Electromagnetic logging response in radial heterogeneous media

The general expressions of the electromagnetic logging response functions of in radial heterogeneous media are deduced by solving the Helmholtz equation of electric field intensity in cylindrical coordinate system.And the effects of the casing thickness on electromagnetic logging responses are analyzed.The computation results show that the little change of the casing thickness will produce an obvious effect on the logging responses.The numerical results of the casing pipe of different electrical conductivity show that the higher the electrical conductivity of the casing material,the lower the signal amplitude of the electromagnetic logging response,and that the higher the magnetic permeability of the casing material,the more difficultly the electromagnetic signal passes hrough the casing.So non-magnetic or low-magnetic steel pipe is superior to magnetic iron pipe.The research results in this paper can provide a theoretical basis for the logging interpretation and the optimization of instrument parameters in cased wells.