(GP/GT) for Additional Water Supply in the Lower Rio Grande

maintains the 25,000 bbl/d rate for about nine years in the maximum case and about six
years in the minimum case. The East Sand maintains the 25,000 bbl/d for the full fifteen
year period of investigation for both the minimum and maximum cases. Gas rates
for all these cases are shown on the appropriate charts, but follow the solution gas relationship
shown on Table 3.
The pattern runs are shown on Figures 13-18. In all cases the patterns of wells
show declining production rates, even for the East Sand which showed no decline at all
in the single well case. To understand the charts and more importantly the reservoir
mechanics, notice how the patterns deviate from the maximum constant rate. As more
wells are added to the pattern, the deviation occurs earlier in time.
Recoverable Volumes
We can take the same data described above to make some additional charts that
show the volumes of brine that are recoverable from the reservoirs. These charts are
shown as Figures 19-24. These charts show the recovery of gas and brine as a function
of the number of wells in the reservoir.
It is of interest to follow the cumulative recovery curves from the minimum
cases to the maximum cases. These show that the smaller reservoirs cannot support as
many wells. Further, the curvature of these cumulative recovery charts shows the
declining effectiveness of adding additional wells to the reservoirs. For example, for
the East Sand Maximum case the fifteen year brine recovery is about 370 million bbl or
123 MMbbl/well. Six additional wells will contribute a total of 477 MMbbl or an
average of only 79.5 MMbbl each, a decrease of about 35% per well. This shows that
the spacing of development wells is an important economic issue.
Discussion
These simulation cases were developed to illustrate the capability of the GP/GT
reservoirs that have been identified. Nearly all the data were estimated from old well
logs or derived from correlations. To the extent that these estimates are accurate, the
predicted performance is reasonable.
Many of the controlling parameters in the various simulations were somewhat
arbitrary. For example, the 25,000 bbl/d maximum production rate is arbitrary. The
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