The key properties for describing a petroleum reservoir are porosity, pore saturation, and
permeability. Definitions of these terms are as follows.
Porosity refers to the capacity of the reservoir to hold fluids. It is basically the interstices,
or pores, present within the reservoir rock. Typical porosities of oil reservoirs are of the
order of 20%.
While porosity represents the maximum capacity of a reservoir to hold fluids, pore
saturation quantifies how much of this available capacity actually does contain fluids. For
example, if a reservoir is 50% saturated with oil, this means that half of the available pore
space in the reservoir actually contains oil.
