Predicting the fate of CO2 in geological reservoirs for modelling geological carbon storage

这一建议是利用自然地质实例来评估在地质构造深处处置二氧化碳的命运和最终安全性。将二氧化碳从发电站燃料或废气中分离出来，并将其注入地下并储存在地质构造中，是全球社会在向低碳经济转型的同时管理能源供应的一种经济实用的方法。天然二氧化碳储存了数百万年的地质地点的存在表明，为了保护气候，需要超过一万年的时间来清除二氧化碳可能是可行和安全的。然而，在充满盐水的含水层中，控制二氧化碳命运的过程是复杂的，为了保证储存的安全和效率，有必要能够在~ 10000年的储存期内预测这些过程，这比目前工业模拟的水库过程要长得多。在地下对超临界或气态二氧化碳进行操作的许多过程可以提高其储存潜力。浮力的二氧化碳会溶解在地层盐水中，形成密度更大的饱和二氧化碳的盐水，这些盐水会下沉。饱和二氧化碳的盐水相对活跃，但目前的模型表明，与储层中的碳酸盐和硅酸盐矿物的反应最终将导致相当大比例的二氧化碳以碳酸盐矿物的形式永久储存。然而，带二氧化碳的盐水也可能与保留二氧化碳的盖层发生反应，目前尚不清楚这是否会通过矿物沉淀来增强封印，还是通过矿物溶解来降低封印。我们预测这些流体-矿物反应能力的一个主要限制是，这些反应以可变速率缓慢进行（几天、几个月到几年），我们对实际油田环境中反应速率的了解非常有限。该项目将研究来自天然二氧化碳储层的流体和气体，并在可能的情况下研究正在地下积极注入二氧化碳的地点的流体和气体，以确定自然环境中矿物-流体反应的速率。我们将在实验室实验中重复这些反应，这样就有可能在受控条件下研究这些过程，研究发生在天然岩石中的复杂耦合反应中的单个反应，并检查不同潜在速率控制参数的影响。最终目标是为地质碳储存的现场评估、风险和监测提供信息。这项研究将有利于环境科学的其他领域，在这些领域中，动力学受限的流体-矿物反应速率控制着重要的过程。

This proposal is to use natural geological examples to evaluate the fate and ultimate safety of disposing of carbon-dioxide deep underground in geological formations. Separation of carbon-dioxide from power station fuels or exhaust products, and the injection and storage of the CO2 underground in geological formations is an economical and practical way for global society to manage energy supplies while transforming to a low carbon economy. The existence of geological sites where natural carbon-dioxide has remained stored for millions of years suggests removal for more than the 10000-year period needed to protect climate maybe practical and safe. However the processes which govern the fate of carbon-dioxide in brine-filled aquifers are complex and to guarantee the safety and efficiency of the storage it is necessary to be able to predict these over the ~ 10000 year storage period, a time much longer than industry currently models reservoir processes. Many of the processes which operate on supercritical or gaseous carbon-dioxide underground may enhance its storage potential. The buoyant CO2 will dissolve in the formation brines to form denser CO2-saturated brine which will sink. The CO2-saturated brine is relatively reactive but current models suggest that the reactions with carbonate and silicate minerals in the reservoir will ultimately lead to a significant proportion of the CO2 being precipitated as carbonate minerals stored permanently. However the CO2-charged brines may also react with the caprocks which retain the carbon-dioxide and it is not known whether this will enhance the seals by mineral precipitation or degrade them by mineral dissolution. A major limitation in our ability to predict these fluid-mineral reactions is that the reactions proceed slowly at variable rates (days or months to many years) and our knowledge of the reaction rates in real field settings is very limited. This project will study fluids and gasses from natural carbon-dioxide reservoirs and, where possible, from sites where carbon dioxide is being actively injected underground, to determine the rates of the mineral-fluid reactions in natural settings. We will duplicate the reactions in laboratory experiments where it will be possible to study the processes under controlled conditions, study individual reactions from the complex set of coupled reactions which take place in the natural rocks and examine the effects of varying potential rate-controlling parameters. The ultimate objective is to inform site assessment, risk and monitoring for geological carbon storage. The research will benefit other areas of the environmental sciences where rates of kinetically-limited fluid-mineral reactions govern important processes.