Page 87 - PVT Property Correlations

Chapter 4

Wet Gases

Wet gases lie between dry gases and gas condensates. This reservoir fluid type
covers a large portion of the gases produced from many basins. The designa-
tion wet gas refers to the behavior of gases that condense some liquids on sur-
face. Hydrocarbon liquids produced on surface from wet gases are less than
those produced from gas condensate reservoirs. The phase behavior of wet
gases is described in Fig. 4.1. Theoretically, wet gases do not drop out conden-
sate in the reservoir. This means that the reservoir gas composition does not
change at any stage of depletion. Also theoretically, the reservoir temperature
is higher than the cricondentherm (i.e., the reservoir temperature line does not
cross the two-phase envelope). Almost any natural gas we produce drops
some condensate at least on surface. When the amount of the condensate pro-
duced on surface (relative to the amount of gas) is low, we can use the wet gas
“model” or wet gas “concept” to describe the fluid.
According to McCain, we can use the wet gas concept for gases that con-
tain C7 1 from 0.8% to 4%. If reservoir gas composition is not available,
the initial gas oil ratio (GOR) (or condensate gas ratio, CGR) can be used

FIGURE 4.1 Theoretical wet gas phase diagram.

PVT Property Correlations. DOI: https://doi.org/10.1016/B978-0-12-812572-4.00004-7
© 2018 Elsevier Inc. All rights reserved. 65