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O‘zMU xabarlari
Вестник НУУз
ACTA NUUz
GEOLOGIYA 3/1 2022
- 261 -
Fig. 1. Boundaries of structural elements (1, 2): 1- II-nd
order, 2 - III-rd order (highs, swells); 3- gas condensate
fields.
Major tectonic elements: I - Aktumsuk system of dislo-
cations (1 - Bayterek swell, 2 - Terengkuduk swell, 3 -
Kassarma swell, 4 - Muynak uplift, 5 - Sarytekiz uplift, 6 -
Kharoy swell, 7 - Muynak-Khazina swell, 8 - Churuk
connection), II - Yarkimbay uplift, III - Barsakelmes
trough (9 - Kul'bai syncline, 10- Atorbay syncline, 11 -
Allan depression, 12-Agyin high), IV - Kuanysh-Koskala
swell, V - Sydochiy trough, VI - Takhtakair and Berdakh
swells, VII - Monchokli uplift, VIII - Sam trough, IX -
Kosbulak trough, X -Central Ustyurt high (13 - Kokbakhti
swell, 14 - Aibugir swell), XI - Assakeaudan trough (15 -
Khoskuduk flat, 16 - Shakhpakhti, 17 - Assakeaudan
depression), XII - Shordzhi uplift, XIII - Dar'yalyk-
Daudan trough, XIV- Aral-Kyzyl Kum fault.
The formation of the Jurassic terrigenous formation took place under essentially constant climatic and tectonic
conditions, more precisely, changing within a very narrow framework. The tectonic differentiation of the territory under
consideration was very active. At the same time, the intensity of movements increased from the Early Jurassic to the Middle
Jurassic. This also determined a directed change in the mineralogical composition of sandy-siltstone rocks: a consistent reduction
in the proportion of quartz, an increase in the proportion of feldspars, and the appearance of rock fragments in sandstones. The
processes of denudation in the sources of demolition and sedimentation in depression zones have become faster, more intense
(well North.Dzhangyzsu-1).
With the successive expansion of the area of sedimentation and the reduction of erosion zones, the conditions changed
from exclusively continental to mixed lagoon-continental and shallow-marine. According to seismic data, the presence of strata
that wedged out on the slopes of large tectonic uplifts is established. This creates the prerequisites for the formation of
lithological traps in the zones adjacent to the wedging lines. In the deposits of the Middle Jurassic, traps of the lithological type
are confined to the channels of ancient rivers and bar sand formations. Bar bodies have a flat bed and a convex upper surface.
The traps confined to the channels of ancient rivers are characterized by sinuosity of contours in plan, a sharp variability in the
lithological composition and sorting of sandy material, as well as a convex base of sand lenses.
The most probable distribution areas of such objects are the Kulbai trough, the northern slopes of the Yarkimbay and
Agyin ledges, as well as the southern and southwestern slopes of the Alan depression.
In addition, several generations of faults of different ages are distinguished here, from those buried in the Paleozoic to
intersecting Jurassic deposits. Extended large-amplitude faults are most confidently recorded at the boundaries of large elements.
Faults in the platform cover are developed mainly in the Jurassic complex and usually die out in the Upper Jurassic.
The Aktumsuk system of uplifts is generally characterized as a zone of sharply reduced Jurassic thicknesses by the
absence of Lower Jurassic deposits. At the southern boundary of this uplifted zone, a sharp increase in power is recorded. High-
amplitude movements in the Early-Middle Jurassic occurred along the Aktumsuk fault. The vertical amplitude of movement in
the Jurassic period was 1.5-1.7 thousand meters.
To the south of the Aktumsuk fault in the Kulbai trough, the thicknesses of the Jurassic deposits are characterized by the
highest values in the territory under consideration - 2.2-2.4 km. The section of Jurassic deposits within this trough is represented
by all sections of the Jurassic, which indicates a constant subsidence throughout the entire Jurassic period.
The Kulbay trough inherited the southern part of the more extensive paleodepression that existed here in the Permian–
Triassic (the northern part of which underwent an inversion and turned into uplifts that make up the southern part of the
Aktumsuk system of swells). The Alan depression actively developed along the Central Ustyurt fault.
Along these extended large-amplitude faults at the
boundary of the Kulbay trough and the Alan depression, the
probability of identifying tectonically screened traps is very
high.
On the northern side of the Kulbay trough, two non-
arched prospecting objects were identified, adjacent to the
Aktumsuk fault - Northern Dzhangyzsu and, to the east,
Razlomnaya. Both have a similar structure. In addition to
these tectonically screened objects in the Jurassic, an anomaly
of the seismic field was revealed in the Northern Dzhangyzsu
area in the Permo-Triassic stage, which probably corresponds
to a lithologically limited trap. On the southern side of the
Kulbai trough, wedging out of layers in the Jurassic sequence,
called the Kulbai non-arched object, was revealed.
Unfortunately, the drilled wells at this site did not give
positive results - at Razlomnaya, the well turned out to be
outside the contour, at North.Dzhangyzsu - at a non-optimal
location, at Kulbay - wedging deposits turned out to be
impermeable. A negative result in these areas cannot serve as a basis for concluding that the region as a whole has no prospects.
Moreover, signs of gas content in the form of formation water degassing during testing were obtained here in the Tleukuduk and
Atorbay areas.