FVF, GEF and Reservoir Fluids in Hydrocarbon Prospect Analysis a Basic Primer

Formation Volume Factors are a key part of the Volumetric Equation
Used to convert reservoir fluids (oil and gas) to standard storage conditions
Oil shrinks when brought to the surface (as well as degassing)
Gas expands when brought to the surface (remember Boyles law from high school) - with heavier hydrocarbons condensing out
Variable parameters for prospect analysis (Low, Mid, High)
Reservoir engineers will supply you with these parameters
Please communicate with them, they do not bite, honest