Geology Reference
In-Depth Information
section but also in the significant part of the upper section.
At the same time the situation is common where the hard
water occurrence zone covers also some part of the lower
section.
t
Alkaline water area increases down the section of the local
highs (see Figure 2.10).
t
The current concept is the inversion of the PT-KT hydro-
chemical profile (the “section's hydrochemical inversion”).
This concept assumes the decrease in total salinity (some-
times by the factor of 20 to 25) and replacement of hard
waters by the alkaline ones down the section over the entire
area of the complex occurrence. The concept is begging for
a significant modification as these phenomena are the exclu-
sive property of maximum deformed (usually crestal) por-
tions of the local highs, of the diapir plug contact zones with
the enclosing rocks, of mud volcano eruptions and other dis-
ruptions in the rocks' integrity. Over the distant flanks and
in the separating lows, which are significantly less deformed,
the hydrochemical profile is normal; i.e., the ground water
salinity and hardness are constant going down the section
and might be even slightly increasing.
t
In some fields and oil-gas areas, ground water composition
(type) depends only on their total salinity. Ground waters of
similar salinity have approximately the same composition in
all areas.
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The stratigraphy and depth of water type transition bound-
ary (i.e., the relationship between hard and alkaline waters
within the stratigraphic volume of a specific field/prospect)
are a function of the tectonic deformation of the structure.
In the strongest-deformed fields/prospects the water type
transition boundary between hard and alkaline waters occu-
pies the highest stratigraphic position.
t
An important role in the current ground water salinity and
composition (hydrochemical type) distribution within the
section belongs to the geologic specifics, i.e., different fault
morphology in both Series of the Middle Pliocene. The
Lower Series is dominated by large lengthwise faults, over-
thrust type, with a significant amount of throw. Common
there are mostly low-salinity alkaline waters or hard low-
salinity formation mixes with elevated alkaline component
content. The Upper Series, where crosscutting reverse and
