The bubble point of reservoir oil is an important fluid property the reservoir engineers seek. It is the pressure where the volatile components present in oil begin to “bubble up.” The pressure at which these bubbles of light hydrocarbons first appear is referred to as the bubble point for the fluid system.
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?