Fluid Types Comparison

Fluid Types: Black Oil • Volatile Oil • Gas condensate • Wet gas • Dry gas • Fluid Types Comparison

Phase diagrams

This diagram puts the phase diagrams for all five fluid types (Black oil, Volatile oil, Gas condensate, Wet gas, Dry gas) on the same scale, and shows quality lines, reservoir temperature, and conditions of the producing wellstream.

It’s important to note that all of these phase diagrams are not exactly right, except as snapshots in time showing what we’d see if we could keep the composition constant. In reality however, as pressure decreases, fluid breaks out, and the reservoir composition changes. The phase envelope should change too.

Guidelines for Determining Fluid Type (McCain, 1994)

	Black Oil	Volatile Oil	Gas condensate	Wet Gas	Dry Gas
Initial GOR, scf/STB	<2000	2000 - 3000	>3200	>50,000	(>100,000)
Initial Oil °API	<45	>40	>40	up to 70
Bo at bubble point	<2.0	>2.0	-	-	-
C7+, mole%	>20 +/-2	12.5 to 20 +/-2	<12.5	(<3)	(<0.7)
Phase change in reservoir	bubblepoint	bubblepoint	dewpoint	no phase change	no phase change
Color of Stock-tank Liquid	dark	colored	lightly colored	water white	-