Study of using square-wave coherent method to extracting IP effect

摘要

Electromagnetic effect is a major disturbance of measured induced polarization data, and it seriously interferes with the induced polarization measurement and its application effect thus reducing the exploration depth. Therefore, to suppress and eliminate electromagnetic effects effectively is very important. Square-wave coherent method, a unique method to decouple in dual-frequency induced polarization, it is a good way to eliminate the influence of electromagnetic effect from the total field, and at the same time extract the induced polarization effect. Restoring the dual waveform is the key to the square-wave coherent method. When restoring the received waveform to a low-frequency and high-frequency square wave, it is essential to select the inflection point of waves, 0 to 1 or 0 to -1, which will directly affect the validity of the results of the follow-up process. But due to the interference of electromagnetic effects and ambient noise, it is difficult to pick the inflection point, and which has a bad impact on the promotion and application of the square-wave coherent method. According to the characteristics of inflection point, there's a large difference of amplitude before and after taking off. This article mainly discussed two approaches to pick up take-off points: Based on the amplitude ratio; Base on the amplitude difference. In noisy environments, using these two methods to pick inflection point can still get good results. After finding the inflection point, we can use the square-wave coherent method to calculate the amplitude frequency of induced polarization effect. Compared to the theoretical amplitude frequency, the calculated one, which proves that square-wave coherent method have a good effect in dual-frequency induced polarization measurement.