Development of Solutions for Rapid Simulation of Solute Transport in Fractured Aquifers

Abstract

Understanding the flow and transport of contaminants in fractured rocks play a fundamental role in geo-environmental problems since subsurface contamination poses a serious threat to human health and the environment. Therefore, it is imperative to understand solute transport in these environments; models are an important tool in the advancement of our understanding. Aquifers in which the flow pattern is dominated by a network of connected fractures present challenges with respect to modeling due to the high degree of heterogeneity in fracture density and geometry. The goal of this research is to develop a suite of modeling tools that are accurate, computationally stable, and efficient enough to simulate solute transport in complex, discrete fracture networks (DFNs). Four research objectives have been designed to achieve this goal: (1) develop a computationally efficient analytical model for simulating two-dimensional spatial and temporal solute transport in discrete fracture networks (DFNs), (2) develop a closed-form solution describing the classical advection-dispersion equation for simulating reactive transport in single, parallel-plate fractures under a range of conditions, (3) develop a numerical model (based on the closed-form solution developed in Objective 2) to simulate solute transport in small-scale (~350 m × 350 m) discrete fracture networks considering mass exchange between the fracture and surrounding matrix, and (4) upscale the frameworks developed in Objectives 1 and 3 to develop an accurate and computationally efficient numerical model simulating solute transport in field-scale fracture networks . The developed analytical model (Objective 1) provides a useful reference tool for the verification of numerical dual-porosity fracture network simulations. The other developed numerical approaches (Objectives 2, 3, and 4) advance solute transport behavior predictions in fractured environments as they are both simpler and more computationally efficient than currently adopted techniques, which is particularly important for simulating fracture networks at the macroscopic scale.