Speaker
Description
Underground gas storage involves periods of injection, production, and storage. During storage periods, the pressure equilibrates and the brine can become locally supersaturated with the gas. In addition, macro-scale rock heterogeneity leads to strong spatial variability in gas saturation, with localized zones of high gas saturation. To investigate pore-scale dynamics during storage under supersaturated conditions and in the presence of macro-scale heterogeneity, we conducted microfluidic storage experiments where macroscale heterogeneity was mimicked by connecting the chip outlet to a small gas reservoir. Experiments were performed for several pre-equilibrated gas/water systems (CO$_2$, H$_2$, and N$_2$). For the CO$_2$ experiments, a pH indicator was added to the water to visualize the concentration of dissolved gas. Our results show that for all studied gas/water systems, even slight supersaturation led to gas exsolution. This process locally depleted the water from gas, generating concentration gradients and leading to diffusive transport of dissolved gas from the outlet towards the inlet. This diffusive transport sustained continued exsolution at the inlet, leading to the formation of a pressure gradient and resulting in multiphase flow toward the outlet. However, the observed flow behavior differs between different gases: exsolved H$_2$ invades the porous media in a smooth way, while invasion via exsolved CO$_2$ happens much earlier and in bursts. These experiments show that, in contrast to homogeneous systems where Ostwald ripening drives redistribution, heterogeneous systems exhibit more complex redistribution behavior during storage.
| Country | Germany |
|---|---|
| Green Housing & Porous Media Focused Abstracts | This abstract is related to Green Housing |
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