Geology Reference
In-Depth Information
crests to the flanks and plunges and increase of the same parameters down
the Upper Cretaceous section.
he
Eocene
complex (the foraminifer beds) includes carbonate-clas-
tic reservoirs (marls, sandstones and siltstones). All over the region
the anticlinal zones contain ground waters of chlorine-calcium type
(Karabulak-Achaluki, Oktyabrskoye, Starogroznenskoye, Sernovodsk,
Malgobek-Voznesenskoye fields, etc.). Total salinity ranges between 70.3
and 124.8 mg-equiv. (20.1-35.7 g/l), secondary salinity factor is 3.2-4.7%-
equiv., sodium/chlorine ratio = 0.96-0.97. Maximum values of this param-
eters form the regional background.
In the exposure area of the complex (Chernogor monocline) there is
a narrow band occupied by fresh (up to 2 g/l) surface sulphate-sodium
waters. It is replaced northward (toward the regional dip) by a band of
higher salinity (up to 15 g/l) hydrocarbonate-sodium waters and then even
more saline (up to 35-40 g/l) chlorine-calcium formation solutions.
Ground waters from the
Oligocene-Lower Miocene
complex (the
Maikopian formation) were produced from mostly Lower Maikopian
sandstone lenses in the Sernovodsk, Starogroznenskoye, Oktyabrskoye,
Malgobek-Voznesenskoye fields, etc. Dominating is the chlorine-calcium
type with the background salinity 90.8-101.7 mg-equiv. (25.9-30.0 g/l),
secondary salinity factor 3.3-3.9%-equiv. and the sodium/chlorine ratio
of 0.95-0.97.
Intervals of the clastic
Middle-Upper Miocene
complex (the Chokrackian,
Karaganian, Sarmatian and Meotian) include waters of rather motley
hydrochemical composition and salinity. In the exposure area (Chernogor
monocline and some areas in the Frontal Ranges) are mostly developed
infiltration fresh (up to 2 g/l) sulphate- and hydrocarbonate-sodium waters
(primary alkalinity factor to 70-97%-equiv. in the Karaganian horizon of
the Starogroznenskoye field). These waters are gradually replaced down
the regional dip by the chlorine-calcium brines (до 100 g/l in the Pri-Terek
zone).
Various ground water genetic types are found in the Middle-Upper
Miocene complex in accordance with lithology in the areas and within the
section intervals with thick high-permeability sand members (Chokrackian,
Karaganian and Meothic horizons in the Starogroznenskoye, Oktyabrskoye
and Malgobek-Voznesensk fields). For this reason is possible practically
unlimited penetration and subsequent transit of fresh meteoric waters.
Low-salinity sulphate-sodium and hydrocarbonate-sodium formation
waters are common and almost completely replace the syngenetic hard
reservoir waters. Dominant in more nonuniform and less permeable mem-
bers (Sarmatian Stage in the Gora-Gorskaya, Adu-Yurt and Chervlennaya
