Investigating the role of natural tracers in subsurface CO2 storage and monitoring

自工业革命以来，化石燃料（煤，石油和天然气）的燃烧大大增加了大气中的二氧化碳（CO2）含量。人们普遍认为，二氧化碳含量较高是造成地球温室效应升温和海洋酸化的主要因素。气候变暖对世界的影响仍然存在争议。然而，许多科学家现在认为，在未来100年内，地球大气层将至少升温2至3摄氏度。这种变暖的影响包括海平面上升，极地冰盖融化以及飓风等恶劣天气事件的风险增加。为了将全球变暖限制在2摄氏度以内，欧盟和世界各国政府都在寻找减少二氧化碳排放的方法。二氧化碳的主要来源之一是发电。全球化石燃料燃烧产生了世界上85%的电力。在未来10-20年内，很难减少化石燃料发电的使用。可再生能源的引进和开发需要时间，世界也需要额外的发电方法来防止间歇性可再生能源短缺-例如，当风吹得不足以转动风车时。现在可以燃烧化石燃料，并在发电站或其他集中排放场所（如水泥厂和炼油厂）捕获二氧化碳。然后，这种二氧化碳可以被加压以使其液化，并通过管道泵送到可以将液态二氧化碳注入地下储存的地方。这项特别的建议审查了影响二氧化碳如何储存在地下的一些控制措施，以及如何检测出水库或地表的任何泄漏。为了储存二氧化碳，需要一个多孔的储层，上面覆盖着一个不可渗透的密封层，比如阻止二氧化碳逃逸和上升到地表的泥岩。二氧化碳必须储存很长一段时间（数千年），以确保它不会导致进一步变暖。不幸的是，第一个工程化的二氧化碳储存项目只运行了10年。因此，为了了解更多关于长期储存二氧化碳的信息，我们需要研究天然二氧化碳气田。天然CO2气田类似于石油或甲烷气田，只是它们含有CO2。在这些气田中也有少量的惰性气体。这些惰性气体有不同的来源，可以用来计算天然二氧化碳的来源。最近的研究表明，世界各地的天然二氧化碳田已经捕获了数百万年的二氧化碳。该研究还表明，大量CO2由于溶解到气田内的孔隙水中而被捕获。该提案将首先开发详细的计算机模型，以独立预测在CO2气田内实际可能发生的化学溶解到孔隙水中的程度。一些科学家还认为，一旦二氧化碳被抽到地下，它将结晶出新的矿物。这将把二氧化碳“锁”在水库里，是最安全的储存形式。这项工作将分析最近在CO2领域内形成的矿物，以测试轻碳（碳12）到重碳（碳13）的量是否与矿物从储存在该领域的CO2中结晶出来的预期相同。该项目还将调查惰性气体是否可以用来记录二氧化碳是否从不同的天然二氧化碳田穿过泥岩密封。据信，当二氧化碳穿过泥岩时，其中所含的一些惰性气体将被留下，粘在有机碎片上。以类似的方式，惰性气体也可以附着在天然煤上。该项目将测试发电站燃烧煤炭产生的惰性气体及其产生的二氧化碳是否存在足够大的数量，以便在二氧化碳注入地下后用于追踪二氧化碳。

Since the Industrial Revolution, burning of fossil fuels (coal, oil and gas) has greatly increased the carbon dioxide (CO2) content of the atmosphere. The higher level of CO2 is widely accepted to be a major contributor to greenhouse warming of the Earth and acidification of the oceans. The effects of this warming on the world are still controversial. However, many scientists now believe that the Earth's atmosphere will heat up by at least 2 to 3 centigrade over the next 100 years. The effects of this warming include rising sea levels, melting of the polar icecaps and increasing risks of severe weather events such as hurricanes. To try to limit this warming to 2 centigrade, governments from the EU and around the world are looking at ways of reducing CO2 emissions. One of the major sources of CO2 is the generation of electricity. Worldwide fossil fuel burning produces 85% of the world's electricity. In the next 10-20 years, it will be difficult to reduce the use of fossil fuel for electricity generation. Renewable energies need time to be introduced and developed, and the world also needs extra methods of generating electricity to safeguard against shortages of intermittent renewable energy - for example, when the wind does not blow enough to turn windmills. It is now possible to burn fossil fuels, and capture the CO2 at power stations, or other concentrated emission sites such as cement works and oil refineries. This CO2 can then be pressurised to liquefy it, and pumped through pipelines to places where the liquid CO2 can be injected underground to be stored. This particular proposal examines some of the controls which affect how CO2 is stored underground and how any leakage out of a reservoir, or to the surface could be detected. To store CO2 a porous reservoir is needed, overlain by an impermeable seal, such as mudstone which stops the CO2 from escaping and rising to the surface. The CO2 must be stored for a long time (thousands of years) to ensure it does not cause further warming. Unfortunately, the first engineered CO2 storage project has only been operating for 10 years. So to find out more about storing CO2 over a long time we need to look at natural CO2 gas fields. Natural CO2 fields are similar to oil or methane gas fields except they contain CO2. Within these gas fields there is also a small amount of unreactive noble gases. These noble gases have different sources and can be used to work out where the natural CO2 has come from. Recent research has shown that natural CO2 fields from around the world have trapped CO2 for millions of years. This research has also shown that a lot of CO2 is trapped as a result of it dissolving into the porewater within the gas field. This proposal will firstly develop detailed computer models to independently predict how much chemical dissolution into the porewater could realistically occur within the CO2 fields. Several scientists also believe that once CO2 is pumped underground it will crystallise new mineral. This would 'lock' the CO2 into the reservoir and is the most secure form of storage. This work would analyze recent minerals formed within a CO2 field to test if the amount of light carbon (carbon 12) to heavy carbon (carbon 13) was the same as would be expected if the minerals were crystallised from the CO2 stored in the field. The project will also investigate if noble gases can be used to record if CO2 has moved through the mudrock seal from different natural CO2 fields. As CO2 moves through the mudrock it is believed that some noble gases contained in it will be left behind, stuck onto organic debris. In a similar fashion noble gases can also be stuck onto natural coals. This project will test if the noble gases derived from coal burnt in a power station and its produced CO2 exist in large enough quantities to be used to trace the CO2 once it is injected underground.