Z-factor, or ideal gas deviation factor, describes the departure of the gas behavior
from that of the Ideal Gas Law (PV = nRT), which does not account for variation in
forces between molecules as a function of pressure. For molar volume (n=1), the Real
Gas Law is
PVm = zRT
where P is pressure, Vm is molar volume, R is the ideal gas constant, T is
absolute temperature and z is the ideal gas deviation factor.
Note that z-factors greater than 1 mean the real gas volume is greater than the Ideal
Gas Law would predict for the given pressure and temperature conditions, while z-factors
less than 1 indicate that the real gas is more compressed than the ideal gas prediction. For
the Bering Basin conditions described below, z-factor increases with depth.