Walker E, Glover P W J
1Département de géologie et de génie géologique, Université Laval, Quebec, G1V 0A6 Canada.
2School of Earth and Environment, University of Leeds, Leeds, LS2 9JT UK.
Transp Porous Media. 2018;121(1):183-206. doi: 10.1007/s11242-017-0954-5. Epub 2017 Nov 13.
A large number (1253) of high-quality streaming potential coefficient ( measurements have been carried out on Berea, Boise, Fontainebleau, and Lochaline sandstones (the latter two including both detrital and authigenic overgrowth forms), as a function of pore fluid salinity ( and rock microstructure. All samples were saturated with fully equilibrated aqueous solutions of NaCl (10 and 4.5 mol/dm upon which accurate measurements of their electrical conductivity and pH were taken. These measurements represent about a fivefold increase in streaming potential data available in the literature, are consistent with the pre-existing 266 measurements, and have lower experimental uncertainties. The measurements follow a pH-sensitive power law behaviour with respect to at medium salinities ( , units: V/Pa and mol/dm and show the effect of rock microstructure on the low salinity clearly, producing a smaller decrease in per decade reduction in for samples with (i) lower porosity, (ii) larger cementation exponents, (iii) smaller grain sizes (and hence pore and pore throat sizes), and (iv) larger surface conduction. The measurements include 313 made at mol/dm , which confirm the limiting high salinity behaviour noted by Vinogradov et al., which has been ascribed to the attainment of maximum charge density in the electrical double layer occurring when the Debye length approximates to the size of the hydrated metal ion. The zeta potential ( ) was calculated from each measurement. It was found that is highly sensitive to pH but not sensitive to rock microstructure. It exhibits a pH-dependent logarithmic behaviour with respect to at low to medium salinities ( , units: V and mol/dm and a limiting zeta potential (zeta potential offset) at high salinities of mV in the pH range 6-8, which is also pH dependent. The sensitivity of both and to pH and of to rock microstructure indicates that and measurements can only be interpreted together with accurate and equilibrated measurements of pore fluid conductivity and pH and supporting microstructural and surface conduction measurements for each sample.
针对贝里亚砂岩、博伊西砂岩、枫丹白露砂岩和洛查林砂岩（后两者包括碎屑和自生过度生长形式），已经开展了大量（1253次）高质量的流动电位系数测量，测量结果作为孔隙流体盐度和岩石微观结构的函数。所有样品都用NaCl的完全平衡水溶液（10和4.5mol/dm³）饱和，然后对其电导率和pH进行精确测量。这些测量使文献中可用的流动电位数据增加了约五倍，与先前存在的266次测量结果一致，并且具有更低的实验不确定性。在中等盐度（单位：V/Pa和mol/dm³）下，测量结果遵循对pH敏感的幂律行为，并且清楚地显示了岩石微观结构对低盐度下的影响，对于具有以下特征的样品，每十年盐度降低导致的流动电位下降幅度更小：（i）孔隙率较低；（ii）胶结指数较大；（iii）晶粒尺寸较小（因此孔隙和孔喉尺寸也较小）；（iv）表面传导较大。这些测量包括在4.5mol/dm³下进行的313次测量，证实了Vinogradov等人指出的确立高盐度行为，这归因于当德拜长度接近水合金属离子大小时，在双电层中达到最大电荷密度。根据每次流动电位测量计算了zeta电位（ζ）。发现ζ对pH高度敏感，但对岩石微观结构不敏感。在低至中等盐度（单位：V和mol/dm³）下，它表现出对pH的对数依赖行为，在pH范围为6 - 8的高盐度下具有极限zeta电位（zeta电位偏移），该极限zeta电位也依赖于pH。流动电位和zeta电位对pH的敏感性以及流动电位对岩石微观结构的敏感性表明，流动电位和zeta电位测量结果只有与孔隙流体电导率和pH的精确且平衡的测量结果以及每个样品的支持性微观结构和表面传导测量结果一起才能得到解释。
