Patterns of entropy production in dissolving natural porous media with flowing fluid

Yang, Yi; Bruns, Stefan; Stipp, S. L. S.; Sørensen, Henning Osholm

doi:10.1371/journal.pone.0204165

Cited by 4 publications

(2 citation statements)

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“…The result is that the fluid breaks through without fully dissolving all solid. In the simulation, breakthrough occurred between porosity 0.4 and 0.6 (Figure c) and was manifested by a sharp decrease in the pressure drop in the flow direction (Yang et al, ; Yang, Bruns, Stipp, et al, ).…”

Section: Resultsmentioning

confidence: 98%

Effect of Cumulative Surface on Pore Development in Chalk

Yang

Hakim

Bruns

et al. 2019

Water Resources Research

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Pore development in natural porous media, as a result of mineral dissolution in flowing fluid, generates complex microstructures. Although the underlying dynamics of fluid flow and the kinetics of the dissolution reactions have been carefully analyzed in many scenarios, it remains interesting to ask if the preferentially developed flow paths share certain general petrophysical properties. Here we combine in situ X-ray imaging with network modeling to study pore development in chalk driven by acidic fluid flow under ambient condition. We show that the trajectory of a growing pore correlates with the flow path that minimizes cumulative surface-the overall surface area available to fluid within the residence time-calculated along streamlines. This correlation is not a coincidence because cumulative surface determines conversion of reactant and thus defines the position of dissolution front. Model simulations show that, as fluid channelizes, the growth of the leading pore in the flow direction is guided by migration of the most far-reaching dissolution front, even in an ever-changing flow field. In addition, we present a complete tomographic time series of microstructure erosion and show a good accord between the in situ observation and the model simulation. Our results suggest that the microscopic pore development is a deterministic process while being sensitive to stochastic perturbations to the migrating dissolution front.

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Section: Resultsmentioning

confidence: 98%

Effect of Cumulative Surface on Pore Development in Chalk

Yang

Hakim

Bruns

et al. 2019

Water Resources Research

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“…Equations used in the model are summarized in the SI. A comprehensive sensitivity analysis of the parameters used in the model has been presented in the context of entropy production patterns . More information can be found in Yang et al , The simulation domains in this study are randomly chosen subvolumes of three tomographic data sets of the chalk pieces.…”

Section: Methodsmentioning

confidence: 99%

Dissolved CO₂Increases Breakthrough Porosity in Natural Porous Materials

Yang

Bruns

Stipp

et al. 2017

Environ. Sci. Technol.

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When reactive fluids flow through a dissolving porous medium, conductive channels form, leading to fluid breakthrough. This phenomenon is caused by the reactive infiltration instability and is important in geologic carbon storage where the dissolution of CO in flowing water increases fluid acidity. Using numerical simulations with high resolution digital models of North Sea chalk, we show that the breakthrough porosity is an important indicator of dissolution pattern. Dissolution patterns reflect the balance between the demand and supply of cumulative surface. The demand is determined by the reactive fluid composition while the supply relies on the flow field and the rock's microstructure. We tested three model scenarios and found that aqueous CO dissolves porous media homogeneously, leading to large breakthrough porosity. In contrast, solutions without CO develop elongated convective channels known as wormholes, with low breakthrough porosity. These different patterns are explained by the different apparent solubility of calcite in free drift systems. Our results indicate that CO increases the reactive subvolume of porous media and reduces the amount of solid residual before reactive fluid can be fully channelized. Consequently, dissolved CO may enhance contaminant mobilization near injection wellbores, undermine the mechanical sustainability of formation rocks and increase the likelihood of buoyance driven leakage through carbonate rich caprocks.

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