Page 143 - PVT Property Correlations

120 PVT Property Correlations

FIGURE 6.1 Typical phase diagram for volatile oil fluid.

The gas condensate produced with volatile oil contains liquids that will
condense on surface. Jacoby and Berry (1957) and Cordell and Ebert (1965)
highlighted the effect of the gas condensate associated with volatile oil on
material balance calculations. They concluded that the material balance
equation developed for typical black oil reservoirs cannot be used to handle
volatile oil reservoirs. To handle material balance calculations for volatile
oil, either the compositional material balance or the modified black-oil
(MBO) approach must be used. Walsh (1994) and Walsh et al. (1994) pre-
sented the use of MBO material balance equations for volatile oil reservoirs.

PVT PROPERTIES FOR VOLATILE OILS

The same PVT properties defined for black-oil (specific gravity, bubble point
pressure, oil formation volume factor, solution GOR, oil density, oil viscos-
ity, and isothermal compressibility of oil) are used for engineering volatile
oil reservoirs. The definitions and the behavior of these properties are
explained in the Black Oil Chapter. An additional PVT property is required,
which is the vaporized oil gas ratio.

Vaporized Oil Gas Ratio
Vaporized oil gas ratio is defined as the amount of oil (condensate) that
will be produced from the surface gas. In the petroleum literature, two sym-
bols are used for vaporized oil gas ratio (R v and r s ). The vaporized oil gas