Gas spreading and mixing in heterogeneous porous media for underground hydrogen storage
The efficiency of operations of underground hydrogen storage (UHS) depends largely on the spreading and mixing behavior of the fluids, affecting gas displacement during injection, and purity upon extraction. Despite this, the link between gas spreading and mixing and the degree of heterogeneity in t...
| Autores: | , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/392889 |
| Acceso en línea: | http://hdl.handle.net/10261/392889 https://api.elsevier.com/content/abstract/scopus_id/105007918995 |
| Access Level: | acceso abierto |
| Palabra clave: | Viscous fingering Fluid mixing Fluid spreading Gas compressibility Gravity override Hydrogen injection efficiency http://metadata.un.org/sdg/7 http://metadata.un.org/sdg/9 http://metadata.un.org/sdg/6 http://metadata.un.org/sdg/3 Ensure healthy lives and promote well-being for all at all ages Ensure availability and sustainable management of water and sanitation for all Ensure access to affordable, reliable, sustainable and modern energy for all Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation |
| Sumario: | The efficiency of operations of underground hydrogen storage (UHS) depends largely on the spreading and mixing behavior of the fluids, affecting gas displacement during injection, and purity upon extraction. Despite this, the link between gas spreading and mixing and the degree of heterogeneity in the reservoir's permeability remains largely unexplored, even more when accounting for the highly non-linear gas flow dynamics that lead to gas compression, gravity override and viscous fingering. We conduct highly-resolved numerical simulations of isothermal hydrogen injection into a methane-saturated heterogeneous reservoir featuring a log-normal distribution of permeability. We examine the evolution of standard measures of spreading and mixing, namely, the interface length, the longitudinal spread and the volume of mixing, as a function of the variance of the log-permeability, σ<inf>Y</inf><sup>2</sup>, which quantifies the degree of heterogeneity, and the Péclet number, Pe, which characterizes the transport regime. The examined measures increase over time at faster rates as σ<inf>Y</inf><sup>2</sup> increases, indicating enhanced spreading and mixing by permeability-induced flow heterogeneity. Gravity override and gas compressibility lead to temporal scalings departing from diffusive, ballistic and dispersive scalings expected for incompressible flows with constant density and viscosity. Gravity override, linked with super-ballistic scalings, diminishes with σ<inf>Y</inf><sup>2</sup>, due to the decreased density contrasts by mixing, and the decreased vertical flow rate by low permeability zones. Gas compression, increasing with Pe due to the higher injection rate, is linked with non-monotonic growth rates of the spread and mixing volume. Viscous fingering effects appear to be of second order due to the moderate viscosity contrast between hydrogen and methane (∼0.3). We use the segregation intensity as a measure of hydrogen injection efficiency, ϵ, defined as the degree of hydrogen segregation, relative to the amount of injected gas. The maximum values attained by ϵ become smaller as σ<inf>Y</inf><sup>2</sup> increases, and occur at earlier times, confirming that hydrogen injection is less efficient as the heterogeneity in the reservoir increases. Further, the non-monotonic evolution of ϵ indicates a fluctuating dominance between injection and mixing rates during the reservoir's saturation. |
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