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Azimuthal resistivity survey for anisotropy studying.

The first aim of resistivity survey is a study of any inhomogeneities. Frequently in practice the effect of anisotropy is displayed together with that of layering or inhomogeneities. It complicates data interpretation within the framework of anisotropic models, and distorts results of interpretation in the framework of layered or inhomogeneous media. Ignoring of anisotropy results in wrong data interpretation. At the same time anisotropy studying can give valuable geological information. That means that anisotropy itself and the mutual influence of anisotropy and inhomogeneities needs to be studied. On definition, rock anisotropy is displayed in apparent resistivity values as dependence on array orientation and as independence on coordinates. Azimuthal (or circular) resistivity survey (ARS) is the best field technology for anisotropy studying. There are several problems of anisotropy which were considered in this study.
0. Origin of resistivity anisotropy in rocks.
1. Choice of array, which is more sensitive to anisotropy.
2. Type of array rotation to find the difference between anisotropy and inhomogeneity influence.
3. Visualization of azimuthal resistivity survey (ARS) data.
4. Data processing and interpretation.
5. Signs of anisotropy and that of inhomogeneity in spectra of ARS data.
6. Anisotropic and pseudo-anisotropic models.
7. Forward problem calculation for different anisotropic models.
8. Field ARS measurements in areas with high and low anisotropy.
9. Software for anisotropy modeling and interpretation.
10. References.

119899, Russia, Moscow, Moscow State University, Geological Faculty, Department of Geophysics.

V.A. Shevnin, I.N.Modin
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