Geology Reference
In-Depth Information
accumulations. Accumulations in the Anastasiyev zone are associated with
the diapir plugs. The hydrocarbon accumulations in the Kerch-Taman area
Neogene are also found with the diapir-type structures, and in the Upper
Cretaceous reservoirs, they have morphology of the massive accumulations.
A typical feature of the oil occurrences in the region is their spatial
association with major deep-seated and their feathering smaller faults.
The largest fields are Zybza-Gluboky Yar, Anastasiyev-Troitsk, NW Afip,
Novo-Dmitriyev, Akhtyr-Bugundyr and Abino-Ukrainskoye. The region
as a whole has three different hydrocarbon type distribution zones: the
upper gas, middle oil and the lower gas-condensate.
1.2.3 The Tersk-Caspian Foredeep
The basin is separated in the north from the Scythian Platform by the
Tersk-Caspian edge fault, in the east by the regional faults in the axial zone
of the Dagestan Piedmont, in the south by the Chernogor fault and flex-
ure system from the Caucasus Major mountains and in the west by the
Mineralovodsky basement high (Figure 1.11).
The sediment cover overlying a Paleozoic basement includes
Permotriassic through Quaternary rocks. Average thickness of the sediment
cover is 12 km; the clay content is 45%. Several lithostratigraphic complexes
are identified in the section. They are: the lower-Middle Jurassic clastic
complex (total thickness up to 2,000 m); the Upper Jurassic-Valanginian
carbonate complex (about 2,000 m thick); the Lower Cretaceous clastic
complex (800
−
1,100 m), the carbonate Upper Cretaceous-Eocene complex
(350
650 m) and the mostly clastic Upper Eocene-Quaternary complex
(over 5,000 m thick). The clastic complexes are composed of granular res-
ervoir members alternating with clays; the carbonate complexes include
fractured limestones, marls, etc.
The highest clay content is identified in the Lower-Middle Jurassic,
Albian, Maikopian and Pliocene rocks.
The foredeep is asymmetric. Its northern external flank facing the plat-
form is broad and low-angle with monoclonal rock dip. Its internal south-
ern geosynclinal flank is narrow and steep, substantially affected by faults
and intense folding. The region is cut by large regional faults into indi-
vidual tectonic blocks and steps generally subsiding from north to south
and from east to west. The lengthwise faults are the Tersk-Caspian, Middle-
Tersk, Argudan-Sunzha and Chernogor. The cross-faults are Cherkassky,
Malkin, Baksan, Chegem, Ardon, Kazbek and Argun. And the diagonal
faults are Nalchik, Datykh-Akhlov, Benoy-Eldar, Gudermes and Samur.
The lengthwise faults have throws of up to 2,000 m; the cross-faults, up
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