There are 2 basic types of natural fractures that need to be studied when characterising naturally fractured reservoirs - whether it be a geothermal or hydrocarbon reservoir. These are extension and shear fractures.
Many natural rock fractures contain minerals or cements which reduce their permeability and the permeability of the fracture network. Here we look at some examples in fractured (N Sea analogue) Permian sandstones and dolomites.
Fracture swarms are concentrated zones of open fractures, over which there is little or no offset. Although there are excellent outcrop examples, these structures can be difficult to identify in the subsurface. An integrated static-dynamic approach is best to successfully identify fracture swarms.