Study On The Response Characteristics Of Deep Reservoirs With MTEM

With the disappearance of shallow mineral resources,it is a general trend to explore deep mineral deposits.The multi-channel transient electromagnetic method uses pseudo-random coded source emission and axial array observation mode.It requires the observation of the emission current while the response is observed.Deconvolution of the two can be used to extract the earth impulse response.The purpose of improving detection depth,detection accuracy and detection accuracy can be achieved.Establish a cross-well MTEM method model with COMSOL Multipysics,and the response characteristics of deep reservoirs are studied through simulation.The ground impulse response is obtained by the correlation identification method,and then cosine noise and white noise are added respectively.The acquired ground impulse response is compared with the analytical solution.The result shows that the ground impulse response is more accurate when the order is 9,the symbol width is 1/10000 s,the M-sequence's cycle number is 9.Based on the above,the factors affecting the response characteristics of deep reservoirs are analyzed,including the study of thickness of anomalous bodies,electrical conductivity,emission source location.The results of the resolution research show that: this model has better resolution for low-resistance bodies;when the emitter is too close to the high-resistance body,the resolution is reduced;for layered high-resistance bodies,the resolution is better,and the resolution varies with high resistance.The increase in body thickness and resistivity increases.The research results of the detection depth show that the detection depth increases with the distance between the emitter and the ground,the thickness of the abnormal body,and the difference between the conductivity of the abnormal body and the conductivity of the formation.Therefore,the depth of detection of deep anomalies can be increased by increasing the distance between the emission source and the ground.The above conclusions lay a good foundation for multi-channel transient electromagnetic method for deep reservoir exploration and provide a theoretical basis for the design of related instruments.