The way reservoir properties (VShale, Poro, Perm, Swi) are deducted from logs only

[catapam]

Hi!

How reliable to have reservoir properties like VShale, Poro, Perm, Swi deducted only from logs?

I'm not geologist and also new in simulation and I want to understand step by step this process.
From what I understood until now the order is:
VSchale is found first from SP or GR curves then porosity is found with more complex curves involved. Then Swi (initial saturation) is found and finally permeability is constructed using a mathematical equation that involved Poro / Swi models.

So everything is somehow flowing one from another.

If you have cores could be better to construct your models (especially permeability) based on core data and to ignore permeability model constructed by geologist?
Cores mean direct measurement and (maybe) a better formula that correlate porosity with permeability.