Page 190 - PVT Property Correlations

164 PVT Property Correlations

FIGURE 7.10 Example static reservoir pressure versus cumulative oil production plot.
Utilizing the Known Bubble-Point Pressure to Improve Accuracy
of Oil PVT Correlations
Knowledge of bubble-point pressure can be used to improve the accuracy in
prediction of other PVT properties, as the bubble point will not be calculated
by a correlation that carries some error (McCain, 1990). The known bubble-
point value can also be used to improve the accuracy of the PVT correlations
prediction even further. McCain (1990) outlines a simple procedure to shift
the calculated solution GOR and formation volume factor. In this procedure,
McCain calculates a “delta pressure” between the calculated bubble-point
pressure from a specified correlation and the actual bubble-point pressure.
He then shifts the pressure values horizontally so the calculated solution
GOR and oil formation volume factor at the bubble point coincide with the
correct bubble-point pressure. McCain’s procedure can be applied to limited
properties and is considered to be a one-dimensional shift in properties.
Kanu and Ikiensikimama (2014) proposed a technique that uses a multiplier
and a shift parameter to move the calculated PVT property from any correla-
tion to match the actual PVT data when available. When the bubble-point
pressure is the only known property, their procedure cannot be used.
The technique presented here is based on two-dimensional shift of the
correlations’ calculated properties. Fig. 7.11 illustrates the 2D shift technique
in the solution GOR property curve. In this graph, the calculated bubble-
point pressure value from a particular correlation is 3432 psig. If the correct
bubble-point pressure is 3000 psig, a backward shift is needed. If the known
bubble-point pressure is 4000 psig, a forward shift is to be made.