Advancements of induced polarisation theory in sediments

用地球物理方法估计水力参数是一个非常重要的研究领域，例如地下水勘探和管理，地热能和环境问题。频谱激发极化法是一种很有前途的测量地下电导率的方法。原则上，水力参数可以通过实验室得出的经验关系从电导率估计。然而，经验关系往往依赖于材料，缺乏普遍适用性，或者它们有很大的误差。在这个项目中，我们研究了多孔介质的电和水力特性之间的关系的理论基础。在进行中的项目过程中，一个现有的半解析模型，描述了一个圆柱形孔隙系统的阻抗扩展到阻抗网络。该扩展允许将可测量的岩石物理参数，如孔隙度，比内表面，或孔隙半径分布，到模型中。我们成功地模拟了实验室测量数据的几个特性，包括无法用传统方法解释的功能。在建议的延长，我们将进一步改进模型，通过修改一些选定的参数化，目的是定量拟合测量的阻抗谱。我们还将扩展与测量数据的比较，以更大的数据集，以测试从理论产生的假设。

The estimation of hydraulic parameters with geophysical methods is a research area of fundamental importance, e.g. for groundwater exploration and management, for geothermal energy, and for environmental problems. Spectral induced polarization is a promising method that measures the frequency dependent electrical conductivity of the subsurface. In principle, hydraulic parameters may be estimated from electrical conductivity through empirical relationships derived in the laboratory. The empirical relationships, however, often depend on the material and lack general applicability, or they have large error margins. Within this project, we investigate the theoretical foundations of the relationships between electric and hydraulic properties of porous media. During the course of the ongoing project, an existing semi-analytical model that describes the impedance of a cylindrical pore system was extended into an impedance network. The extension allows to incorporate measurable petrophysical parameters, such as porosity, specific internal surface, or pore radii distribution, into the model. We succeeded to simulate several characteristic properties of measured laboratory data, including features that cannot be explained with conventional approaches. Within the proposed prolongation, we will further improve the model by modifying some of the chosen parameterizations, with the aim to quantitatively fit measured impedance spectra. We also will extend the comparison with measured data to larger data sets in order to test hypotheses resulting from the theory.