Geology Reference
In-Depth Information
t
Great chlorine / bromine ratio values (over 2,300-2,500)
and sodium / chlorine ratio values (0.61-0.79).
t
Occurrence in lens-shaped reservoir members within the
salt massifs;
t
Quite high static pressure (around 45-55 МПа).
Under the lithological concept of ground water formation substanti-
ated by Valyashko (1964), Kapchenko
et al
. (1972), Zaitsev and Tarasov
(1972), the background chlorine-calcium waters in the entire overlying
stratigraphic section (the carbonate Upper Jurassic through the Upper
Miocene) are a result of a directional transformation of the depositional
waters in the sedimentary basins. These transformations are deemed to
have been a complex function of numerous factors in the basins, which
included paleo-climatic and paleogeographic environments; lithology and
mineralogy of water-saturated rocks; geologic evolution of the region and
its individual parts; paleo- and present-day infiltration of surface waters;
intensity of diagenesis and catagenesis in the course of lithification; time-
dependent and location-dependent thermal and baric environment in the
sedimentary section; and various physicochemical processes (diffusion,
osmosis, etc.).
The conclusion is supported by the described continuous and rigidly
regular increase down the stratigraphic section in the formation water
salinity and metamorphism. Total salinity values are 53.9 mg-equiv. (16.6
g/l), secondary salinity factor 4.9%-equiv., sodium / chlorine ratio is 0.97-
0.99 in the Meotian to, respectively, 490 mg-equiv. (143.3 g/l), 21%-equiv.,
0.84 in the Upper Jurassic-Valanginian complexе.
The mosaic presence of “transitional” formation waters of all hydro-
chemical types with various salinity (2-10 to 50-70 mg-equiv.) and pri-
mary alkalinity factors and secondary salinity about 1-4%-equiv. was
identified in a number of horizons. Their charge regime was determined as
mostly infiltration. These may be objectively interpreted as a result of mix-
ing in varying proportions of fresh surface sulphate- and hydrocarbonate-
sodium agents and syndepositional saline chlorine-calcium ground water.
Changes in the component composition of the resulting formation solu-
tions followed a regular series. When the source components were sul-
phate-sodium and chlorine-calcium waters, sequentially in the direction of
the infiltration flow were generated “transitional” sulphate-sodium, hydro-
carbonate-sodium, chlorine-magnesium and chlorine-calcium waters
of progressing salinity; when the dominating presence was by the fresh
hydrocarbonate-sodium waters, “transitional” alkaline, sulphate-sodium,
