ISSN 1000-3665 CN 11-2202/P

    音频大地电磁法三维勘探在某地热区勘查中的应用研究

    Application of audio frequency magnetotelluric 3D prospecting in a hot area exploration

    • 摘要: 地热资源勘查的方法众多,电磁法因其对温度响应敏感,在地热勘查中得到广泛应用,音频大地电磁法因其探测精度高,探测深度较大,是浅层地热资源探测中最常用的电磁方法。某地热区内温泉出露较大,地热地质特征明显,但区内未进行过详细地热调查和地球物理勘查,为确定某地热区地热系统热储、盖层以及导热通道的空间分布特征,研究利用音频大地电磁法在研究内布设5条音频大地电磁测线,对音频大地电磁数据的进行维性分析与三维反演,结合地热区地热地质资料研究地热系统的分布特征。研究结果表明:(1)研究区地质情况复杂,地下介质具有三维电性结构特征,可以对音频大地电磁数据三维反演;(2)研究区三维电性结构特征显示区内存在10个高阻异常体和2个低阻异常体,深部低阻异常体范围较大,中心电阻率值约为5 Ω·m;(3)确定了研究区热储、盖层以及导热通道的分布范围,热储埋深在300−1500 m,盖层主要为第四纪覆盖层,查明地热热水的循环通道与断层F1、F2有关。上述研究结果表明音频大地电磁法三维勘探可直观展示地热区地热分布情况,为该地热区开发利用提供了重要的技术支持。

       

      Abstract: Various methods are used for geothermal resource exploration, with the electromagnetic method being widely applied due to its sensitivity to temperature changes. Among these, the audio magnetotelluric (AMT) method is the most commonly used electromagnetic method in shallow geothermal resource exploration because of its high detection accuracy and substantial depth of investigation. To determine the spatial distribution characteristics of heat storage, cover layer, and heat conduction channel of a geothermal system located in a hot spring area with clear geothermal geological characteristics, Five AMT survey lines were established in the study area, followed by spatial analysis and three-dimensional inversion of the AMT data. The distribution characteristics of geothermal system were analyzed in combination with geothermal geological data in geothermal areas. The results show that the geological condition of the study area is complex, and the underground medium has the characteristics of three-dimensional electrical structure, which is suitable for three-dimensional inversion of the AMT data. The three-dimensional electrical structure characteristics of the study area show that there are 10 high-resistance anomalic bodies and 2 low-resistance anomalic bodies in the study area. The deep low-resistance anomalic bodies have a large range with the central resistivity value of approximately 5Ω·m. The distribution ranges of heat storage, cover layer, and heat conduction channel in the study area were determined. The buried depth of heat storage is 300-1500 m, with the primary cover layer of Quaternary deposits. It is found that the circulation channel of geothermal hot water is related to fault F1 and F2. These findings demonstrate that the surface AMT method for 3D prospecting can effectively reveal the distribution of geothermal energy, providing important technical support for the development and utilization of thermal areas.

       

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