Discrete Fracture Network (DFN) models

The discrete fracture network (DFN) concept assumes flow through a fractured rock is predominantly through an inter-connected network of flow-conductive fractures with groundwater moving from one fracture to another at the intersections between them. The properties of the network are usually characterised in terms of:

For individual fractures, either deterministic or stochastic, their properties are primarily:

In ConnectFlow, fractures are usually rectangular, but may be right-angled triangles where a complex surface has been triangulated into many pieces. For stochastic fractures, the properties are sampled from probability distribution functions (PDFs) specified for each fracture set. The properties may be sampled independently or correlated with other properties.

The DFN concept is very useful since it naturally reflects the individual flow conduits in fractured rock, and the available field data. However, DFN models can sometimes become computationally challenging, and to understand flow and transport on a larger regional-scale it is often necessary to consider the larger-scale bulk properties in the context of an Equivalent Continuous Porous Medium (ECPM) concept. This requires methods to:

The characterisation of fractures in rocks and their role as conduits for fluid has significance to a wide range of applications including underground disposal of radioactive waste, oil and gas production, storage of carbon dioxde, geothermal energy and underground construction.

DFN models have found use in many areas, including: