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DatoValore
TitleA new two-step particle tracking and channels model method for preferential 3-D flow and transport in large DFNs of fractured aquifers
AbstractA new two-step method has been developed for predicting three-dimensional (3-D) pollutant plumes and breakthrough curves (BTC) in fractured aquifers. Predicting fluid motion fields and pollutant concentrations in groundwater is a challenging task, due to the difficulties in building a 3-D discrete fracture network (DFN) with the same geometry of fractures and interconnections as in the studied aquifer and the computational complexity of the problem being modeled. To improve the representation of DFN, geological characterization of fracture apertures was performed using field well-pumping data as the prerequisite for the modeling approach. The modeling was performed in two steps: first, 3-D particle tracking following streamline (PTFS) simulations in DFN backbones, and second, a 3-D channels model (CM) analytical solution. The PTFS simulations captured the mean properties of the 3-D velocity field relevant to spatial and temporal transport along preferential flow pathways of a fractured aquifer. The 3-D CM solution yielded the exact BTC of concentrations accounting for the slowest flow pathways typically excluded from DFN backbones extraction methods. The PTFS/CM simulations were initially performed at the lab scale on a 3-D 20 m rock block from the Bari (South Italy) fractured aquifer. Results were consistent with the chlorophyll-A BTC obtained from a well-to-well tracer experiment. Subsequently, the capability of the new method was tested by increasing the scale of simulations to a larger 3-D DFN of 200 m with 2,200 fractures. The resultant BTC was obtained in 32 min, showing the proposed PTFS/CM technique can rapidly determine complex 3-D solutions in heterogeneous fracture-dominated aquifers. The applied Lagrangian and Eulerian techniques can provide quasi-deterministic BTCs and 3-D maps of pollutant concentrations, avoiding extensive computations required for conforming mesh methods. Moreover, the solution does not require multiple randomly arranged DFN realizations, as in particle tracking-based stochastic methods. These results have significant implications in modeling transport at the aquifer scale, where DFNs are composed of thousands of fractures.
SourceJournal of hydrology (Amst.)
KeywordsFracture-dominated aquifersWell-to-well tracer experimentsLagrangian transport models3-D DFN particle tracking following streamlines
JournalJournal of hydrology (Amst.)
EditorElsevier, Oxford ;, Paesi Bassi
Year2023
TypeArticolo in rivista
DOI10.1016/j.jhydrol.2023.130566
AuthorsCostantino Masciopinto, Younes Fadakar Alghalandis
Text489879 2023 10.1016/j.jhydrol.2023.130566 Fracture dominated aquifers Well to well tracer experiments Lagrangian transport models 3 D DFN particle tracking following streamlines A new two step particle tracking and channels model method for preferential 3 D flow and transport in large DFNs of fractured aquifers Costantino Masciopinto, Younes Fadakar Alghalandis Consiglio Nazionale Delle Ricerche, Istituto di Ricerca Sulle Acque, Via Francesco De Blasio, 5, 70132 Bari, Italy Alghalandis Computing, Niagara on the Lake, ON, Canada A new two step method has been developed for predicting three dimensional 3 D pollutant plumes and breakthrough curves BTC in fractured aquifers. Predicting fluid motion fields and pollutant concentrations in groundwater is a challenging task, due to the difficulties in building a 3 D discrete fracture network DFN with the same geometry of fractures and interconnections as in the studied aquifer and the computational complexity of the problem being modeled. To improve the representation of DFN, geological characterization of fracture apertures was performed using field well pumping data as the prerequisite for the modeling approach. The modeling was performed in two steps first, 3 D particle tracking following streamline PTFS simulations in DFN backbones, and second, a 3 D channels model CM analytical solution. The PTFS simulations captured the mean properties of the 3 D velocity field relevant to spatial and temporal transport along preferential flow pathways of a fractured aquifer. The 3 D CM solution yielded the exact BTC of concentrations accounting for the slowest flow pathways typically excluded from DFN backbones extraction methods. The PTFS/CM simulations were initially performed at the lab scale on a 3 D 20 m rock block from the Bari South Italy fractured aquifer. Results were consistent with the chlorophyll A BTC obtained from a well to well tracer experiment. Subsequently, the capability of the new method was tested by increasing the scale of simulations to a larger 3 D DFN of 200 m with 2,200 fractures. The resultant BTC was obtained in 32 min, showing the proposed PTFS/CM technique can rapidly determine complex 3 D solutions in heterogeneous fracture dominated aquifers. The applied Lagrangian and Eulerian techniques can provide quasi deterministic BTCs and 3 D maps of pollutant concentrations, avoiding extensive computations required for conforming mesh methods. Moreover, the solution does not require multiple randomly arranged DFN realizations, as in particle tracking based stochastic methods. These results have significant implications in modeling transport at the aquifer scale, where DFNs are composed of thousands of fractures. Published version https //doi.org/10.1016/j.jhydrol.2023.130566 Articolo in rivista Elsevier 0022 1694 Journal of hydrology Amst. Journal of hydrology Amst. J. hydrol. Amst. Journal of hydrology. Amst. Journal of hydrology Lausanne Amst. Journal of hydrology New York Amst. Journal of hydrology Oxford Amst. Journal of hydrology Shannon Amst. Journal of hydrology Tokyo Amst. costantino.masciopinto MASCIOPINTO COSTANTINO DTA.AD002.008.001 DRINKADRIA BARI