2D Forward Modeling Of The TEM Method In Consideration Of IP Effect

The transient electromagnetic method(TEM) is also called time domainelectromagnetic method,which is an important branch of the electrical prospectingmethod. This method has many advantages because there are only secondary fieldafter turn off the current. This approach has been widely used in metal, petroleum andgeothermal exploration of mineral resources as well as the bedrock, engineering,groundwater searching and disaster prevention. The most widely used data processingmethods are based on one-dimensional model due to the complication of theelectromagnetic responses. The three-dimensional data computing are larger. Beforesolved the computational accuracy and speed, three-dimensional electromagneticmethod is difficult to apply in real work. Therefore, the2.5D problems have beenstudied extensively.2.5D problem, which is an effective way to explain the artificialsource data. Compared with the three-dimensional problem, whose speed has anadvantage. Compared with the pure two-dimensional problem, it can be bettersimulation of the field the actual geological conditions. It has long been recognizedthat the nature of the complex resistivity of rocks and minerals. The transientelectromagnetic method often by the induced polarization effect of rocks and minerals.Studying the IP effect is necessary for the transient electromagnetic method.In this article,we use the finite element method for numerical simulation.During computing2.5D electromagnetic response, we divide target area into manysmall part according to the finite element method, then we deduce the functional ofelectric and magnetic field according to Maxwell equation for this blockhomogeneous medium. And we substitute Cole-Cole model to the Maxwell equation.As a result, the calculation speed of2.5D forward problem is improved quickly. Theresults of frequency domains are transformed into the time domains followed by theuse of inverse cosine transform.Based on these algorithms above. I write the codes of2.5D forward onFORTRAN language and visual display of results using Matlab language. Differentparameter settings of the complex resistivity model1(low resistivity body model and high resistivity body model),in order to observe changes in each parameter on thevalue of the secondary magnetic field component Hz transceiver away from a certaintime changes in the transient electromagnetic response results. Through the surface ofthe secondary field transient response of the observation model2(complex geologicalbody model), we can distinguish the middle and late IP anomalies.