Flow path delineation using Alterant Geophysical Tomography
We describe and evaluate a cross-hole geophysical technique used to map flowpaths in fractured rock: Alterant Geophysical Tomography (AGT). The method involves the use of tracers to change the electrical properties of permeable fractures. Measurements of the electromagnetic attenuation factor of a region are performed at various times (before, during, and after the introduction of the tracer). Changes in the medium due to the tracer are determined by subtracting an inversion representative of baseline conditions from an inversion of data obtained after the tracer has caused changes in the rockmass. This method has been used in a granitic rock mass in an attempt to delineate the flow paths followed by the tracers. Comparisons of the alterant geophysical tomography images with fracture information obtained from acoustic televiewer logs have been made. These comparisons suggest that several of the AGT image anomalies appear to be associated with fractures observed in the acoustic televiewer logs. The AGT method appears to provide several advantages including: increased contrast between the fractures and surrounding rock, sensitivity to only those fractures filled by the tracer and possible improvements in the accuracy of the electromagnetic measurements. 8 references, 2 figures.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5009276
- Report Number(s):
- UCRL-90537; CONF-840633-8; ON: DE84009537
- Resource Relation:
- Conference: 25. US symposium on rock mechanics, Evanston, IL, USA, 25 Jun 1984; Other Information: Portions are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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