Dewpoint is the pressure at which the first condensate liquid comes out of solution in a gas condensate. Many gas condensate reservoirs are saturated at initial conditions, meaning that the dewpoint is equal to the initial reservoir pressure. Condensate dissolution is called retrograde condensation because this is counter to the behavior of pure substances, which vaporize when the pressure drops below the saturation pressure under isothermal (constant temperature) conditions.
The phase diagram divides the fluids into three distinct regions. The liquid region is to the left of the critical point and above the bubble point line. The gas region is to the right of the critical point and above the dew point line. The two-phase region (i.e. saturation envelope) is enclosed by the bubble point and dew point lines. The important elements of the phase diagram are defined below:
- Bubble Point Line: The point at which the first bubble of gas comes out of the liquid
- Dew Point Line: The point at which the first drop of liquid drops out of the gas
- Critical Point: Represents the condition where the properties of liquid and gas are identical
- Cricondentherm: The highest temperature on the saturation envelope
- Cricondenbar: The highest pressure on the saturation envelope
- Two Phase Region: Region where gas and liquid coexist
- Retrograde Region: Region where liquid condensate forms by lowering pressure or increasing temperature (see Retrograde condensation)
- Quality Lines: The lines showing liquid %’s which intersect the critical point
http://www.jmcampbell.com/tip-of-the-month/2007/06/why-do-i-care-about-phase-diagrams/ - Why do I care about phase diagrams?