Transport and intersection mixing in random fracture networks with power law length distributions

The importance of fracture intersection mixing rules, complete mixing and s treamline routing, on simulated solute migration patterns in random fractur e networks is assessed, For this purpose, a-ad based on geological evidence , two-dimensional model networks having power law fracture length distribut ions and lognormal fracture permeability distributions are considered. Diff erent fracture network structures are accounted for by the power law length distribution, ranging from networks composed of infinite length fractures to percolation networks, with constant length fractures. Comparison of solu te particle statistics shows that there is no significant difference betwee n the bulk transport properties calculated with the two mixing rules. In fa ct, it is found that the choice of. Mixing assumptions has a significant in fluence in less than 5% of the total number of fracture intersections in mo st fracture networks. This result can be attributed to the small mean effec tive coordination number, defined as the number of branches connected to an intersection with nonzero flux. It is concluded that solute transport in f racture networks is strongly influenced by variability and uncertainty in p arameters defining the geometrical structure of networks and that, by compa rison, the choice of mixing rules at fracture intersections is of little im portance.