| Transient electromagnetic method(TEM)for formation Resistivity Detection through casing is a new type of logging method,which has become one of the hot spots in related fields.Based on transient electromagnetic method,this paper studies the transient electromagnetic logging technology,and worked on the both aspects of related theory and the circuit system design.In the aspect of theory research,In this paper,the transient response waveform of the secondary filed is calculated by using the secondary filed formula given by Doll.And in this paper,the transient electromagnetic logging response and the Doll secondary field response of the actual excitation source are researched.By using Doll electromagnetic induction theory and the exact solution of infinite homogeneous medium,we can get the total response of different excitation conditions and the response waveform of Doll secondary field.And we also thoroughly studied the two responses of transient electromagnetic resistivity logging through casing and the theory of signal transmission.As for the circuit system design,this paper mainly focuses on the software and hardware development of the formation signal acquisition and transmission system.The system consists of underground part and ground part,and the underground part is divided into front-end conditioning circuit,signal acquisition circuit,MCU control circuit,signal processing circuit and emission control circuit.The acquisition part realized the synchronous sampling on four response signals and measurement of two DC voltage signals.And the synchronous control can be carried out on the excitation sequence of the transmitting board by the emission control circuit.And the function of the signal processing circuit is to transmit and receive the signals according to the protocol requirements.The signal is collected from the underground part and then transmitted to the ground part by cable,and is transmitted from the ground part to the upper computer for display. |
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