The magnetic field in a medium with two cylindrical interfaces

The Magnetic Field in a Medium with Two Cylindrical Interfaces 

Consider the determination of the field of the transversal magnetic dipole in a medium with two cylindrical interfaces. Analysis of the solution permits us to investigate the influence of the resistivity and the radius of the invasion zone on the radial response of probes with transversal induction coils. 

Making use of results, derived in the second section, in a general case with N interfar es potentials can be written in the form  

From condition of excitation it follows that Uj = Ci = —1, but a field behavior at infinity requires equality bN+ — = 0. Other 4N coefficients are found from system 

The expression for the magnetic field on the borehole axis has the form  

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