Page 131 - Principles of Applied Reservoir Simulation 2E

116 Principles of Applied Reservoir Simulation

predictions and then uses measurements to assess their validity. In this particular
case, a reservoir characterization based on seismically controlled properties
yielded more accurate predictions of reservoir properties than predictions made
using a reservoir characterization based only on well data.
Table 12-4
Predictions at New Wells from Seismic and Well Data
[de Buyl, et al., 1988]
Well Measured Seismic Well Data
Values Predicted Predicted
I Top of Reservoir (m) -178.0 -175.0 -181.0
Gross Porosity (vol %) 15.0 15.5 15.4
Net <j)h (m) 1.78 1.53 1.96
J Top of Reservoir (m) -182.0 -179.0 -174.0
Gross Porosity (vol %) 13.9 10.6 8.0
Net (|)h (m) 1.08 1.05 0.15

Although reservoir geophysical techniques are still evolving, it is possible
to make some general statements about the relative value of this emerging
technology. Table 12-5 summarizes the advantages and concerns associated with
reservoir geophysics.
Table 12-5
Reservoir Geophysics
Advantages Concerns
4 Able to "see" between 4 Cost of data acquisition and analysis
wells 4 Limited applicability
4 Single realizations enhance 4 Validity of realization unknown without
0 communication sensitivity analysis
0 understanding

To demonstrate the limits of applicability of reservoir geophysics, the
reservoir geophysical algorithm in WINB4D was used to study a hypothetical
reservoir system in which we could expect to see significant changes in seismic
properties as a function of field performance over time. In particular, a dipping
gas reservoir with aquifer influx was studied. The reservoir grid is shown in
Figure 12-6. The reservoir has an initial gas saturation of 70% and an initial