Geology Reference
In-Depth Information
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Down the section, the salinity and metamorphism of the
syndepositional chlorine-calcium ground water increase.
Minimum salinity values correspond with the lowermost
secondary salinity factor values.
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The following regional pattern is recorded in all complexes:
the salinity and hardness increase (growth of the second-
ary salinity factor in the chlorine-calcium brines, decline in
the primary alkalinity factor in the hydrocarbonate-sodium
waters) of the formation solutions from south to north
(from the Chernogor monocline to the Pri-Terek zone of
highs) with increasing depth of natural reservoirs and their
improved isolation from the surface.
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Fresh (low-salinity) sulphate-sodium and hydrocarbonate-
sodium waters in the Eocene-Upper Miocene stratigraphic
range are genetically foreign to the enclosing reservoirs. They
are of clearly meteoric origin. On the way of their flow from
the charge areas they replace in the most permeable inter-
vals their syndepositional chlorine-calcium waters, mix with
them and form a range of “transitional” sulphate-sodium,
hydrocarbonate-sodium, chlorine-magnesium and chlo-
rine-calcium formation solutions whose salinity and type
depend on the ratio of the original and foreign components.
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Areas and intervals of hard saline waters in the Eocene-
Upper Miocene section are most common with the most
deformed structures and their individual intensely faulted
and hydraulically isolated parts. Low-salinity hydrocar-
bonate-sodium and sulphate-sodium waters are associated
mostly with weakly-faulted reservoirs not blocked from the
hydraulic communication with the meteoric water charge.
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The development of typical chlorine-calcium brines in the
Jurassic and Cretaceous sediments of prospects closest to their
exposure areas (Chernogor monocline) indicates the absence
of a substantial effect from the present-day fresh meteoric
water infiltration onto the formation of regional hydrochem-
ical environment in the Mesozoic natural reservoirs.
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The following phenomenon is established in the Mesozoic
complexes within the fields of all anticlinal zones in the
trough: the areal distribution of the ground water salin-
ity and composition shows a clear salinity and metamor-
phism decline from the crests to the flanks and plunges. It
