Inherent Tracers for Carbon Capture and Storage in Sedimentary Formations: Composition and Applications

Inherent tracersthe “natural” isotopic and trace gas composition of captured CO2 streamsare potentially powerful tracers for use in CCS technology. This review outlines for the first time the expected carbon isotope and noble gas compositions of captured CO2 streams from a range of feedstocks, CO2-generating processes, and carbon capture techniques. The C-isotope composition of captured CO2 will be most strongly controlled by the feedstock, but significant isotope fractionation is possible during capture; noble gas concentrations will be controlled by the capture technique employed. Comparison with likely baseline data suggests that CO2 generated from fossil fuel feedstocks will often have δ13C distinguishable from storage reservoir CO2. Noble gases in amine-captured CO2 streams are likely to be low concentration, with isotopic ratios dependent on the feedstock, but CO2 captured from oxyfuel plants may be strongly enriched in Kr and Xe which are potentially valuable subsurface tracers. CO2 streams derived from fossil fuels will have noble gas isotope ratios reflecting a radiogenic component that will be difficult to distinguish in the storage reservoir, but inheritance of radiogenic components will provide an easily recognizable signature in the case of any unplanned migration into shallow aquifers or to the surface.本征示踪剂——即捕集的二氧化碳气流的"天然"同位素与痕量气体组成——是碳捕获与封存（Carbon Capture and Storage，CCS）技术中极具应用潜力的示踪剂。本综述首次系统梳理了不同原料、产二氧化碳工艺以及碳捕获技术所得到的捕集二氧化碳气流的预期碳同位素与稀有气体组成特征。捕集二氧化碳的碳同位素组成主要受原料控制，但捕获过程中可能发生显著的同位素分馏；稀有气体浓度则由所采用的捕获技术决定。通过与潜在本底数据对比可知，化石燃料原料产生的二氧化碳的δ¹³C通常可与储层二氧化碳区分开来。胺法捕集的二氧化碳气流中稀有气体浓度普遍较低，其同位素比值取决于原料；但富氧燃烧电厂捕集的二氧化碳中，氪（Kr）与氙（Xe）可能会显著富集，二者均为极具应用价值的地下示踪剂。化石燃料来源的二氧化碳气流中，稀有气体同位素比值会体现出放射成因组分特征，该组分在储层中难以被区分，但如果发生非计划运移进入浅层含水层或地表，放射成因组分的继承性将成为极易识别的特征标识。