An Inverse Channel Model for Flow and Transport in a Single Fracture

Abstract

Abstract Recent experimental and theoretical investigations of transport in a fracture indicate that fluid flows preferentially through flow channels in the fracture plane. Several one dimensional (1D) channel models have been introduced to interpret flow and transport through 2D fractured medium. However, those models couldn't reproduce a tracer breakthrough curve accurately and aperture distributions (i.e. aperture mean and standard deviation) could not characterize flow channels in the fracture. In this paper, we present a new 1D channel model using an inverse algorithm. If a breakthrough curve is given, we divide its time into a limited number of intervals using the superposition theory, and then determine aperture distribution of each channel inversely. The new channel model reproduced the tracer breakthrough curve of a fracture almost exactly at any given pressure drop, and also matched the distributions of flow channels in the fracture. Using parameters analysis, we discovered that flow channeling becomes dominant in a fracture flow if the coefficient of variation is over 0.3. Therefore, the new channel model can simulate flow and tracer transport in a fracture effectively in that range. We developed a 2D transport simulation model in a fracture and verified the model using experimental data. We used the model to compare the results of the 1D channel model with. Since we developed a 1D channel model to analyze 2D flow, it considerably reduces calculation time and computer memory.