Hi everyone,

At the moment I'm trying to figure out how to estimate shale volume by using the following formula: Vsh = (GRl - GRmin) / (GRmax - GRmin).
Regardless simplicity the formula itself, i cannot understand how to derive GRl from a GR log. A gamma ray curve is represented by tens or hundreds values of SGR in an area of interest.
How do we come to only one value from the range?

Thanks.