Anomalous Transport in Three‐Dimensional Discrete Fracture Networks: Interplay Between Aperture Heterogeneity and Injection Modes

We study how the interplay between fracture aperture heterogeneity and tracer injection mode controls fluid flow and tracer transport in three‐dimensional (3D) discrete fracture networks (DFNs). The direct 3‐D DFN simulations show that tracer injection mode has substantial effects on tracer spreadin...

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Bibliographic Details
Published in:Water resources research 2020-11, Vol.56 (11), p.n/a
Main Authors: Kang, Peter K., Hyman, Jeffrey D., Han, Weon Shik, Dentz, Marco
Format: Article
Language:English
Subjects:
Apertures
Computational fluid dynamics
Distribution
Fluid flow
Heterogeneity
Injection
Tortuosity
Tracer transport
Tracers
Transport
Velocity
Velocity distribution
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Summary:We study how the interplay between fracture aperture heterogeneity and tracer injection mode controls fluid flow and tracer transport in three‐dimensional (3D) discrete fracture networks (DFNs). The direct 3‐D DFN simulations show that tracer injection mode has substantial effects on tracer spreading across all levels of aperture heterogeneity. The key controlling factor for effective transport is the initial Lagrangian velocity distribution, which is determined by the interplay between injection mode and aperture heterogeneity. The fundamental difference between initial Lagrangian velocity distribution and domain‐scale Eulerian velocity distribution plays a vital role in determining anomalous transport. We effectively capture the observed anomalous transport using an upscaled transport model that incorporates initial velocity distribution, stationary velocity distribution, velocity correlation length, and average advective tortuosity. With the upscaled transport model, we accurately capture the evolution of Lagrangian velocity distribution and predict longitudinal spreading in 3‐D DFN. Key Points Tracer injection mode has strong impact on transport in 3‐D DFNs across all levels of aperture heterogeneity Initial Lagrangian velocity distribution determines the late‐time power‐law scaling of a breakthrough curve A Bernoulli CTRW model effectively captures anomalous transport in 3‐D DFNs
ISSN:0043-1397
1944-7973
DOI:10.1029/2020WR027378