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

to coastal barrier sandstone on the west to distal shoreface sands
on the east.
Individual sands within the section thin and show a
more marked variation in resistivity.
Within Reservoir Area C,
the Bond Sand occurs within the
interval from 8,550 to 9,520 feet in well No.5, to 11,670 to
12,220 in well No.3 (Fig. 5). The average depth is 10,626 feet,
and the average thickness is 635 feet. The net sand average is 334
feet, or 53 per cent sand.
Pressure at the top of the sand
averages 8,045 psi, and the average gradient is 0.76 psi! ft.
Average temperature (A.A.P.G. corrected) is 296°F. Temperatures are
again higher than the average nearer the center of the reservoir.
Porosity and permeability were estimated from the resistivity and
spontaneous potential character of the logs.
These values were
compared to reported values, and the lower values were used for
simulation purposes. Porosity averages 18 per cent, and
permeability 13.8 md. The average KH is 4,609.
The spontaneous potential curves were not good in all the
wells; therefore, estimates of sand characteristics were derived
primarily from the resistivity curves.
Log characteristics would
indicate the Bond Sand to be a more distal fine-grained shoreface
sand with less reworking of sediment than the Marks Sand.
Like the Marks Sand, which was deposited in shallower water,
the Bond Sand dips from east to west towards the McAllen fault, and
thickens towards the fault. A flattening of dip also occurs toward
the northeast along the axis of the high which extends from
Edinburg to Donna (Fig. 2).
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