{'fraction_non_alphanumeric': 0.0216515609264854, 'fraction_numerical': 0.012084592145015106, 'mean_word_length': 5.113846153846154, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Pore-Scale Study of the Residual Trapping of Air in a Doddington Sandstone Using In-Situ Micro-CT Imaging

Introduction Deep saline aquifers have been identified as promising sites for storing large volumes of CO2. To prevent the buoyant migration of CO2 and ensure secure subsurface storage, the injected CO2 must be immobilised and trapped in the porous media as isolated clusters (Nhunduru et al. 2020). This residual trapping activates as the plume of the injected CO2 progresses through the formation and is then entrapped 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 (Chaudhary et al. 2013). 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. X-ray computed tomography (CT) is a non-destructive and non-invasive technique for imaging and direct observation of properties and processes in a wide range of materials, including rocks (Jahanbakhsh et al. 2020). Coupling this 3D imaging method with core flooding experimentation can facilitate the visual investigation of different multiphase phenomena at the pore scale. For that purpose, 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 highresolution CT scanning device. By using this rig, we aim to study the process of residual trapping in an air/brine system within a Doddington sandstone at the atmospheric pressure and ambient temperature conditions.