| Based on transient electromagnetic method,this paper studies the transient electromagnetic logging technology,and has developed a set of system which is used in oil wells to verify the technology.The aim is to provide the reference for the applied research of transient electromagnetic method in well logging and instrument design.Firstly,based on the open hole,this paper proposes a two-medium model and the radial geometry factor theory of induction log is applied to the transient electromagnetic logging technology.The model is calculated by using the radial integral factor and the radial differential geometric factor.The results show that the radial differential geometry factors are negative,which are not suitable for the geometric factor theory.Then,a new three-medium model is proposed,which is combined with the influence of the well.The feasibility and rationality of the model are verified by calculation.Therefore,it can be used to describe the characteristics of the radial depth of the transient electromagnetic logging response,and provide a reference for the instrument design.Then,from the point of view of circuit parameters the whole underground circuit system is analyzed and studied,including the study of the parameters of the transmitter coil,the switch tube and the parallel resistance.The underground launch system includes control system,launch system,coil system,filter amplifier system and power supply system.Finally,on the basis of a large number of experiments,the theoretical research and experimental data are combined to study and verify.The results show that: in the open hole,the secondary field amplitude is the largest in shutdown time.The experimental secondary field changes are in good agreement with the theoretical computations,which further determine the application of the geometry factor to the transient electromagnetic method is feasible.This also provides an important reference for the non-contact measurement through casing resistivity logging. |
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