Impact of velocity correlation and distribution on transport in fractured media: Field evidence and theoretical model. Issue 2 (18th February 2015)

• Record Type: Journal Article
• Authors: Kang, Peter K.; Le Borgne, Tanguy; Dentz, Marco; Bour, Olivier; Juanes, Ruben
• Is Part Of: Water resources research. Volume 51:Issue 2(2015:Feb.)
• Page Start: 940
• Page End: 959
• Publication Date: 2015-02-18
• Subjects: fractured media -- anomalous transport -- tracer test -- velocity distribution -- velocity correlation -- continuous time random walks; Hydrology -- Periodicals; 333.91
• DOI: 10.1002/2014WR015799
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: Flow and transport through fractured geologic media often leads to anomalous (non‐Fickian) transport behavior, the origin of which remains a matter of debate: whether it arises from variability in fracture permeability (velocity distribution), connectedness in the flow paths through fractures (velocity correlation), or interaction between fractures and matrix. Here we show that this uncertainty of distribution‐ versus correlation‐controlled transport can be resolved by combining convergent and push‐pull tracer tests because flow reversibility is strongly dependent on velocity correlation, whereas late‐time scaling of breakthrough curves is mainly controlled by velocity distribution. We build on this insight, and propose a Lagrangian statistical model that takes the form of a continuous time random walk (CTRW) with correlated particle velocities. In this framework, velocity distribution and velocity correlation are quantified by a Markov process of particle transition times that is characterized by a distribution function and a transition probability. Our transport model accurately captures the anomalous behavior in the breakthrough curves for both push‐pull and convergent flow geometries, with the same set of parameters. Thus, the proposed correlated CTRW modeling approach provides a simple yet powerful framework for characterizing the impact of velocity distribution and correlation on transport in fractured media. Key Points: Velocity distribution and correlation induce anomalous transport Field tracer experiments in fractured media show role of velocity correlation The proposed model incorporates both velocity distribution and correlation