音频大地电磁测深在羌塘盆地天然气水合物勘探中的应用研究

发布时间：2019-05-29 21:01

【摘要】：近年来,随着世界工业化的快速发展,石油、煤等化石能源日益枯竭,天然气水合物作为未来新型的化石能源受到了世界各国的广泛关注。羌塘盆地是我国陆域天然气水合物最有利的成藏区域之一,其永久冻土层广泛发育,作为陆域天然气水合物形成的必要条件,永久冻土层是开展水合物地球物理调查的首要目标体。音频大地电磁测深(AMT)可以探测从几米到1000 m以上深度地质体的电性分布特征,而永久冻土层和天然气水合物与围岩存在明显的电性差异。因此,在羌塘盆地天然气水合物的有利成藏区域开展AMT试验研究,能为我国陆域天然气水合物的调查研究提供借鉴。本文首先根据多年冻土层和天然气水合物的电性特征,构建了简单的地球物理理论模型进行研究。通过对地电模型的正反演数值模拟,研究了AMT对冻土层的识别效果,并对比分析了TE模式和TM模式的理论模拟数据对永久冻土层和浅层构造的分辨能力及其优缺点。从理论上总结了AMT对冻土层及其覆盖下地质构造的电性反应特征,为实测数据的处理和解释提供了理论依据;然后通过详细对比实测资料TE模式和TM模式下的勘查效果,分析了两种模式的反演结果在识别冻土层和构造方面的优缺点。结果表明:无论TE模式还是TM模式,反演结果对冻土层的识别效果都很理想,而且对于浅部构造的识别,两种模式都表现出各自的特点;最后根据反演解释结果,推断了区内永久冻土层的厚度和断层的分布情况,并初步推测了天然气水合物的有利成藏位置,为该区天然气水合物的成矿潜力及资源评价提供了地球物理依据。最后,总结了AMT在冻土区天然气水合物勘查方面的效果和不足,并针对研究及成文过程中遇到的问题进行了认真的思考,在此基础上对未来研究工作做了展望。
[Abstract]:In recent years, with the rapid development of industrialization in the world, oil, coal and other fossil energy is increasingly exhausted. Natural gas hydrate as a new type of fossil energy in the future has been widely concerned by all countries in the world. Qiangtang Basin is one of the most favorable reservoir forming areas for natural gas hydrate in the continental region of China. Its permafrost layer is widely developed as a necessary condition for the formation of natural gas hydrate in the continental region. Permafrost layer is the primary target of hydrate geophysical investigation. Audio magnetotelluric bathymetric (AMT) can detect the electrical distribution characteristics of geological bodies from several meters to more than 1000 m depth, but there is obvious electrical difference between permafrost layer and natural gas hydrate and surrounding rock. Therefore, the AMT experimental study in the favorable reservoir forming area of natural gas hydrate in Qiangtang Basin can be used for reference for the investigation and study of natural gas hydrate in the continental region of China. In this paper, a simple geophysical theoretical model is constructed according to the electrical characteristics of permafrost and natural gas hydrate. Through the forward and inverse numerical simulation of geoelectric model, the recognition effect of AMT on frozen soil layer is studied, and the resolution ability, advantages and disadvantages of TE model and TM model to permafrost layer and shallow structure are compared and analyzed. The electrical response characteristics of AMT to frozen soil layer and its covered geological structure are summarized theoretically, which provides a theoretical basis for the processing and interpretation of measured data. Then, by comparing the exploration results of the measured data TE model and TM model in detail, the advantages and disadvantages of the inversion results of the two models in identifying frozen soil layer and structure are analyzed. The results show that the inversion results are ideal for the recognition of frozen soil layer, and the two models show their own characteristics for the recognition of shallow structures, whether TE model or TM model. Finally, according to the results of inversion interpretation, the thickness of permafrost layer and the distribution of faults in the area are inferred, and the favorable reservoir forming position of natural gas hydrate is preliminarily deduced. It provides geophysical basis for metallogenic potential and resource evaluation of natural gas hydrate in this area. Finally, the effect and deficiency of AMT in natural gas hydrate exploration in permafrost area are summarized, and the problems encountered in the process of research and writing are seriously considered, on the basis of which the future research work is prospected.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.13;P631.325

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