Geology Reference
In-Depth Information
Miocene) include brine waters with salinity 332.5-367.5 mg-equiv. (95-
105 g/l), secondary salinity factor 23-27%-equiv. and sulphate content of
2.1-3.1 mg-equiv.
Somewhat higher ground water salinity and sulphate of this interval
compared with the underlying Asmari complex are due to evaporites in
the section (rock salt and anhydrites).
The information about the underlying intervals of the sediment cover
(the Cambrian, Silurian, Devonian, Carboniferous, Permian (Huff forma-
tion) and Triassic) is purely qualitative. The only known fact is that the
ground waters in these stratigraphic subdivisions are chlorine-calcium
brines (up to 200-300 g/l) with the salinity increasing down the section.
Maximum salinity was recorded in Cambrian rocks of the extreme south-
eastern portion of the region where the section includes thick rock salt and
other evaporites.
The following conclusions are based on all available information:
t
The vertical hydrochemical zoning in the region is generally
normal. Down the stratigraphic section is recorded continu-
ous increase in the ground water total salinity, increase in
the secondary salinity factor values and in metamorphism
factor.
t
Some deviations of this general rule are encountered. They
are slight local decreases in total salinity and secondary salin-
ity factor values. They are recorded in the intervals affected
by sedimentation lacunas and denudation, which corre-
sponds with the effect of ancient meteoric water infiltration;
t
Areal water distribution over the local highs displays a clear
trend of decreasing the salinity and hardness from most
fractured and faulted crestal areas toward the periphery.
t
In each waterhead complex the minimum salinity values
belong with the hydrochemical background, the maximum
values (local positive anomalies) belong with the areas of
elevated reservoir fracturing and maximum oil productivity.
Thus, patterns are identified in the ground water spatial distribution
within individual structures by salinity and composition. These patterns
are in the association between changes in water salinity and hardness in
the section and over the area and in the location of their maximum values
in the most faulted and fractured zones of reservoirs. These patterns depict
mechanisms of mixing waters belonging to different stratigraphic units
(background watershed complexes and injected water from the underlying
