Geology Reference
In-Depth Information
with the faulting and oil and gas occurrences are identical with the under-
lying complex.
he
Upper Cretaceous
complex is composed of fractured pelitomorph
limestones with some clayey material. Typical of them is regional develop-
ment of typical chlorine-calcium solutions with total salinity 102.9-450
mg-equiv. (31.2-133.6 g/l), secondary salinity factor 3.7-16.1%-equiv.,
sodium/chlorine ratio 0.84-0.97 (Datykh, Benoy, Zamankul, Karabulak-
Achaluki, Sernovodsk, Starogroznenskoye, Oktyabrskoye, Arak-Dalaterek,
Akhlovo, Malgobek-Voznesenskoye-Ali-Yurt, Orlinoye, Eldarovo, Khayan-
Kort, Andreyevskoye, Braguny, Gudermes, Galyugayev, Mineralnoye,
Chervlennaya and Pravoberezhnoye fields). Positive hydrochemical anom-
alies (59-132 g/l, 14-16%-equiv.) defining the upper values of total salin-
ity and secondary salinity factor were identified and usually found in the
faulted and elevated fracturing zones, which indicates injection into the
Upper Cretaceous reservoir of higher salinity and metamorphism waters
from the underlying intervals. The same zones usually have elevated oil-
saturation of the reservoirs.
The first anomalous water salinity area is positioned on the west plunge
of the Karabulak-Achaluki prospect. There, along a large fault was pro-
duced water of the salinity greater by 40-140 mg-equiv. (11.8-41.2 g/l)
than in the adjacent blocks.
The second and the largest is a hydrochemical anomaly covering
Orlinaya, the west part of Khayan-Kort and the east end of the Malgobek-
Voznesensk prospects. Maximum water salinity reaches 230.0-240.0 mg-
equiv. (67.6-70.6 g/l). Eastward and westward the salinity declines to
170.0-180.0 mg-equiv. (50.0-52.9 g/l). The anomaly is found in the area
of a complex tectonic node in the merger area between the Khayan-Kort,
Orlinaya, Eldarov and Malgobek-Voznesensk structures cut by a number
of large faults.
The third area was identified over the western portion of the Malgobek-
Voznesensk structure. The water was produced there with the salinity
above the normal for that part of the area by 32.0-65.0 mg-equiv. (9.4-
19.1 g/l).
The fourth area is associated with the Benoy gas-condensate field
(Chernogor monocline). There, the water with salinity 350.0-450.0 mg-
equiv. (102.9-132.3 g/l) was collected from the Upper Cretaceous sediments.
In all trough's anticlinal zones the regional hydrochemical background
is formed by waters with salinity of 140-160 mg-equiv. and secondary
salinity factor of 6-12%-equiv.
The general pattern in all structures of the region is the salinity decrease
(by about 15-25 mg-equiv.) and secondary salinity factor values from the
