Abstract Geological storage of Carbon Dioxide (CO2) can safely and permanently store a huge amount of anthropogenic greenhouse gases. However, the possible leakage of mobile gases through the cap rock that confines them within the reservoir is a cause of safety concerns. Residual and solubility trapping of the injected gas in the pores of the rock can reduce the amount of mobile gas lying below the cap rock. These trapping mechanisms will only begin at the end of several decades of gas injection, which implies that there is an imminent risk of discharge of large amount of gas in the event of a leak. This paper presents a method to fast-track and enhance residual and solubility trapping process while gas injection is in progress, such that only a fraction of the injected gas will migrate and be trapped beneath the cap rock after injection ceases. The method involves cyclic injection of gas and water (containing small amount of foaming agent). Foams are known to have gas trapping characteristics during flow in porous medium. A series of laboratory experiments was conducted on representative rock samples at different reservoir conditions. The results show a sequential and cumulative growth in trapped gas during cyclic injection of gas and foam based on in-situ and real time measurements of gas saturation in the samples using electrical resistivity tool. The amount of trapped (residual) gas depends on the type of gas (N2 or CO2), water salinity, concentration of the foaming agent, and temperature. The highest residual gas saturations (50%–70% of reservoir pore volume) occurred at a temperature and water salinity typical of a deep saline aquifer (45 °C and 58,000 ppm water). At a high water salinity of 242,000 ppm, the residual gas saturation was significantly lower (27%–30%). Similarly, at a high temperature of 90 °C, the residual gas saturation reduced to 27%. Residual gas could not be sustained when CO2 is injected compared to N2 because of the low interfacial tension between CO2 and water, which reduces the foam quantity and strength. The importance of foam stabilizing agents (e.g. polymers and nanoparticles) in addressing the observed shortcomings in CO2 foam and for foam injection in high salinity - high temperature reservoirs is discussed. A field scale application of this method is also highlighted.

中文翻译：

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通过系统和循环泡沫注入对地质地层中的气体进行顺序储存和原位跟踪 - 用于降低注气过程中泄漏风险的有用应用

摘要 二氧化碳（CO2）地质封存可以安全、永久地封存大量的人为温室气体。然而，流动气体可能通过将它们限制在储层内的盖层泄漏，这是一个安全问题。注入的气体在岩石孔隙中的残余和溶解性捕获可以减少位于盖层下方的流动气体的数量。这些捕集机制只会在几十年的气体注入结束时开始，这意味着一旦发生泄漏，就会有排放大量气体的迫在眉睫的风险。本文提出了一种在注气过程中快速跟踪和加强残余和溶解度圈闭过程的方法，以便在注入停止后只有一小部分注入的气体会迁移并被圈闭在盖层下。该方法包括循环注入气体和水（含有少量发泡剂）。已知泡沫在多孔介质中流动期间具有气体捕集特性。对不同储层条件下的代表性岩石样品进行了一系列实验室试验。基于使用电阻率工具对样品中的气体饱和度进行原位和实时测量，结果显示在气体和泡沫的循环注入过程中被困气体的连续和累积增长。截留（残留）气体的数量取决于气体类型（N2 或 CO2）、水的盐度、发泡剂的浓度和温度。最高残余气体饱和度（储层孔隙体积的 50%–70%）出现在深部咸水含水层（45 °C 和 58,000 ppm 水）的典型温度和水盐度下。在 242,000 ppm 的高水盐度下，残余气饱和度显着降低（27%–30%）。同样，在 90°C 的高温下，残余气体饱和度降低到 27%。与 N2 相比，注入 CO2 时残余气体不能持续存在，因为 CO2 和水之间的界面张力较低，这降低了泡沫数量和强度。讨论了泡沫稳定剂（例如聚合物和纳米颗粒）在解决 CO2 泡沫中观察到的缺点以及在高盐度 - 高温储层中注入泡沫的重要性。还强调了该方法的现场规模应用。与 N2 相比，注入 CO2 时残余气体不能持续存在，因为 CO2 和水之间的界面张力较低，这降低了泡沫数量和强度。讨论了泡沫稳定剂（例如聚合物和纳米颗粒）在解决 CO2 泡沫中观察到的缺点以及在高盐度 - 高温储层中注入泡沫的重要性。还强调了该方法的现场规模应用。与 N2 相比，注入 CO2 时残余气体不能持续存在，因为 CO2 和水之间的界面张力较低，这降低了泡沫数量和强度。讨论了泡沫稳定剂（例如聚合物和纳米颗粒）在解决 CO2 泡沫中观察到的缺点以及在高盐度 - 高温储层中注入泡沫的重要性。还强调了该方法的现场规模应用。