Pore-Scale Study of the Residual Trapping of Air in a Doddington Sandstone Using In-Situ Micro-CT Imaging

Deep saline aquifers have been identified as promising sites for storing large volumes of CO₂. As the plume of the injected CO₂ progresses through the formation, the residual trapping mechanism activates and entraps the CO₂ due to the natural or engineered flow of water. Core-scale findings and pore-network flow models’ estimations for residual trapping in saline aquifers range from 10% to 90% of the total injected volume of CO₂. This widely varying range of CO₂ trapping potential necessitates the pore-scale observation of this phenomenon to facilitate a fundamental understanding of the controlling parameters of this trapping mechanism.

To investigate this phenomenon at the pore scale, we have designed and developed a unique micro-CT core flooding system, which is an excellent tool for providing valuable 3D information of flow processes at realistic subsurface conditions. The main components of this in-situ imaging flow rig are an X-ray transparent flow cell, capable of withstanding elevated pressure and temperature to provide the conditions of typical deep saline aquifers and a high-resolution CT scanning device. By using this rig, we study the process of residual trapping in an air/brine system within a Doddington sandstone at the atmospheric pressure and ambient temperature conditions.