The rock must have a place for the oil and gas to be stored. These storage areas are called pores . These pores are not visible to the naked eye and must be viewed using a microscope. The number of pores that a rock contains indicates how much oil or gas can be stored. The more pores the more oil or gas that can be contained in the rock.
Scientists measure the amount of pore space by determining the rock's porosity .
The greater the porosity, the more oil and gas can be stored in the rock. Porosity does not mean that there is oil or gas in the the rocks. In fact the pores could be filled with water. Not only must the rocks have pores, the pores must be connected so that the oil and gas can move through the rock. Scientists measure the ability of oil and gas to move through rock by determining its permeablity .