What is the primary factor that defines absolute permeability in porous media?Group of answer choicesPorosityWater contentRock typeFlowrate velocity

Absolute permeability in porous media is primarily defined by the rock type.

Here's why:

1. Porosity: While porosity is an important factor in determining the storage capacity of the reservoir, it does not directly define the absolute permeability. Porosity refers to the void spaces in the rock, but it doesn't tell us about the connectivity of these spaces.

2. Water content: Water content can affect the relative permeability of a reservoir to different fluids (like oil, gas, and water), but it does not define the absolute permeability, which is the capacity of the rock to transmit any fluid when it is 100% saturated with that fluid.

3. Rock type: The rock type is the primary factor that defines absolute permeability. This is because the size, shape, and distribution of the pores in the rock, as well as the connectivity between them, are all determined by the rock type. These characteristics directly influence the absolute permeability.

4. Flowrate velocity: The flowrate or velocity of the fluid can affect the apparent or effective permeability, especially in cases of non-Darcy flow. However, it does not define the absolute permeability, which is a property of the rock itself, not of the flowing fluid.

So, the correct answer is Rock type.