Numerical Simulation on the Electrical Conductivity of Ternary Mixtures Containing NaCl Solution, Quartz, and Smectite

IF 3.9 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Journal of Geophysical Research: Solid Earth Pub Date : 2024-10-29 DOI:10.1029/2024JB029063

K. Aoyama, T. Hashimoto

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Abstract

While the electrical conductivity of smectite-rich rocks is high, previous studies have only partially revealed its dependence on temperature, salinity, and porosity. This knowledge gap mainly arises from challenges in controlling various experimental conditions when measuring the conductivity of real smectite-bearing rock samples and quantifying the smectite content. To mimic conductivity measurements under ideal conditions, this study aimed to develop a simulator capable of accurately configuring the conditions to predict the direct-current conductivity of saturated rocks composed of an aqueous NaCl solution, quartz, and smectite under various temperatures (20°C–200°C), salinities (10⁻⁴–5 mol kg⁻¹), porosities (0–1), and smectite fractions (0–1). The simulator reproduced the experimental conductivity measurements from drilled core samples by giving the anisotropy of those components' distribution. In addition, simulations with randomly assigned components revealed that when rocks contain abundant smectite, the bulk conductivity partially decreases with increasing NaCl solution's salinity or volume fraction. These negative slopes were approximated using empirical equations derived from previous studies. Percolation analysis further revealed that when the components are randomly assigned, conductive paths begin to form between the ends of the modeled sample once the sum of the volume fraction of bulk pore and smectite reaches 0.1.

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含 NaCl 溶液、石英和 Smectite 的三元混合物导电性的数值模拟

虽然富含镜铁矿岩石的电导率很高，但以往的研究仅部分揭示了其与温度、盐度和孔隙度的关系。造成这一知识空白的主要原因是，在测量真实含闪长玢岩样本的电导率和量化闪长玢岩含量时，难以控制各种实验条件。为了模拟理想条件下的电导率测量，本研究旨在开发一种模拟器，能够准确配置条件，预测由氯化钠水溶液、石英和直闪石组成的饱和岩石在不同温度（20°C-200°C）、盐度（10-4-5 mol kg-1）、孔隙率（0-1）和直闪石组分（0-1）条件下的直流电导率。模拟器通过给出这些成分分布的各向异性，再现了钻孔岩芯样本的实验电导率测量结果。此外，随机分配成分的模拟结果表明，当岩石中含有丰富的直闪石时，随着 NaCl 溶液盐度或体积分数的增加，体积电导率会部分降低。这些负斜率是利用先前研究得出的经验公式近似得出的。渗流分析进一步表明，在随机分配成分的情况下，一旦块状孔隙与铁石棉的体积分数之和达到 0.1，模型样本的两端之间就会开始形成导电路径。

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来源期刊

Journal of Geophysical Research: Solid Earth Earth and Planetary Sciences-Geophysics

CiteScore

7.50

自引率

15.40%

发文量

559

期刊介绍： The Journal of Geophysical Research: Solid Earth serves as the premier publication for the breadth of solid Earth geophysics including (in alphabetical order): electromagnetic methods; exploration geophysics; geodesy and gravity; geodynamics, rheology, and plate kinematics; geomagnetism and paleomagnetism; hydrogeophysics; Instruments, techniques, and models; solid Earth interactions with the cryosphere, atmosphere, oceans, and climate; marine geology and geophysics; natural and anthropogenic hazards; near surface geophysics; petrology, geochemistry, and mineralogy; planet Earth physics and chemistry; rock mechanics and deformation; seismology; tectonophysics; and volcanology. JGR: Solid Earth has long distinguished itself as the venue for publication of Research Articles backed solidly by data and as well as presenting theoretical and numerical developments with broad applications. Research Articles published in JGR: Solid Earth have had long-term impacts in their fields. JGR: Solid Earth provides a venue for special issues and special themes based on conferences, workshops, and community initiatives. JGR: Solid Earth also publishes Commentaries on research and emerging trends in the field; these are commissioned by the editors, and suggestion are welcome.