Release of Particulate Iron Sulfide during Shale-Fluid Interaction.
Release of Particulate Iron Sulfide during Shale-Fluid Interaction.
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DOI：
10.1021/acs.est.7b05350
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发表时间：
2018-01
影响因子：
11.4
通讯作者：
Y. Kreisserman;S. Emmanuel
中科院分区：
文献类型：
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作者：
Y. Kreisserman;S. Emmanuel
在水力压裂过程中，大量的水被注入地下，这是一种经常用于从页岩中提取碳氢化合物的技术。尽管注入的流体通常含有各种试剂，但它可能会因与岩石中存在的矿物相互作用而进一步受到污染。黄铁矿在有机含量丰富的页岩中很常见，是包括砷和铅在内的有毒元素的潜在来源，人们普遍认为，要使这些元素被活化，必须首先溶解黄铁矿。在这里，我们使用原子力显微镜和环境扫描电子显微镜来表明，在流体-岩石相互作用过程中，Eagle Ford页岩中碳酸盐矿物的溶解导致了嵌入的黄铁矿颗粒的物理剥离和活化。在pH、盐度和温度范围内进行的实验中，我们发现在所有情况下，黄铁矿颗粒都会从页岩表面分离出来。平均分离出的黄铁矿数量相当于6.5×10-11molm-2 S-1，比类似条件下预期的黄铁矿氧化速率高一个数量级以上。这一结果表明，黄铁矿颗粒的机械剥离可能是水力压裂作业和含页岩地下水系统中砷的活化的重要途径。
During hydraulic fracturing, a technique often used to extract hydrocarbons from shales, large volumes of water are injected into the subsurface. Although the injected fluid typically contains various reagents, it can become further contaminated by interaction with minerals present in the rocks. Pyrite, which is common in organic-rich shales, is a potential source of toxic elements, including arsenic and lead, and it is generally thought that for these elements to become mobilized, pyrite must first dissolve. Here, we use atomic force microscopy and environmental scanning electron microscopy to show that during fluid-rock interaction, the dissolution of carbonate minerals in Eagle Ford shale leads to the physical detachment, and mobilization, of embedded pyrite grains. In experiments carried out over a range of pH, salinity, and temperature we found that in all cases pyrite particles became detached from the shale surfaces. On average, the amount of pyrite detached was equivalent to 6.5 × 10-11 mol m-2 s-1, which is over an order of magnitude greater than the rate of pyrite oxidation expected under similar conditions. This result suggests that mechanical detachment of pyrite grains could be an important pathway for the mobilization of arsenic in hydraulic fracturing operations and in groundwater systems containing shales.