Dje Loic Bethel, Radonjic Mileva
Barrier Materials and Geomimicry Lab, School of Chemical Engineering, Oklahoma State University, Stillwater, OK 74078, USA.
Materials (Basel). 2025 Jul 18;18(14):3382. doi: 10.3390/ma18143382.
Understanding mineral-fluid interactions in shale under supercritical CO (scCO) conditions is relevant for assessing long-term geochemical containment. This study characterizes mineralogical transformations and elemental redistribution in five Caney Shale samples serving as proxies for reservoir (R1, R2, R3) and caprock (D1, D2) facies, subjected to 30-day static exposure to pure scCO at 60 °C and 17.23 MPa (2500 psi), with no brine or impurities introduced. SEM-EDS analyses were conducted before and after exposure, with mineral phases classified into silicates, carbonates, sulfides, and organic matter. Initial compositions were dominated by quartz (38-47 wt.%), illite (16-23 wt.%), carbonates (12-18 wt.%), and organic matter (8-11 wt.%). Post-exposure, carbonate loss ranged from 15 to 40% in reservoir samples and up to 20% in caprock samples. Illite and K-feldspar showed depletion of Fe, Mg, and K at grain edges and cleavages, while pyrite underwent oxidation with Fe redistribution. Organic matter exhibited scCO-induced surface alteration and apparent sorption effects, most pronounced in R2 and R3. Elemental mapping revealed Ca, Mg, Fe, and Si mobilization near reactive interfaces, though no secondary mineral precipitates formed. Reservoir samples developed localized porosity, whereas caprock samples retained more structural clay integrity. The results advance understanding of mineral reactivity and elemental fluxes in shale-based CO sequestration.
了解超临界CO₂（scCO₂）条件下页岩中的矿物-流体相互作用对于评估长期地球化学封存至关重要。本研究对五个作为储层（R1、R2、R3）和盖层（D1、D2）相代表的卡尼页岩样品中的矿物学转变和元素重新分布进行了表征，这些样品在60°C和17.23MPa（2500psi）下静态暴露于纯scCO₂ 30天，未引入盐水或杂质。在暴露前后进行了扫描电子显微镜-能谱分析（SEM-EDS），矿物相分为硅酸盐、碳酸盐、硫化物和有机质。初始组成以石英（38-47重量%）、伊利石（16-23重量%）、碳酸盐（12-18重量%）和有机质（8-11重量%）为主。暴露后，储层样品中碳酸盐损失范围为15%至40%，盖层样品中高达20%。伊利石和钾长石在颗粒边缘和解理处显示出铁、镁和钾的损耗，而黄铁矿发生氧化并伴有铁的重新分布。有机质表现出scCO₂诱导的表面改变和明显的吸附效应，在R2和R3中最为明显。元素映射显示在反应界面附近有钙、镁、铁和硅的迁移，尽管没有形成次生矿物沉淀。储层样品形成了局部孔隙，而盖层样品保留了更多的结构粘土完整性。这些结果推进了对基于页岩的CO₂封存中矿物反应性和元素通量的理解。
