| According to the 2022 annual economic operation report of China’s petroleum and chemical industry: In 2022,the income of China’s petroleum and chemical industry is 16.56 trillion yuan,but China’s dependence on foreign oil is still as high as 71.2%.In order to get rid of this passive situation,we must further strengthen oil exploration,innovate oil exploration methods,and firmly grasp the power of discourse in oil exploitation.Transient electromagnetic method is widely used in petroleum,coal and other fossil energy exploration work,but the traditional transient electromagnetic method is affected by the topography and surrounding environmental factors because the transmitting device and receiving device are located on the ground,resulting in the detection accuracy decreasing with the increase of depth.In this paper,based on the traditional TEM working mode of "ground transmission,ground reception",the receiving device is placed underground and the "groundwell" working mode is adopted,so as to overcome the shortcomings of the traditional TEM.This paper starts from the basic theory of electromagnetic field,uses the theory knowledge of ground-well transient electromagnetic method and COMSOL Multipysics finite element software to complete the modeling of ground-well exploration model,and verifies the correctness of the established model by comparing the analytical solution with the numerical solution.Based on the established ground-well exploration model,the forward analysis of the model is carried out through numerical calculation,and the response characteristics of the uniform model,the non-uniform model and eight typical formation models are analyzed respectively.The results show that the response characteristics under the uniform model are closely related to the emission current intensity,formation resistivity and downhole location of the receiving device.The response characteristics of the non-uniform model are affected by the resistivity,buried depth,thickness and inclination angle of the abnormal body.In a typical stratigraphic model,when the resistivity of different layers is different,the received response characteristics will be different.Finally,on the basis of forward modeling,the inversion interpretation of D-type and K-type geoelectric models is carried out by using Occam inversion method.The results show that the Occam inversion method can invert and interpret the established model,and with the increase of the number of iterations,the fitting degree between the inversion effect and the initial model becomes better and better.The above analysis makes up for the shortcomings of the traditional transient electromagnetic method,provides theoretical guidance for the ground-well transient electromagnetic method in the practical exploration work,and also provides a theoretical basis for the design of related instruments. |
