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Session: Novel experimental measurement methods IV
Session starts: Wednesday 05 November, 15:40
Presentation starts: 16:00
Room: Lecture room A

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Rajat Dehury (Indian Institute of Technology Madras)
Jitendra S. Sangwai (Indian Institute of Technology Madras)

Abstract:
Immediate actions are required to mitigate current extreme climatic events caused by the increasing concentration of anthropogenic carbon dioxide (CO2) in the atmosphere. Depleted oil and gas reservoirs emerged as a promising option for large-scale, long-term CO2 storage, utilizing the pre-existing installations from hydrocarbon extraction for CO2 injection and monitoring processes. However, a limited understanding of flow dynamic investigations and visualization when CO2 is injected into subsurface porous media already filled with several fluids, needs to be addressed to ensure efficient storage capacity and long-term security. This study investigates the pore-scale displacement dynamics and trapping mechanisms during CO2 injection into the underground porous domains initially saturated with different interstitial fluids (oil, brine with varying salinity, or gas). Microfluidic experiments were carried out with initially saturated oil or brine microfluidic chip, followed by CO2 injection to analyse the fluid dynamics at the pore scale, observe the non-uniform displacement patterns, and quantify trapped CO2. Three-phase microfluidic studies were also performed to optimize the gas injection strategies and evaluate the role of interfacial properties such as interfacial tension and wettability in these processes. The results gave pore-scale insight for both enhanced oil recovery and CO2 sequestration efforts. In-situ foam formation using non-ionic surfactants and fingering displacement patterns were visualised with a digital microscope. The observation of non-uniform fingering patterns and snap-off events provides insight into stratigraphical and residual trapping mechanisms. Analysis of oil, brine, and CO2 ganglia distribution reveals the interfacial contact of CO2 and interstitial fluids. This interfacial contact may enhance solubility and mineral trapping of injected CO2 gas. Image processing techniques enable the quantification of viscous and capillary fingering patterns. Microfluidic experiments using a physical rock network which mimics subsurface sandstone porous media are conducted under a high-resolution digital microscope, with a pressure sensor attached to the flow path to measure pressure drops. Figure 1 presents the observations from a typical two-phase flooding experiment. Polymers, co-solvents, surfactants, and nanoparticles are used to improve fluid compatibility, viscosity enhancement, mobility ratio, and recovery efficiency in these microfluidic experiments. Organic acids such as humic and lignoceric acids often alter the wettability of the system more towards CO2-wet; the impact of this change on pore-scale fluid dynamics is observed. Figure 1 Non-uniform displacement patterns observed for an oil-CO2 two-phase flow dynamics in a porous microchannel for subsurface CO2 storage. Analysing the amount of trapped gas amount and its corresponding trapping mechanisms will inform strategies to optimize long-term CO2 storage. Introducing chemical additives (as described earlier) alters surface properties, thereby influencing displacement dynamics. The insights from this study can be integrated into reservoir-scale modelling to enhance the understanding of CO2 sequestration in subsurface porous geological formations.