Pressure dependence of permeability and spectral induced polarisation (SIP)

从电性数据（光谱激发极化，SIP）推导砂岩水力输运参数的一个基本前提是对砂岩孔隙空间中电荷载流子输运的基本理解。离子在孔隙流体中的流动性将受到与岩石基质相互作用引起的极化的阻碍。相互作用的程度由许多参数控制，如盐度、孔隙流体的化学性质、矿物组成、孔隙空间的内表面和粘土矿物的阳离子交换能力。因此，在电化学双层（DL）中的电荷载流子的传输在斯特恩层和双层的扩散部分中显著不同，而两个传导过程对总电导率的贡献由化学参数和孔隙特定的岩石物理性质（如孔隙度、渗透率、内表面、孔隙半径分布等）决定。这些参数彼此之间的相互作用的详细知识对于建立公共模型概念是必不可少的，这将允许将电传输参数分配给测量的SIP签名。解释先前在不同类型砂岩上进行的SIP测量的问题在于，基本电化学和岩石物理参数被非常精确地确定，但是由于砂岩的不同孔隙几何形状，无法创建与渗透率的一般相关性。因此，不同的小组解释SIP频谱使用不同的模型方法。这些都是测试方面的一般信息价值，但是，一般的关系，迄今无法建立。但是SIP的压力依赖性的测量可以有助于解决这个基本问题，因为在这些测量中系统岩石/孔隙流体的总化学性质将是恒定的，而变量是压力引起的孔隙度和渗透率的变化，特别是孔隙系统的互连程度。因此，只有在斯特恩和扩散部分的电化学双层（EDL）的电荷传输的贡献将被改变。因此，SIP测量的复电导率的虚部（正交分量）的变化然后可以与独立测量的压力依赖性渗透率的变化相关。

An essential precondition for a derivation of hydraulic transport parameters of sandstones from electric data (spectral induced polarization, SIP) are a basic understanding of the transport of charge carriers in the pore space of sandstones. The mobility of ions in the pore fluid, will be hampered by polarizations caused by interaction with the rock matrix. The degree of interaction is controlled by numerous parameters like salinity, chemistry of the pore fluid, the mineralogical composition, the inner surface of the pore space and the cation exchange capacity of the clay minerals. The transport of charge carriers in the electrochemical double layer (DL) is thus in the Stern layer and the diffuse part of the double layer significantly different, whereas the contributions of the two conduction processes to the total conductivity are determined by chemical parameters and pore-specific petrophysical properties such as porosity, permeability, inner surface, pore radius distribution, etc.. A detailed knowledge of the interactions of these parameters with each other are essential to establish common model concepts, which would allow to assign the electrical transport parameters to measured SIP signatures. The problem to interpret the previously performed SIP measurements that were performed on different types of sandstones, is that the fundamental electrochemical and petrophysical parameters were determined very precise, but due to the different pore geometries of the sandstones a general correlation with the permeability could not be created. Thus various groups interpreted the SIP spectra using different model approaches. These were tested with respect to a general informational value, however, a general relationship could not be established so far. But measurement of the pressure dependence of the SIP can contribute to solve this fundamental problem, since the total chemistry of the system rock/pore-fluid will be constant in these measurements, while variables are the pressure induced changes in porosity and permeability, especially the degree of interconnection of the pore system. Consequently only the contributions of the charge transport in the Stern- and the diffuse part of the electrochemical double layer (EDL) will be changed. Thus the change in the imaginary part of the complex conductivity (quadrature component) of the SIP measurement can then be correlated with the independently measured change of the pressure-dependent permeability.