Speaker
Description
Small-scale heterogeneities influence the migration and trapping of CO$_2$ in porous rocks. Quantifying their impact is essential for accurately predicting CO$_2$ migration in the subsurface for geological carbon storage. Here, we investigate the influence of small-scale heterogeneities in a core sample obtained from the monitoring well of an active geological carbon storage site; the Otway International Test Centre. Using micro-CT X-ray tomography at 10$\mu m$ resolution, we directly imaged CO$_2$ distribution and assessed its flow behaviour in a heterogeneous core. We observed highly channelized CO$_2$ flow, resulting in a low core-averaged CO$_2$ saturation. As CO$_2$ saturation increased, CO$_2$ connectivity rose at the expense of brine connectivity, which declined rapidly over a narrow saturation interval. At the continuum scale, these pore-scale dynamics manifest as steep water relative permeability curves and a limited saturation range being sampled. To assess the potential field-scale implications, we implemented a simplified reservoir model. The resulting CO$_2$ plume exhibited faster lateral spreading and improved pore-space utilization when using the relative permeability functions derived from this study. This work provides a foundation for revising how relative permeability functions are parameterized and applied in reservoir simulations. Capillary pressure heterogeneity governs the displacement dynamics, underscoring the need to conduct experiments in the capillary-dominated regime to capture the controlling physics. Our results further suggest that connectivity may be an important metric to incorporate into relative permeability functions.
| Country | United States |
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