| The influence of the loop device of the multi-turn small loop transient electromagnetic method increases the off-time of the transmitting current,the received signal is distorted,and the strong mutual inductance between the sending and receiving loops makes the detection result greatly different from the actual conductive characteristics of the formation.In this paper,starting from the equivalent circuit of the transceiver loop,the influence of the multi-turn small loop transient electromagnetic device is studied in depth.The increase in the inductance of the multi-turn small loop device will cause the receiving loop to work in an over-damped state,so it needs to be increased.Match the resistance value to make it work in the critical damping state.For the transmission loop,the increase of the time constant greatly prolongs the turn-off time.In addition to reducing the intensity of the eddy current in the geological body,it will also increase the time during the induction phase,resulting in a backward shift of the received signal attenuation time.A significant increase.For the study of mutual inductance between the sending and receiving loops,Ansoft Maxwell electromagnetic simulation software was used to simulate the mutual inductance strength of the sending and receiving devices at different positions,and the experimental method was used to verify that the axial separation of the two loops had a better weakening effect on the primary field.A comprehensive analysis of the influencing factors of the coil inductance and distributed capacitance,and on this basis,the quality factor Q of the multi-turn small loop coil is calculated.Due to the small side length of the coil,the Q value is large,and the shutdown current in the launch loop is affected.Serious impact.Finally,the oscilloscope and Terra experiments are used to study the delay and increase of the decay time of the induced signal when the multi-turn small loop is used as the sending and receiving loop. |
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