Dedução e análise dos campos elétrico e magnético gerados por transmissor quadrado de um sistema geofísico eletromagnético a multi-freqüência

The multi-frequency EM method is being tested successfully for oil exploration and reservoir fluid monitoring at on-shore environments. The inversion procedures presently used for obtaining the electrical parameters of the underground from the data registered<br>at the receiver assumes that the finite-size sourcetransmitter (a current square loop on the ground) is a point-source vertical magnetic dipole. This approximation implies limitation on the transmitter-receiver separation minimum distance to be at least 6 times the side of the loop. In this paper the fields are deduced for finite source, of square and circular shapes, and compared to each other and to point dipole-source fields, as well. New graphics have been constructed for showing the inversion function of the measured data, for a finite source square loop, and compared to the dipole-source. It is shown that when using, for instance, T-R separation 1.5 times the side of square loop, that approximation is not valid at all.