Page 115 - PVT Property Correlations

Gas Condensates Chapter | 5 93

TABLE 5.1 Recovery Efficiency of NGL Components from Different Plants
NGL Absorption or Lean Refrigeration Cryogenic
Components Oil Plants Plants Plants
Ethane 0.15 0.30 0.80 0.85 0.85 0.90
Propane 0.65 0.75 1 1
Butanes 0.99 1 1
Pentanes and C5 1 0.99 1 1

y i M i
GPM i 5 0:3151 gallons=Mscf ð5:3Þ
γ oi
The GPM can be converted to bbl/MMscf according to the following
equation:
bbl gal Mscf 1 bbl
GPM in 5 GPM in 3 1000 3
MMscf Mscf MMscf 42 gal
5 23:81 GPM in bbl=MMscf ð5:4Þ
Complete recovery of these liquids is not possible. Recovery efficiency
depends on the technology used in the gas plant. Table 5.1 summarizes the
NGL component recovery efficiency of different types of plants.
The lean oil plants are the simplest type of plants. Kerosene type oil is
circulated through the plant to absorb light hydrocarbon components from
the gas. The light components are separated from the rich oil and the lean oil
is recycled. Refrigeration plants use propane to chill the gas and remove
more liquids. Cryogenic plants use turbo expander technology to cool the
gas to subzero temperatures to remove liquids.

Modified Black Oil Approach for Gas Condensate
Modified black oil (MBO) approach can be adequately used in many appli-
cations to model gas condensate behavior (El-Banbi et al., 2000a; Fevang
et al., 2000). If MBO approach is used to model the gas condensate fluid
behavior, it is preferable to derive the MBO PVT properties from an equa-
tion of state (EOS). Several techniques are available to derive the MBO
properties from an EOS (Fattah et al., 2006). Four PVT properties are needed
as a function of pressure in the MBO approach. These are (1) oil formation
volume factor; (2) gas formation volume factor; (3) solution gas oil ratio;
and (4) vaporized oil gas ratio.