Speaker
Description
Over the last decades, the continuous increase in atmospheric CO₂ concentrations has intensified the search for effective mitigation strategies capable of reducing greenhouse gas emissions while supporting global energy demand. Among the available solutions, carbon capture and storage (CCS) has emerged as an important approach, with geological carbon storage (GCS) in saline aquifers standing out due to its large storage capacity and global availability. However, the long-term security of CO₂ storage strongly depends on the mechanisms that immobilize the injected gas within the porous medium, particularly capillary trapping.
Capillary trapping efficiency is governed by a complex interplay between rock properties, fluid characteristics, and flow conditions. Among these factors, rock permeability and flow orientation play a fundamental role in controlling CO₂ displacement, residual saturation, and storage performance. In this study, core flooding experiments were conducted to systematically evaluate how variations in plug permeability and flow direction influence CO₂ trapping efficiency under conditions representative of deep saline aquifers.
To investigate permeability effects, core flooding tests were conducted using carbonate plugs with different permeability levels under identical pressure, temperature, and fluid conditions. The results show that permeability controls fluid displacement during both drainage and imbibition. Lower-permeability plugs required higher injection pressures and promoted greater brine displacement during CO₂ injection, while medium-permeability plugs favored the development of continuous water pathways during imbibition, enhancing CO₂ immobilization. Consequently, storage efficiency was governed by the combined fluid redistribution throughout the injection sequence rather than by residual gas saturation at a single stage.
The influence of flow orientation was evaluated by comparing horizontal and vertical injection configurations using plugs with similar permeability and pore size distributions. Although differences in gas distribution were observed, the overall impact on trapping efficiency was limited. Under the studied conditions, characterized by small density contrasts between CO₂ and brine and short core lengths, gravitational effects were secondary, resulting in only minor differences between the two flow orientations.
Overall, this study demonstrates that CO₂ storage efficiency in saline aquifers emerges from the coupled effects of permeability, pore structure, flow configuration, and fluid properties, rather than from a single controlling parameter. The results highlight how multiphase displacement dynamics during drainage and imbibition govern phase connectivity and residual trapping at the core scale. By elucidating the roles of permeability and flow orientation in capillary trapping, this work provides experimental insight into the physical mechanisms controlling CO₂ immobilization in multiphase flow through porous media.
| Country | Brazil |
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