Influence of fracture statistics on advective transport and implications for geologic repositories

[1] Large-scale (2.5 km by 2.5 km) simulations of fluid flow and solute transport through low-permeability fractured rock are assessed to determine suitability for hosting a nuclear waste repository. Multiple realizations of fracture networks with statistically realistic features are generated according to established methods. A novel continuum method provides a basis for solving flow and simulating particle trajectories through the fracture networks. Classical and fractional advection-dispersion models form the analytic foundation for statistical summaries of the transport of 25,000 conservative particles through the backbone of each network realization. Particle retention in low-velocity fractures, fast transport, and anomalous dispersion are all observed in the simulated plumes. Predictability is addressed by measuring the deviation of individual plumes from their ensemble average, taken over all realizations for each set of fracture network statistics. Fifteen sets of fracture network statistics are examined, ranging from dense networks of relatively short fractures to sparse networks of rather long fractures. Finally, the plume statistics are carefully examined in order to develop recommendations for suitable geologic repositories on the basis of fracture network statistics.