  This chapter presents a descriptive and illustrative account of phase
behavior in the seven naturally occurring petroleum fluids and ties all the
known eleven phase-transition concepts in a unified narrative. The figures and
tables contained in this report are designed so that they could effectively
support the discussion about molecular make-up of petroleum fluids, P- and
T-effects on phase behavior and phase transition points.
  Seven naturally occurring hydrocarbon fluids are known as petroleum fluids.
They include, in the order of their fluidity, natural gas, gas-condensate
(NGL), light crude, intermediate crude, heavy oil, tar sand and oil shale. In
this report we present a generalized description of the various phase
transitions, which may occur in petroleum fluids with emphasis on heavy
organics deposition.
  At first the nature of every petroleum fluid is presented. Their constituents
including their socalled impurities are identified and categorized. Heavy
fractions in petroleum fluids are discussed and their main families of
constituents are presented including petroleum wax, diamondoids, asphaltenes
and petroleum resins. Then the generalized petroleum fluids phase behavior is
discussed in light of the known theory of phase transitions. The effects of
variations of composition, temperature and pressure on the phase behavior of
petroleum fluids are introduced. Finally eleven distinct phase-transition
points of petroleum fluids are presented and their relation with state
variables and constituents of petroleum fluids are identified. This report is
to generalize and relate phase behaviors of all the seven naturally occurring
petroleum fluids into a unified perspective. This work is the basis to develop
a comprehensive computational model for phase behavior prediction of all the
petroleum fluids, which is of major interest in the petroleum industry.
