基于自然电位的多孔介质孔隙度与弥散度解析

发布时间：2018-01-29 14:39

  本文关键词： 自然电位 非耦合分析理论 孔隙度 弥散度　出处：《南京大学》2015年硕士论文　论文类型：学位论文

【摘要】：自然电位作为地球物理探测的重要于段之一,在水文地质领域中得到了广泛的应用。由于自然电位能够直接反应水流流动和溶质运移过程,其在反应水流流动和获取水文地质参数方面有着其它地球物理学方法所不具备的优势。因此,研究基于自然电位获取多孔介质孔隙度与弥散度的方法具有十分重要的意义。利用自然电位获取多孔介质孔隙度和弥散度的方法目前大体上可分为两类：一是基于耦合分析理论的方法,二是基于非耦合分析理论的方法。基于耦合分析理论获取孔隙度和弥散度的方法计算复杂且用时较长,而基于非耦合分析理论获得孔隙度与弥散度的方法目前也没能对所测的自然电位曲线进行完整的拟合,实现对相关参数的准确提取。为此,在本研究中,通过室内砂柱、砂箱的盐脉冲实验,同时高密度的监测实验过程中不同观测位置的自然电位时问变化过程,通过自然电位非耦合分析理论理论和渗流理论,探讨了获取多孔介质的有效孔隙度和弥散度的方法,为室内获取多孔介质的孔隙度和弥散度提供一种便捷、无损和高密度的方法。通过本研究获得了以下成果：(1)采用非耦合分析理论建立了针对一维均质多孔介质的自然电位拟合模型。通过该模型对实测自然电位的拟合,获得了实验用多孔介质的孔隙度和弥散度参数。通过与渗流理论获得的参数的比较,说明了所得孔隙度和弥散度参数是可靠的。由于所得孔隙度为水流实际通过孔隙的孔隙度,本研究中所获得的孔隙度为有效孔隙度。(2)通过渗流理论获取孔隙度的方法不仅适用于均质介质条件同时也适用于非均质介质条件。但基于自然电位的非耦合分析理论获取孔隙度的方法在非均质多孔介质条件下存在一定的不足,对实测自然电位的拟合结果不理想。多孔介质的非均质性在实测自然电位的时间变化曲线上通过双峰甚至多峰的现象体现出来,说明自然电位仍然能够在一定程度上反映出多孔介质的非均质性。(3)高密度的自然电位监测和由此所获得的参数,为我们建立多孔介质孔隙度和弥散度的空间分布场创造了条件。虽然在本研究中我们仅仅获得了孔隙度和弥散度在一维空间的分布,但它为我们在二维甚至三维条件下建立孔隙度和弥散度的空间分布场提供了一条重要的途径。(4)在二维条件下通过自然电位成像监测本研究实现了对二维溶质运移过程的监测,这为我们研究实际流场、验证渗流场的数值模拟结果、认识多孔介质中的溶质运移过程等都具有重要意义。
[Abstract]:As an important part of geophysical exploration, natural potential has been widely used in hydrogeology, because natural potential can directly reflect the flow of water and solute transport process. It has advantages not available in other geophysical methods in terms of reacting the flow of water and obtaining hydrogeological parameters. It is of great significance to study the methods of obtaining porosity and dispersion of porous media based on natural potential. At present, the methods of obtaining porosity and dispersion of porous media by natural potential can be divided into two categories:. One is the method based on coupling analysis theory. The second is the method based on the decoupling analysis theory, the method of obtaining porosity and dispersion based on the coupling analysis theory is complicated and takes a long time. However, the method of obtaining porosity and dispersion based on decoupling analysis theory has not been able to complete fitting the measured natural potential curve, and to achieve the accurate extraction of relevant parameters. Therefore, in this study. Through the indoor sand column, sand box salt pulse experiment, at the same time, the high-density monitoring experiment process of different observation positions of natural potential time change process, through the natural potential non-coupling analysis theory and seepage theory. The method of obtaining effective porosity and dispersion of porous media is discussed, which provides a convenient method for obtaining porosity and dispersion of porous media in laboratory. Nondestructive and high-density methods. The following results have been obtained from this study: 1). The natural potential fitting model for one-dimensional homogeneous porous media is established by using the theory of non-coupling analysis, and the measured natural potential is fitted by the model. The parameters of porosity and dispersion of porous media for experimental purposes are obtained and compared with those obtained by seepage theory. It is shown that the obtained porosity and dispersion parameters are reliable, because the obtained porosity is the porosity of the flow through the pore. The porosity obtained in this study is effective porosity. The method of obtaining porosity by seepage theory is not only suitable for homogeneous medium condition but also suitable for heterogeneous medium condition. However, the method of obtaining porosity based on uncoupled analysis theory of natural potential is applied in heterogeneous porous media. There are some shortcomings under the condition. The heterogeneity of porous media is reflected in the time-varying curve of measured natural potential by the phenomenon of double peaks or even multiple peaks. It shows that the natural potential can still reflect the heterogeneity of porous media to some extent) the high density of natural potential monitoring and the parameters obtained therefrom. The conditions are created for us to establish the spatial distribution field of porosity and dispersion in porous media, although in this study we have only obtained the distribution of porosity and dispersion in one-dimensional space. But it provides an important way for us to establish the spatial distribution field of porosity and dispersion under two-dimensional or even three-dimensional conditions. Monitoring of Solute Migration in Two-Dimensional condition by Natural potential Imaging in this study. It is of great significance for us to study the actual flow field, verify the numerical simulation results of the seepage field, and understand the solute migration process in porous media.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.3;P641.7
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本文编号：1473649