Geology Reference
In-Depth Information
chlorine-magnesium and chlorine-calcium waters were generated in the
direction of the infiltration flow.
The mixing process was controlled mostly by the spatial consistency,
extent of variability and permeability of the reservoirs. This caused the for-
mation in different areas of the ground waters substantially different in
salinity and type. The final effect of such phenomenon was a clear areal
hydrochemical zoning, manifested by a directional regional change in the
ground water composition and salinity along the track of infiltrants' move-
ment in the porous medium.
Exceptionally important in the formation of water hydrochemistry in
the stratigraphic range from the carbonate Upper Jurassic through the
Upper Cretaceous where vertical interformational ground water cross-
flows from the lower to the upper intervals of the sediment cover. Their
existence and influence are supported by the aforementioned positive con-
centration anomalies and by the areal zoning in ground water distribu-
tion by the salinity and metamorphism within local structures (a decrease
in the stated parameters from the crests to the flanks and plunges). The
hydrochemical anomalies and the development of higher salinity waters
are associated exclusively with crestal areas of the structures. These areas
are faulted through the entire Mesozoic section. And less deformed periph-
eral areas are occupied by less saline and less metamorphosed varieties. It
shows a clear effect in the former case of mixing syndepositional waters
and the waters invaded from down the section through faults.
Thus, the cross-flow/injection genesis hydrochemical anomalies are
established in all drilled Mesozoic complexes. But the Upper Jurassic evap-
orite facies cannot be their charge area due to the absence of reservoirs
and therefore of sufficient amounts of free water. Hence, we must recog-
nize that only the Lower-Middle Jurassic and possibly Permotriassic clastic
deposits could be their charge area
4
.
The objective uniqueness of such hydrodynamic model enables a suf-
ficiently reliable forecast in the yet-undrilled pre-Upper Jurassic section
4
A suggestion was made
that the water underlying crestal areas of the Upper Cretaceous res-
ervoirs has been desalinated from the complex's internal sources such as dehydration water
of clay minerals, condensation and solution water (Volobuyev, 1986; Nikanorov, Tarasov and
Fedorov, 1983). Objections here are the predominantly carbonate Upper Cretaceous section
with minuscule role of clays and the directly opposite trend in formation water alterations
in the process of hydrocarbon fluids transformation (Rachinsky, 1981, 1983).The solution
water is a desalinated water emitted directly in a trap from an oil-water emulsion in the pro-
cess of natural gravity separation due to the density difference between oil and water but not
due to the condensation of water vapors from a gas-condensate mix (Kolody, 1975).
