Research On The Forward Modeling Of Magnetic Welllogging And Its Application In Magnetite Exploration

Magnetic well-logging is an extension of surface magnetic survey in underground boreholes.It is a borehole geophysical method based on the study of magnetic differences of various rocks and ores and the resulting changes of geomagnetic field.Compared with surface magnetic survey,its probe is closer to deep minerals,and at the same time,it is far away from the surface of various electromagnetic interference,which overcomes the problems of weak response of surface magnetic survey to magnetic anomaly information from deep magnetic body and poor vertical resolution of inversion interpretation.In recent years,the degree of near surface exploration is increasing,the probability of deposits being found near the surface is decreasing,mineral exploration work is gradually transferring to the deep,and the role of borehole magnetic survey in the exploration of deep magnetic deposits is becoming more and more important.Starting from the basic theory of borehole magnetic survey,this paper studies the analytical model of magnetic field of sphere and thick plate model,analyzes the magnetic field distribution and variation law of sphere and thick plate model under the condition of different model parameters,and studies the actual borehole magnetic survey project in Huangyinchong mining area of Lujiang County(1)Based on the basic theory of borehole magnetic survey,the analytical solution of magnetic field of sphere and thick plate in underground half space is derived;(2)The magnetic field distribution characteristics of the sphere model in different distances and directions of drilling and the sphere in different magnetization directions are analyzed by using the analytical formula;the magnetic field characteristics of the thick plate model in different distances and directions of drilling,when the thick plate has different magnetization directions and inclination directions,when the drilling passes through the thick plate and when the drilling has bottom anomaly are analyzed,and the variation rules are summarized.(3)The three boreholes in Huangyinchong mining area are inversed and interpreted in detail by using the summarized rules and combined with the difference of the modulus of the horizontal component.At the same time,the spatial distribution state of the magnetic body is determined by comprehensive analysis of the surface magnetic survey data.