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

high, the sands are not thick enough nor laterally persistent. The
trend is also extensively faulted with numerous transverse faults
and antithetic faults relative to the main faults.
Reported
porosities and permeabilities of the sands are also extremely low.
Focus was then directed to the central and eastern fairways
which were designated Reservoir Areas C and B respectively. Using
the available published information in addition to proprietary
fault maps from Magma Gulf Co., and isopach maps from Mayfair
Minerals Co., an analysis of all sands below the top of geopressure
was conducted.
Some 30 well logs in the two areas were analyzed,
and 5 wells in each reservoir were chosen as key wells to represent
the lateral variations of the sands within the reservoir (Tables 1
and 3). Two sands in Reservoir Area C were determined to have the
optimum characteristics for production based on log characteristics
(Fig. 4 and 5).
These were primarily based on uniformity and
lateral continuity of the sands, which
included thicknesses
sufficient to offset variation caused by faulting (Fig. 3).
One
sand in Reservoir area B was chosen, primarily because of the depth
and extremely low salinity of the water (Fig. 6).
Potential
porosity and permeability values were based on both spontaneous
potential and resistivity characteristics.
Although there are
numerous seismic lines in the area, no seismic data were acquired
or evaluated because of budget limitations.
Geology
In the Rio Grande Embayment the Oligocene lower and middle
Frio Formations are characterized by enormous thicknesses of
II-4