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

Part A -
Geologic Assessment
Introduction
The South Texas area within the Rio Grande Embayment has long
been of interest for the possibility of geopressured-geothermal
energy production from the high temperature, thick, massive sands
of the deep Frio and Vicksburg Formations. These sands are part of
a sequence of thick wedges of sediment containing enormous volumes
of rock. The wedges consist of interbedded sand and shale, massive
sandstone, and massive shale. originally, these sand bodies formed
extensive aquifers with considerable lateral extent (Henry and
Morton, 1982). Within the Rio Grande Embayment, depositional
pattern is also strongly affected by a series of major growth fault
systems which affected both the sediment distribution and resulting
structural style (Fig. 1).
Two
reservoir areas, containing thick sand sequences and
outlined by major north-south trending growth faults, have been
defined (Fig. 2). Reservoir area C, defined by the major McAllen
growth fault on the west, and the Donna fault on the east, contains
two potential sand sequences:
the Marks sand (Fig. 4), with an
average depth of 9,881 feet, average pressure gradient of 0.73
psi/ft and an average temperature of 279°F, and the Bond sand (Fig.
5), with an average depth of 10,626 feet, average pressure gradient
of 0.76 psi/ft., and an average temperature of 296°F.
Reservoir area B, defined by the Donna fault on the west and
the Weslaco fault on the east, contains several thick sand
sequences.
However, the sand at 10,000 feet (Fig. 6) with an
II-I