Solving the evolution of carbonate porosity: a dynamic solution for enhanced oil recovery and carbon capture and storage

石油、天然气和煤炭等化石燃料提供了全球约80%的能源供应。在燃烧化石燃料的过程中，碳以二氧化碳的形式释放。二氧化碳是一种强有力的温室气体：当释放到大气中时，它会捕获传出的长波辐射，即所谓的“温室效应”。自工业革命以来，在过去的250年里，大气中的二氧化碳浓度一直在增加，加剧了温室效应，从而导致了全球变暖。我们继续依赖碳基燃料的一个创新解决方案是碳捕获和储存，它寻求通过捕获一些二氧化碳并将其深埋在地下来减少化石燃料燃烧过程中释放的二氧化碳。这种在深层地下岩石中注入二氧化碳的方法也被石油行业用来帮助提高石油采收率。将碳储存在地下有许多挑战，其中最重要的一项是了解它将与周围岩石发生的化学反应。当注入二氧化碳时，它会溶解在岩石内的孔隙流体中。溶解的二氧化碳是一种弱酸，可以溶解在弱酸性条件下溶解的矿物质。由于这些碳酸盐矿物的溶解性，这对由石灰岩组成的岩石特别有影响。这些矿物的溶解在水库中创造了更多的空间，允许储存更多的二氧化碳，但如果达到极端，可能会导致水库坍塌。在储集岩中加入溶解的二氧化碳可以进一步刺激微生物的活动，从而为碳酸盐矿物的形成创造有利条件。这些都是有益的，因为它们在化学上是稳定的，因此可以长期储存注入的二氧化碳。然而，碳酸盐矿物的形成也可能导致岩石内部空间网络的破坏(“孔隙度”)，这使得进一步注入变得不可能。孔隙度的破坏还会导致储集层的封闭，使进一步的化石燃料回收变得不可能。我们对碳酸盐岩在二氧化碳注入过程中发生的事情缺乏了解，这是我们将碳储存在地下的能力的一个重大缺口。该奖学金旨在了解向碳酸盐储集层中添加二氧化碳将如何刺激微生物活动，以及这将如何导致孔隙度的产生或破坏。这将通过最初运行多个实验室实验来进行，以确定注入液体的化学物质如何影响储集岩中的微生物过程。我将使用多种高分辨率的地球化学工具来追踪反应堆内碳酸盐矿物的沉淀或溶解情况。实验室实验的结果将被输入到可用于预测目的的数值模型中，并将确定注入流体的化学成分和储集层性质的变化如何相互作用，影响孔隙度的演变。还将对多个碳酸盐储集层的样品进行测量，以便将实验室数据与当前或潜在的碳捕获和储存地点进行比较。一旦用实验室和现场数据进行了训练，这些数值模型将被用来创建一个预测框架，以预测应注入任何潜在储集层以进行碳捕获和储存的流体的化学成分，以及特定流体将如何导致孔隙度的产生或破坏，具体取决于所需的结果。

Fossil fuels, such as oil, natural gas and coal, provide approximately 80% of the world's energy supplies. During the burning of fossil fuels, carbon is released as carbon dioxide. Carbon dioxide is a potent greenhouse gas: when released into the atmosphere it traps outgoing longwave radiation, called the 'greenhouse effect'. Over the last 250 years, since the industrial revolution, carbon dioxide concentrations in the atmosphere have been increasing, enhancing the greenhouse effect and hence, global warming. An innovative solution to our continued reliance on carbon-based fuels is Carbon Capture and Storage, which seeks to reduce the amount of carbon dioxide released during the burning of fossil fuels by capturing some carbon dioxide and storing it deep underground. This carbon dioxide pumping, or flooding, in deep underground rocks is also used within the oil industry to aid in Enhanced Oil Recovery.There are many challenges related to storing carbon underground, and one of the most important of these is understanding the chemical reactions it will have with the surrounding rock. When carbon dioxide is injected it dissolves in the pore fluid within the rock. Dissolved carbon dioxide is a weak acid, and can dissolve minerals that are soluble in weakly acidic conditions. This particularly impacts rocks made of limestone, due to the solubility of these carbonate minerals. The dissolution of these minerals creates more space within the reservoir, which allows for the storage of further carbon dioxide, but may lead to reservoir collapse if taken to extreme. The addition of dissolved carbon dioxide to reservoir rocks can further stimulate microbial activity, which can create conditions favourable to the formation of carbonate minerals. These can be beneficial as they are chemically stable and therefore store the injected carbon dioxide over long time scales. However the formation of carbonate minerals can also lead to the destruction of the network of spaces within the rocks ("porosity"), which makes further injection impossible. The destruction of porosity also leads to the sealing of the reservoir, making the recovery of further fossils fuels impossible.Our lack of understanding of what happens to carbonate rocks during carbon dioxide injection represents a major gap in our ability to store carbon underground. This fellowship seeks to understand how the addition of carbon dioxide to a carbonate reservoir will stimulate microbial activity, and how this will lead to the generation, or destruction, of porosity. This will be conducted by initially running multiple laboratory experiments to determine how the chemistry of the injected fluid affects the microbial processes within the reservoir rocks. I will use multiple high resolution geochemical tools to track the precipitation or dissolution of carbonate minerals within the reactors. The results from the laboratory experiments will be fed into numerical models, which can be used for predictive purposes, and will identify how changes in the chemistry of the injected fluid and reservoir properties interacts to impact the porosity evolution. Samples will also be measured from multiple carbonate reservoirs in order to compare the laboratory data to current or potential sites for carbon capture and storage. The numerical models once trained with both the laboratory and field data will be used to create a predictive framework to predict the chemistry of the fluid that should be injected into any potential reservoir for carbon capture and storage, and how the particular fluid will lead to the creation or destruction of porosity, dependant upon the required outcome.