A particle-tracking approach to simulating transport in a complex fracture

Abstract

Nearly all of the studies of flow and transport in fractured rocks have assumed that each fracture can be modeled as an open space between two surfaces with constant or variable separation. Field observations of rock fractures have shown that a fracture in the field can be rather more complex. Recent studies indicate that a complex fracture can be characterized as a thin fracture zone having several interconnected subfractures, which can contain mechanically dislodged and chemically altered materials with an enhanced porosity. This paper proposes a particle-tracking approach to calculate solute transport in a complex fracture, with structures in the fracture thickness normal to the fracture plane. These structures include subfractures, dead-end pores, gouge materials, small matrix blocks, and the adjacent rock matrix, all providing material in which solute diffusion and sorption can occur. The method is described; an example is provided to show its feasibility and the reasonableness of its parameter dependence; and, finally, direction for its further development is discussed.