• Porosity consists of the tiny spaces in the rock that hold the oil or gas.  Porosity of a rock is a measure of its ability to hold a fluid,
• Permeability is a characteristic that allows the oil and gas to flow through the rock. It is a measure of the resistance to the flow of a fluid through a rock.  If it takes a lot of pressure to squeeze fluid through a rock, that rock has “low permeability” or “low perm.”  If fluid passes through the rock easily, it has “high permeability,” or “high perm.

Oil and gas is mostly produced from sandstones.  These rocks usually have high porosity, and are usually “high perm.”