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typical of distant beyond-the-OWC areas of the accumulations (and the
crestal areas have the minimum values). Total alkalinity, sulphate content
and sodium content grow in the opposite direction. The Palmer's param-
eters behave accordingly: in the structures' elevated portions the secondary
salinity factor is suppressed and the primary salinity and secondary alka-
linity are at their maximum.
As the hydrocarbon saturation in the Apsheron rocks appears only in
the crestal, most faulted zones of local structures and has definitely sec-
ondary origin (Apresov, 1947; Gorin and Buniat-Zadeh, 1971; Mekhtiyev,
Rachinsky and Akhundov, 1966; Mekhtiyev and Rachinsky, 1967; Potapov,
1954), the association between the water type, structural conditions, oil
and gas occurrences and the communication between productive inter-
vals and the accumulations in the underlying sediments becomes obvious.
It is noteworthy that the zones of commercial hydrocarbon-saturation in
all fields correspond with the lowermost salinity and minimum secondary
salinity factor values of the ground waters.
The described water salinity and ion-salt composition distribution
over the individual structures, similar to the Middle Pliocene Productive
Sequence, is a testimony to the definitive effect of vertical cross-flows
of lower salinity, lower secondary salinity factor values waters from the
underlying sediments on the formation of the present-day local hydro-
chemical zoning in the Apsheron Stage.
The comparison of ground waters in the Lower Kura Depression and the
Apsheron Peninsula showed relative similarity in their ion-salt composition
with a significantly differing salinity. This is interpreted as a result of sub-
stantial ground water desalination in the Lower Kura Depression caused by
the effect of paleo-rivers (Paleo-Kura, Paleo-Araks and Paleo-Pirsagat) on
the hydrochemical depositional environment of the Apsheron sediments.
2.1.1.2
On The Formation Mechanism of the Region's Ground
Water Ion-Salt Composition and Salinity, and the Nature of
the Inversed Hydrochemical Profile
These issues were subjected to extended studies, which resulted in numer-
ous views and hypotheses.
Several mechanisms were considered to be definitive. They include the
following:
t Differences in the lithological composition of water-satu-
rated rocks;
t The processes of cation exchange between rocks and ground
waters;
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