1. A method comprising: modeling movement of hydrocarbons through kerogen-related porosity, the movement through a first model volume, and the modeling by a computer system; estimating a first permeability of a kerogen-rich layer of a layered shale formation based on the modeling; and then modeling hydrocarbon production from the layered shale formation by: utilizing the first permeability for the kerogen-rich layer of the layered shale formation; and utilizing a second permeability for a kerogen-poor layer of the layered shale formation, the second permeability different than the first permeability.