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.
This blog looks at pairs of faults known as conjugates. Often, one fault is older than the other which can be determined if that fault has been displaced by the other. The example faults here are actually made up of deformation bands so could be described as compound zones of deformation bands.
Faults often have more than 1 slip surface. In this blog, we present a major fault with multiple surfaces which juxtaposes the Upper Devonian Sediments (at arbroath) against the Lower Devonian Sediments.
In this blog, we discuss the value of log slippage and how it is essentially the same as vertical shear restoration on a cross section without the use of wells.
A variety of recent and old structures can be found on the karst limestone blocks of the Natih Formation, Oman. These include solution enhanced joints, Rillenkarren and tension gashes.
Induced fractures are not always easy to distinguish from open fractures. It is important though as induced fractures should not be included in the reservoir model.
Here we look at two broad categories of natural fractures which are very useful to consider when characterising naturally fractured reservoirs in the subsurface. These are diffuse fractures and fracture swarms.
Veins are useful indicators of the sense of shear - here we look at some calcite veins in limestone in Oman which have a sigmoidal geometry in places and indicate a sinistral sense of shear.