The Channel Network Model and Field Applications

Abstract

AbstractThe Channel Network model describes the fluid flow and solute transport in fractured media. The model is based on field observations, which indicate that flow and transport take place in a threedimensional network of connected channels. The channels are generated in the model from observed stochastic distributions and solute transport is modelled taking into account advection and rock interactions, such as matrix diffusion and sorption within the rock. The most important site-specific data for the Channel Network model are the conductance distribution of the channels and the flow-wetted surface. The latter is the surface area of the rock in contact with the flowing water. These parameters may be estimated from hydraulic measurements. For the Äspö site, several borehole data sets are available, where a packer distance of 3 metres was used. Numerical experiments were performed in order to study the uncertainties in the determination of the flowwetted surface and conductance distribution. Synthetic data were generated along a borehole and hydraulic tests with different packer distances were simulated.The model has previously been used to study the Long-term Pumping and Tracer Test (LPT2) carried out in the Äspö Hard Rock Laboratory (HRL) in Sweden, where the distance travelled by the tracers was of the order hundreds of metres. Recently, the model has been used to simulate the tracer tests performed in the TRUE experiment at HRL, with travel distance of the order of tens of metres. Several tracer tests with non-sorbing and sorbing species have been performed.