Fracture Porosity and Permeability From Fracture
Fracture aperture exaggeration on acoustic image logs is even more severe and these logs probably should not be used for aperture estimation.
visual difficulties can be overcome with a post-processing technique
that uses a resistivity inversion model and the mud filtrate
resistivity to calculate aperture, independent of any visual
is based on the concept that higher electrical conductivity means a larger
open fracture. The fracture aperture and fracture frequency can
be combined to obtain fracture porosity and fracture permeability.
Note: Equations 2, 3, and 4 give identical results.
These examples represent well fractured reservoirs. You can see that the volume of hydrocarbon is very small but the permeability is very high.
If you believe that the phrase “fracture porosity” is a literal definition, then this porosity will usually be pretty small - in the order of 0.0001 to 0.01 fractional porosity (0.01 to 1.0%). If you believe that the phrase includes vuggy and solution porosity related to the presence of fractures, then the value could be much higher. The important thing is to recognize that there are two definitions for “fracture porosity”.
An example of a fracture aperture log from a program called Frac-View is shown below. The permeability calculation was not available in this program.
Calculating Permeability From Stoneley Attenuation
Permeability from Stoneley wave attenuation
The attenuation data can be represented as pseudo-permeability and presented on a qualitative scale: low attenuation corresponding to low permeability and high attenuation to high permeability. To facilitate comparisons of pseudo-permeability to actual formation producibility, the attenuation data can be integrated to provide a potential flow profile for comparison to an actual spinner flowmeter log. .
curve could be correlated to core permeability to obtain a calibrated
permeability curve. Correlation is usually as good as porosity
and saturation correlations, which have been used for many years,
and often much better than these in fractured and vuggy zones.
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