Investigating Apparent Deviations from Darcy’s Law in Heterogeneous Rocks: Insights from Neutron Imaging
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| Titel: | Investigating Apparent Deviations from Darcy’s Law in Heterogeneous Rocks: Insights from Neutron Imaging |
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| Autoren: | Vieira Lima, Fernando, Hall, Stephen A., Engqvist, Jonas, Tudisco, Erika, Woracek, Robin, Athanasopoulos, Stefanos, Vestin, Philip |
| Weitere Verfasser: | Lund University, Faculty of Engineering, LTH, Departments at LTH, Department of Construction Sciences, Solid Mechanics, Lunds universitet, Lunds Tekniska Högskola, Institutioner vid LTH, Institutionen för byggvetenskaper, Hållfasthetslära, Originator, Lund University, Faculty of Engineering, LTH, Departments at LTH, Department of Construction Sciences, Geotechnical Engineering, Lunds universitet, Lunds Tekniska Högskola, Institutioner vid LTH, Institutionen för byggvetenskaper, Geoteknik, Originator |
| Quelle: | Transport in Porous Media. 152(7) |
| Schlagwörter: | Engineering and Technology, Civil Engineering, Geotechnical Engineering and Engineering Geology, Teknik, Samhällsbyggnadsteknik, Geoteknik och teknisk geologi |
| Beschreibung: | Darcy’s law provides a fundamental framework for understanding fluid flow through porous media. However, deviations from its linear superficial velocity-hydraulic gradient (v-i) relationship have been widely reported, at high and low flow rates. While previous studies have attributed the low flow rate deviations to factors such as fluid properties, boundary effects, and experimental artifacts, the role of material heterogeneity has received less attention. This study employs neutron imaging to investigate how rock heterogeneity influences macroscopically observed flow behavior. Volume-controlled percolation tests were conducted on Idaho Gray sandstone cores under near-single-phase conditions using heavy water (D2O) and normal water (H2O) across a wide range of flow rates. Bulk measurements (pore pressure at the sample boundaries and the controlled injection flow rate) revealed a decline in hydraulic conductivity at lower injection rates. Through a novel method for interpreting the breakthrough curves (BTC) derived from the neutron imaging data, we are able to quantify the volume of pores active in the flow during each test. The neutron radiography imaging acquired during the flow tests revealed that flow paths were strongly influenced by the rock’s heterogeneous pore structure, with higher flow rates promoting more uniform front propagation. This suggests greater pore space access at higher injection rates and implies the presence of threshold pressure gradients needed to access different parts of the pore network. The BTC analysis from neutron image shows a decrease in the volume of pores active in the flow (effective porosity) with decreasing injection rates, aligning with the observed reduction in hydraulic conductivity. By linking nonlinearity in vi-curves to variations in effective porosity, this study highlights the critical role of heterogeneity in controlling the fluid flow behavior. These findings underscore the importance of understanding the role of spatial variability in porous media when interpretingmacroscopic (bulk) permeability measurements, especially when interpreting apparent deviations from Darcy’s law. |
| Zugangs-URL: | https://doi.org/10.1007/s11242-025-02185-1 |
| Datenbank: | SwePub |
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Nájsť tento článok vo Web of Science | Abstract: | Darcy’s law provides a fundamental framework for understanding fluid flow through porous media. However, deviations from its linear superficial velocity-hydraulic gradient (v-i) relationship have been widely reported, at high and low flow rates. While previous studies have attributed the low flow rate deviations to factors such as fluid properties, boundary effects, and experimental artifacts, the role of material heterogeneity has received less attention. This study employs neutron imaging to investigate how rock heterogeneity influences macroscopically observed flow behavior. Volume-controlled percolation tests were conducted on Idaho Gray sandstone cores under near-single-phase conditions using heavy water (D2O) and normal water (H2O) across a wide range of flow rates. Bulk measurements (pore pressure at the sample boundaries and the controlled injection flow rate) revealed a decline in hydraulic conductivity at lower injection rates. Through a novel method for interpreting the breakthrough curves (BTC) derived from the neutron imaging data, we are able to quantify the volume of pores active in the flow during each test. The neutron radiography imaging acquired during the flow tests revealed that flow paths were strongly influenced by the rock’s heterogeneous pore structure, with higher flow rates promoting more uniform front propagation. This suggests greater pore space access at higher injection rates and implies the presence of threshold pressure gradients needed to access different parts of the pore network. The BTC analysis from neutron image shows a decrease in the volume of pores active in the flow (effective porosity) with decreasing injection rates, aligning with the observed reduction in hydraulic conductivity. By linking nonlinearity in vi-curves to variations in effective porosity, this study highlights the critical role of heterogeneity in controlling the fluid flow behavior. These findings underscore the importance of understanding the role of spatial variability in porous media when interpretingmacroscopic (bulk) permeability measurements, especially when interpreting apparent deviations from Darcy’s law. |
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| ISSN: | 01693913 15731634 |
| DOI: | 10.1007/s11242-025-02185-1 |