Research progress of geophysical vector magnetic field survey technology

Abstract

Vector magnetic survey technique is one of the most effective methods for engineering and environmental geophysical exploration. Compared with the traditional geophysical magnetic survey methods, i.e., measurement of the total magnetic field intensity or its gradient, vector magnetic survey can simultaneously obtain the modulus and direction information of the earth magnetic field, which can effectively reduce the multiplicity on data inversion, contribute to the quantitative interpretation of the magnetic body and obtain more precise information and characteristics of magnetic field resource, so as to improve the detection resolution and positioning accuracy of the underground target body. In this paper, based on different application fields, we summarize the application situation, the technical feature and the instrument development of ground vector magnetic survey technique, wells vector magnetic survey technique, marine vector magnetic survey technique, airborne vector magnetic survey technique and satellites vector magnetic survey technique, respectively. As the basic method of the vector magnetic survey technique, ground vector magnetic survey development is the earliest and the technique is the most mature. The accuracy of the instrument system for ground vector magnetic survey is high and the working performance is reliable. But there are also some problems, e.g., the detection depth is shallow and working efficiency is low. Wells vector magnetic survey is one useful tool for the earth’s deep mineral resources exploration. It can finish the detection work that the ground vector magnetic measurement can’t do. But due to the limit of the bore diameter and the high temperature in well, the detection accuracy of the instrument system is lower than the ground magnetic instrument. Marine vector magnetic survey has the irreplaceable effect in the application of military or other ocean engineering. Its working mode changes from the method of ship drag-and-drop to small unmanned underwater vehicle, which can measure more precise underwater magnetic anomaly. Airborne vector magnetic survey has the superiority of fast detection, high efficiency and strong practicality to geophysical environment, etc. But because of magnetic interference and the posture change of the aircraft carrier, detection accuracy reduces. The study of magnetic compensation and data processing methods of aero three-component and full-tensor magnetic gradient is also needed. Satellites vector magnetic survey can obtain high-quality and whole global magnetic field data. Compared with the research abroad, the development of satellites vector magnetic survey in China is later and the technique is relatively backward although lots of exploration work has been done in recent years. We should take full advantage of the opportunity of China aerospace business development to actively carry out research work for the satellites vector magnetic survey. In conclusion, each magnetic survey method has its unique superiority and defect. Any single method has difficulty meeting the requirement of modern geophysical detection application. With the development of magnetic survey technique and instrument system, the future magnetic survey will change from the traditional work mode, i . e ., measuring the total magnetic field intensity or its gradient to the vector information of magnetic field, then to multi-parameter measurements. The magnetic survey application field will change from the traditional ground magnetic survey method with low efficiency and shallow detection depth to high efficient airborne magnetic survey, deep well magnetic survey and abysmal sea magnetic survey, then gradually to the joint detection and interpretation combining with the five kinds of magnetic survey methods mentioned above. Through the combination of a variety of detection methods to realize advantageous complementarities, further improvement of detection accuracy and inversion resolution for earth magnetic field will be implemented.