Pore-scale investigation of the evolution of residually-trapped CO2 droplets in the frame of geologic carbon storage
EMSL Project ID
49524
Abstract
Carbon storage, the process where CO2 is injected into the subsurface where it is expected to remain trapped, is a technology that has the potential to greatly reduce carbon dioxide emissions. Although significant efforts have been deployed over the last decade to increase the performance and predictability of carbon dioxide sequestration in deep formations, uncertainties still remain due to the complexity of the fundamental science that underlies the behavior of supercritical CO2 in brine-filled rocks. One key issue that still needs to be addressed is the long-term reliability of residual trapping, which is one major process for storage security beyond the primary stratigraphic seal. Although residually-trapped CO2 droplets are generally considered permanently immobilized in the porous media, multiples mechanisms exist which could possibly lead to the remobilization of the CO2. In particular, Ostwald ripening mechanism would cause the gradual growth of CO2 ganglia with low capillary pressures, at the expense of ganglia with higher capillary pressures. Ostwald ripening has been extensively studied in homogeneous bulk media, however the extension of the process to porous media requires further investigation. Furthermore the importance of Ostwald ripening for residually trapped CO2 remobilization is unknown and should be assessed. Pore-scale imaging and quantification of trapped CO2 ganglia evolution over time after imbibition will bring valuable insights into potential redistribution due to diffusion-driven mass transfers, e.g. Ostwald ripening. In a real rock the wetting and non-wetting phases (brine and CO2 respectively in this study) may present very small features, suggesting the use of a high-resolution imaging technics. Furthermore, as the present study requires continuous imaging over a significant period of time, microfluidic experiments appears as the most adequate technics to visualize pore-scale dynamic processes. The experiments conducted with the reservoir conditions (around 50ºC and 90 Bars) using brine and CO2 (in supercritical state) rock-based micromodels will provide a unique dataset to quantify potential trapped CO2 ganglia shrinkage and growth, coalescence and remobilization.
Project Details
Start Date
2016-10-01
End Date
2017-09-30
Status
Closed
Released Data Link
Team
Principal Investigator