Study On Effection And Extract Of IP From Frequency Domain Electromagnetic Method

Influenced by the induced polarization effect, earth resistivity is a plural whichconstantly changing with frequency, and the signal from electromagnetic method in thefrequency domain must contain IP information. Studying the effect of the IP effect infrequency domain electromagnetic method, then extracting the IP information, can solve thepolarizability problem of deep exploration, improve then inversion and interpretationprecision of the frequency domain electromagnetic method. The study have greatsignificance in the mineral exploration in the "second prospecting space".Based on the Cole-Cole model, I have studied the1D discrete CSAMT forward methodand2D finite-element MT forward method with IP effect. Replaced plural resistivity withresistivity, I have modeled the change characteristics of the electromagnetic field, apparentresistivity and phase with polarization medium. Influenced by the IP effect, the response curveof different resistivity models have significantly anomaly. And the MT and CSAMT have thesimilar characteristics and influence. The CSAMT response characteristics of IP effect aremore obvious which is influenced by the near field distortion effect. So it is more optimistic toextract of IP effect from the CSAMT signal.This paper have studied the commonly used methods to extract IP from the CSAMTsignal, analyzed the problems of the existing methods about theory research and practiceapplication. Based on the electric field relative to the magnetic field of the IP effect reflectsmore sensitive, we raised a step-by-step inversion method to extract the IP information.Using the step-by-step inversion method with the Hy and Ex components calculate the IPparameters of three layers geoelectric section, and compared the result with the generalinversion method.The inversion calculations show we can use the step-by-step inversionmethod extract the appropriate IP parameters, in some degree.We apply this inversion methodto the CSAMT data of some area exploring for Nickel, Copper polymetallic ore in Shanxiprovince. The inversion IP result and logging data has good correspondence.