Geology Reference
In-Depth Information
their genetic association based on acquirement of the pressure in the
enclosing clay massif by reservoirs.
Regarding AHPP spatial development in the Paleogene-Miocene range,
the nature and intensity of their manifestations were studied in consider-
ation of basin's geologic evolution and geotemperature conditions of rocks
at their present-day depths. A conclusion was made that they are synge-
netic and are a product of three major mechanisms. These mechanisms are:
t
Normal clay consolidation while subsiding in an immersion
cycle under the environment with severely limited outflow
of pore fluids.
t
Subsequent montmorillonite dehydration under the ther-
modynamic environment favorable for this process (this is
indicated by a decrease in clays down the stratigraphic sec-
tion of the montmorillonite amount and the simultaneous
increase of the hydro-micaceous associations (Aliyev and
Akhmedov, 1968; Akhmedov, Salayev and Ismailov, 1961).
t
Compression by the lateral and vertical stress of individual
fault-blocks and basement in tectonic motions.
he
Middle Pliocene
sediments
(
the Productive-Red Bed Sequence
PT
-KT) are penetrated and tested in numerous wells all over the South
Caspian Basin. As previously mentioned they are composed of a thick (5
km and greater) alternation of clays, siltstones, sandstones and in some
areas sands (Balkhan zone of highs, Central Apsheron). The section repre-
sents a typical molasses. Clay content in the section widely ranges between
31and 98%. A general trend is its increase down the regional dip toward
the South Caspian's deep-water portion. Specific PT-KT features are:
t
Environment of avalanche deposition (sediment accumula-
tion rate of about 900-1,300 m/1,000,000 years).
t
Rhythmicity [periodic replacement in vertical direction
(down-to-up) of clays by sands].
t
Pinch-out of stratigraphic components in the direction both
toward the flanks and toward the basin's center. The least
clayey section (clay content of 30-75%) is typical of the
Apsheron Peninsula, North-Apsheron zone of highs, South-
Apsheron trough, Apsheron-Balkhan Sill, Balkhan zone of
highs. Over the rest of the South Caspian Basin the clay con-
tent in individual areas increases to 95-98% (south portion
of the Baku Archipelago).
