Suresh G. Thadani
Welex, a Halliburton Company, Houston, Texas
Hugh E. Hall, Jr.
Consultant, Huntsville, Texas
ABSTRACT
The geometric factor concept is of great utility in the analysis of induction logging tool performance and in formation resistivity calculations. However, it is well known that this factor can be significantly modified by propagation effects that accrue from the attenuation and phase shift of the electromagnetic field as it propagates through the formation. This paper presents a unified approach for the computation of geometric factors which filly accounts for propagation effects. These geometric factors are called propagated geometric factors.
The proposed technique can in general be used to compute propagated geometric factors in formations with cylindrical symmetry. This class of formations includes homogeneous formations, vertically stratified (thick beds with invasion) formations, and horizontally stratified (plane layered beds) formations. In addition, the technique can also be applied to combination geometries including the borehole plus invaded bed formation model.
The theoretical relationship between propagated geometric factors and the classical Doll geometric factor is developed in this paper. In addition, the propagated geometric factor approach is numerically evaluated against Doll’s geometric factor on the various formation geometries mentioned above.
Detailed results of this evaluation are presented.