A triple continuum one-dimensional transport model for colloid facilitated contaminant migration in sets of parallel fractures with fracture skin

A triple continuum one-dimensional transport model is developed to analyse colloid facilitated contaminant transport in fractured geological formations. The model accounts for contaminant transport in the fracture, reversible deposition onto fracture surfaces and onto the colloids, diffusion into the rock formation and irreversible deposition of colloids onto the fracture surfaces. Sorption of the contaminant onto the fracture surfaces and onto suspended and deposited colloids are assumed to follow the linear equilibrium assumption (LEA); whereas the irreversible deposition of colloids onto the fracture skin surface is assumed to be governed by the linear kinetic sorption isotherms. The resulting coupled contaminant transport equations are solved using a numerical model employing fully implicit finite difference method based formulation. Results clearly demonstrate that the presence of the fracture skin significantly influences colloid facilitated contaminant migration in fractured formations. Fracture skin porosity and fracture skin diffusion coefficient are demonstrated to be the critical fracture skin properties that affect colloid facilitated contaminant migration in fractures. The impact of different colloid parameters on contaminant transport is investigated. The distribution coefficient for contaminant sorption onto the suspended colloids is found to be the most significant colloid related parameter influencing contaminant migration in fractured formation with fracture skin.

Figure optionsDownload as PowerPoint slideResearch highlights▶ A finite difference based numerical model is developed to analyze colloid facilitated contaminant transport in sets of parallel fractures with fracture skin. ▶ Influence of previously deposited colloids on contaminant migration is incorporated into the model. ▶ Colloid facilitated contaminant migration is demonstrated to be significantly affected by the presence of fracture skin. ▶ Fracture skin porosity and fracture skin diffusion coefficient are the most critical fracture skin properties affecting contaminant migration in presence of colloids in fractures.