The Applied Research Of Audio-frequency Magnetotelluric In The Exploration Of Natural Gas Hydrate In Chang Tang Basin

In recent years, with the rapid development of industrialization in the world, oil, coal and other fossil energy are depleting. As a new type of fossil energy in the future, natural gas hydrate has been widely concentrated on around the world. The Qiangtang basin is one of the most beneficial accumulation area of China’s terrestrial gas hydrate, its permafrost is widely developed which is the necessary conditions of gas hydrates, and is the primary goal of hydrate geophysical survey. Audio-frequency magneto-telluric(AMT) can detect the electric distribution characteristics of geological body from a few meters to over 1000 m depth, and the permafrost and gas hydrates have obvious electric difference with the surrounding rock. Therefore, it can provide a reference for investigation and study of terrestrial natural gas hydrate in our country to carry out experimental research through the study of AMT method in the favorable area of natural gas hydrates reservoir.In this thesis, built a simple geophysical model firstly based on the electrical characteristics of permafrost and gas hydrate. Studied the effects of AMT on permafrost recognition results, and comparative analysis of the resolving power of subsurface structures coverage under the permafrost between TE mode and TM mode coverage under the permafrost, and its advantages and disadvantages. And summarized the electrical response characteristics of AMT for permafrost and covered geological structure, which provided a theoretical basis for the processing and interpretation of the measured data. Then analyze the advantages and disadvantages of the two mode’s inversion results in the identification of permafrost and construction, through comparing the exploration effect of TE mode with TM mode for the measured data. As a result showed that: the recognition effect for shallow layer of permafrost is very good either TE mode or TM mode, and both show their own characteristics for the shallow structure. Finally, according to the results of the inversion, inferred the distribution of permafrost thickness and faults, and speculated the favorable accumulation position of natural gas hydrates, which provided geophysical basis for metallogenic potential and resource evaluation of gas hydrates in this area.Finally, summarized the effect and deficiency of AMT for gas hydrate exploration in the permafrost region, and carried on serious thinking on the problems encountered during the study on which the future research will be based.