Speaker
Description
Salt precipitation during CO₂ injection into saline reservoirs is widely recognized as a critical challenge for maintaining injectivity and ensuring long-term storage security. Precipitation-induced pore blockage can significantly impair multiphase flow, yet the pore-scale mechanisms governing salt formation, growth, and spatial distribution during brine-CO₂ displacement remain poorly understood. In particular, the coupling between displacement dynamics, residual-brine distribution, and salt-growth kinetics has not been systematically resolved due to limitations in experimental visualization.
In this study, we investigate salt precipitation under controlled brine-CO₂ displacement conditions using a glass microfluidic model combined with a dual imaging strategy. A high-resolution microscope imaging system (MIS) is employed to resolve pore-scale salt nucleation and growth dynamics, while a full-field imaging system (FFIS) provides chip-scale monitoring of multiphase displacement and residual-brine evolution. This combined MIS-FFIS approach enables observation of salt precipitation processes at both the pore and network scales within the same experiment.
Microscope-scale observations reveal two distinct salt morphologies that systematically emerge under multiphase flow conditions. Compact, transparent salt crystals preferentially develop in brine-rich regions, particularly near brine-CO₂ interfaces, where evaporation and local supersaturation are enhanced. In contrast, dark, porous salt aggregates dominate gas-rich regions, where thin brine films persist along solid surfaces. Quantitative image-based analysis shows that porous aggregates grow at rates approximately six times higher than those of compact crystals, highlighting the strong influence of local phase distribution and flow environment on salt-growth kinetics.
Full-field imaging captures the dynamic evolution of the residual-brine field during CO2 invasion and establishes a direct link between salt accumulation patterns and brine trapping. At low injection rates, CO2 initially advances with a relatively smooth displacement front, followed by the development of localized instabilities near the outlet that promote brine trapping and concentrated salt precipitation. At higher injection rates, the displacement becomes strongly unstable and finger-like, leading to earlier gas breakthrough and a more spatially dispersed residual-brine distribution. Repeated experiments under identical conditions demonstrate pronounced variability in displacement pathways and brine retention, confirming the inherently stochastic nature of multiphase flow in porous microstructures.
By integrating pore-scale salt-growth tracking with chip-scale displacement monitoring, the combined MIS-FFIS methodology provides a unique experimental framework for resolving the interplay between multiphase flow dynamics, residual-brine evolution, and salt precipitation. The results demonstrate that salt precipitation is not solely governed by thermodynamic conditions but is strongly controlled by flow-induced phase configurations and trapping processes. These findings provide pore-scale insights into salt precipitation during CO2-brine displacement under idealized microfluidic conditions and clarify how flow dynamics and residual brine configurations control salt formation and growth.
| Country | Denmark |
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