Solubility trapping of CO2 in deep saline aquifers

深层咸水层中 CO2 的溶解度捕集

• 批准号: RGPIN-2015-04406
• 负责人: Hassanzadeh, Hassan
• 金额: $ 2.19万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612948
• 关键词: Solubility; trapping; CO2; deep; saline

Carbon capture and storage is one of the major global challenges. Long-term storage of carbon dioxide (CO2) in deep underground saline aquifers is a key opportunity that offers the possibility of sustaining access to fossil fuels such as oil sands in Canada while reducing emissions. However, prior to implementation, associated risks of CO2 leakage need to be addressed to ensure safety of storage. This requires development of tools in order to assess all the factors involved. CO2 storage takes place by several mechanisms. These include dissolution in brines, trapping in the reservoir rocks in form of residual or through mineralization. However, there is a knowledge gap in how these mechanisms contribute to and affect the long-term (century-to-millennium time scales) fate of CO2. Also, the storage capacity of these underground reservoirs is uncertain. Studies have shown that the Alberta basin is well suited for CO2 storage with a dissolution capacity of 4000 gigatons assuming that all the pore water could become saturated with CO2, which is not likely. Our recent studies have shown that in the short-term (~30 years) only 8% of CO2 can be trapped in brines. The rest may remain in the free phase, which is prone to leakage. However, long-term mechanisms such as convective dissolution may increase this limit and reduce the risk of leakage. The injected CO2 in deep saline aquifers is less dense than the resident brines. Driven by density contrast, it will spread under a sealing rock as a free phase while there is risk of leakage. However, CO2 slowly dissolves into the underlying brines. The resulting CO2-saturated brines are slightly denser than resident ones, making them sink to the bottom of the aquifer. Enhanced dissolution of CO2 by continuous sinking of CO2-saturated brines as well as upward flow of fresh brine from bottom to the top reduces the volume of the free phase CO2 and thus reduces the risk of leakage. The main point is that once CO2 sinks to the bottom of the aquifer, it cannot migrate upwards easily and it may be retained with minimal risk of leakage. Therefore, dissolution trapping could enable secure storage. This research program expands our knowledge and provides required methodologies by performing studies that help secure and safe implementation of geostorage. Currently, large-scale modeling of dissolution trapping using reservoir models poses a great challenge and requires prohibitively expensive computational resources and time. Therefore, efficient models that can accurately simulate the process at geological scale are required. In particular, scaling laws, which can be incorporated into reservoir simulators, are of great importance and will be a key and novel contribution of this proposal. The proposed research will provide a venue for incorporation of new formulations into numerical reservoir simulators leading to a computationally less expensive and efficient field scale simulations.

碳捕获和存储是全球主要的挑战之一。在深地下盐水含水层中的长期存储二氧化碳（CO2）是一个关键机会，它提供了维持加拿大诸如加拿大油砂等化石燃料的可能性，同时减少排放。但是，在实施之前，需要解决相关的二氧化碳泄漏风险，以确保存储的安全性。这需要开发工具才能评估所涉及的所有因素。 二氧化碳存储是通过多种机制进行的。这些包括在盐水中溶解，以残留或矿化形式捕获在储层岩石中。但是，这些机制如何贡献和影响CO2的长期（千年到千年时间尺度）的知识差距。同样，这些地下水库的存储容量尚不确定。 研究表明，艾伯塔省盆地非常适合二氧化碳储存，其溶解容量为4000千万孔，假设所有孔隙水都可能被二氧化碳饱和，这不太可能。我们最近的研究表明，在短期（约30年）中，只有8％的二氧化碳可以被困在盐水中。其余的可能保留在自由阶段，这很容易泄漏。但是，诸如对流溶解等长期机制可能会增加此限制并降低泄漏的风险。 深盐水含水层中注射的二氧化碳的密度不如常驻盐水。在密度对比度的驱动下，它将在密封岩石下作为自由阶段扩散，而泄漏的风险。但是，二氧化碳慢慢溶解到下面的盐水中。所得的二氧化碳饱和盐水比固定的盐水略稠，使其沉入含水层的底部。通过连续下沉CO2饱和的盐水以及从底部到顶部的新鲜盐水向上流动，可以增强CO2的溶解，从而减少了自由相CO2的体积，从而降低了泄漏的风险。要点是，一旦二氧化碳沉入含水层的底部，它就无法轻易向上迁移，并且可以以最小的泄漏风险保留。因此，溶解陷阱可以实现安全存储。 该研究计划扩大了我们的知识，并通过执行帮助确保GeoStorage实施的研究提供了所需的方法。当前，使用储层模型对溶解捕获的大规模建模构成了一个巨大的挑战，并且需要过高的昂贵计算资源和时间。因此，需要在地质规模上准确模拟该过程的有效模型。特别是，可以将缩放定律（可以纳入储层模拟器中）非常重要，这将是该提议的关键和新颖贡献。拟议的研究将为将新配方掺入数值储层模拟器中提供一个场所，从而导致计算上便宜且有效的现场尺度模拟。