Electromagnetic response for medium with elongated magnetically permeable conductors

Several ore deposits possessing different electrical and/or magnetic properties are found in nature in the form of elongated structures with alteration of mineralization zoning. Such situations can be approximated by a composite two-shell cylindrical model. In the present study, modifications in the response parameters due to changes in conductivity and magnetic permeability of the outer and inner shells have been illustrated for multifrequency EM measurements when the spacing between the shells is large and small. It is shown that usually the changes are reflected only when the spacing between the shells is large. However, in some cases the effect is seen when the spacing between the shells is small. Hence, the studies related to spacing between the cover and the target conductor not only affect the shielding characteristics of the overlying formations but also provide insight into the characteristic inductive interaction between the cover and the target conductors.