Sandia National Laboratories, PO Box 5800, Mail Stop 0779, Albuquerque, New Mexico 87185-0779, USA.
Environ Sci Technol. 2013 Jan 2;47(1):219-26. doi: 10.1021/es301208k. Epub 2012 Aug 13.
Capillary trapping of a nonwetting fluid phase in the subsurface has been considered as an important mechanism for geologic storage of carbon dioxide (CO(2)). This mechanism can potentially relax stringent requirements for the integrity of cap rocks for CO(2) storage and therefore can significantly enhance storage capacity and security. We here apply ganglion dynamics to understand the capillary trapping of supercritical CO(2) (scCO(2)) under relevant reservoir conditions. We show that, by breaking the injected scCO(2) into small disconnected ganglia, the efficiency of capillary trapping can be greatly enhanced, because the mobility of a ganglion is inversely dependent on its size. Supercritical CO(2) ganglia can be engineered by promoting CO(2)-water interface instability during immiscible displacement, and their size distribution can be controlled by injection mode (e.g., water-alternating-gas) and rate. We also show that a large mobile ganglion can potentially break into smaller ganglia due to CO(2)-brine interface instability during buoyant rise, thus becoming less mobile. The mobility of scCO(2) in the subsurface is therefore self-limited. Vertical structural heterogeneity within a reservoir can inhibit the buoyant rise of scCO(2) ganglia. The dynamics of scCO(2) ganglia described here provides a new perspective for the security and monitoring of subsurface CO(2) storage.
在地下深处，非润湿流体相的毛细管捕获被认为是二氧化碳（CO2）地质封存的重要机制。这种机制可以潜在地放宽对 CO2 储存中盖层完整性的严格要求，因此可以显著提高储存容量和安全性。我们在这里应用神经节动力学来理解在相关储层条件下超临界 CO2（scCO2）的毛细管捕获。我们表明，通过将注入的 scCO2 分解成小的不连续的神经节，可以极大地提高毛细管捕获的效率，因为神经节的迁移率与其大小成反比。超临界 CO2 神经节可以通过在非混相驱替过程中促进 CO2-水界面不稳定性来形成，并且可以通过注入模式（例如，水交替气）和速率来控制其大小分布。我们还表明，由于在浮力上升过程中 CO2-盐水界面不稳定，一个大的可迁移神经节可能会分裂成较小的神经节，从而变得不那么迁移。因此，地下深处 scCO2 的迁移率是自我限制的。储层内的垂直结构非均质性可以抑制 scCO2 神经节的浮力上升。此处描述的 scCO2 神经节动力学为地下 CO2 储存的安全性和监测提供了新的视角。
