Page 315 - Principles of Applied Reservoir Simulation 2E

300 Principles of Applied Reservoir Simulation

cantly different for some oils. The actual behavior of the production process is
some combination of the differential and flash processes. The assumption
normally made in preparing PVT data for use in a black oil simulator is that the
differential liberation data represent the process occurring in the reservoir and
the flash data represent production to stock tank conditions. Thus, for use in the
simulator, the differential liberation data should be corrected to flash values at
field separation conditions. This procedure is described in the literature [Arnyx,
et al, 1960; Moses, 1986] and is summarized below.
Physical property data obtained from a testing laboratory for a black oil
system will generally be a differential liberation study coupled with a separator
study. Most reservoir simulators require that these data be converted to flash
form so that the effects of the surface separation facility are included. Conversion
of the data is restricted to oil formation volume factor and solution gas-oil ratio
data. If the separator B 0 and R so are known, the conversion equations are:

"odbp

and

B
ofbp
"odbp

where subscripts are defined as:
d = differential liberation data
/ = flash data
bp - bubble point

28.4 Extrapolating Saturated Curves

Guidelines for extrapolating PVT data to pressures above the measured
saturation pressure are presented below.

i. The B g versus pressure curve is strongly non-linear and an extrapolation
of this curve to small B g values at high pressures can result in errors. For