In reality, the reservoir rock space is a very complex metamerism; however when caculating according to the common way, in many cases, we consider the void structure in the rocks as similar fractal, and use suitable statistical approximate formula to demonstrate the space in form of effective homogene. When researching the layers, we take the rock samples from one layer with different collector parameter. To get a parameter value (grain density, porosity, permeability, saturation etc.) of a researched object, we calculate the average value of parameters measured from samples of the same object. Therefore, the real space is inhomogeneous (metamerism) when we consider it in a small scale (core sample), however we consider it.
