A unified perspective on the phase behaviour of petroleum fluids

We present a coherent and unified group of general explanations for the various phase transitions, which may occur in the seven naturally occurring petroleum fluids with emphasis on their heavy organics. The seven petroleum fluids include, in the order of their fluidity, natural gas, near-critical gas-condensate, light crude, intermediate crude, heavy oil, tar sand and oil shale. At first the nature of every petroleum fluid is presented including their constituents and their heavy fractions. Then their main families of constituents are presented. The generalised petroleum fluid phase behaviour is introduced in light of the well-known theory of phase transitions. The effects of variations of composition, temperature and pressure on petroleum fluids phase behaviour are introduced. Their 11 distinct phase-transition points are presented and their relation with state variables and constituents are identified. This report is the basis for development of a unified phase behaviour prediction model of all the petroleum fluids. (Received: September 9, 2008; Accepted: November 15, 2008)