Ann: Contingent oil resources at Red Gully North-1, page-9

I may have misread your comment. Volatile oils under the correct pressure will behave much like a gas allowing the oil (light oil/condensate) to flow thru the structure somewhat unobstructed. As the pressure declines however the lighter components of the mixture (C2,C3,C4) will flash off lowering the liquid recovery rate. The ideal is to maintain critical pressure subsurface to effectively transport the heavier (higher value) components of the volatile oil mix to surface for separation.

These ones are a good read.

http://www.fekete.com/SAN/WebHelp/F...al/General_Concepts/Reservoir_Fluid_Types.htm
http://petrowiki.org/Oil_fluid_characteristics