Researchers Hannah P. Menke, Julien Maes, and Sebastian Geiger from the University of California, Berkeley have uncovered a new pattern of mineral dissolution in porous media that could have significant implications for the energy sector. Their findings, published in the journal Water Resources Research, challenge the existing understanding of how acids dissolve minerals in complex porous structures, such as those found in geological formations.
The current model of mineral dissolution in porous media describes three patterns, or regimes, that develop based on the interplay of flow, diffusion, and reaction rates. These are wormhole, compact, and uniform dissolution. However, Menke and her colleagues have identified a fourth regime, which they term “channeling.” This occurs when there is a significant variation in pore throat size within the porous medium, leading to vastly different flow rates in different pathways. In such cases, the dissolution process preferentially widens the existing fast flow pathways, rather than creating new ones.
The channeling regime is characterized by a rapid increase in permeability with only a small change in porosity. This is unlike any of the previously known dissolution regimes. The researchers used numerical simulations to examine the evolution of pore structure during acid injection in two porous media structures of increasing complexity. They found that the boundaries between the different dissolution regimes are more complex than previously thought and that the channeling regime can occur in a wider range of conditions than initially expected.
The discovery of the channeling regime has important practical applications for the energy sector. For instance, in geologic carbon storage, understanding how CO2 reacts with and dissolves minerals in underground formations is crucial for predicting the long-term storage security and efficiency. Similarly, in geothermal energy production, the dissolution of minerals can affect the permeability of the reservoir, which in turn impacts the efficiency of heat extraction. Accurate predictions of dissolution patterns can help optimize these processes and improve their overall performance.
In conclusion, the work of Menke and her colleagues highlights the need to update the current conceptual model of dissolution regimes to include the newly identified channeling regime. This will enable more accurate predictions of dissolution in a range of energy-related applications, from carbon storage to geothermal energy production. The research was published in the journal Water Resources Research, a publication of the American Geophysical Union.
This article is based on research available at arXiv.