Page 365 - Fundamentals of Reservoir Engineering
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NATURAL WATER INFLUX                                   300

                     aquifer to reservoir radius r eD = r e/r o, for radial aquifers. In contrast, plots of W D versus

                     t D for both radial and linear geometry and, in the former case, for select values of r eD
                     are included as figs. 9.3 - 9.7. The plots are taken from the published solutions of
                                                            1
                     equ. (7.18) by Hurst and van Everdingen . Each chart has a different resolution of the
                     dimensionless time scale. It should be noted that the graphs are valid for all values of
                     t D and hence are applicable for calculating both the early, unstable influx (infinite
                     aquifer case) and for the influx occurring once the aquifer boundary effects have been
                     felt. There are differences in the way in which the dimensionless time and aquifer
                     constant are calculated, dependent on the geometry. These are summarised in
                     figs. 9.1 and 9.2.






                                         Water



                                                 Oil                        t =  θ°
                                                         θ                     360 °



                                                           r o
                                                                                 θ
                                                                             =      Radians
                                                                                2 π
                                                                    r e



                     Fig. 9.1   Radial aquifer geometry

                                   Darcy Units                                Field Units

                                       kt                                                kt
                                  t =     2                              t = constant×      2      (9.7)
                                                                          D
                                  D
                                     φµ cr 0                                           φµ cr 0
                                                              the constant =   .000264 (t-hours)

                                                                           =   .00634 (t-days)
                                                                           =   2.309    (t-years)
                                                                                         2
                                          2
                             U = 2π fφhcr  (cc/atm)                      U = 1.119 fφhcr  (bbl/psi)  (9.8)
                                          o
                                                                                        o
                                                                    Oil
                                                                                    h


                                                 Water



                                                                     L


                                                  W
                     Fig. 9.2   Linear aquifer geometry
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