Page 22 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2
P. 22
10 Reservoir Engineering
PRESSURE. psig
Figure 5-8. Effect of pressure on crude oil viscosities [4].
by gas going into solution as pressure is increased form atmospheric to the
saturation pressure.
If the pressure is above the bubble-point pressure, crude oil viscosity in the
reservoir can be estimated with Figure 51 1 [5]. This figure shows the increase in
liquid viscosity due to compressioon of the liquid at pressures higher than the
saturation pressure. Viscosity of the crude can be estimated from the viscosity at the
bubble point pressure, and the difference between reservoir pressure and bubble-
point pressure.
Recent correlations [7] were presented in equation form for the estimation of
both dead oil and saturated oil viscosities. These correlations, which are presented
in the section on programs for hand-held calculators, neglect the dependence of oil
viscosity on composition of the crude. If compositional data are available, other
correlations [S-101 for oil viscosity can be used.
Water Viscosity. In 1952, the National Bureau of Standards conducted tests [ 111
which determined that the absolute viscosity of pure water was 1.0019 cp as
compared with the value of 1.005 cp that had been accepted for many years.
Effective July 1, 1952, the value of 1.002 cp for the absolute viscosity of water was
recommended as the basis for the calibration of viscometers and standard oil
samples. Any literature values based on the old standard are in slight error. Water
viscosity decreases as temperature is increased as shown in Table 5-1.