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.
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