The Research For The Mechanism And Suppression Method Of Electromagnetic Induction Coupling In Dual Frequency Induced Polarization Logging

The dual frequency induced polarization method proposed and implemented by the academician He Jishan has been widely used and promoted. In recent years, the dual frequency induced polarization method is used for logging, which is a new application area for this method, however, in the actual logging. there is large coupling effect of electromagnetic induction, which is due to the well environment and frequency domain IP's characteristics. This paper describes the basic principles of the dual frequency induced polarization method and the effect mechanism of electromagnetic induction coupling, and on this basis, proposes the use of pre-amplifier in the initial segment in signal measurement for the signal amplification to improve the SNR and to suppress the interference of electromagnetic induction coupling in logging. The dual frequency induced polarization logging preamplifier based on the AD620 has been designed and implemented, which include debugging the amplifier circuit and power circuit, designing and assembling the shielded casing, selection for the shielded cable. The series of work above improve the dual frequency induced polarization logging preamplifier's SNR and anti-coupling ability. A series of indoor equipment performance testing were carried out to ensure the accuracy, consistency and stability of the instrument meet the requirements of practical field work. Finally, the results of the flume simulation coupling experiment, the field simulation coupling experiment and the logging experiment validate the anti-coupling ability of dual frequency induced polarization logging preamplifier, which can be well applied in the field logging work.