Geology Reference
In-Depth Information
is supported by the evolution in time (in the process of field
development) of the areal ground water salinity and compo-
sition distribution.
t
Positive hydrochemical anomalies are recorded within a broad
stratigraphic range (Valanginian through Chokrackian).
Their expression is drastic local ground water salinity and
metamorphism increase in the complexes compared with
the hydrochemical background. These manifestations are
usually associated with most faulted field zones where ver-
tical hydrodynamic communication between the lower and
upper sediment cover intervals is clearly implemented.
t
On the local structures, the contrast (manifestation extent)
of positive hydrochemical anomalies is in direct proportion
with faulting. The strongest faulted structures display the
presence in the formation waters of maximum amounts of
high-salinity waters injected from down.
t
The Eocene-Upper Miocene interval is saturated with both
alkaline and hard formation waters. In the former case, the
elevated oil-saturation areas are associated with zones of
maximum concentrated hydrocarbonate-sodium varieties
with minimum primary alkalinity factor value. In the lat-
ter case they are associated with zones of high salinity and
maximum secondary salinity factor values of the chlorine-
calcium waters.
t
In the Mesozoic complexes positive hydrochemical anoma-
lies are spatially associated with the areas and fault-blocks of
elevated hydrocarbon saturation.
Based on the described patterns in the ground water regional distribu-
tion over the area and in the section and as a function of the local struc-
tures' tectonics and oil and gas occurrences, some considerations may be
suggested as to the formation mechanism of the waters' hydrochemical
outlook in the trough's sediment cover.
The following features classify ground waters of the Upper Jurassic
evaporite facies as depositional metamorphosed chlorine-calcium forma-
tion brines, derivatives of the water medium in the salt accumulation basin:
t
High salinity (320-355 g/l).
t
Specific composition with a substantial role played by cal-
cium and magnesium chlorides (20-40%-equiv.).
