Experimental determination of noble gases and SF6, as tracers of CO2 flow through porous sandstone
Experimental determination of noble gases and SF6, as tracers of CO2 flow through porous sandstone
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稀有气体和 SF6 的实验测定，作为 CO2 流经多孔砂岩的示踪剂
DOI：
10.1016/j.chemgeo.2017.09.022
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发表时间：
2017
期刊：
影响因子：
3.9
通讯作者：
R. Haszeldine
中科院分区：
文献类型：
--
作者：
Rachel Kilgallon;S. Gilfillan;K. Edlmann;C. McDermott;M. Naylor;R. Haszeldine
为了标记注入地下的CO2进行地质储存，并使其与自然来源区分开来，已经提出了一系列添加剂化学示踪剂。然而，这些示踪剂相对于CO2在孔隙空间的运输目前受到很大的限制。这导致不确定性示踪剂是否将作为一个早期预警CO2的到来，或优先保留在孔隙空间使他们无效。在这里，我们提出的因素影响运输的惰性气体和SF6相对于CO2在多孔岩石。使用多孔砂岩岩心，将每种示踪剂加载到样品回路中，并在五种不同的实验压力下（上游10-50 kPag至下游环境压力）将其作为离散气体脉冲注入CO2载流中。使用四极质谱仪测量示踪剂到达曲线。值得注意的是，我们的结果表明，在每个压力梯度下，氦气的峰值到达时间比其他惰性气体慢。氦和其他惰性气体之间的峰值到达时间的差异随着沿着系统的压力梯度的减小而增大，并且每种惰性气体的曲线轮廓显著不同。较重的惰性气体（氪和氪）沿着与SF6显示出更早的到达时间和更宽的曲线轮廓相比，通过CO2载气流的He和Ne曲线。这表明Kr和K2 O可以在示踪应用中取代SF6，SF6是一种有效的温室气体。为了进行比较，CO2脉冲通过N2载气，导致与惰性气体和SF6相比，峰值到达时间明显较慢。因此，所有调查的示踪剂，当共同注入CO2可能作为早期预警示踪剂的CO2的到来，虽然我们发现，氪，氪和SF6将提供最强大的提前警告。对实验结果的分析表明，这不能用简单的一维渗流模型来解释。我们概述了一个概念模型，它结合了不同的优先流路取决于个别气流的流速。该模型可以解释观测数据，并表明惰性气体和SF6示踪剂的流动受到孔隙尺度非均匀性的影响。
In order to label the CO2injected underground for geological storage and allow it to be differentiated from natural sources, a panoply of additive chemical tracers have been proposed. Yet, the transport of these tracers relative to CO2in pore space is currently poorly constrained. This leads to uncertainty as to whether tracers will act as an early warning of CO2arrival, or be preferentially retained in the pore space making them ineffective. Here, we present the factors affecting transport of noble gases and SF6relative to CO2in a porous rock. Using a porous sandstone core, each of the tracers were loaded into a sample loop and injected as discrete gas pulses into a CO2carrier stream at five different experiment pressures (10–50 kPag upstream to ambient pressure downstream). Tracer arrival profiles were measured using a quadrupole mass spectrometer. Significantly, our results show that peak arrival times of helium were slower than the other noble gases at each pressure gradient. The differences in peak arrival times between helium and other noble gases increased as the pressure gradient along the system decreased and the curve profiles for each noble gas differ significantly. The heavier noble gases (Kr and Xe) along with SF6show an earlier arrival time and a wider curve profile compared to He and Ne curves through the CO2carrier gas stream. This shows that Kr and Xe could be substituted for SF6, a potent greenhouse gas, in tracer applications. For comparison, CO2pulses were passed through a N2carrier gas resulting in significantly slower peak arrival times compared to those of noble gases and SF6. Hence, all investigated tracers when co-injected with CO2could potentially act as early warning tracers of CO2arrival, though we find that Kr, Xe and SF6will provide the most robust advance warning. Analysis of our experimental results shows that they cannot be explained by a simple one dimensional flow model through a porous medium. We outline a conceptual model that incorporates different preferential flow paths depending on flow velocities of individual gas streams. This model can explain the observed dataset and shows that the flow of noble gases and SF6tracers is influenced by pore-scale heterogeneity.
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作者：
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