Fingerprinting captured CO2 using natural tracers: Determining CO2 fate and proving ownership

碳捕获和储存（CCS）已成为降低化石燃料燃烧二氧化碳排放量的一种有前途的手段。然而，对有害二氧化碳泄漏可能性的担忧导致该技术的广泛采用缓慢。迄今为止的研究还没有找到一种廉价而有效的方法来明确地确定注入的CO2的泄漏，也没有找到一种可行的方法来确定注入的CO2的所有权。这意味着，如果多个运营商注入的储存地点发生泄漏，就不可能确定是谁泄漏了CO2。关于泄漏和如何检测泄漏的持续辩论经常在大众媒体和科学出版物中记录在案。这造成了公众的困惑和恐惧，特别是在拟议的封存地点附近，导致取消了几个大型封存项目，如荷兰的Barendrecht项目，减少公众对CCS的恐惧的一种手段是展示一种简单的方法，能够可靠地检测封存地点的CO2泄漏并确定CO2的所有权。对惰性气体（氦、氖、氩、氪和氙）以及天然CO2气田中碳和氧的轻重稳定同位素比率的测量表明，CO2是如何自然储存数百万年的。惰性气体也被证明能有效地确定亚利桑那州一个二氧化碳储层和怀俄明州一个油田上方的二氧化碳自然泄漏，并排除加拿大韦伯恩储存地点的二氧化碳泄漏。最近的研究表明，从巴西一家硝酸盐化肥厂捕获的二氧化碳中，氪的含量高于氩和氦的含量。这种富集是由于较重的稀有气体具有更大的溶解度，因此它们更容易溶解在用于捕获的溶剂中。这种指纹已被证明是跟踪注入巴西和美国油田以增加石油产量的二氧化碳的有效手段。在煤、煤层气和富含有机质的油气源岩中，重惰性气体的类似富集，沿着高氦浓度，都有很好的记录。由于惰性气体不活泼，这些浓缩不会受到发电站燃烧气体或煤的影响，因此会被转移到烟道气中。从法国Lacq的氧燃料试验性CO2捕集工厂获得的CO2样品中含有远高于大气值的氦和氪浓缩物，证实了这一点。尽管这些独特的指纹被识别出来，但还没有研究调查它们与不同的CO2捕集技术或燃烧的化石燃料之间是否存在关联。我们建议测量碳和氧稳定同位素和惰性气体指纹捕获二氧化碳后，前和氧燃料试点捕获工厂。我们将查明独特的指纹是否来自所使用的捕获技术或燃烧的燃料。我们将确定这些指纹是否足够独特，以跟踪二氧化碳一旦注入地下，而不需要添加昂贵的人工示踪剂。我们将调查他们是否足以区分所有权的多个CO2流注入到同一个存储站点，如果他们可以提供一个早期预警的计划外CO2运动的存储site.To做到这一点，我们将确定从边界大坝发电厂捕获的CO2的指纹之前，其注入到Aquistore盐水含水层存储站点在加拿大Saskatechwan。通过将其与距离注入井约100米的Aquistore监测井产生的CO2指纹进行比较，我们将能够看到CO2在穿过盐水层后是否保留了指纹。这将表明，如果这种技术可以用来跟踪二氧化碳在未来的工程存储地点，特别是海上咸水层，将用于未来英国大容量二氧化碳存储的运动。

Carbon capture and storage (CCS) has emerged as a promising means of lowering CO2 emissions from fossil fuel combustion. However, concerns about the possibility of harmful CO2 leakage are contributing to slow widespread adoption of the technology. Research to date has failed to identify a cheap and effective means of unambiguously identifying leakage of CO2 injected, or a viable means of identifying ownership of it. This means that in the event of a leak from a storage site that multiple operators have injected into, it is impossible to determine whose CO2 is leaking. The on-going debate regarding leakage and how to detect it has been frequently documented in the popular press and scientific publications. This has contributed to public confusion and fear, particularly close to proposed storage sites, causing the cancellation of several large storage projects such as that at Barendrecht in the Netherlands.One means to reduce public fears over CCS is to demonstrate a simple method which is able to reliably detect the leakage of CO2 from a storage site and determine the ownership of that CO2. Measurements of noble gases (helium, neon, argon, krypton and xenon) and the ratios of light and heavy stable isotopes of carbon and oxygen in natural CO2 fields have shown how CO2 is naturally stored over millions of years. Noble gases have also proved to be effective at identifying the natural leakage of CO2 above a CO2 reservoir in Arizona and an oil field in Wyoming and in ruling out the alleged leakage of CO2 from the Weyburn storage site in Canada.Recent research has shown amounts of krypton are enhanced relative to those of argon and helium in CO2 captured from a nitrate fertiliser plant in Brazil. This enrichment is due to the greater solubility of the heavier noble gases, so they are more readily dissolved into the solvent used for capture. This fingerprint has been shown to act as an effective means of tracking CO2 injected into Brazilian and USA oil fields to increase oil production. Similar enrichments in heavy noble gases, along with high helium concentrations are well documented in coals, coal-bed methane and in organic rich oil and gas source rocks. As noble gases are unreactive, these enrichments will not be affected by burning the gas or coal in a power station and hence will be passed onto the flue gases. Samples of CO2 obtained from an oxyfuel pilot CO2 capture plant at Lacq in France which contain helium and krypton enrichments well above atmospheric values confirm this.Despite identification of these distinctive fingerprints, no study has yet investigated if there is a correlation between them and different CO2 capture technologies or the fossil fuel being burnt. We propose to measure the carbon and oxygen stable isotope and noble gas fingerprint in captured CO2 from post, pre and oxyfuel pilot capture plants. We will find out if unique fingerprints arise from the capture technology used or fuel being burnt. We will determine if these fingerprints are distinctive enough to track the CO2 once it is injected underground without the need of adding expense artificial tracers. We will investigate if they are sufficient to distinguish ownership of multiple CO2 streams injected into the same storage site and if they can provide an early warning of unplanned CO2 movement out of the storage site.To do this we will determine the fingerprint of CO2 captured from the Boundary Dam Power Plant prior to its injection into the Aquistore saline aquifer storage site in Saskatechwan, Canada. By comparing this to the fingerprint of the CO2 produced from the Aquistore monitoring well, some 100m from the injection well, we will be able to see if the fingerprint is retained after the CO2 has moved through the saline aquifer. This will show if this technique can be used to track the movement of CO2 in future engineered storage sites, particularly offshore saline aquifers which will be used for future UK large volume CO2 storage.