Geology Reference
In-Depth Information
t Clear salinity increase and alkalinity decline is recorded for
the individual structures toward the regional dip (Table 2.7,
see Figure 2.11).
t Waters drastically differing in the salinity and type are
recorded in different (even closely positioned) areas and struc-
tures (especially in the Upper series of the Middle Pliocene).
t In all Middle Pliocene intervals the edge waters and bot-
tom waters of commercial oil accumulations have slightly
elevated salinity compared to the waters of more subsided
areas of local structures.
t In the course of field development, the ground water salin-
ity most commonly tends to decrease during the first period
which is replaced at later stages by continuous growth (to
a certain limit). Such temporal variations indicate the pres-
ence within productive horizons of a specific hydrochemical
zoning: the hydrocarbon accumulations are encircled by a
narrow band of relatively high-salinity water followed by the
ring of lower-salinity water and farther down, in the most
subsided areas, by high-salinity water.
Ground water flows from the Upper Pliocene (the Apsheron Stage) were
obtained on the Apsheron Peninsula (Balakhany-Sabunchi, Surakhany,
Karachukhur, Peschany Island, Kala, Zyrya and Bibieybat fields); in the
lower Kura Depression (Kyurovdagh, Karabagly, Babazanan, Khilly,
Neftechala, Kalamadyn, Kharami Bank, Mishovdagh, Kalmas, Kyursangya,
Pirsagat fields and from the Khydyrly prospect); in the Balkhan (Cheleken,
Nebitdag, Koturtepe, Barsagelmes, Bankali and Burun fields), Urunjuk-
Boyadagh (Kumdagh and Boyadagh prospects) and Gorgandagh-
Chikishlyar (Gorgandagh, Okarem, Adam-Kuduk and some other
prospects) zones of highs.
In the stated interval on the Apsheron Peninsula, east of the Balkhan,
in the Urunjuk-Boyadagh and Gorgandagh-Chikishlyar zones of highs
almost everywhere are found chlorine-calcium brines with the salinity
of 350-760 mg-equiv. (100-217 g/l). The Stage waters practically do not
include sulphates, contain some carbonates (0.1-2 mg-equiv.) and display
the domination by magnesium ions over calcium. The primary salinity fac-
tor is 70-80%-equiv., the secondary salinity factor is 18-27%-equiv. and
the secondary alkalinity factor is 0-2%-equiv.
The Lower Kura Depression and the western Balkhan zone are also
dominated by chlorine-calcium brines. Together with these, however, are
sometimes encountered lower salinity chlorine-magnesium and alkaline
varieties forming isolated spots. Waters of these types are usually localized
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