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Description
The immiscible displacement of a wetting fluid by a non-wetting fluid in rough fractures is essential for optimizing subsurface operations such as enhanced oil recovery and geological carbon sequestration (GCS). Despite its importance, a comprehensive understanding of drainage flows in fractures, considering factors such as fracture geometry, fluid properties, and flow regimes, remains elusive. To address this, we have developed an analog experimental setup featuring a transparent fracture flow cell with self-affine rough-walled surfaces, matched above a specific correlation length and with a precisely controlled mean aperture. We generate realistic synthetic fracture geometries numerically, characterized by the Hurst exponent, fracture closure, and correlation length. The fracture walls are then obtained by micro-machining transparent PMMA plates, using these geometries. X-ray tomography of the empty fracture provides the exact in situ fracture geometry. High-speed imaging captures the dynamic spatial distribution of fluid phases between the fracture walls during drainage. We vary the mean aperture across experiments for a given fracture geometry and investigate a broad range of capillary numbers, spanning both viscous- and capillary-dominated regimes, while also varying viscosity ratios to characterize the resulting displacement regimes. An extended phase diagram for drainage in geological fractures is thus obtained as a function of the viscosity ratio between the two fluids, the capillary number, and the fracture aperture.
| References | Yang, Z., Méheust, Y., Neuweiler, I., Hu, R., Niemi, A., & Chen, Y. F. (2019). Modeling immiscible two‐phase flow in rough fractures from capillary to viscous fingering. Water Resources Research, 55(3), 2033-2056. Neuweiler, I., Sorensen, I., & Kinzelbach, W. (2004). Experimental and theoretical investigations of drainage in horizontal rough-walled fractures with different correlation structures. Advances in Water Resources, 27(12), 1217-1231. Méheust, Y., & Schmittbuhl, J. (2001). Geometrical heterogeneities and permeability anisotropy of rough fractures. Journal of Geophysical Research: Solid Earth, 106(B2), 2089-2102. |
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| Country | France |
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