Geology Reference
In-Depth Information
one or the other may have become dominating, thereby defining the total
water salinity and its hydro-geochemical type (Rachinsky, Vezirova and
Fridman, 1972).
The hydrochemical description of the
Pliocene
complex is based on
the integration by the authors of over 50,000 of ground water analyses
(Abramovich, 1934; Akhundov, Mekhtiyev and Rachinsky, 1976; Kolody,
1969; Kurbanmuradov, 1963; Melik-Pashayev, 1959; Mekhtiyev, Akhundov,
and Rachinsky, 1970; Salle and Debizer, 1976). Individual prospects and
fields of the region are dealt with in numerous publications including
Akhundov, Mekhtiyev and Rachinsky (1976); Gurbanov, Moldavsky and
Rachinsky (1966); Mekhtiyev, Rachinsky and Fridman (1968); Mekhtiyev,
Akhundov and Rachinsky (1970); Mekhtiyev, Rachinsky and Fridman
(1971); Rachinsky, Fridman and Chernomordikov (1966); Rachinsky,
Dzhavadov and Fridman (1973)
and many others. That is why we will pro-
vide here only a summary and interpretation of the data.
The ground waters in the
Middle Pliocene
(the Productive Sequence -
Red-Bed Sequence) belong to two major types: the chlorine-calcium
brines and relatively low-salinity hydrocarbonate-sodium (see Table 2.1).
The chlorine-calcium waters saturate mostly the reservoir members of
the upper section although sometimes they are recorded in the lower
intervals (Buzovny-Mashtagi, Kala, Zyrya, Yuzhnaya and some other
fields). Their salinity widely ranges (70-100 to 700-800 mg-equiv. or
20-228 g/l); maximum sodium and potassium content does not exceed
310 mg-equiv.; the chlorine content is between 70 and 420 mg-equiv.;
sulphate concentration is usually no greater than 3-5 mg-equiv.; total
alkalinity does not exceed 5-10 mg-equiv. The secondary salinity fac-
tor is within 0.1 to 36%-equiv. Hydrocarbonate-sodium waters are
found mostly in the lower formations but sometimes are encoun-
tered much higher, up to the Upper Pliocene intervals. It happens in
the Central Apsheron: Balakhany, Surakhany, Karachukhur and Zykh
fields; the Lower Kura Depression: Neftechala, Kalmas and other fields;
the Apsheron Archipelago: Neftyanyye Kamni field; the Balkhan zone
of highs: Barsagelmes and Bankali fields. Their salinity ranges between
30 and 200-220 mg-equiv. (8.6-63 g/l); the chlorine content is 10 to
100 mg-equiv.; sulphate concentration reaches 22 mg-equiv. (Zyrya
field). The primary alkalinity factors are 0.1-55%-equiv.
Beside the indicated major types, the local structures include (in transi-
tion zones from hard to alkaline waters) some amounts of the sulphate-
sodium and chlorine-magnesium varieties; as we will show later, those
are the result of mixing in different proportions of chlorine-calcium and
hydrocarbonate-sodium waters.
