Geology Reference
In-Depth Information
0
2,0
4,0
6,0
8,0
10,0
I.
South Caspian Depression
Western flank
Eastern flank
II.
-1000
III.
-2000
-3000
-4000
-5000
1
3
-6000
H,m
Figure 2.12
South Caspian Depression. Ground water sulphate content and accumulation
type vs. depth:
1.
Gas-condensate accumulations,
2
.
Oil accumulations,
3.
Nonproductive
intervals.
pyrite (Smirnov, 1980; Sultanov, 1958); pyrite is an indicator of a reducing
environment at the diagenetic stage of lithogenesis.
Other theoretically possible mechanisms of sulphates occurrence in
ground waters were reviewed. They are: infiltration into reservoir rocks of
sulphate-ion bearings meteoric waters; life activity of thiobacteria oxidiz-
ing sulfides and native sulfur; leaching of salt rocks (evaporite formations)
by the filtering water; and invasion into a given interval of foreign waters
enriched in sulphates. It was found that the former three mechanisms are
not realistic in the specific environment of the South Caspian Depression.
This finding is based on low likelihood of the current meteoric water infil-
tration into the Middle Pliocene complex; the absence in this complex of
allothigene sulfur-containing compounds and zones of free water-exchange
and ground water aeration as main conditions for the functioning of thio-
bacteria; and typically molasses type of the section (Bagir-Zadeh, 1969;
Bagir-Zadeh, Kerimov and Salayev
,
1988; Sultanov, 1958). Based on the
