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

Part B - Simulation of GP/GT Resource Potential
Introduction
The Geologic Assessment of the areas of interest identified three potential reservoirs,
one in Area B and two in Area C. These are shown on Figure 1 of Part A. The
reservoir rocks were described by well logs and correlated across the two areas of
interest.
This information was then digitized to form the input to a numerical simulator.
Using simulation techniques, flow rates and pressures can be calculated for wells
drilled into each potential reservoir. A predicted performance for a test well in each
reservoir was computed and a pattern of multiple wells was also calculated for each·
reservoir.
Model Development
The areas between the major faults as shown on Figure 1 were broken into
computing grid blocks. In Area C the grid consisted of a 29 by 22 grid block mesh that
covers an area of 220 mi 2 . This represents the area between the McAllen Fault and the
Donna Fault. This is intended to represent the maximum reservoir area possible. As
an alternate to show the sensitivity to reservoir size a second grid was constructed that
covered 90 mi 2 . This area represents only the area included within the limits of well
control. Area B was covered by a 30 by 34 grid block mesh. This grid covers the 120
mi 2 included between the Donna Fault and the Weslaco Fault and is further represented
as the maximum case. The minimum case for this East Sand again represents the
minimum area included within the well control.
The reservoir properties used were determined by the geologic assessment and
shown on Tables 2 and 4. These properties include sand thickness, porosity, permeability,
and initial pressure gradient. The remaining properties needed for the simulation
include the fluid descriptions and the well parameters. The PVT relationships
were developed for brines using the best correlations available. The PVT properties of
the gas and brine are shown below.