonic imaging. ► A fast approach is suggested to satisfactorily invert tomographic data. ► An iterative and convergent ray tracing algorithm was improved.
ISSN:0926-9851
1879-1859
DOI:10.1016/j.jappgeo.2011.02.007